‘UNITED STATES DEPARTMENT OF COMME ¢ “Luther H. Hodges
WEATHER ‘BUREAU BW. Roce Chief

MANUAL OF

ite METEROLOGICAL
Re 38 _ OBSERVATIONS
iia. |e s 3
Teh ie ® an Ss ee “ *
Re ‘
ie * CIRCULAR M ~
‘% ELEVENTH EDITION
;

DATA LIBRARY

ERENCE COLLECTJO
pais OCEANOGRAPHIC ae te

Feast “oe ges WASHINGTON, D.C,

Price $1.50

¥
pom Aor Fgh es

&. 2

UNITED STATES GOVERNMENT PRINTING OFFICE

) hbO@EOO TOEO O

“uma

1OHM/18IN

oe
MANUAL OF

MARINE METEOROLOGICAL
OBSERVATIONS

WOODS HOLE

es Il OCEANOGRAPHIC INSTITUTIOP:

LABORATORY
BOOK COLLECTION

PURCHASE ORDER No. 16%5 3
APR 10 4969 OW Atlantis

CIRCULAR M

ELEVENTH EDITION

JANUARY 1963

_DATA LIBRARY
AEP Er RE} VCE COL ECTION

“AD »DS HOLE OCEANOGRAPHIC INSTITUTE

o :
Aa

‘

AN APPRECIATION

The continuing demand for more and better weather information for
ships is being met by the cooperation of the users themselves. Weather
reports received from cooperating ships by radio and mail provide the
basis for forecasts and navigation charts issued to the maritime service.

The Weather Bureau wishes to thank the masters and officers who are
contributing so effectively to the success of the ocean weather service.

F. W. Reichelderfer
Chief of Bureau

III

Introduction
Chapter

CONTENTS

fi (Gxetavencreyl WWoKsnmetelewmolais! 5 4 4415 GS sod 6 8 8 8 ee oe oueee foe Gn ae

Ship's Weather Observations--Form 615-5.......
Radio Transmission of Weather Observations .....
Oeiering Supp Mes.) a cca coat leis agnor atte ae eer Bee
Wieather Bureau Port Offices’. = =... 0s seus

II Identification Data
General ...
Day of Month

oa 8) Ss 6 ew OS eke we 8 te we ee ete ere.

a. 6 Oe 8 eS ee CU ee ee es el lk

aim) 6.) ie je a) 6) 6 6 i le 8 wt es ws ne 8: tw ce) 8

OAc Ol WIGS (NO) tains wate aie Were Ware Nera at are Twa. or Gaetan een
©ctantmotGlobex(@) Germain em enn er ee
Neonates Ua ley Ley) enge pee eran e ls, came g Ue, Wt a seeue ie

Longitude (Lio

is ON ne ar ee eee ae

Greenwich Civil Time (GG). .................

Ship's Course

(US) seats en caeses ae pneen Pe oe ae

DIOS OD CEC Vici) rarer ins eure Gime Poker ameter e asa ae meee

III WANG ie jo. 5 ane

Wind Speed .

* 6 6 8 we fe we Ue fe. 6 el em 8 8 ee OU ee Oe,

2) ee 6) 8: ow Je. oe: 6) 0) 0. se. eee. ee} el 8, ee a= 3), ce) a). a

BL O20 16 een ese. 6) Yer ere se’ foe) sel) cet ce: ces oe oe) ce, 58). @: 8 fence

True Wind from the Apparent Wind ............

Wind Shifts .
IV VAIS Towa yjenmatene Pee

General......

@; isi ‘e) f0: 9° (©: 46, @ 6) © @ © ie ie je 6 i @ 6 je) S:/.0° “eke «ie.

©; et) ret Tel 6i we Le el 16; fe) ew. fa ve. o> ew ‘eh ie “ee: Se) ei facie el

.

DSteeM ina COMO, VlSMoUlty rs eus ear ee aie wine seuie
Coding and Entry of Visibility Data (VV) on
Or any) OD aah ue canines hipaa ao os BER KA cen aor pig 21s

S feu ee) isi eh Je; 16,> evs eee eye) ace Fel we: Ge: “a Nay, ten [cet Xa

ShundenstOcm s and Lightnine). can = eee = 2! sy ea &
Water spouus and sGUa lisa) ai euwreite se seir tc eicrrenys cuien

Precipitation
Fog and Rime
Faze, Smoke,

OTe Ne, te) ser eel jen ar mie Sel fw ce me) We ie fai Ye! ce) Net oie, eh oe) et be: ue

Oo 56) eB he. ee: 8: ie. “ey ce" ce! Sst, ce ce) eis! 6: Yai. tei te! weet ie: ey a. ie

ANIC US tee eee ee OMY ce cities! oa els

Miscellaneous ...........
Present Weather (ww)l. sl. 1s ee eka ee we:

Past Weather

GV) Ramee Samewa oS Pe ae, re eee Sn at Ge

Chapter
VI

VII

IX

VI

dep eketol =) DE Ole ay ee Pe Meee re Re epee ac une eres ert moog Serie
General 2222 Aa ns veoh Reo eee ep IAD Sh pee oe Ser te ey Sra
WNraveneropiel letsstonagloid-wais) noe ae qla 9 te Dlg mn ac coe Oe Oo
Barocraph., Ware ye ve cny-cearre ta ae incy ee teenies
Three Hour Pressure MendenGye. a. <a ees) ue) ere
Coding and Entry of Pressure Data (app) on
Fiori Oita 51 Scharrer ome ee aem cee anion Teme onton onc eenee
AR Sey elope yvhes: Ream a amor See: hun a Oo et eet ae ono anc
General
Air Temperature Measurements. 23.00 ai. ele eee
Sea Water Temperature Measurements .........
Coding and Entries of Temperature Data on
Pocm GUS=5.5 cists, S atehs om Seer wiBetsh Ue Ges ne eee ies ce

Determinaiwoneobtsky COV a ree aewn cent nrene
(GAkoyeKon Staves oy teehee aeote cedpate: ocho Madore cree eG bo a <
Coding and Entry of Cloud Data on Form 615-5. ..
WeVieS tae. cars

General Bec. ws eee

Nien oenD yi ckeves ola Rees: Abs Reo are eee Oe ees at GO 6 2 6 &
Waves POrlOgdsorc1.% euceks Seka Measles a aaa outset, ee nee
IWraivie ICT OIG To ties ete mys creme Gh etc) cuca te gre meg mee mea eee
Coding and Entry of Wave Data on Form 615-5 ...

OBSERVATION TABLES

Elements: of the-Code: 273 245 sss a 6 eu og ee Sea eae
Determination of Wind Speed by Sea Condition........
Apparent Wind SpeCGs 2 hacer cn steve eo stees ele eter ete bene
Distance (oO Object: on the Horizon at Seas ie oe ee eee
Intensity, Of Raina aieces es orcwel ere ee ae) been fore dcp eer ee
Intensity: Of SMOW? ey -weaecmosi el ce eee) eras) eee eke tons efteyte ary suet

CODE TABLES

Code Table No.

i ovinoOlse=— Way Or the Weele sas wus.6 6 oe eset eus + eae
ZeesyimMnol @ —Octant. of the Globe... G . a6 4.6 +. 8 vee a ase e 4
3 Symbol N - Fraction of the Celestial Dome Covered by
Cloud sin ie PNOTIENISS once tea er a siento Gene Gqutacce, Watt 0 Yee azote
Symbol N, - Fraction of Celestial Dome Covered by
diype.of Cloud Reported tor Cy, (or Chg) 2% ace oe nla ee
4 Symbol dd - True Direction from Which Wind is Blowing. . .
Symbol dd, - Direction from Which Waves Come.......
OM OD OUI AVIS PDE LREY ce Sein a gee Goatboy de, he ty ina Boke, vac bentt
Oe yIMbolwwWo="Present Weather” yic5 4: 6.0. aaa ale 4uede ee ee
eID OlWie—aabuWedt Nel, civ Sa. iis, Gla eisuata acolahes See
de oymDOlWriP = Corrected Barometric Pressure, ... fay. ss
9 Symbol Cy; - Clouds of Types Stratocumulus, Stratus,
Cumulus, and Cumulonimbus... 2 ve. 6 So we ee ee
10 Symbol Cy - Clouds of Types Altocumulus, Altostratus,
BH CAINDIDOSUG ALLS nor sce een aR, seh Baht ines Ghrey'a ier lar eda gs 9
11 Symbol Cy, - Clouds of Types Cirrus, Cirrostratus, and
Cire OC MINUS 9 yews .w sya. a wes ohoaa.6. BS plore be ve. a sete ance, eee ten le
12 Symbol h - Height of Base of Lowest Cy, (or Cy) Cloud
ENDOOV Ga Ame e mony (Oa beien JidanG. klar sic eine lnivian wite¥h Gu ois Meee
i eoy Won a = Ship! Ss COUNS Cais) aac ce ecw a le ayadbine ies ale
eo OOL Vane OMIp S SPCC. | saa a0ele. cue acs wr acelentte sve ee
15 Symbol a - Barometer Change Characteristics in the Last
SBLIOUI Ors sewage ah ae eile: Gaur Mee ea A ee, tale does yale tel See
16 Symbol pp - Amount of Barometric Change in Last 3 Hours...
Beep Ol = Pero Ol WAVES Nis. aisle <r 4 os eee eee
eee wymbolH. “Height of Waves... aiat4 ses ae ee Ge xs
Pinoy mbolcoe— Description of Kind of lee. oa as ee ost
20 Symbol K - Effect of Ice on Navigation...............
Zio ovOl be Bearing Ol lee=Iaimit a. ce oe wae eee ee
22 Symbol r - Distance to Ice from Reporting Ship.........
23 Symbol e - Orientation of Ice-Limit.................
MISCELLANEOUS TABLES
Table No.
24 Celsius (Centigrade) to Fahrenheit Temperatures .......
Zo hemperature of Dew Point in Degrees Celsius ......:.4.%
26 Hahrenheit to Celsius Temperatures .......2+-s80s866-
2( Correction of Mercurial Barometer for Temperature. ....

ee

Table No. Page

28 Reduction of Barometric Reading to Mean Sea Level........ 130
29 Reduction of Mercurial Barometer to Standard Gravity...... 130
Zoe Maltimeters to VE bavs™ 2), ec. amcrn 2) grep tkencae te ee nay eso 130
30 -1Q=Code ‘Signalsh(Seleeted)) 20: ater. cuene a) oom chemin ee) eel
CHARTS
Chart
1, Greenwich andilocal Time... ol saa so eneke coe Seek) een re 133
LIST OF ILLUSTRATIONS
Figure
1 Ship's Weather Observations--Form 615-5.............. 4-5
2 } ourtace Wind at Sea--Porm 12092, 23 2a. os. +1 ss ees eee 25
3 Plotting Board for Finding True Wind at Sea............. 26
42 Non=Unitorm: Visibility los ysis tees aie inle sce es cele ee 32
Die ANeTOldsbarOMmeter. css. 2.2 seis cat a elas oes) .ateene est eit eat ee 48
G .GBarosraph, Marine Model G-220., 023 .0.52 4.46245 6. 50
i Barosraph Chart tye ste an setae whe es ls See e 4 Se ene 51
& “Barograph, Marine W. BB. Model’ G=222 55... 3 a s< 5 2 ae 53
2) Sans ES yichrOmeten ls vei... ails cmiideadias 5 Crease s (ele ae 62
10 Psychrometer (Portable, Aspirated, Electric) ........... 63
fi pection:of Trace from Wave Recorder ... 2)... ses an eee 83
f2-- Wave length and Height. «. < 4.6 6 « em =o = = «4. «) ss Je sane one 85

VTE

INTRODUCTION

The Conference of Brussels, called in 1853, was the first International
Maritime Conference ever held. It sponsored the idea that governments
should foster systematic weather observations on ships, and should prepare
and publish charts of the prevailing winds, ocean currents, average sea and
air temperatures, and tracks of dangerous storms based on the additional
data. With the introduction of radio and fast ships, weather information be-
came of vital importance to safe and efficient ship operation. Many countries
began regularly scheduled weather forecasts to ships in nearby waters.

Today, weather forecasts as well as charts are prepared from data
collected through ship observations, Forecasts of weather and sea condi-
tions are prepared to ship operation, air-sea rescue missions, over-water
air travel, military operations, etc. The need for accurate data is apparent,
since the forecast cannot be any better than the basic observation.

Organization of the Manual. This manual has been designed to serve
primarily as a guide in the taking of weather observations at sea. It will be
helpful in using the manual to keep in mind that the material in it has been
organized to accord with the order of the various elements of the observa-
tion as they are entered in the basic Weather Bureau Form 615-5, "Ship's
Weather Observations.'' Each major element of the observationis completely
covered in a separate chapter. The first portion of each chapter is pre-
sented from the point of view of observing and evaluating the element without
reference to its ultimate use; and the second portion, from the point of view
of making a permanent record of it and preparing it for dissemination
(coding).

IX

CHAPTER I. GENERAL INSTRUCTIONS

CONTENTS

Page

sbiTmMeHOle Ob Ser vatiOnienen acs < ree tsemc hoes st cole cits ove cecewrem rs, velo oe .ce eran 3
SV MOPLICMREDOGIS! 05 aya) ae + eve GocSMe anle Lol even atau 8 lates Js) «on ielhys 3

SDS Gt UCDO US a trea sales es aad s sane Gucan ena lsiajle ii emal ar seine 3
Ship's’ Weather Observations = Form 6159-9 2... 25.08.5864 6. 3- 6
Genesee were copie tween ce serene hh, tease ea gedaan ne teen a. eA eS 3
Eb mOUMOA Ll: wap veuaiamra (tier ot avausia niente: Sexi erm, ate daar 3-5
SCARS WCU Sarin eucu aie le im caer wn kateece wh crete fee eekay, fo oe) See pace 6
Observer Sh imitvalsiee vue tels elise eis cre wom elena vl olcanonsey-c, Pen ewe) ve) % 6

AV Eee BUTS a4 ap ve a ea dale a) a eee anise eine Oe Cane Mahar @ al cate le 6
Radio Transmission of Weather Observations .............. 6
Ships Authorized to Transmit Scheduled Message......... 6
poyoXcVealk oll) 1 fe5 oo ag do] ry ra ee ee oe ee ee ee ee 6
cansmussion wOvohore StatlonsSes castes © clo suse. ueeelene ses cue 6
Meteorological Radiotelegram, W.B. Form 630-9........ 6
CodcetioneMlransmiu'sisiion’ . 45: sa etsls ss eis on ws oly anaes 7- 9

CigG cml oP OUPDINCSin a ew oe 2 eae, eae be sien ake. eB ard Oba ea wees $)
Addresses of Weather Bureau Marine Centers and Port Offices... 10-12

OBSERVATION TABLES
Table 1-1. - Elements of the Code ..................... 8

FIGURES

Figure 1. - Ship's Weather Observations - 615-5............ 4-5

CHAPTER I. GENERAL INSTRUCTIONS
1000. TIME OF OBSERVATION

1010. SYNOPTIC REPORTS. Cooperating ships are requested to make and
record synoptic weather observations at the hours of 0000, 0600, 1200 and
1800 Greenwich Civil Time (GCT) while at sea. If it is not possible to make
four observations daily, as many observations as convenient should be taken,
Observations should be made in sufficient time for delivery to the Radio
Officer by the synoptic observation time,

1011. Weather observations should be made to within 25 miles of the
coast except in sparsely traveled areas. When underway along the coasts
of Central America and the U. S. Pacific Coast (including Alaska but not
the Inland Passage), observations should be taken and reported regardless
of the distance from shore,

1020. SPECIAL REPORTS. In accordance with the International Conven-
tion for Safety of Life at Sea, masters of all ships are requested to take
special weather observations and report by radio when tropical or severe
storms are encountered. These reports are not limited to synoptic hours
but may be reported regardless of hour.

1021. When a tropical storm is reported, the Weather Bureau may
broadcast requests for special radio weather reports from all ships in the
vicinity of the storm. These requests will always include instructions rel-
ative to the time and frequency of the reports and the address to which the
reports should be sent.

1100. SHIP'S WEATHER OBSERVATIONS- FORM 615-5

1110. GENERAL. All weather observations made at sea will be re-
corded on Form 615-5, Ship's Weather Observations. To assist coding
weather data, a complete international Ship's Weather Code and Cloud Code
Chart are included with each pad of Form 615-5, The individual sheets,
when used, may be torn off along the perforation and stored in the back of
the folder until the end of the trip.

A new page of Form 615-5 will be started:

(a) For the first observation of a new month.
(b) At the beginning of each voyage.

(c) Upon sailing from one octant to another.
(d) Upon sailing from one ocean to another,

1120. ENTRY OF DATA. Enter the observations as legibly as possible,
using a well sharpened black pencil or a pen. The data should be entered in
the columns appropriate to them as indicated by the column headings.

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

NAME OF CAPTAIN WB ron 6155
(e02)

Wie VESSEL
(is

jury Ecnawin S, ®WYDBERE

COUNTRY OF REGISTRY

BAROMETER NO.

FROM

: SHIP'S WEATHER OBSERVATI
BALBIA

WORTH

JSavvdry 9 b3 wR

Check (4

mor<xo<

TEMPERATURES (COLS, 1618, 28-30, 32-33); Wee

HOUR
PRESSURI
TENDENC

POSITION OF SHIP TOTAL
oF cLouo] ,

Time | AMT.

ocramT|CaTiTUuDE| LONcr
TUDE
(Newest
(0, 1, 2, hour
3,5, 6,

00-23) |(Ceded)|
aie): (Degrece and tenths) | (GeCeT) | (0-9)

cLoups

OAMOMF TER) OAROMETER
AS heaL cORMMECTED

wee
AEfensieR
eweecn
(Coded)
COURSE OF SHIP
10-9)
SPEED OF SHIP
(0-0)
Aron
iene
(0-9)

(Coded (tre sphvr
‘6 wane)

3 4 5 6 7

<

Q aS LPs co "

Ww

Jt

5S | orc] 8H | O° | 7
Ls

S(O | asF] So | cu] 8

u
v
°
(a
ay
4
we
Nv
k
a
iv]
ca)
a
iv
=f:

F
Va
qQ
ss
ao
=
2
&

Ww we
tT ee ele Pee
i
Gi
ka)
4
in 3
&
=
oo
ae
oe
N

(5) VOYAGE FROM - TO. - Enter port of departure and destination.

(6) TEMPERATURES. - Check the appropriate square in the center
of the page indicating whether temperatures are observed
and recorded in degrees Celsius (°C) or degrees Fahrenheit
(°F). Reports are preferred in degrees Celsius.

(7) WIND SPEED. - Under column 9 place a check in one of the squares
to indicate the wind speed was estimated or measured.

(8) CORRECTION. - Enter barometer correction in space provided
under the heading of column 13.

(9) DATE COMPARED, - Enter date of last barometer comparison
under the heading of column 15.

GENERAL INSTRUCTIONS 5

Form Approved; Budget Bureau No. 41-R1258.3
U.S, DEPARTMENT OF COMMERCE IKSTRUCTIONS
WEATHER OUREAU
« Begin a new sheet: Code the message in a@tordance with the ‘'International
9, For the first observation of a new month, Weather Code for Ships."
b, At the beginning of each voyage. . Ac end of each voyage, remove all forms with completed ob-
€. Upon sailing from one octant to another. servations and mail in the postage-free envelopes provided.
JBSERVATIONS d. Upon sailing from one ocean to another. . Radio transmission - Copy coded data for radio transmission
. Fill in the blanks on each page of the form. (Name of from the unshaded numbered groups of columns. Each code
vessel, barometer number, etc.) group consists of five figures with the letter X indicating
. Enter the coded synoptic (0000, 0600, 1200, 1800 G.C.T.) missing data. Omit code group 8, 9 and 10 in message if no
or special weather observations in columns | through 50, data is available,

Seaiies

|
i
I< [ele]

il wie gle

Bean 64ie
7 seden oF

Figure 1. - Ship's Weather Observations- Form 615-5
1121. Fill in the identification blanks on both sides of the form. These
include the following:
(1) VESSEL. - Enter name and type of vessel.
(2) COUNTRY OF REGISTRY. - Enter nationality or registry of vessel.
(2A) CALL SIGN. - Enter the ship's radio identifier.
(3) MONTH. - Enter month and year.

(3A) BAROMETER, WEATHER BUREAU NUMBER. - Enter W. B. serial
number in the space provided.

(4) CAPTAIN. - Enter the master's name.

6 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

1122. SEA AND SWELL. When both sea and swell are observed, both
systems are to be recorded in Form 615-5 and included in the coded weather
message on Form 630-9. The sea data will be entered in columns 34-36
and coded in columns 41-43; swell data will be entered in columns 37-39
and coded in columns 45-47.

1130. OBSERVER'S INITIALS. The initials of the observer taking the
observation will be entered on the appropriate line in column 50,

1140. MAILING. At the completion of each trip all Forms 615-5,
which have one or more entries, and used barograph charts should be mailed
promptly in the postage-free envelopes provided. Instructions for mailing
the records are printed on the envelopes,

1200. RADIO TRANSMISSION OF WEATHER OBSERVATIONS

1210. SHIPS AUTHORIZED TO TRANSMIT WEATHER OBSERVATION
MESSAGES BY RADIO. Weather Bureau Marine Centers will designate the
ships that are authorized to transmit by radio, 0000, 0600, 1200 and 1800
G C T, weather observation messages to United States and foreign mete-
orological service ship collection centers. Meteorological ship collection
centers to which these regular weather observation messages should be
addressed from all ocean areas are contained in Weather Bureau publication
entitled, "United States and Foreign Radio Coast Stations Accepting Ships'
Weather Messages."

1220. SPECIAL REPORTS. All ships are requested to transmit a spe-
cial weather message under the conditions described in paragraphs 1020
and 1021.

1230. TRANSMISSION TO SHORE STATIONS. Weather observation
messages addressed to "Observer Washington" and ''Observer San Francisco,"
from ships in western North Atlantic and eastern North Pacific waters, re-
spectively, should be checked 'Government" and transmitted to the nearest
United States Government or commercial shore station. The Weather Bureau
will assume the cost for transmitting weather messages to these addresses.

1240. METEOROLOGICAL RADIOTELEGRAM. WB Form 630-9. The
Weather Bureau supplies meteorological radiotelegram blanks for con-
venience in transmitting weather observation messages by radio. After the
message is transmitted the form may be disposed of by the radio operator.
It should not be mailed to the Weather Bureau,

GENERAL INSTRUCTIONS 7

1241, The coded weather message will be copied from Form 615-5 to
Form 630-9.

1250. CODE FOR TRANSMISSION. Weather messages will be encoded
in the International Code for Radio Weather Reports from Ships, as indicated
below. Each element in the coded weather observation message is indicated
by one or more symbol letters. The symbolic form of the code (FM21A) is
as follows:

YOUAUaIs, WoboloGG Nddii. V¥wwW PPPITT
NpCpbCy CH Dgvgapp OTST .TqTq Dy de ay elas

ICE CoKD; re

Additional groups may be added in accordance with paragraphs 6431 and 9410.

1251. The symbols of the ship's code are listed and defined in Table
1-1 in the order of their appearance inthe message. The relevant paragraphs
and code tables in this manual are listed in adjacent columns,

1252, The "coKDjre' group is used to report ice. When it is included,
it must be preceded by the identifying word, "ICE,"

1253. When the data for an element of the message cannot be determined,
the letter 'X" will be substituted as required by the code table appropriate
to the missing data. Each group will then be composed of five characters,
either numerals or X's. If data for an entire group is missing from the
first seven groups of the message, five X's (XXXXX) will be reported for that
group. .

1253.1, When the seventh group (Dgvgapp) is omitted from the message,
30 will be added to the time in coding GG. A group of five X's will not be
sent to indicate a missing seventh group.

1253.2. When the sixth group (NpCyhCyCy) and the seventh group
(Dgvgapp) are omitted, 60 will be added to the time in coding GG. Groups
of five X's will not be sent to indicate missing sixth and seventh groups.

1253.3 When allthe elements of one ofthe groups OT,T.sTqTq, ldwdwPwHw
ICE cC9KDjre are missing, that group willbe omitted from the coded message.
Five X's will not be sent to indicate missing groups.

664508 O - 62 - 2

8 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

1254, When sea waves and swell waves are distinguished simultaneously
at the time of observation, both systems should be reported. At least two
(ldwdyPwHw) groups should be included in the coded message; the first group
containing data for sea waves and the second group swell waves. When more
than two wave systems are present, data for each system of waves should be
included in the coded report. Code each system separately and enter each
code group in the column headed ''waves''on Form 615-5. In cases when more
than two wave systems are observed, enter the additional wave groups to right
under REMARKS.

Table 1-1. --Elements of the Code

“Coding in- [Code
structions |Table
(Par. No.)|No.

‘Observing
instructions
(Par. No.)

Definitions of symbols

NeCISCo BD Sg OW CO Soe 2201 1
Qi-=-=-— (OVE HEVAS G)? fallejeys) SS SSS SS SSS SSIS || SaaeeSecor 2301
eral |ua bide: Inkde prec Ser en Cs ae 2401 =
Liolkolo: | ongitude:in degrees:and tenths s-=-=-- =~ aroma mn nn ens | Sone ena aK 2501 =e
GGeaas Greenwich civil time of observation, to nearest hour ------ | ---------- 2601 aa
IN SSeS Fraction of celestial dome covered by clouds ------------- 8110-30 8310 3
elsl =e Direction from which the wind is blowing (tens of degrees) - 3110 3120
ff Wind speed in knots --------<--~<~--= <= - == — == ne 3210 3220 a=
VV----- WAU boy Ub US (Choy exete (3) Sa 4101-3 4201 5
WW=-=-— het eLep ahs WASEN Ha vep (Gb (eYefo\ 2) I 5710 5720-32 6
Wis IEE: (ieee (bby kefelo (2) Se 5810 5820 7
PPP --- | Sea-level pressure (tens, units, tenths) mb.-------------- 6120 6410-11 8
ADT om Temperature of the air (whole degrees Celsius) ~---------- 7110-20 7310 ==
Nios ==— Fraction of celestial dome covered Cy, or Cy cloud ------- 8110-30 8320 3
Oe Clouds of types stratocumulus, stratus, cumulus,

tum WOnTm DU SRC OCC 8340 9
|g Height of base of lowest Cy, or Cyy cloud above sea -------~- 8201 8330 10
Cm ---- | Clouds of types altocumulus, altostratus, nimbostratus

(Ghat (eXorels)) Se | oo 8350 11
Cyass== Clouds of types cirrus, cirrostratus, cirrocumulus (in

COde) --- no rn rrr rr rrr cc nnn crccnn | carr c rrr 8360 12
Dea DS hns USiec OUT: S em LTC Ole ge 2701 13
Wa Se Speed of ship in knots (in code) ------------------------9- | ---------- 2801 14
EU SI Characteristic of barometric tendency (in code) -------~---- 6310-30 6420-22 15
Dp —-=-=— Amount of barometric change (units and tenths) mb. ------- 6310-30 6420-22 16
Qs5==== GROUPIE Si One EO Ta ea eae ==
TsT,--- | Difference between air and sea temperature ( half degrees

Celsius) =-<s- 3 =< << enn wn ne eee ee || SoH = 7330 =
TaTq--- | Temperature of dew point (whole degrees Celsius)--------- 7133-44 7310-12 --
Sea GYFOUPRGE'ST TNE GO ee | a
dyd,,--- | Direction from which waves are coming (tens of degrees) -- 9101-2 9420 4
Poa Period’ of waves (inicode)==-—--=--—====~—--=- === 9210-20 9430 17
Hy----- Meanvheight ofswaves(inicode) leon oon a no aera 9310-22 9440 18
TCH ———— |G oupidesiipnat orf Ord. C en gr OUP mare omer a de 10280 ==
Coa Description of kind of ice (inicode) == a= =a 10120 10220 19
oa oS= Hite ctrofice onmayvagationl (in code) =-=—=——— Sana os na 10230 20
Dy SSeS Bearing of ice limit (in code)------<-<----~--------------- 10130 10240 21
r------ Distance of ice from ship (in code)----------------------- 10130 10250 22

e ------ Orientation of ice field (in code) ------------------------- 10130 10260 23

GENERAL INSTRUCTIONS 9

1255. Example of a coded report: 40480 62106 62614 SAG} 1
06402 45420 96308 05201 12631 ICE 10403

Code
Code Symbols Figures Decoded Data
YQL,L,bLa 40480 4th day of week; octant, 0; latitude, 48.0°.
LoLoLyGG 62106 Longitude, 62.1°; time, 0600 G C T
Nddff 62614 6 eighths of sky covered; wind direction,
260°; speed, 14 knots,
VVwww S026.7 Visibility, 5 miles; present weather, snow
showers in past hour; past weather, snow.
Beer Tr 06402 Pressure, 1006.4 mb., temperature 2° C.
NpCLhCyCy 45420 4 eighths stratocumulus; height of lowest

cloud 1000-2000 feet. Altostratus or nimbo-
stratus also present. No type Cy clouds.
Dgvgapp 56308 Ship's course, southwest; ship's speed 16 to
18 knots; barometer falling then rising;
barometric change, 0.8 mb. higher.

OT>sTsTaTa 05201 Group designator, 0; sea temperature 1° C.
higher than air temperature; dew point
ile OF

ldydyPwHy 12631 Group designator, 1; wave direction, 260°;
wave period, 6 to 7 seconds; wave height
1-1/2 feet.

ICE iC Designator for ice group.

c9KDjre 10403 New ice; navigation unobstructed; ice limit

toward south; less than one mile distant;
ice edge lying in a direction SE to NW
with ice situated to the NE.

1300. ORDERING SUPPLIES

1301. Weather Bureau forms and supplies (including envelopes) may be
obtained directly from any of the Weather Bureau Marine Centers and port
stations listed in section 1401. These supplies may also be obtained through
the mail by checking the needed items on the back of Form 615-5 in the sec-
tion headed ''Check Forms or Supplies Needed.'"' When supplies are requested
on Form 615-5, the ship's mailing address should be included in the space
above the section for requesting supplies,

10 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

1400. ADDRESSES OF WEATHER BUREAU MARINE:
CENTERS AND PORT OFFICES

1401. Weather Bureau Marine Centers have personnel who visit ships
in port for the purpose of checking and calibrating shipboard barometers and
other meteorological instruments. In addition the port meteorologists assist
the masters and mates in problems regarding weather observations, prepa-
ration of weather maps and forecasts, Meteorological manuals, forms and
some instruments are also provided by the following Weather Bureau
Marine Centers.

ATLANTIC AREA

Weather Bureau Office Weather Bureau Office
30 Rockefeller Plaza U. S. Customhouse, Room C-6
New York 20, New York 101 E. Main Street

Norfolk 10, Virginia
Weather Bureau Office

U. S. Coast Guard Base Weather Bureau Airport Station
427 Commercial Street Box 17, Travis Field
Boston 13, Mass. Savannah, Ga.

U. S. Weather Bureau Airport Station
Isla Verde International Airport
Dankidan, eke

GULF AREA
Weather Bureau Office Weather Bureau Office
701 Loyola Avenue 1002 Federal Office Building
New Orleans 12, La. Houston 14, Texas

Weather Bureau Office
516 U. S. Court & Custom House
Mobile, Ala.

PACIFIC AREA

Weather Bureau Office Weather Bureau Office
Room 216, Custom House Pier A, Berth 9
5590 Battery Street Long Beach 2, Calif.

pan Hranciseo 11) Calin,

GENERAL INSTRUCTIONS 11

Weather Bureau Office
703 Federal Building
Seattle 4, Wash.

Weather Bureau Airport Station
Lindbergh Municipal Airport
San Diego 1, Calif.

Weather Bureau Office

Box s650 Piers2
Honolulu, Hawaii

1402. The following Weather Bureau Offices or Airport Stations provide
forecasts and climatological data, and will check barometers at the Weather

Bureau Office:

ATLANTIC AREA

Weather Bureau Airport Station
Portland City Airport
Portland, Maine

Weather Bureau Airport Station
East Boston 28, Mass.

Weather Bureau Airport Station
ib. Green Airport
Hillsgrove, R. I.

Weather Bureau Airport Station
Municipal Airport
New Haven, Conn.

Weather Bureau Airport Station
Bridgeport Municipal Airport
Stratford, Conn.

Weather Bureau Airport Station
New Terminal Bldg., Intl. Airport
Philadelphia, Pa.

Weather Bureau Airport Station
Friendship International Airport
Baltimore, Md.

Weather Bureau Airport Station
National Aviation Facilities

Experimental Center
Atlantic City, N. J.

Weather Bureau Airport Station
Washington National Airport
Washington, D. C.

Weather Bureau Airport Station
Norfolk Municipal Airport
Norfolk, Va.

Weather Bureau Airport Station
Municipal Airport
Charleston, S. C.

Weather Bureau Airport Station
Imeson Airport
Jacksonville, Fla.

Weather Bureau Airport Station
International Airport
Miami, Fla.

Weather Bureau Airport Station
Wilmington, North Carolina

12

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

GULF AREA

Weather Bureau Airport Station
Fort Myers, Fla.

Weather Bureau Office
Post Office Building
Pensacola, Fla.

Weather Bureau Airport Station
Lake Charles Air Force Base
Lake Charles, La.

Weather Bureau Office
Post Office Building
Galveston, Texas

Weather Bureau Airport Station
International Airport
Brownsville, Texas

Weather Bureau Airport Station
Tampa International Airport
Tampa, Fla.

Weather Bureau Airport Station
Bates Field
Mobile, Ala.

Weather Bureau Airport Station
Jefferson County Airport
Beaumont, Texas

Weather Bureau Airport Station
Corpus Christi Intl. Airport
Corpus Christi, Texas

PACIFIC AREA

Weather Bureau Airport Station
International Airport
Anchorage, Alaska

Weather Bureau Airport Station
5420 N. E. Marine Drive
Portland 13, Oregon

Weather Bureau Office
Eureka, California

Weather Bureau Airport Station
Lindbergh Field
San Diego, California

U. S. Weather Bureau Office
Guam, M., I.

Weather Bureau Airport Station

San Francisco International Airport

San Francisco, California

Weather Bureau Airport Station
Juneau Airport
Juneau, Alaska

Weather Bureau Airport Station
Clatsop County Airport
Astoria, Oregon

Weather Bureau Airport Station
Oakland Municipal Airport

Oakland, California

Weather Bureau Airport Station

Los Angeles International Airport

Los Angeles, California

Weather Bureau Airport Station
Honolulu International Airport
Honolulu, Hawaii

CHAPTER II, IDENTIFICATION DATA

CONTENTS
General . Mareen cy oe oie retpcrs ctee stele oy ovis ciel fae Nia eg Ce NaUROU ay we Vee Sy Cen
MVM VLOG woegi yin asc S Ge 8 cua @r8 Woe Wid eGR Re te ce epiel We'd 6 Scat our ween’
1 DE SF SCS AEYS4 (a (ANG) MN sn cm aa eae aa ee
Drain enOte Gl Obes (GQ) setae te ee Geese 4 Vee noe Sade haar eee Aen
Preteen ler abr iletey agree cree rate as ee rk HS Mao 1s recite aia Aiea anes Yana shee
renee el Om lees lary lacy) is ace ect ak Sais een os Gi aeeG Sie Wa ok Ss Ree awe
Succ wichmeivil Mamie (GG) acdc wo) ove) air gteclan eee give ee ow) Sle eae
Svea Oa Ces) eats raya arches ia ears st erin’ SP aunts waar a8 wer Geeh ae Ayaedoe ks
Sees DeCeCt(Vcy 14. 21 ais oe vebs die goose! oa dee dye a tee bess
CODE TABLES
Code Table i. = Symbol Y=-Day of Week 5... 6¥ 6.656540 .24.84 25
Code Table 2. - Symbol Q--Octant of the Globe..............
Codeslaple 13. =ysymbol Do--Ship's Course... :,n22G 55 ses ao

Code Table 14. — Symbol vg--Ship's Speed... 2.222.452.0256 4252

13

15
16
nf
LY

15

CHAPTER II. IDENTIFICATION DATA
2000. GENERAL

2001. Each weather message must be identified in regard to the time
of the report and the position of the ship taking the observation. The identi-
fication data includes the following: Day of month, day of week, octant of
globe, latitude, longitude, time of report, and course and speed of the ship.
These data will be entered on Form 615-5 in the columns specified in the
following paragraphs,

2100. DAY OF MONTH
2101. Enter the day of the month (GCT), in column 1. A new day begins
at 0000 (midnight) GCT. The Greenwich date is not affected when crossing
the International Date Line (180th meridian for most routes).

2200. DAY OF WEEK (Y)

2201. Select the code figure from Code Table 1 corresponding to the
day of the week (Greenwich civil date) and enter the figure in column 2.

Code Table 1

Symbol Y. - Day of the Week

Wednesday
Thursday

2300. OCTANT OF GLOBE (Q)

2301. Select the code figure from Code Table 2 for the octant of the
globe corresponding to the latitude and longitude of the ship. Enter the
figure in column 3,

16 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

Code Table 2

Symbol Q. - Octant of the Globe

Latitude

2400. LATITUDE (L,L,L,)

2401. Enter the latitude Of the ship, at the time of the observation, in
degrees and tenths without decimal point in column 4. The tenths are ob-
tained by dividing the minutes of arc by 6 and neglecting the remainder. If
the group contains only two figures, add a zero as the first figure, e.g., 9.5°
is entered as 095.

Examples:
(a) 48°20'=48.3° (i.e., 20+6=3, remainder neglected), which is
entered as 483,
(b) 7°11' is entered as 071.

2500. LONGITUDE (LoLoLo)
2501. Enter the longitude of the ship in degrees and tenths in column
5. The tenths of longitude are obtained in the same manner as tenths of lat-
itude (§2401). If the longitude is 100° or more, the first figure (1) will be
omitted. The octant of the globe will show that the hundreds figure has been
omitted,
Example: 126°25' longitude is entered as 264.
2600. GREENWICH CIVIL TIME (GG)

2601. Enter the time of the observation to the nearest hour (GCT)
in column 6. The time should be entered to two figures in accordance with

IDENTIFICATION DATA Tif

the 24-hour clock, e.g., 00, 06, 12, 18. Twenty-four (24) should not be
used to indicate midnight, e.g., midnight of the 7-8 should be entered as 00
on the 8th. Chart 1 (at the back of this manual) gives the local time corre-
sponding to Greenwich mean noon,

2700. SHIP'S COURSE (Dg)

2701. Select the code figure from Code Table 13 corresponding to the
course (true) made good by the ship in the 3 hours preceding the time of ob-
servation, and enter the figure in column 24.

Code Table 13

SYMBOL Dg. - Ship's course (true) made goodin 3 hours preceding
the time of observation.

No information

2800. SHIP'S SPEED (v,)

2801. Select the code figure from Code Table 14 corresponding to the
average speed of the ship during the 3-hour period prior to the observation.
Enter the figure in column 25,

Code Table 14

SYMBOL vs. - Ship's average speed made good during 3 hours
preceding the time of observation.
Code

“ode
figures Speed figures Speed

Ship stopped 5 13 to 15 knots
1 to 3 knots 6 16 to 18 knots
4 to 6 knots t 19 to 21 knots
7 to 9 knots 8 22 to 24 knots
10 to 12 knots 9 More than 24 knots

Lig)

CHAPTER III. WIND

CONTENTS
Page
COCMIC Lh CIEE OL cy seh sat Sot” GPw Gite, Gk ca var Velen aa, @; ee a! @ Senet al a Bees 21
SV WDV Cle IRIS GROE aocx es oad ar tec ow, Soe, Ca ees Be dls a Bn Res 21
Teel ee | rei me t i iecer la yaeg tay Gas oh fas, awe of, ase onset Tem, auras wala Sadie nae Nel eee 21
Entry of Wind Direction Data (dd) on Form 615-5.......... Zi
SVEN CH SNS CUR anda aes 2) tte co cet ean Teng fate vclere ie ule Gace. fw Doi wt Bech w 23
eG arin ganas Shere ses (serie (oar a des a kas ce Ge ere pen te 23
Entry of Wind Speed Data (ff) on Form 615-5............. 23
True Wind from the Apparent Wind (Vector Method)........... 23-27
(S10 (ceed a cn ee ae eee wee Sim wie: Was CUR GLA ee Poe 23
Suritace Winds at Sea -- Form 1209. 22.4 1.6 his we we ss 24
Plotting Board Method for Computing True Wind at Sea...... 26-27
IWettbctmo MTL tien cele, dhck ice, ove. i os gfe of os eae sl alte wate Giese Os Boggy fe 27-28
See Ere tlm eh eae ar eee a eey be aoa erie ede eee eie aed a isuele aoe a eile 27
Bit OrWind Suitts Om FP Orin Glb—5y Joo 12 cycle ese ees GP ees 28
mado Neportine Ol Wind SHItS . 4 44.6. 446 oe eae Secs wt 28
TABLES
Table 3-1. --Determination of Wind Speed by Sea Condition...... 22
Table o=2:——Apparent Wind Speeds... 4... 6 ee ee ee ee 25
CODE TABLES

Code Table 4. --Symbol dd--True Direction from Which Wind

Det TERVOWAUTIES © care auttes aie te seep, asian seers 21
FIGURES

Figure 2. --Surface Wind at Sea - Form 1209 ............... 25

Bictheer sa, <-Suupboar.d. Wind: POPE <2... acs [se arSoe Wicieet wee & aoe 26

21

CHAPTER III. WIND
3000. GENERAL

3001. Marine observers may determine the direction and speed of the
wind from the direction and character of the ripples, waves and spray. Wind
determined in this manner is termed the true wind, and will be entered in

Form 615-5.

3002. The wind experienced on a moving ship is termed the apparent
wind, and is the result of two motions--that of the ship and that of the air.

3003. Wind is classified as "gusty'' when it is characterized by sudden,
intermittent increases in speed, with at least 9 knots variation between
peaks and lulls.

3100. WIND DIRECTION

3110. GENERAL. Wind direction is the true (not magnetic) direction
from which the wind is blowing. Whenever possible, the true wind direction
will be determined by observing the direction from which ripples, small
waves and sea spray are coming, since they run with the wind. When the
true wind direction cannot be determined in this manner, use the procedure
described in paragraph 3310.

3120. ENTRY OF WIND DIRECTION DATA (dd) ON FORM 615-5. Select
the code figures from Code Table 4 corresponding to the true wind direction
(dd), and enter the two figures in column 8.

CODE TABLE 4
Sympou dd.—Trne direction, in 10's of degrees, FROM which wind is
blowing (00-36)

|
vated Direction Ptlck | Direction
| |
00 | Calm, | 19 | 185° to 194°. |
01 | 5° to 14°. 20. 195° to 204°.
02 | 15° to 24°, 21 | 205° to 214°.
03 | 25° to 34°. 22 -215° to 224°.
04 | 35° to 44°. 23. 225° to 234°.
05 | 45° to 54°, 24 |: 235° to 244°.
06 | 55° to 64°. 25 | 245° to 254°.
07 | 65° to 74°, 26 | 255° to 264°. |
08 | 75° to 84°. | 27 | 265° to 2742. |
° € ° °
10 | 98° to 1042 Wasa ee oe. |
11 | 105° to 114°. | 30 295° to 304°. |
12 115° to 1242 | 31 | 305° to 314°. |
2 ° « | 4°) °
TL ee ae ea
15. | 145° to 154°. | 34 | 335° to 344°.
16 | 155° to 164°. 35 | 345° to 354°. |
17. | 165° to 174° 36 | 355° to 4°. |
18 | 175° to 184°. Pa eee |

Notr.—In ease the true wind speed exceeds 99 knots, 50 will be added
to “dd” and only the wind speed in excess of 100 knots will be coded.
For example, if direction=163° and speed=12) knots, the wind will
be coded as 6621" (dd= 16+ 50; ff=121—100)

22 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TABLE 3-1. - Determination of Wind Speed by Sea Condition

Probable
wave
Descrip- height
tive Sea Conditions in ft.

Calm Sea smooth and mirror-like.
Light -air Scale-like ripples without foam crests.

Light Small, short wavelets; crests have a glassy appear-
breeze ance and do not break.

Gentle Large wavelets; some crests begin to break; foam of
breeze glassy appearance. Occasional white foam crests.

Moderate Small waves, becoming longer; fairly frequent white
breeze foam crests.

Fresh Moderate waves, taking a more pronounced long form;
breeze many white foam crests; there may be some spray.

Strong Large waves begin to form; white foam crests are more
breeze extensive everywhere; there may be some spray.

Near gale Sea heaps up and white foam from breaking waves begin
to be blown in streaks along the direction of the wind;
spindrift begins.

Moderately high waves of greater length; edges of crests
break into spindrift; foam is blown in well-marked
streaks along the direction of the wind.

High waves; dense streaks of foam along the direction
of the wind; crests of waves begin to topple, tumble, and
roll over; spray may reduce visibility.

Very high waves with long overhanging crests. The re-
sulting foam in great patches is blown in dense white
streaks along the direction of the wind. On the whole,
the surface of the sea is white in appearance. The
tumbling of the sea becomes heavy and shocklike.
Visibility is reduced.

Violent Exceptionally high waves that may obscure small and
storm medium-sized ships. The sea is completely covered
with long white patches of foam lying along the direction
of the wind. Everywhere the edges of the wave crests
are blown into froth. Visibility reduced.

Hurricane The air is filled with foam and spray. Sea completely
white with driving spray; visibility very much reduced.

WIND 23

3200. WIND SPEED

3210. GENERAL. The wind speed is the average speed in knots of the
wind blowing over the surface of the sea, The speed will be determined from
the size and character of the waves that are running with the wind. Table
3-1 will be used to determine the wind speed by the sea condition,

3220. ENTRY OF WIND SPEED DATA (ff) ON FORM 615-5. Enter two
figures for the wind speed (knots) in column 9. Example: 9 knots entered
as 09; 15 knots entered as 15,

3300. TRUE WIND FROM THE APPARENT WIND

3310. GENERAL. When the surface of the sea cannot be observed, the
true wind will be determined from the apparent wind as follows:

3310.1. Estimate the apparent wind direction to the nearest 10 degrees
off the bow of the ship and the apparent wind speed to the nearest 5 knots by
observing the effects of the wind on the ship's flag, smoke, or rigging
(see Table 3-2). If the ship has an anemometer, the speed of the apparent
wind may be obtained from it.

3310.2. Construct a vector diagram or use Form 1209 to find the true
wind (see Fig. 2).

Table 3-2. - Apparent Wind Speed

Speed (anaes

Less thanl... Calm; smoke rises vertically.
Smoke drifts from funnel.
Wind felt on face.
Wind extends light flag.

Wind raises dust and loose paper on deck.
Wind waves and snaps flag briskly.
Whistling in rigging.

Inconvenience felt walking against wind.
Walking becomes difficult.

3311. The following may be used to check the results obtained from a
vector diagram or from Form 1209:

3311.1. The true direction of the wind is usually on the same side as, but
farther from the bow than the apparent direction.

664508 O - 62 - 3

24 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

3311.2. The true speed of the wind is greater than the apparent whenever
the apparent direction is aft of the beam.

3311.3. The true speed of the wind is less than the apparent whenever the
true direction is forward of the beam,

3320. SURFACE WIND AT SEA--FORM 1209. This chart is designed
to aid in the computation of the true wind from the apparent wind (see Fig. 2).
If a supply of the forms is desired for use aboard ship, they may be obtained
from the Weather Bureau when requested in accordance with §1301.

3321, A wind scale, in knots, is printed on concentric circles that are
drawn around the center of the chart. If the wind speed exceeds the printed
scale, a new scale may be made by doubling or tripling the printed one. Wind
direction for every 10 degrees is printedonlines that radiate from the center
of the chart. The wind direction in degrees off the bow is plotted with refer-
ence to the black degree markings (top figures) printed at the ends of the
radial lines. A separate slide, with a ship's-speed scale similar to the
wind-speed scale used on the chart, is furnished with the forms. With the
slide, the ship's speed is laid off vertically downward from the plotted point
that represents the wind speed and the direction off the bow. The point
plotted at the ship's speed has coordinate values representing the true wind
speed and the true wind direction with respect to the ship's heading. The
wind direction, in degrees off the starboard bow (0° to 360°), is read from
the green-colored figures (bottom figures). The ship's heading in degrees
must be added to the wind direction, as read from the chart, in order to
have the true wind direction with respect to north (360°).

3322. Form 1209 is used as follows:

3322.1, Select the radial line coresponding tothe angle, in degrees off the
bow (port or starboard), from which the wind is blowing and plot a point on it
at a distance from the center (scale printed on concentric circles) equal to the
speed of the apparent wind in knots.

3322.2. Place the O (arrow point) of the ship's speed slide at the point
plotted in §3322.1 and measure the ship's speed vertically downward toward
the bottom of the chart. Plot a point on the chart opposite the value on the
slide corresponding to the ship's speed at the time of the wind observation.

3322.3. Read the wind speed corresponding to the point plotted in §3322.2,
estimating for the values between the concentric circles. This value is the
true wind speed.

3322.4, Read the angular value, from the figures printed in green (bottom
figures), corresponding to the radial line from the center through the
point plotted in §3322.2. Add the value of the angle to the ship's heading in
degrees to obtain the true wind direction. If the total exceeds 360°, subtract
360° from it.

WIND 25

AL /

la)

WY KP

oe
SS

es
a

ee

SHIP'S SPEED
(KNOTS)

chats

Figure 2.--Determination of true wind from the apparent wind, using
Form 1209 and the associated ship's-speed scale. Given an apparent wind of
15 knots, 60° off the port bow, ship's speed 20 knots and heading 160°. Note
the use of the scale in locating point 2, which is always below point 1 (the
apparent wind) on a line through point 1 parallel to the vertical (green) lines
on the form. The upper figures at the end of the radial lines (used in deter-
mining the direction of point 1) represent direction from 0°--180° off the
bow (measured clockwise when off the starboard bow and counterclockwise
when off the port bow); the lower figures (in green) are used when determin-
ing the direction of point 2, which is measured clockwise from the bow. The
sum of the ship's heading and the direction of point 2 (226°) is 386°. Since
this sum exceeds 360, the true wind direction is 386-360=26°.

26

3330.

PLOTTING BOARD

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

METHOD FOR COMPUTING TRUE WIND

AT SEA. Ships that are not equipped with wind transmitting and indicating
instruments should estimate the apparent wind direction and wind speed in

accordance with instructions

contained in 9§3310.1. True wind may be

computed with the aid of a plotting board. Anemometer equipped vessels
Should obtain apparent wind direction and speed from wind indicators.
The true wind may be determined from the apparent wind relative to the
ship's bow, and from the course and speed of the ship.

r++
eset
HH cH
Poet CH 2
fefe(sfetef chats tstatelal ZB
EEE HES (WO
= BOGES SESaseeneee fee
= CCC wz
<8 Soest Eetec coceveccercrect eect WAGE
= coo SSeseeeeeeeeen Her <2
=e Pee eee ere Senaneegeoneea ae
oS poe f BSens =
=N L+H =
3 ie:
a A a =
2 SEegUgUEEEEEGESEGSETSEeEE =
=>) SRE aaeee =
zs r= 10H Coo ==
eed co aan H+ S =
eS an HS seegeaee 2
= oOo = Coo =
aN HOE es
ac Sosseoeoeeeeeeee: eeileletett AOS
Ze gaeeae at}

Gq,"
Pe OBE | OFF yt \

Figure 3, -- Shipboard Wind Plotter

3331,

The apparent wind is a resultant of the true wind direction and
speed or movement of the ship.

The apparent wind relative to the bow of

the ship is converted to a true compass bearing by adding the apparent wind

direction to the _ ship's

heading if the wind is off the starboard bow and

subtracting the Apparent wind direction if the wind is off the port bow,

WIND 27
EXAMPLE:
3331.1. APPARENT WIND IS OFF STARBOARD BOW

(a) slitpls heading geyser cts ste eu ce 6 cc ae oe 270° true
(b) Apparent wind (relative to Shipls#bDoOw)i sme a 040°
(c) True bearing... 310°

3331.2. APPARENT WIND IS OFF THE PORT BOW

(a) Ship's heading ... onsen es dit is 270° true
(b) Apparent wind (relative to ship! Ss ; bow) ee eee - 040°
(c) True bearing... 230°

3332, The procedure for computing true wind direction and speed with
the aid of a plotting board follows: From the center of the board or from the
pin, a scale is ruled off equal-distant on top and bottom of the scale, from
0 to 50. Should the apparent windexceed 50 knots, the scale may be doubled
and the computing procedure carried on as described. At the top of the
board is a red arrow. In this discussion when referring to the top of the
board, it will be with reference to this arrow. An example of how the
method is used is outlined below:

(a) Ship's course and speed... sae. Moe POW RnOts
(b) Apparent wind (wind relative to ship! s bow) 040° - 20 knots
(c) Apparent wind converted to a true bearing 310°

3332.1. Set 270 degrees at the index on top of the plotting board; using
any convenient linear scale, measure vertically downward from the center
peg of the plotting board a distance equivalent to 15 knots. Mark this spot
"S'" (for ship). Rotate the protractor disk of the plotting board until 310 de-
grees is at the index (red arrow) at the top of the plotting board. Using the
same linear scale as for ship's speed, plot vertically downward from the
center peg of the plotting board a distance equivalent to 20 knots. Mark this
point 'W." Rotate the protractor disk until the '"'S'' is vertically above the
"wW,'' using the vertical lines on the plotting board to line up the two points.
Read the true wind direction at the TOP of the plotting board. The distance
between points '"'S'' and 'W'' is the true wind speed, using the same scale as
in plotting the points "S' and "W." The: true wind direction is 357 degrees
and the speed is 13 knots.

3332.2. Anemometer equipped vessels may obtain a plotting board by re-
quest in accordance with §1301.

28 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS
3400. WIND SIFTS

3410. GENERAL, Wind shift is the manner in which the wind changes
direction. It is generally considered an abrupt change in the wind direction
of at least 90 degrees. Wind shifts are associated with the phenomena charac-
teristic of a cold-front passage that are listed below:

(a) Gusty winds shifting in a clockwise direction in the Northern
Hemisphere (south shifting to west, or southwest shifting to
northwest), and counterclockwise in the Southern Hemisphere
(north shifting to west, or northwest shifting to southwest).

(b) Rapid drop in dew point.

(c) Rapid drop in air temperature.

(d) Rise in pressure,

(e) In summer; lightning, thunder, heavy rain, and possible hail.

(f) In winter; frequent rain or snow squalls withcloud heights changing
rapidly--to either higher or lower heights than existed before
the wind shift.

3411. When a fast vessel overtakes a slow-moving cold front, items (a),
(b), (c), and (d) of §3410 will occur in the reverse of the manner described.
For example, the wind will shift counterclockwise inthe Northern Hemisphere,
and the dew point will rise rapidly. However, phenomena described in
items (e) and (f) may be encountered in the frontal zone.

3412. Wind shifts may occur without precipitation, but they are usually
accompanied by strong winds,

3420. ENTRY OF WIND SHIFTS ON FORM 615-5. Enter the time
(GCT) of wind shifts that occurred during the previous 6 hours in the column
headed ''Remarks'' on the line pertaining to the observation. Example:
Wind shifted SW to NW at 0835.

3421. RADIO REPORTING OF WIND SHIFTS. Wind shifts that occur
during the six (6) hours prior to the standard ship's weather observation
should be reported. This information is to be added, in plain language, to the
regular coded ship's weather observation. EXAMPLE: SHIPS 40493 06612
62614 97216 06448 45420 56308 00347 12664 WIND SHIFTED SW TO NW
AT 08352,

CHAPTER LV. VISIBILITY

CONTENTS
Gera enc alllpeesy emren i cme emcee care er chic Geet gah co, Ua de cel ach) oe. 1s Gop teat whe Co eae: agai
IDYeyreucioaliayehncoyal Con: Wialspllopilbhine ene Gog Go ceo oon ole do ona olan ose
Coding and Entry of Visibility Data (VV) on Form 615-5.......
TABLES

Table 4-1. - Distance to Objects on the Horizon at Sea........

CODE TABLES

Gode Table 5. = symbol VV = ViISibIIty . 4s sb c sce See Sade ets

FIGURE

Figure 4. - Non-uniform visibility - +--+ +--+ ee ee ee ee ee eee

29

Page

31
31-32
32-33

31

33

32

31

CHAPTER TV... VISIBILITY
4000. GENERAL

4001. Visibility is a term that denotes the greatest distance from an ob-
server that an object of known characteristics can be seen and identified.
For purposes of weather reports, the term expresses the maximum visibility
common to one-half or more of the horizon circle. This is called the
prevailing visibility.

4100. DETERMINATION OF VISIBILITY

4101. Whenever possible, estimations of visibility will be based upon
objects whose distance from the observer is known (i.e., the horizon or
other ships). Estimations of the distance to a ship may be based on its
apparent size and the portion visible. Visibility may also be estimated by
determining the distance of a passing vessel by means of radar. Table 4-1
is a guide to determining the distance to the horizon and to objects such as
a familiar type of ship whose height is known, e.g., the horizon, when
viewed from a height of 40 feet above sea level, appears at a distance of
7.6 nautical miles.

4102. Estimations of visibility will be based on the sharpness with
which the object stands out. Sharp outlines, with little or no blurring of
color, indicate that the visibility is much greater than the distance to the
object. On the other hand, blurred or indistinct objects indicate the pres-
ence of haze or other phenomena that has reduced the visibility to about
the distance to the objects.

TABLE 4-1.—Distance to objects on the horizon at sea (nautical miles)

Heightvok observers Height of object above sea level (feet)

eyes above sea

lev

evel (feet) 0 | 10 | 20 | 30 | 40 | 60 | 80 | 100} 150 | 200 | 300 | 400 | 600 | 800 | 1,000
ee eee eee 3.8) 7.2} 8.7] 9.9] 10.8] 12.5] 13.9] 15.1] 17. 7| 19.8] 23.5] 26.5] 31.6] 36.0
Tose es 4.6 8 0| 9.5] 10.7 11.6] 13,3] 14.7] 15.9] 18.5] 20.6| 24. 3/ 27.31 324 Se Sl coe
ra ibe hi a aan 5.4| 8.7] 10. 2| 11. 4) 12.3] 14. 0| 15. 4] 16. 6| 19. 2| 21.3) 25.0] 28.0] 33. 1| 37.5] 41.3
een ase ED 6.0] 9.3] 10. 8| 12.0) 12.9] 14. 6| 16. 0| 17. 2] 19. 8| 21.9] 25.6] 28.6] 33. 7/ 38 1/ 41.9
SME ee ee ces l ad 6.6 9.9] 11. 4] 12.6) 13. 5| 15. 2] 16. 6| 17. 8} 20. 4| 22. 5| 26.2] 29. 2| 34.3/ 38.7] 42.5
i ee Cen mI 7. 1| 10. 4| 11. 9] 13. 1] 14. 0] 15. 7] 17. 1] 18.3] 20.9] 23 0} 26. 7| 29.7] 34.8] 39.2] 43.0
7 aa ee Ra 7. 6| 10. 8| 12. 3] 13.5] 14. 4] 16. 1| 17. 5| 18. 7| 21.3] 23. 4] 27. 1] 30.1] 35. 2| 39.6] 43.4
OR aa 8. Q| 11. 3] 12.8] 14.0] 14.9] 16. 6| 18.0) 19. 2} 21. 8| 23. 9| 27. 6| 30. 6| 35. 7| 40.1] 43.9
Biss ee 8. 5| 11. 7| 13.2) 14. 4) 16. 3] 17.0] 18. 4| 19. 6| 22. 2| 24.3] 28 0] 31.0] 36.1) 40.5] 44.3
Ole se ender 9. 3| 12. 5| 14.0] 15. 2) 16. 1] 17. 8| 19. 2| 20. 4] 23.0] 25. 1] 28. 8| 31.8] 36.9] 41.3] 45.1
(OR ae een 10. 0| 13. 2] 14. 7] 15. 9] 16. 8| 18.5] 19. 9] 21. 1] 23. 7| 25.8] 29.5] 32.5] 37.6] 42.01 43.8
7 a a 10. 7| 13. 9| 15. 4| 16. 6| 17. 5| 19. 2| 20. 6| 21.8) 24. 4] 26.5] 30.2/ 33.2] 38.3] 42 71 46.5
ie, eee ace 11. 4| 14. 5] 16.0] 17. 2| 18. 1] 19. 8| 21. 2| 22. 4] 25. o| 27. 1| 30.8] 33.8] 38.9] 43.3] 47.1
100802 2... 1.5. 12. 0| 15. 1] 16. 6| 17. 8| 18 7| 20. 4| 21. 8| 23. 0| 25. 6| 27. 7| 31. 4| 34. 4| 39. 5| 43.91 47.7

32 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

4103. When the visibility is not the same in all directions, the highest
value common to one-half or more of the horizon circle should be coded on
Form 615-5. For example, if fog limits the visibility in the north and east
quadrants of the horizon circle to 1 mile, while the visibility in the other
two quadrants is 6 miles, the maximum visibility common to one-half of the
horizon circle is 6 miles, and code figure 97 would be used.

OAS
WON

AR
AAR
Wy

Figure 4. --Non-uniform visibility

4104, Figure 4 illustrates non-uniform visibility when may be the
result of squalls in one quadrant of the horizon circle, light showers and
haze in another and haze only in the third quadrant. Since the maximum
visibility common to one-half of the circle is 3 miles, it would be reported
as 2 miles (code figure 96).

4200. CODING AND ENTRY OF VISIBILITY DATA (VV) ON FORM 615-5

4201. Select the code figures from Code Table 5 corresponding to the
visibility and enter the figures in column 10.

VISIBILITY 33

Code Table 5

SYMBOL VV. --Visibility

Code 1
figures Visibility range

Less than 50 yards (50 meters).

50 yards (50 meters).

200 yards (200 meters).

1/4 nautical mile (500 meters).

1/2 nautical mile (1, 000 meters).

1 nautical mile (2,000 meters).

2 nautical miles (4, 000 meters).

5 nautical miles (10 kilometers).

10 nautical miles (20 kilometers).

25 nautical miles (50 kilometers) or more.

1. Incase the observed visibility is between two of the
distances inthe table, the code figure for the lesser distance
will be reported, e.g., when the visibility is between 50
and 200 yards, code the visibility as 91.

v

Vy

CHAPTER V. WEATHER

CONTENTS

Gener alte hweer suey es eye sermons ad evaiis lene Tatolt sy atelys enon ft
ibhunderstorms and Lightning. . a5. a6. a0 +6 #2 6s se 5 615
Generale. ecto seer memonsire ome cae Melos cews ne a oh yie

Mp eHS ub ys Ole ntTrcler SOI, ats hatte slg sicsi's ave bapea cal cite ee
Slvche BhuNndersiOnim 2 ic. o-. sy eens auelee sel ease ek
NodeBale wm bhuncderrS Or Timms ameter nl sale irn cm itci ase iron:

Hea va BP NUNGEr STOMM i tea ae taielae tera oe wie ete eke ts

WEES DOULSmalll Ces CUalliSie emem tense na lsierite: c) 12 eure eerste! 6 ellie
IPGECIDICATION AG spo G fol w Ae to 6 wi ee ew wise es ee ge
Gere walle hese as) cr caesar rene einen ne meme Meg oli etener rere
C@haracterion Precipitation’ is. so.)s ee <a een ee
COntinUOWS ip te tease serene or tc si coiisarer parents clmene

TMV EnerMGE SIGs mepemranae eee cra teteemtenttcam sie delves isicetie et stroma. te

SHOWICKyg pacer ts oi seksecemrent cl fevente unserer ie, nome) eaters etc crei eeu
(COMMbINa LIONS 2 axe seas Gos wes we le te ae fo wea oe yee
IhoyeSreysnkay (ont JeAetexenjonirehalolalens tg ces 5 ee teokG fy oepeo 6 6 0 Gap
ihVDeS OL Precipitation {oss as eee os ee ee
(ETOQUIGME POCTOINATLON a1 ec as sea jag a a se eee Swe

DetzZlSe vee sees Gee ee eae) wine, escusee «Sates ees coyace

aU e ceawenie: teeter comeectn ete) nee eer Wo tena h recsrist ees scon conta eee

HTeGeZing IP reeipitablOm. 2 hk. a 6 wy 5.0165 yoo le et oe

Im ielexevahales Iatcnhay ae cle oon Oooo can oo Onoee

Iiboleie sau ateaga) Dhani Azadll ee se we Scere ayer en treo eal ers OE ae

lstiopAciel IB eaopyieymieyal, 4 5s gob 4a bono ea oko Oe

CERRO MGES ic. cana dete oe ese ear Gees Gen eee

Inlewill, Se 2 oe

SLO WPM fo oc Maaintshtet “s orey 1S) fowres var oie Conia? ©: ar nets

Snow Pellets (Soft Hail).............066.

Snow Grains (Granular Snow)............

TiGesEriST Sas ces tees ie adie eo etnies eens hee oe

ERC Sat Cl Ecler e ren Ms) ule el ernie git geen ena Se GIS as ah, Gn
SE © DiBeee ses ecg icvir crack oe hice wae ei te sen ce? Sel “cigs cs doe taylom ine, SveIe © G

35

36

Page
Miscellaneous) vate a was ca ‘os a eifoes Banat acc, Beet mene nee eras 41
Presentewicatiier (ww). cas Ge oc en cge ten ote Pao cee re 41
GONG anaes ie mie pees, aie tans Ce Jer Ot ar Ao eh oe ccc, 41
Coding Gir s.9 3) ce ta go aciw eites ks) EMR ee eee 42
Entry of Present Weather Data on Form 615-5 ........... 42
Pastaweather- (Wiis nos. ous a Ges cn oreo ec a Nees oe en 42
GENERA iee ps eles wale iene se ns Ge ahha ure oon ne ee eee 42
Coding and Entry of Past Weather Data (W) on Form 615-5...
TABLES
mablers=ts-Intensity Of Raimin s oc. sels sew sce casi sh tien ae oh oman ere 39
Mablevo=2 s==Intensity Of SHOW. <3 4. ese © aoe Seas sce) ae eee 39

CODE TABLES

Code Table 7--Symbol W. --Past Weather..............2200- 44

37

CHAPTER V. WEATHER
5000. GENERAL

5001. Weather elements of an observation comprise thunderstorms,
lightning, waterspouts, squalls, and precipitation in any form. Fog, haze,
smoke, and dust are classified as obstructions to vision, Rainbows, halos,
coronas, and auroras are recorded as atmospheric phenomena.

5002. Clouds are not described here, since they are considered sepa-
rately in Chapter VIII, and cloud code charts are illustrated in the back of
WBForm 615-5.

5100. THUNDERSTORMS AND LIGHTNING

5110. GENERAL. A thunderstorm is regarded as occurring at the ship
when thunder is heard. Lightning occurs as an electrical discharge within a
cloud, from cloud to cloud, or from cloud to sea. Distant lightning is any
lightning that occurs so far from the observer that the resulting thunder can-
not be heard. It may be observed as streaks or sheets.

5120. INTENSITY OF THUNDERSTORM. Classification of a thunder-
storm as slight, moderate, or heavy is based upon the appearance of the
storm from the point of observation, The thunderstorm may be classified as
Slight throughout its history as viewed from this point, or it may be classi-
fied during its passage by the ship as slight, moderate, heavy; and, as it
recedes, moderate and slight. Each classification is described below.

9121. Slight Thunderstorm, Lightning occurs within the cloud and rain-
fall is light or moderate. Small hail may also occur. Thunder is not loud,
and lightning occurs at intervals of a minute or more. The surface wind
speed, at the beginning of or during the storm, does not exceed 26 knots,
and any sudden increase in speed is of short duration.

5122, Moderate Thunderstorm. Loud peals of thunder occur at brief
intervals, and frequent flashes of lightning occur from cloud to surface, as
well as from cloud to cloud; rain is moderate or heavy, and small hail is
light or moderate. An onrush of wind may precede the storm, with a speed
as high as 35 knots. Extensive masses of dark clouds showing visible indi-
cations of turbulence and rapid horizontal motion are usually observable.

5123. Heavy Thunderstorm. Sharp and pronounced thunder and light-
ning occur almost continuously. Heavy rain occurs, sometimes accompanied
by hail. The wind preceding and accompanying the storm may reach a speed
in excess of 35 knots. A rapid drop in temperature occurs, sometimes as
much as 10°C. in 5 minutes.

38 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS
59200. WATERSPOUTS AND SQUALLS

5201. Waterspouts occur when conditions are favorable for intense
thunderstorm activity. The distinguishing feature is the funnel-shaped ap-
pendage that hangs from the base of the cloud. The storm is described as
a tornado when it occurs over land.

5202. A squall is a strong wind that increases suddenly in speed, main-
tains a peak speed over a period of minutes, and decreases in speed; similar
fluctuations will occur at succeeding intervals.

5300. PRECIPITATION

5310. GENERAL. Precipitation includes all forms of moisture that
fall to the earth's surface--rain, drizzle, snow, hail, sleet, and ice crys-
tals. Precipitation is classified as to its character, intensity, and type.

5320. CHARACTER OF PRECIPITATION. The classification of pre-
cipitation with respect to character is described below,

5321. Continuous. Precipitation usually associated with stratiform
clouds. Any increase or decrease of intensity is gradual.

0322. Intermittent. Intensity increases or decreases gradually, and
precipitation stops and recommences at least once within the hour preceding
the time of observation.

5323. Showery. Precipitation associated with cumuliform clouds, es-
pecially swelling cumulus and cumulonimbus. Intensity varies rapidly.
Showers begin and end abruptly.

5324. Combinations... When showers occur with continuous or inter-
mittent precipitation, the precipitation does not always stop between showers.
Under these conditions, precipitation is marked by a sudden increase and de-
crease in intensity as the showers abruptly begin and end.

9330. INTENSITY OF PRECIPITATION. The intensity of precipitation
may be determined by its rate of fall and by the amount it reduces the visi-
bility. The intensity is classified as light, moderate, or heavy. Tables
d-1 and 5-2 will be used as guides in determining the intensity of rain and
snow respectively.

WEATHER 39
Table 5-1. --Intensity of rain

Individual drops are easily identifiable; spray over
hard surfaces is slight; pools form very slowly;
over 2 minutes may be required to wet decks and
similar dry surfaces.

Moderate .. Individual drops are not clearly identifiable; some

spray over hard surfaces; pools form rapidly.

Rain seemingly in sheets; individual drops are not
identifiable; heavy spray to height of several inches
is observable over hard surfaces; visibility is
greatly reduced.

Table 5-2. --Intensity of snow
Visibility 1, 100 yards (1,000 meters) or more.

Moderate .. Visibility less than 1, 100 yards (1,000 meters), but

not less than 550 yards (500 meters).

Visibility less than 550 yards (500 meters).

5340. TYPES OF PRECIPITATION. Precipitation comprises liquid,
freezing, and frozen types. These types are described below,

5341. Liquid Precipitation. Liquid precipitation is classified as drizzle
or rain as follows:

5341.1. Drizzle. Very small and uniformly dispersed droplets that ap-
pear to float in the air and to follow very light air currents. Drizzle usually
falls from low stratus clouds and is frequently accompanied by low visibility
and fog.

5341.2. Rain. Falling drops of liquid water that are larger than those
in drizzle. Rain, as used in this manual, does not include drizzle and
freezing rain.

664508 O- 62-4

40 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

0342. Freezing Precipitation. Freezing precipitation is classified as
freezing rain or freezing drizzle, as follows:

0342.1. Freezing Rain. Rain that falls in liquid form and freezes to
exposed surfaces. When the fall is so rapid that runoff occurs, the ice will
usually appear as glaze.

5342.2. Freezing Drizzle. Drizzle that freezes similarly to rain.
0343, Frozen Precipitation. Solid precipitation is classified as follows:

5343.1. Ice Pellets: Precipitation of transparent or translucent pellets
of ice, which are spherical or irregular, rarely conical, and have a diam-
eter of 0.2 in. or less, They are of two types: type (a) comprises frozen
raindrops or largely melted and refrozen snowflakes (synonymous with
"Sleet''in the U. S.) and are reported by using ''ww"' table figures 23 or 79,
as the case may be. Type (b) consists of pellets of snow encased in a thin
layer of ice and are reported by using code figures 87 or 88, as appropriate.

5343.2. Hail. Ice balls or stones, ranging in diameter from that of
medium-size raindrops to an inch or more. They may fall detached or
frozen together into irregular, lumpy masses. They are composed either
of clear or of alternating clear and opaque layers. Hail often accompanies
thunderstorm activity. Surface temperatures are usually above freezing
when hail occurs. The size is based on the diameter, in inches, of normally
shaped hailstones.

9343.3. Snow. White or translucent ice crystals chiefly in complex
branched hexagonal form (six-pointed stars), often mixed with simple crys-
tals. Snow occurs under conditions that are similar, temperature excepted,
to those of corresponding forms of rain.

5343.4, Snow Pellets (Soft Hail). White, opaque, round, or occasion-
ally conical kernels of snow-like consistency, 1/16 to 1/4-inch in diameter.
They are crisp and easily compressible, and they may rebound or burst when
striking hard surfaces. They occur almost exclusively in showers.

5343.5. Snow Grains (Granular Snow). The solid equivalent of drizzle.
They take the form of minute, branched, star-like snowflakes, or of very
fine, simple crystals. At times they have the appearance of rime. They
occur under conditions similar to those of drizzle, except that the tempera-
ture is lower.

5343.6. Ice Prisms. Small, unbranched ice needles or prisms in the
form of rods or plates that have a descending motion and that may be ob-
served when the sky is clear. Ice prisms are associated with halo pheno-
mena and with temperatures near or below -17.8°C (0°F).

WEATHER 41
5400. FOG AND RIME

5410. FOG. Minute droplets suspended in the atmosphere. These
droplets have no visible downward motion. Fog differs from clouds in that
the base of fog is at the surface, while the base of clouds is above the sur-
face. It is easily distinguished from haze by its dampness and grey color.
It is unusual for fog to form when the difference between the air tempera-
ture and the temperature of the dew point is greater than about 2.2°C (4°F).

5411. Shallow Fog. Low-lying fog that does not reduce horizontal
_ visibility at a level 33 feet (10 meters) or more above the surface.

5412. Ice Fog. Suspended particles in the form of ice crystals. It
occurs at low temperatures, and usually in clear, calm weather in high
latitudes. The sun is usually visible and may cause halo phenomena,

5420. RIME. Rime is classified as soft or hard.

5420.1. Soft rime consists of white layers of ice crystals deposited
chiefly on vertical surfaces--especially on points and edges of objects--
generally in super-cooled fog. On the windward side of the rigging, soft
rime may grow to very thick layers, long feathery cones, or needles pointing
into the wind and having a structure similar to that of frost.

5420.2. Hard rime is an opaque, granular mass of ice deposited chiefly
on vertical surfaces in wet fog at temperatures below 0°C (32°F). It is
more compact and shapeless than soft rime, and may build out into the wind
as glazed cones or feathers.

5500. HAZE, SMOKE, AND DUST

5501. Haze, smoke, and dust may be observed near land. Haze re-
sembles a uniform veil with a bluish tinge when viewed against the sun or
clouds at the horizon. When smoke is present the sun has a reddish tinge.
Dust imparts a tannish or grayish hue to distant objects, and the sun appears
pale with a yellowish tinge.

5600. MISCELLANEOUS

5601. In the column headed ''Remarks" of Form 615-5, enter halos
(solar or lunar), coronas (solar or lunar), rainbows, fog bows, and auroras,

5700. PRESENT WEATHER (ww)
5710. GENERAL. The term "present weather" refers to the state of

the weather occurring at the time of the observation or within the 1-hour
period prior to the observation. Code Table 6, 'Present Weather" (in tables

42 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

at the back of this manual) lists 100 weather situations, numbered from 00 to
99, which includes one or more of the weather elements discussed in the
first portion of this chapter.

5720. CODING. Select the number from Code Table 6 (listed at the
back of this manual, or from WB _- Form 615-5) that corresponds most
nearly to the weather occurring at the time of the observation, or within 1
hour preceding the time of the observation. When precipitation is not occur- ©
ring at the ship at the time of observation, the selection of ''ww' should be
made from code figures 00 to 49, and 98.~ When precipitation is occurring
at the time of the observation, the selection should be made from figures 50
to 99, inclusive.

59730. ENTRY OF PRESENT WEATHER DATA ON FORM 615-5. The
code number selected as best representing the present weather (ww) should
be entered in column 11 of Form 615-5. If more than one code number
appears to be required, the highest should be entered in column 11, and all
other appropriate numbers entered in the column headed ''Remarks."

59731. Whenever fog is encountered, enter the character of the fog as
"slight," "heavy," 'shallow," or "ice fog,'' and the time (GCT) of beginning
and ending in the column headed "Remarks" of WB Form 615-5.

5732. Enter the time (GCT) of beginning and ending of precipitation in
the column headed ''Remarks."

5800. PAST WEATHER (W)

5810. GENERAL. The term "past weather" refers to the state of the
weather during the 6-hour interval prior to the time of the 00, 06, 12, and
18 GCT observations. However, when the ship is in the vicinity of a tropical
storm, the Weather Bureau may request additional observations at 03, 09,
15, and 21 GCT (see §1021). For these extra observations, ''past weather"
refers to the state of the weather during the 3-hour interval prior to the
time of the observation, and references in the following instructions to 6
hours will be understood, under these special circumstances, to refer to
3 hours,

5820. CODING AND ENTRY OF PAST WEATHER DATA (W) ON FORM
615-5. Select the code figure from Code Table 7 listed on page 44 of this
manual, or from Table 7 on cover of Ship's Weather Observations, corre-
sponding to the weather during the preceding 6 hours, and enter it in column
12. To a certain extent, the combined data coded as 'W"' and "ww" should

A When not accompanied by precipitation.

WEATHER 43

give a complete description of the weather during the preceding 6 hours.
When the weather occurring at the time of the observation (rather than the
hour before it) is coded as "ww," the weather during the full 6 hours prior
to the time of the observation must be coded as 'W,'' When the weather
that has occurred during the hour ending with the observation is coded as
"ww,'' weather during the 5 hours preceding the hour covered by "ww" will
be coded as "W."' For example, if a rain shower has occurred during the
hour preceding the 0600 GCT observation, and the weather was generally
cloudy during the entire 6-hour period prior to the observation, ''ww'' would
be coded as 25, and "W'' as 2. If showers were general throughout the
6-hour period, including the hour before the observation, "ww'' would be
coded as 25, and "W'"' as 8. When precipitation has occurred during the 6
hours preceding the time of the observation, but has not occurred during
the hour preceding the observation, code figures 5, 6, 7, 8 or 9, as appro-
priate, will be used for "W,"'

5821. When thunder has been heard during the 6-hour period before
the observation, but too early to be coded as "ww," 'W"' will always be
coded as 9, regardless of other aspects of the weather. In general, when
two or more code figures are appropriate for symbol ''W," the highest
figure will be used.

44 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

Code Table 7
SYMBOL W. --Past eaters

(During 3 or 6 hours preceding the ACTUAL time of observation)

Code
Figure Past Weather

Cloud covering 1/2 or less of the sky throughout period.

Cloud covering more than 1/2 of the sky during part
of period, and less than 1/2 during part of period.

Cloud covering more than 1/2 of sky throughout
period.

Sandstorm, duststorm, or drifting or blowing snow.
Fog, or ice fog, or thick haze.
Drizzle.

Rain. 3
Snow, rain and snow mixed, or ice pellets.
Shower(s).

Thunderstorm(s), with or without precipitation.

When precipitation or thunderstorms have occurred and have not been
reported by ww, code figures 5 to 9 will be used as appropriate even
though they do not represent the generally prevailing weather.

When code figure 8 or 9 is reported and the showers or thunderstorms
were accompanied by hail add ''past hail" to end of message.

3 The term ice pellets means frozen raindrops or largely melted and re-
frozen snowflakes and is synonymous with the U. S. term sleet.

CHAPTER VI. PRESSURE

CONTENTS

ano merer COLbeCUlONSys a. » osu ele ss use woe ae a 2 Se ne
PmehOuG Misa TOMVeCtet oy cin a adn wae a fe Gee Ge oye ee ae Gee es
Ey ENC tects Maes oh ga a rae feeb ganar arias a gaa tre eran te Wim eg erm eae. eee a were res
eaonie en OldvbaPOMIGLEGS alate sl al elet'¢ alee eta: Gn etl oe anene

HS DIGO Oi AO Ld Speers ree ai voetan ew esurcuc eno nro eaefne ed sare be cmncinom some cota nn. s bore: Neei
CG cme MeN ee sinks aiid ic ores ce sete siete c. ep yen Mes aign eee sea
Readme (hesbarOrrapil.| 4 4.4.4.6 se se4vece en GG! ¥ Ga @ Soe ee
Barosrapn, Charts=-Porm 459-12 2.56% was ee we es & ress
Entries on the Barograph Chart ..................
installation: ofcBarograph Charts. .0,. <0. 6s 5 « «le « 6 a

Raia LUTNU LV) Aen oat OMe as Give of puter er tm a Sate) Wale yah ieee au Soars

Static @harge-on Marine Barograph . 0.23. 6s oe we es ee
Mhicee=Hour Pressure: Tendency ....: 064 i. eee ce ne ewe ee
SC tee oh Wiehe Sing icy 2a, a enon eters sl ele ore vel at a ene eeee a eee
Determination of Tendency from the Barograph...........
Determination of Tendency from the Barometer. ..........
Coding and Entries of Pressure Data on Form 615-5 ..........
Barometric Pressure (PPP)..0« 4 66% 06-6 efee 0 6 bw a & ww 4-8
GiHaracteristlGs (a)! 2 cts es oe cia) 5 of al oc ee bo 4 0e a4 «eee w 3s
Pressure Change (pp)ts.icis baw ee 6 made aie ele ee oe ae eee

CODE TABLES

Code Table 8. --Symbol PPP--Corrected Barometric Pressure...
Code Table 15. --Symbol a--Barometer Change Characteristics
inthe last o-hOuUrs 74 6%4.624 562.245
Code Table 16. --Symbol pp--Amount of Barometric Change
MPCheaSb ao sROUrs, sic: «aw es ele oa oe

45

46

FIGURES

Figure 5. --Aneroid Barometer
Figure 6. --Barograph, Marine Model G-220
Figure 7. --Barograph Chart
Figure 8. --Barograph, Marine W. B. Model G-222

«© 4s) 8) i) fa, Keaeied isl) fei ce) ce -0t (erie

oa fe) See

e 8 © © © © © «© © «© «©

ove: 0) (ese. “ef ie; We je ce) Se

fe. ie Wim liv: Jeu Se) jee 8, 6 ve

48
50
51
53

47

CHAPTER VI. PRESSURE
6000. GENERAL

6001. Atmospheric pressure is the pressure exerted by the weight of a
column of air, of unit area, extending vertically from a given surface (sea
level, for instance) to the top of the atmosphere. Atmospheric pressure may
be measured with aneroid or mercurial barometers and aneroid barographs.

6010. INSTALLATION OF BAROMETERS. Barometers used in taking
weather observations should be mounted in the chart room. The location
should be as free as possible of vibrations and rapid changes in temperature.
It should not be mounted close to sources of artificial heat, such as steam
pipes or electric lights. The barometer should be placed at about the
eye level of the observer.

6020. BAROMETER CORRECTIONS. To insure comparability of pres-
sure data, the Weather Bureau tests andassigns a number to each barometer.
The correction applicable to the barometer is entered ona tag, WB Form
455-2. The correction tag should be posted in a convenient place near
the barometer and the correction applied to each barometer reading. The
amount of the correction should be entered opposite the caption ''correction"'
at the head of column 13 of each Form 615-5. A revised correction should
be obtained at least once every 3 months. The correction is determined
by comparing readings of the ship's barometer with pressure values obtained
from a standard barometer, For this purpose, a precision aneroid may
be cairied aboard ship by a Weather Bureau representative, or the com-
parison may be made by telephone contact with one of the port offices listed
in §1400. When comparisons indicate that a barometer is defective, the
Weather Bureau representative will recommend that it be replaced or
repaired,

6021. When barometric comparisons cannot be made directly or by
telephone, Form 455-1 ''Request for Barometer Comparison" may be filled
out in accerdance with the instructions printed on it and mailed to the near-
est Port Meteorological Office. Upon receipt of the request, a Weather
Bureau representative will visit the ship during the ship's inport period
and compare all ship's barometers. A barometer correction tag will be
attached to each barometer corrected.

6100. ANEROID BAROMETERS
6110. GENERAL. Pressure is indicated on an aneroid barometer by

the position of a hand on a graduated dial. Aneroids have dials graduated at
intervals equivalent to inches and hundredths of mercury, millibars and

48 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

tenths, or millimeters (see Fig. 5). To insure that a precision aneroid
barometer will retain its calibration, it must be protected from shocks

or other violent motions.

6120. READING ANEROID BAROMETERS. To determine sea-level
pressure from the aneroid barometer:

6120.1. Tap the face of the instrument lightly with the finger or the eras-
er-end of a pencil to bring the hand to its true position.

6120.2. Read to the nearest 0.01 inch, 0.1 millibar, or 1 millimeter,
estimating for values between the scale graduations,

6120.3. Apply the correction established in accordance with J§6020.

6120.4, Example: mene
Barometenas Geadiay. 25.0 ai 5) oe eee 29.88
CORRECHONS ras are cco OMe ee) tar ee el ae -.07

Barometer corrected >. 9.3 5. . 5. « 29.81

Figure 5.--Aneroid barometer, W. B. Model G-101

PRESSURE 49

6121. To avoid errors of parallax when the aneroid barometer is read,
the line of sight should be perpendicular to the index hand on the instrument.
If the aneroid has a mirror surface on the dial, parallax may be avoided by
viewing it in a position such that the index hand and its image coincide.

6200. BAROGRAPHS

6210. GENERAL, The barograph is a continuous recorder of atmospheric
pressure. A pen moves across the chart 2.5 inches of distance for each
inch of mercury (1 inch equals 33.864 millibars of pressure). The barograph
consists of an aneroid pressure unit, Suitable linkage and a clock driven
drum upon which the chart is fastened. A knurled knot at the top of the
bellows housing provides a means of setting the pen to the proper pressure
(see Figures 6 and 7).

6211. Barographs furnished or tested by the Weather Bureau are ad-
justed to read sea-level pressure when installed aboard ship. The barograph
should be adjusted to read sea-level pressure each time the instrument
chart is changed.

6212. For purposes of the weather observation, the atmospheric pres-
sure, as entered on Form 615-5 will not be obtained from the barograph, but
will be read from the barometer. The 3-hour pressure tendency, however,
will be read from the barograph trace (see §6300).

6220. READING THE BAROGRAPH. The distance between horizontal
pressure lines on the chart is equivalent to 1.0 millibar of pressure. For
convenience of reading, each five millibar line is identified by bold type
numerals. Barometric pressure will be read to the nearest 0.1 millibar of
pressure. Three-hour pressure tendencies should be determined in accord-
ance with the instructions contained in J6300.

6221. When the pressure changes an amount sufficient to cause the pen
arm to reach the top or bottom of the chart, turn the thumbnut on top of the
aneroid cell enough to move the pen approximately 30 millibars toward the
center of the chart. Renumber the pressure lines accordingly. After the
pressure has returned to normal, move the pen approximately 30 millibars
in the opposite direction, Adjust the pen, making sure that it checks with the
corrected sea-level pressure reading of the ship's aneroid barometer,

6230. BAROGRAPH CHARTS - FORM WB = 455-12. The Weather
Bureau will supply barograph charts upon request, All requests for charts
Should include the Weather Bureau form number. If charts do not have a
Weather Bureau form number, the Weather Bureau should be consulted be-
fore the forms are ordered. Requests for forms should be made in accord-
ance with 91301.

6230.1. The barograph chart should always be changed immediately
following the 0000 GMT observation of the first of each month, and each
time the clip bar on the drum approaches within 3 to 6 hours of the pen.

50 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

Figure 6.--Barograph, W. B. Marine Model G- 220

6231, Entries on the Barograph Chart (see Fig. 7). Before placing a
chart on the barograph, use a typewriter or pen and ink to enter the following
data in the spaces provided.

6231.1. Name of ship.

6231.2. Departure port.

6231.3. Destination port.

6231.4. Date and time the chart is placed on the drum and the pen set.

51

PRESSURE

OCTOBER 1957

AXIS IS 3.375 INCHES ABOVE CLOCK FLANGE

U.S. DEPARTMENT OF COMMERCE, WEATHER BUREAU

PEN ARM IS 7.625 INCHES LONG.

FORM 455-12

BAROGRAM
-route rom. 770514, Pla,

Campeche dreq

Well E¥ine (2S

sip 45eGE BLREKTHORM,

ALL TIMES GREENWICH MERIDIAN,

a

CHART ON DATESZOM A 11mMEZZ OZ CHART OFF DATE

LOG SHIP'S POSITION AT 1200GMT FOR EACH DAY AFTER REMOVING CHART

00 03 O06 O9

00 03 O06 O9 12

00 03 06

Figure 7, --Barograph chart with entries made in accordance with §6231.

The 3-hour pressure tendencies for the period are entered on

Form 615-5.

52 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

6232. INSTALLATION OF BAROGRAPH CHART. On most types of
barographs the form is removed and the new one put on in the following
manner:

6232.1. Remove the case cover. Barograph Model G220 is unlatched at
the base and the cover swung to the left allowing the case cover to rest
on the same plane as the base. Barograph Model G-222 is provided with an
airtight case. To remove the cover rotate the catch wings clockwise and
swing the catches away from the case. Lift the case cover STRAIGHT UP
carefully so that its flange will not catch the pen.

6232.2. Raise the pen from the form with the lever provided for that
purpose and open the case and remove the cylinder from the barograph.
Loosen the clip holding the form and remove the used sheet (use care
to avoid smearing the wet ink). Wind the clock. If any adjustments are
necessary for gain or loss of time, barograph Model G-220 is provided
with a small inspection hole in the top of the cylinder for this purpose.
Clock adjustments to barographs Model G-222, when necessary, will be
made by the Weather Bureau personnel.

6232.3. Wrap the new chart around the barograph cylinder so that it fits
the cylinder tightly, and that its bottom edge is in contact with the flange at
the bottom. When the chart is correctly placed, the ends of the horizontal
coordinate lines will match.

6232.4. Place the clip bar over the end of the chart and smooth out the
bulges. While holding the chart snugly in place, slide the metal retainer into
the slot in the chart drum flange and into the recess in its upper rim.

6232.5. Fill the pen with No. 10 barograph ink. This is a slow drying ink
which does not require a large pen reservoir. Take care to avoid getting
ink on the exterior surfaces of the pen or spilling ink on parts of the instru-
ments

6232.6. Place the cylinder on the barographandturn it clockwise until the
pen has nearly reached the time line on the chart. Lower the pen on the
chart. The clock is then set to time by turning the chart drum clockwise
until the recording pen is brought to the proper time line on the chart.

6232.7. Replace the case cover. In the case of Barograph Model G-222
care should be taken not to touch the pen with the case flange. The case
should be lowered STRAIGHT DOWN.

6233. CHART ENTRY. On each chart removed from the barograph:

6233.1. Enter the date and pen-up time in the spaces provided for
"Chart-off and date and time,"

PRESSURE 53

6233.2. Enter across the top of the chart the date and position of each
day's record in appropriate spaces on the 1200 (Noon) line.

6233.3. All time entries should be in Greenwich Meridian Time.

6233.4. When the pen has been reset (see §6221) to compensate for a
large pressure change, indicate and check the points of change to be cer-
tain that the pen was reset to its normal position following return to normal
pressure.

6234, Marine barograph, Weather Bureau Model G-222 is similar to
Weather Bureau Model G-220, however, it differs somewhat in construction.
Model G-222, due to its improved inherent balance is more adaptable for
shipboard use. It is contained in an airtight case with two vent holes in
the base, one a plug and the other a hose connection. These vents provide
a convenient means of connecting the barograph to a static head exposed
to outside air pressure when necessary.

6234.1. Static Charge on Marine Barograph. The window of the Model
G-222 marine barograph is made of plastic and when cleaned with a dry cloth
develops a static charge. If the air is dry the static charge does not dissi-
pate and may become strong enough to pull the pen off the chart. Damage
may result if the covering case is removed when the pen arm is held against
the window by the static charge. Wiping the barograph case with a damp
cloth will provide sufficient conductivity to bleed off the static charge, how-
ever, a more lasting effect can be gained by rubbing a few drops of liquid
detergent, or a small amount of powdered graphite on the window.

Figure 8.--Barograph, Marine, W. B. Model G-222

54 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS
6300. THREE-HOUR PRESSURE TENDENCY

6310. GENERAL. The pressure tendency is composed of three ele-
ments:

6311. The net change in barometric pressure within the 3-hour period
before an observation.

6312. Indication as to whether the barometric pressure is higher or
lower at the end of the period than at the beginning of the period.

6313. The characteristic of the change during the period,

6320. DETERMINATION OF TENDENCY FROM THE BAROGRAPH.,. The
pressure tendency may be determined from the barograph as described
below:

6321. Find the net amount of pressure change over the 3-hour period by
determining to the nearest 0.1 mb., the difference in pressure between the
beginning and the end of the period. No barometer correction (see §6020)
is to be applied to the value of the trace at these points.

6322, Observe whether the pressure is the same as, higher, or lower
than it was at the beginning of the period.

6323. Determine the characteristic of the trace by observing whether the
trace shows a falling or rising, steady or unsteady character, or a combina-
tion of these. If the characteristic is so variable over the 3-hour period that
it cannot be identified, determine it for the 1-hour period immediately
preceding the observation, Code Table 15 indicates the 10 possible charac-
tenIistcs.

6330, DETERMINATION OF PRESSURE TENDENCY FROM THE BAROM-
ETER. If the ship does not have a barograph, determine to the nearest
0.1 mb. the difference in pressure between the barometric reading at the
time of the observation and the pressure that existed three hours prior to the
observation. These data may be obtained from the ship's log (by inter-
polation if necessary). If the pressure has increased or remained unchanged
during the preceding 3 hours, record the characteristic as code figure '2"
from Code Table 15, and as ''7'' if the pressure has decreased. Other code
figures listed in Code Table 15 will not be used when the tendency is deter-
mined from the barometer.

6400. CODING AND ENTRIES OF PRESSURE DATA ON FORM 615-5

6410. BAROMETRIC PRESSURE (PPP). Enter the barometric pres-
sure exactly as read (in the original units and before any corrections have
been applied) in column 13, ''Barometer as read.'' Apply the correction

PRESSURE 55

entered at the top of column 13 and enter the corrected reading in columns
14-15, "Barometer corrected."

6411. The pressure is entered in column 15, "Barometer corrected
(mb.),"" in "tens," "units," and "tenths" of millibars, and the initial EOD oa:
'40"' in column 14, If the barometer reading is in inches, use Code Table 8
to convert the value to millibars. If the reading is in millimeters, use
Table 29A (in the back of this manual). Example: A pressure of 981.7 milli-
bars is entered in column 15 (PPP) as 817, and in column 14 as 9:

CODE TABLE 8
SymBot PPP.—Corrected barometer reading

Code in ‘‘tens,”’ ‘‘units,’’ and tenths of millibars, omit initia] 9 or 10]

1 inch =33.86395 mb. 1 mb.=0.02952993 inch]

Milli- Milli- Milli- | Milli- Milli- Milli-
In. bars In. bars In. bars In. bars In. bars In. | bars
| |
27. 50) 931.3] 28.00] 948. 2} 28.50) 965.1] 29.00) 982.1) 29.50) 999.0) 30. 00'1, 015. 9} 30. 50/1, 032. 9
27.51] 931.6] 28.01] 948.5} 28.51) 965.5] 29.01] 982. 4] 29.51] 999. 3] 30.011, 016. 3] 30. 511,033. 2
27. 52) 931.9] 28.02) 948.9] 28.52] 965. 8] 29.02} 982. 7] 29.52! 999. 7} 30. 02/1, 016. 6] 30. 52/1, 033. 5
27. 53) 932. 3] 28.03] 949.2] 28.53) 966.1] 29.03} 983. 1] 29. 53/1, 000. 0} 30. 03/1, 016. 9] 30. 53/1, 033. 9
27. 54| 932.6] 28.04) 949.5] 28.54) 966.5] 29.04) 983. 4] 29. 54/1, 000. 3} 30. 04/1, 017. 3] 30. 54/1, 034. 2
27. 55| 933. 0} 28.95} 949. 9} 28.55) 966. 8) 29.05) 983. 7] 29. 55/1, 000. 7] 30. 05/1, 017. 6) 30. 55/1, 034. 5
27. 56) 933. 3] 28.06) 950.2] 28.56) 967. 2} 29.06) 984. 1) 29. 56/1, 001. 0} 30. 06/1, 018. O} 30. 56:1, 034. 9
27. 57| 933. 6] 28.07) 950. 6] 28.57) 967.5] 29.07! 984. 4] 29. 57/1, 001. 4] 30. 07/1, 018. 3] 30. 57/1, 035. 2
27.58] 934.0] 28.08} 950. 9} 28.58} 967. 8} 29.08} 984. 8} 29. 58/1, 001. 7] 30. 08/1, 018. 6] 30. 581, 035. 6
27. 59| 934. 3] 28.09] 951.2] 28.59) 968.2] 29.09) 985. 1] 29. 59/1, 002. O] 30. 09/1, 019. 0} 30. 59/1, 035. 9
27. 60} 934. 6] 28.10] 951.6] 28.60) 968. 5} 29.10) 985. 4] 29. 60/1, 902. 4) 30. 10/1, 019. 3] 30. 60/1, 036. 2
27.61) 935.0] 28.11) 951.9] 28.61) 968. 8} 29.11) 985. 8] 29. 61/1, 002. 7] 30. 11/1, 019. 6] 30. 61/1, 036. 6
27. 62) 935. 3] 28.12} 952. 3] 28.62) 969.2] 29.12) 986. 1] 29. 62/1, 003. 1] 30. 12/1, 020. O} 30. 62/1, 036. 9
27. 63} 935.7] 28.13] 952. 6] 28. 63] 969.5] 29.13) 986.5] 29. 63/1, 003. 4] 30. 13/1, 020. 3] 30. 63'1, 037. 3
27. 64) 936.0] 28.14) 952.9] 28.64) 969.9] 29.14) 986. 8} 29. 64/1, 003. 7] 30. 14/1, 020. 7] 30. 64/1, 037. 6
27. 65| 936. 3] 28.15} 953. 3] 28.65} 970.2] 29.15] 987. 1] 29. 65/1, O04. 1] 30. 15/1, 021. O| 30. 65/1, 037. 9
27. 66| 936. 7] 28.16} 953. 6] 28. 66} 970.5) 29. 16) 987. 5) 29. 66/1, O04. 4] 30. 16/1, 021. 3] 30. 66/1, 038. 3
27. 67) 937.0} 28.17} 953.9] 28.67} 970.9] 29.17} 987. 8} 29. 67/1, 004. 7] 30. 17/1, 021. 7] 30. 67|1, 038. 6
27. 68} 937. 4) 28.18] 954. 3] 28.68! 971.2] 29.18] 988. 2] 29. 68/1, 005. 1] 30. 18/1, 022. 0] 30. 68/1, 038. 4
27. 69| 937.7] 28.19} 954.6] 28.69) 971.6] 29.19) 988.5} 29. 69/1, 005. 4{ 30. 19/1, 022. 4] 30. 69/1, 039. 3
27. 70| 938. O| 28. 20] 955.0] 28. 70) 971.9] 29.20) 988. 8] 29. 70)1, 005. 8] 30. 20/1, 022. 7] 30. 70/1, 039. 6
27. 71| 938.4] 28.21) 955.3] 28.71) 972.2] 29.21) 989. 2] 29. 71/1, 006. 1] 30. 21/1, 023. 0} 30. 71/1, 040. 0
27. 72| 938.7] 28.22] 955.6] 28. 72| 972. 6] 29.22) 989. 5] 29. 72)1, 006. 4] 30. 22/1, 023. 4] 30. 72/1, 040. 3
27. 73) 939.0] 28. 23) 956.0] 28. 73) 972.9] 29. 23) 989. 8] 29. 73/1, 006. 8] 30. 23/1, 023. 7] 30. 73)1, 040. 6
27.'74| 939.4] 28.24) 956. 3] 28. 74) 973.2] 29. 24) 990. 2] 29. 74/1, 007. 1] 39. 24/1, 02+. O] 30. 74/1, 041. 0
27.75} 939.7] 28.25] 956.7] 28. 75| 973.6] 29.25] 990. 5} 29. 75/1, 007. 5] 30. 25/1, 024. 4] 30. 75/1, 041. 3
27. 76| 940. 1] 28. 26} 957.0} 28. 76} 973. 9] 29. 26; 990. 9] 29. 76\1, 007. 8} 30. 26/1, 024. 7] 30. 76/1, 041. 7
27. 77| 940.4) 28.27} 957.3] 28.77) 974.3] 29.27) 991. 2) 29. 77/1, 008. 1] 30. 27/1, 025. 1] 30. 77\1, 042. 0
27. 78| 940. 7| 28.28] 957. 7] 28.78) 974. 6] 29. 28} 991. 5) 29. 78/1, 008. 5} 30. 28/1, 025. 4] 30. 78/1, 042. 3
27. 79| 941.1] 28.29) 958.0] 28. 79) 974.9) 29.29) 991.9] 29. 79/1, 008. 8} 30. 29/1, 025. 7] 30. 79/1, 042. 7
27. 80| 941.4] 28. 30] 958. 3} 28. 80} 975. 3} 29.30) 992. 2] 29. 80/1, 009. 1] 30. 30/1, 026. 1] 30. 80/1, 043. 0
27.81| 941.8] 28.31] 958. 7] 28.81} 975. 6] 29.31) 992. 6] 29. 81/1, 009. 5) 30. 31/1, 026. 4) 30. 81/1, 043. 3
27. 82| 942.1] 28. 32] 959.0] 28.82) 976.0] 29.32} 992.9) 29. 82/1, 009. 8} 30. 32/1, 026. 8] 30. 82/1, 043. 7
27. 83| 942.4] 28.33] 959.4] 28. 83) 976. 3] 29. 33} 993. 2} 29. 83/1,010. 2} 30. 33/1, 027. 1] 30. 83/1, 044. 0
27. 84, 942. 8] 28.34) 959. 7] 28.84) 976. 6] 29. 34) 993. 6] 29. 84/1, 010. 5) 30. 34/1, 027. 4] 30. 84/1, 044. 4
27. 85} 943.1] 28.35} 960.0] 28.85) 977.0] 29. 35) 993. 9] 29. 85/1, 010. 8] 30. 35)1, 027. 8] 30. 85/1, 044. 7
27. 86) 943.4] 28. 36] 960. 4] 28. 86) 977. 3] 29.36) 994. 2] 29. 86/1, 011. 2} 30. 36/1, 028. 1] 30. 86/1, 045. 0
27. 87| 943. 8] 28.37] 960. 7| 28.87) 977. 7| 29.37} 994.6] 29. 87/1, 011. 5] 30. 37/1, 028. 4] 30. 87/1, 045. 4
27. 88) 944.1] 28.38) 961.1] 28.88) 978.0} 29.38) 994. 9] 29. 88/1, 011. 9} 30. 38/1, 028. 8} 30. 88/1, 045. 7
27. 89| 944.5) 28.39) 961.4] 28.89) 978.3] 29.39} 995. 3} 29. 89/1, 012. 2] 30. 39/1, 029. 1] 30. 89/1, 046. 1
27.90) 944. 8] 28.40) 961.7] 28.90! 978. 7} 29.40) 995. 6] 29. 90/1, 012. 5] 30. 40}1, 029. 5} 30. 90)1, 046. 4
27.91| 945.1] 28.41) 962.1] 28.91) 979.0) 29.41) 995. 9; 29. 91/1,012. 9] 30. 41/1, 029. 8} 30. 91/1, 046. 7
27. 92| 945.5] 28.42) 962.4] 28.92) 979. 3] 29.42] 996. 3] 29. 92)1, 013. 2} 30. 42/1, 030. 1] 30. 92/1, 047. 1
27. 93} 945. 8] 28.43] 962. 8] 28.93] 979.7] 29.43) 996. 6] 29. 93/1, 013. 5] 30. 43/1, 030. 5] 30. 931, 047. 4
27. 94| 946.2] 28. 44| 963.1] 28.94) 980.0] 29. 44) 997.0] 29. 941,013. 9] 30. 44/1, 030. 8] 30. 94/1, 047. 8
27. 95| 946.5] 28.45] 963.4] 28.95) 980. 4] 29.45) 997. 3] 29. 95/1, 014. 2} 30. 45/1, 031. 2} 30. 95/1, 048. 1
27. 96] 946. 8] 28.46) 963. 8] 28.96) 980. 7] 29.46) 997.6] 29. 961, O14. 6] 30. 46/1, 031. 5} 30. 96,1, 048. 4
27.97) 947.2) 28.47) 964.1] 28.97; 981.0] 29.47) 998.0} 29. 97/1, 014. 9} 30. 47/1, 031. 8] 30. 97/1, 048. 8
27. 98| 947. 5| 28.48) 964.4] 28.98) 981.4] 29.48} 998. 3] 29. 98/1, 015. 2} 30. 48/1, 032. 2] 30. 98/1, 049. 1
27. 99| 947.9] 28. 49} 964. 8] 28.99) 981.7] 29.49] 998. 6] 29. 99/1, 015. 6} 30. 49)/1, 032. 5} 30. 99/1, 049. 5

664508 O - 62-5

56 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

6420. CHARACTERISTIC (a). Code Table 15 will be used to select the
appropriate code for the characteristic of the 3-hour pressure tendency.
The code value should be entered in column 26 of Form 615-5. It should
be noted that if the pressure is the same as three hours ago (that is, "pp"
is coded 00), then ''a'' must be coded as 0, 4 or 5.

Code Table 15

Symbol a. --Barometer change characteristics in the last 3 hours

DESE MIE TION OF CHARS CIERISUC NOMINAL GRAPHIC REPRESENTATION?
PRIMARY ADDITIONAL (For Coding Purposes) 5
UNQUALIFIED _|REQUIREMENTS

REQUIREMENT PRs wk ewes hake

HIGHER

Atmospheric pres-
sure now higher
than 3 hours ago.

Decreasing or

steady, then in-

creasing; or __

increasing, then /

Res more 3

Increasing, then
decreasing.

THE SAME

Atmospheric pres-
sure now same as
3 hours ago.

Steady or un-
steady

Decreasing, then
increasing.
Decreasing, then
increasing.

Decreasing, then
steady; or
decreasing, then
decreasing more
LOWER ees
Atmospheric pres- i
sure now lower .
than 3 hours ago. ee — ae |

Steady or increas-
ing: then decreas-

PRESSURE 57

6430. Determine the amount of pressure change (pp) in accordance with
96321, and use Code Table 16 to convert the value to millibars and tenths.
Enter the amount, without the decimal point, in column 27, Example: A
pressure change of 3.9 millibars would be entered in column 27 as 39.

6431. When the amount of the barometric pressure change equals or
exceeds 9.9 millibars, the group '99ppp" should be inserted in the message
following the 'D,gv,app" group. The "99" is the group identifier, and "ppp"
is the total amount of the pressure change (in tens, units, and tenths of
millibars) during the preceding 3 hours. When the group is inserted, "99"
should be reported for "pp" in the 'Dgvgapp" group. For example: If the
total amount of the pressure change is 13.4 millibars, the groups should be
coded "Degvga99 99134." If the amount is 9.9 millibars, the groups are coded
"Dgvg299 99099." ("'Dgvga"' should be given appropriate values.)

58 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

Code Table 16

SYMBOLS "pp" and "ppp. ''--Amount of barometric change
in the last 3 hours

Amount of rise or fall

pp Ppp

Code Inches of P Code Inches of Code Inches of Code Inches of F
figure mercury Millibars figure mercury Millibars figure mercury Millibars figure mercury Millibars

00 0. 000 0.0 100 | 0. 295 10. 0
02 - 005 ne 52 0. 155 5. 2 102 . 300 10. 2
03 - 010 .3 54 . 160 5.4
05 . 015 5 56 - 165 5. 6 103 . 305 10. 3 154 | 0.455 15. 4
07 . 020 ou 58 - 170 5. 8 105 . 310 10. 5 156 460 15. 6
08 . 025 -8 59 - 175 5.9 107 - 315 10.7 157 465 15.7
108 - 320 10.8 159 470 15. 9
10 . 030 1.0 61 . 180 6.1 110 . 325 11.0 161 475 16. 1
12 . 035 12 63 - 185 6.3
14 . 040 1.4 64 . 190 6.4 112 . 330 11. 2 163 - 480 16. 3
15 - 045 1.5 66 - 195 6.6 113 . 335 11.3 164 - 485 16.4
17 . 050 1.7 68 . 200 6.8 115 . 340 11.5 166 490 16. 6
117 . 345 11.7 168 - 495 16. 8
19 . 055 1.9 69 . 205 6.9 119 . 350 11.9 169 - 500 16.9
20 . 060 2.0 71 . 210 7.1
22 - 065 2.2 73 . 215 7. 3 120 . 355 12.0 171 - 505 17.1
24 . 070 2.4 75 . 220 7.5 122 . 360 12. 2 173 - 510 17.3
25 . 075 2.5 76 . 228 7. 6 124 . 365 12. 4 174 - 515 17.4
125 . 370 12.5 176 - 520 17. 6
27 . 080 2.7 78 . 230 7.8 127 . 375 12.7 178 - 525 17. 8
29 - 085 2.9 80 235 80
30 . 090 3.0 81 °240 &1 129 . 380 12.9 17S - 530 17.9
32 . 095 3.2 83 . 245 83 130 . 385 13. 0 181 - 535 18.1
34 - 100 3.4 85 . 250 85 132 . 390 13. 2 183 . 540 18.3
134 . 395 13. 4 185 . 545 18.5
36 - 105 3. 6 86 . 255 8.6 135 - 400 13. 5 186 .550 |- 186
37 - 110 3.7 88 260 8.8
39 115 3.9 90 265 9 137 - 405 13. 7 188 - 555 18. 8
41 - 120 4.1 91 . 270 9.1 139 . 410 13. 9 190 - 560 19.0
42 . 125 4.2 93 . 275 9.3 141 - 415 14. 1 191 - 565 19. 1
142 . 420 14. 2 193 . 570 19.3
44 - 130 4.4 95 . 280 9.5 144 - 425 14. 4 195 - 575 19.5
46 . 135 4.6 97 285 9:7
47 . 140 4.7 98 290 9.8 146 - 430 14. 6 196 . 580 19. 6
49 - 145 4.9 295 10. 0 147 - 435 14.7 198 . 585 19. 8
51 - 150 5. 1 199 300 10. 2 149 - 440 14.9 200 .590-| 20.0
ete. etc. 151 - 445 15. 1 201 - 595 20. 1
152 - 450 15. 2 203 - 600 20. 3

1 When the amount of the barometric pressure charge equals or exceeds 9.9 millibars, the group seePDDie should be inserted in the message followin,
the “D.v.app” group. The ‘‘99”’ is the group identifier, and ‘“‘ppp’’ is the total amount of the pressure change (in tens, units, and tenths of millibars)
during the preceding 3 hours. When the group is inserted, ‘‘99"’ should be reported for ‘‘pp"’ in the pergheed aie group. Forerample: Ifthe total amount
of the pressure change is 13.4 millibars, the groups should be coded “‘D,v.a99 99134.’’ If the amount is 9.9 millibars, the groupsare coded ‘‘D,v.899 99099.
(“‘D.v.a” should be given appropriate values.)

ae,

CHAPTER VII, TEMPERATURE

CONTENTS
Page
(Geese Meares ei meet ese de Wie, a sy ty SARS eee ye rat sy at ne home ace Soe AN a tiers 61
Mirehemperatice IVicasSuGementS 4). ssw gsi cce)s sl elses sows 1 61
DSITINIETON Sie meaaeeedee Laat, Pe ecta! Ghee Goda Gi idee Gud sa al wa ero e 4. ao lame 61
ReacinG tic Mier MOMiCTCY (cs wit-a tae. hale onal sees yenee oe ake S 61
EYSV.GhBOTM Cl CIGS am nents, Asie 8. Bn Cale Wk, as wo chi Saas Diced ose) dy ey BY Os Shee 61
Psychrometer (Portable, Aspirated, Electric) ........ 62
Carervon thes Psy charoniereryauwen. eisies chee ais) eons bens ne rt 62
SMO SV ChrPOMGLCT: 5.5 1s ies, Sustain oee 01m, Gude Shaeenw arwee 62-63
cy chirOmetera Readies we TPs 8s n:lea aise ZA toa eter a Rhee dese ba, se 64
Computation of the Dew-=Point TPemperature 200. 9h... sae: 64
Depression of the Wet-Bulb Thermometer ........... 64-65
Rounded Wet Bulb Memperature fs)... : 6 a we see es 65
hounded Depressionior the Wet Bulb =.2-. 2 see ee es 65
Peyonromethic Pables. Oe... yes cea oh we ale alan ws See oe 65
sea-Water Demperature Measurements . 752.5. ...5.45. 5.26... 66
GONeT al Uahtes ay ngs eee ee Hae aoe wilh a alan ea ae eg) mln 66
Coding and Entries of Temperature Data on Form 615-5........ 66
Aip bemperatures (UR, Rail). @ aa ess OME Ce eds 6 ee 66
WiyGre Veibilloy IbSboahoxeneehnibhetey », Gigeg for Solon Gon aloe Gace Cnc gene © 66
De Welt ewer aGthtC asa! gcc) latey sited: Wes) ohana ay a ehsemene eee 66
SEE Weniere Ieieayoxeretehabhetey 5 6 Ge neo Oo oom eo oe eo oe © 66
Air=Sea Temperature Difference (T5T5). 26 6 sd ea we Ge ee 66
FIGURES
isittes m—= Sling PSyVeChrOMiCrer, aig. a.6g 4 send o Wee dn eG 62

Figure 10.--Psychrometer (Portable, Aspirated, Electric)...... 63

61

CHAPTER VI. TEMPERATURE
7000. GENERAL

7001. Temperature readings are made at sea to determine the free-air
temperature, the dew-point temperature, and the temperature of the sea
surface.

7100. AIR- TEMPERATURE MEASUREMENTS

7110. DEFINITIONS. The following terms are used in connection with
air-temperature measurements.

7111. Free-air temperature. The temperature (or dry bulb measured by
an ordinary thermometer exposed to the free air on the windward side of
the ship under conditions that eliminate as completely as possible the effects
of extraneous sources of heat.

7112. Wet-bulb temperature. The lowest temperature to be secured by
evaporating water from a muslin-covered bulb of a thermometer ata
specified rate of ventilation. The wet-bulb temperature differs from the
dry-bulb temperature in an amount dependent on the temperature and relative
humidity of the air.

7113. The dew point. The temperature at which condensation would occur
if the air were cooled. The dew point can be computed when the difference
between the dry-bulb and the wet-bulb temperature is known,

7120. READING THE THERMOMETER. Temperatures indicated by any
mercurial or spirit-filled thermometer may be determined as follows:

7121. Stand as far from the thermometer as is consistent with accurate
reading, to prevent body heat from affecting the instrument.

7122. Insure that the line of sight from the eye to the top of the liquid
column makes an angle of 90° with the thermometer tube, This will avoid
an error of parallax.

7123. Read the thermometer to nearest 0.1°. A degree interval begins
at the middle of the dejree marking etched on the tube.

7130. PSYCHROMETERS. Air-temperature measurements may be made
with a psychrometer. Psychrometers consist of one dry and one wet-bulb
thermometer mounted on a single frame. The psychrometer should be so
ventilated that the minimum speed of air passing over the thermometer

62 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

bulbs is at least 15 feet per second (9 knots). Psychrometer tables are
based upon this rate of ventilation, which must be maintained to obtain
accurate measurements.

7131. PSYCHROMETER (portable, aspirated, electric). The aspirated
psychrometer was designed primarily for shipboard use. The instrument
consists of a pair of matched wet and dry-bulb thermometers, a ventilating
fan which is powered by three standard size ''D" flashlight batteries. The
illumination and the "on-off" switching system is operated by a knob on the
side of the psychrometer case. Thermometers are shielded from external
heat radiation by means ofa removable plastic air intake shield. (See Fig. 10.)

7131.1. Care should be exercised when replacing the air intake ther-
mometer shield, Slide the shield in place with the wide open nozzles point-
ing outward from the instrument. Ventilation will be limited if replaced in
a reverse position.

7132. Care of the Psychrometer. The bulb of the wet-bulb thermometer
iS covered with muslin, which must be saturated with water before the
psychrometer is ventilated and a reading of the wet-bulb temperature is
made. Use only clean, fresh water, preferably distilled water or cooled
water from the condenser, to moisten the muslin. Change the muslin when-
ever it becomes soiled or encrusted with lime or salt.

7133, Sling Psychrometer. The sling psychrometer is readily adapt-
able to shipboard use since it is easily carried to the most suitable exposure.
The dry and wet-bulb thermometers are mounted on a single frame that is
attached to a handle in such a way that the thermometers can be whirled in a
circle (see Fig. 9). Errors in reading arising from exposure to rain or
direct sunlight are overcome, to a large extent, by the strong ventilation to
which the thermometers are subjected. When not in use, the psychrometer
should be stored at outdoor temperature in a safe, sheltered place (e.g., in
a padded box secured to the bulkhead),

Figure 9. --Sling psychrometer

TEMPERATURE 63

7133.1. Psychrometers should be used in accordance with the following
instructions:

7133.11. The wet-bulb wicking should be thoroughly moistened, taking pre-
caution to prevent the moisture from contacting the dry bulb.

7133.12. Select a shady spot on the windward side of the bridge which is
free from spray and has no obstructions within a radius of the whirling sling.

7133.13, Face into the wind.

7133.14. Whirl the psychrometer as far infront of the body as conveniently
possible,

7133.15. When the apparent wind is greater than nine knots, do not whirl
the psychrometer. The psychrometer may be properly ventilated by holding
the instrument in the direct wind stream and pointing the bulbs into the wind.

7133.16. Read the wet and dry thermometers while holding the instrument
as far from the body as practicable,

7133.17. Repeat the ventilating until a minimum wet-bulb temperature
has been reached.

Figure 10. --Psychrometer (Portable, Aspirated, Electric).

64 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

7134. Psychrometric Readings. Readings from the dry and wet-bulb
thermometers should be obtained in accordance with the following instructions.

7134.1. Saturate the muslin of the wet bulb with clean water. Use care
to avoid wetting the dry-bulb thermometer, which must be thoroughly dry be-
fore the readings. Ventilate the psychrometer for about 10 seconds and
quickly read both thermometers, the wet-bulb thermometer first. Repeat
the alternate ventilating and reading until two successive readings of the wet-
bulb thermometer are the same and indicate that the thermometer has reached
its lowest temperature.

7134.2. When the wet-bulb temperature is below 0°C., moisten the wet-
bulb thermometer with water having a temperature between 18° and 24°C,
(65°- 75°F.) in order to melt completely any accumulation of ice on the muslin,
since a very thin coating isnecessary foraccurate data. When the psychrom-
eter is ventilated at below freezing temperatures, and there is doubt as to
whether the muslin is frozen, the muslin should be brought to the frozen
state by touching it with clean ice or snow, or some other object whose
temperature is approximately the same as or less than the dry-bulb temper-
ature. After the muslin has become ice-covered, continue to ventilate the
psychrometer until successive readings indicate that the lowest wet-bulb
temperature has been reached.

7140. COMPUTATION OF THE DEW-POINT TEMPERATURE. The
temperature of the dew point is computed with tables furnished with this
manual (see §7144). To use the tables, it is necessary to know the temper-
ature of the wet bulb and the wet-bulb depression.

7141. Depression of the Wet-Bulb Thermometer. The depression of
the wet-bulb thermometer is the algebraic difference between the dry and
wet-bulb temperatures,

Examples:
(1) Dry-bulb temperature « <2). «ss «6 « 40.6
Wet-bulb temperature... 2.2. «6 we ss 34,1
IDYchonelstcichlich al Haney are ts Men cert oo orohet cc 6.5
(2) Dry-bulb temperature 4 4.. 2. a ela a coe 1.2
Wet-bulbitemperature. G4 20. 2 68. ws ss =O

Depressions... seeste eure ges ssn reys a]

TEMPERATURE 65

(3) Dry-bulb temperature. .....6.26.<6..-s -3.4
Wet-bulbitemperature 4). 4 ke ale cw oe =o (
DEPRESSIONS wos) sss kel ee 8 ee AS

7141.1. When the wet-bulb is covered with water and a depression can-
not be obtained, the dew-point temperature will be regarded as the same as
that of the wet-bulb temperature.

7142. Rounded Wet-Bulb Temperature. After the depression of the wet
bulb’ has been determined, the wet-bulb temperature will be rounded to the
nearest 0.5°C., e.g., a temperature of 61.2° is rounded to 61.0°; 37.7° to
37.5°; 25.3° to 25.5°; -4.7° to -4.5°% etc. This rounded wet~bulb temperature
will be used in determining the dew-point temperature from Table 25 (see
$7144).

7143. Rounded Depression of the Wet Bulb. Ifthe actual depression of the
wet bulb is between 0.0° and 2.0°, this value will be used to find the dew point
in Table 25. When the depression is above 2.0°, the value will be rounded
to the next .2° by adding .1° and then used with Table 25; e.g., a depression
of 1.5° is used directly, a depression of 6.5° is rounded to 6.6°, etc.

7144, Psychrometric Tables, Table 25, "Temperature of the Dew Point
in Degrees Celsius' at the back of this manual, will be used to compute
the dew point. Touse the tables, find(a) the appropriate wet-bulb temperature
in the vertical column printed at the left edge, and (b) the corresponding
depression of the wet-bulb,. Follow (a) horizontally across, and (b) vertically
downward. The tabular value at the intersection is the dew point.

Examples:
Depression
Dry Wet Depression Wet bulb of wet bulb Dew
bulb bulb of wet bulb rounded rounded point
2nliedl 25.0 ra | Unchanged 2.2 24
14.5 10.3 4.2 10.5 Unchanged q
ies 4.8 2.5 5.0 2.6 Z
344 =) 0.5 3.9 Unchanged 4,0 - 9
- 2.1 - 4.1 2.0 - 4.0 Unchanged - 9
- 5.4 - 8.7 3.3 =a0.0 3.4 -26

66 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

7200. SEA-WATER TEMPERATURE MEASUREMENTS

7210. GENERAL. The condenser (or comparable) intake thermometer
will be read to the nearest 0.1°C. (0.2°F.) at each observation to secure
the sea-water temperature. Intake thermometer readings previously entered
in the engine room log book will not be used for the weather observation.

7300. CODING AND ENTRIES OF TEMPERATURE DATA ON FORM 615-5

7310. AIR TEMPERATURE, Enter the dry-bulb temperatures to degrees
and tenths of column 17. Prefix a minus sign (-) when the temperature is ,
below O°C. Enter the dry-bulb temperature to the nearest whole degree
(two digits) in column 16 (TT). Ifthe dry-bulb temperature is exactly between
two values, 10.5° for example, increase the values entered in column 16 to
the next higher value (11 in this case).

7311. When the air temperature is below O0°C, the minus sign will be
disregarded and 50 added to the temperature before entry in column 16.
For example, -4.6°C would be entered in column 17 and 55 in column 16.

7312. When the air temperature is between +0.4°C and -0.4°C the actual
value will be entered in column 17 and 00 entered in column 16,

7320. WET-BULB TEMPERATURE. The actual value of the wet-bulb
temperature will be entered in column 18 to degrees and tenths, Prefix a
minus sign (-) when the temperature is below 0°C.

7330. DEW-POINT TEMPERATURE. The value ofthe dew-point tempera-
ture in whole degrees as determined from Table 25 will be entered in
columns 30 and 33. When the dew-point temperature is below 0°C a minus
Sign (-) will precede the actual value in column 30.

7331. When the dew-point temperature is below 0°C, the minus sign will
be neglected and 50 added to the dew- point temperature value for entry
in column 33,

7340. SEA-WATER TEMPERATURE. Enter the temperature of the sea
water in degrees and tenths Celsius in column 28.

7350. AIR-SEA TEMPERATURE DIFFERENCE. The actual difference
between the air temperature and the sea temperature will be entered in
column 29 to the nearest tenth of a degree Celsius. For example, if the
air temperature is 10.7°C and the sea temperature is 8.1°C, (10.7 - 8.1)
or 2.6° will be entered in column 29. When the air temperature is less
than the sea temperature a minus sign (-) will be entered before the actual
value. If the air temperature is 5.5°C and the sea temperature is 6.2°C,
(5.5 - 6.2) or -0.7 will be entered in column 29.

TEMPERATURE 67

7351. The actual value of the air-sea temperature difference to the
nearest tenth of a degree as entered in column 29 will be multiplied by 2
and rounded. This figure will represent the number of half degrees difference.
If the air temperature is higher than the sea temperature, as in the example
above, (2.6 degrees difference) the value 2.6 will be multiplied by 2 to
equal 5.2; 05 will be entered in column 32. In the second case above (-0.7
degrees difference), -0.7 x 2 = -1.4 rounded = -1, 51 will be entered in
column 32. That is, 50 added to the rounded value to indicate the sea
temperature warmer than the air temperature. EXAMPLES:

when and the number of half-degrees column 32
column 17 column 28 difference half-degrees rounded should be
is is in column 29 is is
31.4 17.6 1326 27.6 28 28
26.8 ins a Tae 15.4 15 15
2 14.4 2.8 5.6 6 06
8.9 (Os: 1.6 3.2 3 03
4.4 444 0.3 0.6 il 01
4.4 4.2 0.2 0.4 0 00
3.6 3.8 - 0.2 - 0.4 0 00
4.2 4.5 - 0.3 - 0.6 - 1 a
6.5 gex6 - 3.2 - 6.4 - 6 56
12.4 16.7 ~ 4,3 - 8.6 - 9 ah)
13.8 20.7 - 6.9 -13.8 -14 64
3.2 - 0.6 3.8 7.6 8 08
= 1.1 2.1 - 3.2 - 6.4 - 6 56
3 ie) 8.9 Loss 18 18

69

CHAPTER VIII. CLOUDS

CONTENTS

Page
GeMeE Al lt aig ane srs a ane. aay & eee Co nctre ee sam sean beateeeen ce era (au
Mererminatlionson Sky"COVeKr fees ie ce wes ce eee er eels) stele el Tal
ee eal Fey 2a Sse es as ena be AG wi ire O18 Se wane, hs) & fal
bay eG CAN OSs oat aerate cs sent Gor 64 bm ae le Re eS @ Sines. fil
Obs CuBedySkiyawey suet seems ey claaes cue) et calutelietouie celica) er fetee ol taMew apie ue sats Al
Panes et UN eer yk es far: Ae, iano (el ei ane i ueltapeep eso i eive oui) &. © © Wee 71-72
Coding and Entries of Cloud Data on Form 615-5.............. 72
orale oud AammoOunt ICN) picivincs eet cus ees eee eh ee Oe ie

Fraction of the Celestial Dome Covered by Specified Cy,

Orin Cloudy uN) sors ck kh Se a oe Oe a Se eS ee Ho 72
Height of Lowest Cloud of Types Cy; or Cy -(h)......-..-.- 13
Clouds Of “Ey Pe Gy eo. a: we Weais ae G e e at are ed Bele & ie oe She 74-75
Giondsror hype Chie. wea-4 eh. > eo ee ee a SD le a ee OS ee 76-77
Cloudsror ype Crp ieee s: oes 4 a0 be el mae be Bsa ee Se BS 78-79
(COU G ROU peer eke tio ewe, sue cd or y-isel el csy col me yepuiotss) fon et coon euseihes ee ese 80

CODE TABLES
Code Table 3. Symbol N--Fraction of the Celestial Dome
Covered by Clouds, in Eighths...... ‘ 73
Code Table 3. Symbol N)--Fraction of Celestial Dome Covered
by Cloud Reported for Cy; (or Cy)... .- v3)
Code Table 9. Symbol Cy; --Clouds of Types Stratocumulus,
Stratus, Cumulus, and Cumulonimbus . 15)
Code Table 10. Symbol h--Height of Base of Lowest Cy (or Cy)
Cloud AbOVEG SCA a... ca tecnre als aete are Ss 73
Code Table 11. Symbol Cy,--Clouds of Types Altocumulus, Alto-
stratus, and Nimbostratus......... lal
Code Table 12. Symbol Cy--Clouds of Types Cirrus, Cirrostratus,

hale! (CalserexofeybhaanblNbis} 4 & Wa oa ooo) os oo ee 79

ql

CHAPTER VII. CLOUDS
8000. GENERAL

8010. Code numbers for cloud forms and states of the sky are described
in detail in International Cloud Atlas, 1956. Instructions in this chapter
are confined to those necessary for observing clouds with respect to their
amount and height of base. For easy reference by the observer, cloud
pictures of the principal type clouds, their definitions and respective code
numbers are included in WB Form 615-5.

8100. DETERMINATION OF SKY COVER

8110. GENERAL. "Sky cover" is a term used to denote the amount, in
eighths, of sky covered by clouds. The eighths of sky cover plus the eighths
of sky visible will always equal 1.0, that is 8/8.

8120. SKY QUADRANTS. The sky may be regarded as divided into
quadrants, with the zenith regarded as the center, and the north, east, south,
and west compass points forming the dividing lines. Each quadrant contains
2/8 of the total sky.

8121. Determine the amount of sky cover by use of quadrants as follows:
8122. Estimate the amount covered by clouds in each quadrant.

8123. Add the estimated amounts together. The sum of the amounts will
be the sky cover.

Example: If an advancing cloud layer completely covers two quadrants
and scattered clouds of another type cover one-half of each of the remaining
two quadrants, the total sky cover is 2/8 + 2/8 + 1/8 + 1/8 or 6/8.

8130. OBSCURED SKY. When the sky is completely obscured, other
than by clouds, e.g., by fog, falling snow, haze, smoke, etc., the sky is
classified as 'obscured.'' However, when only a portion of the sky is ob-
scured, estimate the total amount of clouds on the basis of those that are
visible.

8200. CLOUD HEIGHT

8210. The height of the lowest cloud layer should be estimated after the
type of cloud has been determined by use of the tables in this chapter and
photographs in W. B. Form 615-5. Cloud definitions and photographs
contained in the International Cloud Atlas and WB’ Form 615-5 are useful

664508 O - 62-6

72 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

guides in estimating the height of clouds, Some indication of the height of
the clouds may be obtained from the detail with which the small indentations
on the bottom surface can be observed. At night it may be possible to use a
ship's searchlight to observe the cloud base.

8220. There is no reliable way to determine exact cloud height by
estimation. However, when an observer is required to give his best esti-
mate without the aid of cloud measuring devices, he may resort to one or
more methods mentioned in §8201. For clouds caused by convection, such
as cumulus, and stratocumulus during high winds, the temperature and dew-
point formula may be used to obtain an indication of the level where conden-
sation takes place.

8230. The approximate cloud height formula is: Height of clouds =
(temperature-dew point) x 396 feet. Air temperature and dew point are in de-
grees Celsius. For example, when the air temperature is 14.6°C and the
dew point is 9.4°C, the difference of 5.2 multiplied by the constant gives the
approximate height of the convective cloud base, e.g., 5.2 x 396 = 2,000
(to the nearest thousand feet).

8300. CODING AND ENTRIES OF CLOUD DATA
ON FORM 615-5

8310. TOTAL CLOUD AMOUNT (N). Select the approximate code figure
from Code Table 3 corresponding to the total amount of sky covered by all
types of clouds, and enter the figure in column 7 of Form 615-5. A few
clouds or fragments of clouds are entered as "1," If the sky is completely
covered (overcast), N is entered as 8; however, if a few patches of blue sky
are visible, N is entered as 7.

8320. FRACTION OF THE CELESTIAL DOME COVERED BY SPECIFIED
Cy, OR Cyqy CLOUD - (Np). Select the code figure from Code Table 3 cor-
responding to the amount of sky covered by the type or types of cloud reported
by Cy, (not necessarily the amount of allCy, clouds present), or by Cy clouds
when no Cy, clouds are present (see §8340 and 8350). Code figure ''0" is
entered for Ny, when there are no Cy, or Cy clouds present. Less than one-
eighth but more than none (i.e., fragments") is coded as 1. ''Overcast but
with openings'' (less than eight-eighths but more than seven-eighths) is
coded as 7. Code figure 9 is usedto report ''Sky obscured by fog, rain, snow,
smoke or other phenomena or obstruction except clouds."

8321. The coded value for Nj is entered on WB Form 615-5 in column
19,

CLOUDS 73

CODE TABLE 3
SymspoL N—Fraction of the celestial dome covered by clouds
SymBo.t N,—Fraction of celestial dome covered by type of cloud reported for Cy (or Cy if no C, cloud present)

Cloud amount
(eighths of sky
covered)

Code figures

0 None

1 1!

2 2

a 3

4 4

5 5

6 6

vi 72

8 8

9 Sky obscured 3

NOTES

! “Fragments of clouds’’ are coded as 1.

2 “Overcast but with openings” is coded as 7.

3 Sky obscured by fog, rain, snow, smoke or
other phenomena or obstruction except clouds.

8330. HEIGHT OF LOWEST CLOUD OF TYPES Cy, OR Cy - (h). Select
the code figure from Code Table 10 corresponding to the height of the lowest
cloud (including fragments, i.e., less than 1/8 but more than none) of the
classes Cy, or Cy and enter the figure in column 21. (Note that this height
is not necessarily the height of the base of the lowest cloud reported as Cy,
or Cy in accordance with J8340 and 8350.) Enter 9 when there are no C],
or Cyy clouds present; enter X when the cloud base cannot be reported owing
to darkness or any other reason, except that when the sky is obscured by
rain, snow, fog, smoke or other phenomena, code "h'' as 0 and ''Nj),"'as 9.

Code Table 10
Symbol h. --Height of base of lowest cloud (Cy, or Cyy) above sea

Code
figure Height in Feet Height in Meters

O- 149, O- 49.
150- 299. 50- 99.
300- 599. 100- 199.
600- 999. 200- 299.

1000-1999. 300- 599.
2000-3499. 600- 999.

0
1
2
3
4
5
6
7
8
9
x

3500-4999.
5000-6499.
6500-7999.

8,000 or higher or no clouds
Height cannot be reported

owing to darkness or

other reason not covered
by Note 2 below.

1000-1499.
1500-1999.
2000-2500.

2,500 or higher or noclouds.

74 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

8340. CLOUDS OF TYPE C,. Enter the appropriate code figure from
Code Table 9. Report the code figure for the predominant type, and when
several types are present in equal amounts, report the code figure for the
type whose base is at the greatest height above the sea. Exceptions follow:

8340.1. Whenever types coded as 1 and 2 only are present, report code
figure 2, regardless of amount.

8340.2. Whenever types coded as 3 or 9 are present, 3 or 9, as appro-
priate, will be coded, regardless of the amount of other Cy, types present.

8341. The coded value for Cy, is entered on WB Form 615-5 in column
20.

CLOUDS

CODE TABLE 9

Symbol C,—Clouds of types Stratocumulus, Stratus, Cumulus,

and Cumulonimbus

Technical language specifications

Plain language specifications

bo

>

oOo wn

~I

io<)

INO Gp clouds... +o 2s<s-2eueees

Cumulus
bad

Cumulus humilis, or
fractus other than of
weather, or both.

Cumulus mediocris or congestus,
with or without Cumulus of
species fractus or humilis, or
Stratocumulus; all having their
bases at the same level.

Cumulonimbus calvus, with or
without Cumulus, Stratocumu-
lus or Stratus.

Stratocumulus cumulogenitus - - --

Stratocumulus other than Strato-
cumulus cumulogenitus.

Stratus nebulosus or Stratus frac-
tus other than of bad weather,
or both.

Stratus fractus or Cumulus frac-
tus of bad weather or both
(pannus) usually below Alto-
stratus or Nimbostratus.

Cumulus and Stratocumulus,
other than Stratocumulus cu-
mulogenitus, with bases at dif-
ferent levels.

Cumulonimbus capillatus (often
with an anvil), with or without
Cumulonimbus calvus, Cumu-
lus, Stratocumulus, Stratus or
pannus.

Clouds Cy not visible owing to
darkness, fog, blowing dust or
sand, or other similar phe-
nomena.

No Cumulus, Cumulonimbus, Strato-

Cumulus

Cumulonimbus,

cumulus or Stratus.

with little vertical extent
and seemingly flattened, or ragged
Cumulus other than of bad weather,
or both.

Cumulus of moderate or strong verti-

cal extent generally with protuber-
ances in the form of domes or
towers, either accompanied or not
by other Cumulus or by Strato-
cumulus; all having their bases at
the same level.

Cumulonimbus the summits of which,

at least partially, lack sharp out-
lines, but are neither clearly fibrous
(cirriform), nor in the form of an
anvil; Cumulus, Stratocumulus or
Stratus may be present.

Stratocumulus formed by the spread-

ing out of Cumulus; Cumulus may
also be present.

Stratocumulus not resulting from the

spreading out of Cumulus.

Stratus in a more or less continuous

sheet or layer, or in ragged shreds
or both, but no Stratus fractus of
bad weather.

Stratus fractus of bad weather or

Cumulus fractus of bad weather
or both (pannus) usually below
Altostratus or Nimbostratus.

Cumulus and Stratocumulus, other

than those formed from the spread-
ing out of Cumulus; the base of
Cumulus is at a different level than
that of the Stratocumulus.

the upper part of
which is clearly fibrous (cirriform)
often in the form of an anvil; either
accompanied, or not by Cumulo-
nimbus without anvil or fibrous
upper part, by Cumulus, Strato-
cumulus, Stratus, or pannus.

No Cumulus, Cumulonimbus, Strato-

cumulus or Stratus visible owing to
darkness, fog, blowing dust or
sand, or other similar phenomena.

—

Note: ‘Bad Weather’ denotes the conditions which generally exist during
precipitation and a short time before and after.

76 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

8350. CLOUDS OF TYPE Cy. Enter the appropriate code figure from
Code Table 11. Report the code figure for the predominant type, and when
several types are present in equal amounts, report the code figure for the
type whose base is at the greatest height above the sea. Exceptions follow:

8350.1. Whenever Ac (Altocumulus) are present in a chaotic sky (see
International Cloud Atlas), regardless of amount, report code figure 9.

8350.2. Whenever the sky is not chaotic but tufted or turreted altocu-
mulus (see International Cloud Atlas) are present, report code figure 8.

8351. The coded value for Cu is entered on WB Form 615-5 in column
PAPD

CLOUDS

CODE TABLF 11

Technical language specifications

Symbol Cm—Clouds of types Altocumulus, Altostratus, and Nimbostratus

Plain language specifications

INot@w cloudse2—-2se-- 4-2 eee

Altostratus translucidus__-_—— ~~ _-

Altostratus opacus or Nimbo-
stratus.

Altocumulus translucidus at a
single level.

Patches of Altocumulus translu-
cidus (often lenticular), contin-
uously changing and occurring
at one or more levels.

Altocumulustranslucidus in
bands, or one or more layers
of Altocumulus translucidus or
opacus progressively invading
the sky; these Altocumulus
clouds generally thicken as a
whole.

Altocumulus cumulogenitus (or
cumulonimbogenitus).

Altocumulus translucidus — or
opacus in 2 or more layers, or
Altocumulus opacus in a single
layer, not progressively invad-
ing the sky, or Altocumulus
with Altostratus or Nimbo-
stratus.

Altocumulus castellanus or floc-
cus.

Altocumulus of a chaotic sky,
generally at several levels.

Clouds Cm not visible owing to
darkness, fog, blowing dust or
sand, or other similar phe-
nomena, or because of a con-
tinuous layer of lower clouds.

No Altocumulus, Altcstratus or Nim-
bostratus.

Altostratus, the greater part of which
is semitransparent; through this
part the sun or moon may be
weakly visible as through ground
glass.

Altostratus, the greater part of which
is sufficiently dense to hide the sun
(or moon), or Nimbostratus.

Altocumulus, the greater part of which
is semitransparent; the various
elements of the cloud change only
slowly and are all at a single level.

Patches (often in the form of almonds
or fishes) of Altocumulus, the
greater part of which is semitrans-
parent; the clouds occur at one or
more levels and the elements are
continually changing in appearance.

Semitransparent Altocumulus in
bands or Altocumulus in one or
more fairly continuous layers (semi-
transparent or opaque) progres-
sively invading the sky; these Alto-
cumulus clouds generally thicken
as a whole.

Altocumulus” resulting from the
spreading out of Cumulus (or Cu-
mulonimbus).

Altocumulus in two or more layers
usually opaque in places and not
progressively invading the sky; or
opaque layer of Altocumulus not
progressively invading the sky; or
Altocumulus together with Alto-
stratus or Nimbostratus.

Altocumulus with sproutings in the
form of small towers or battle-
ments, or Altocumulus having the
appearance of cumuliform tufts.

Altocumulus of a chaotic sky gen-
erally at several levels.

No Altocumulus, Altostratus or Nim-
bostratus visible owing to darkness,
fog, blowing dust or sand, or other
similar phenomena, or more often
because of the presence of a con-
tinuous layer of lower clouds.

Ut

78 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

8360. CLOUDS OF TYPE Cy. Enter the appropriate code figure from
Code Table 12. Report the code figure for the predominant type, and when
several types are present in equal amounts, report the code figure for the
type whose base is at the greatest height above the sea.

8361, The coded value for Cy is entered on WB Form 615-5 in column
23.

CLOUDS

CODE TABLE 12

Symbol Cy—Clouds of types Cirrus, Cirrostratus, and Cirrocumulus

Code
fig-
ures

Technical language specifications

Plain language specifications

INOfCrClOUdS). 22 eee ee eae

Cirrus fibratus, sometimes un-
cinus, not progressively invad-
ing the sky.

Cirrus spissatus, in patches or en-
tangled sheaves, which usually
do not increase and sometimes
seem to be the remains of the
upper part of a Cumulonimbus;
or Cirrus castellanus or floccus.

Cirrus spissatus cumulonimbo-
genitus.

Cirrus uncinus, or fibratus, or
both, progressively invading
the sky; they generally thicken
as a whole.

Cirrus, often in bands, and Cirro-
stratus, or Cirrostratus alone,
progressively invading the sky;
they generally thicken as a
whole, but the continuous veil
does not reach 45° above the
horizon.

Cirrus, often in bands, and Cirro-
stratus, or Cirrostratus alone,
progressively invading the sky;
they generally thicken as a
whole, but the continuous veil
extends more than 45° above
the horizon, without the sky
being totally covered.

Cirrostratus covering the whole
sky.

Cirrostratus not progressively in-
vading the sky, and not entirely
covering it.

Cirrocumulus alone, or Cirrocu-
mulus predominant among tbe
cirriform clouds.

Clouds Cy not visible owing to
darkness, fog, blowing dust or
sand or other similar phenom-
ena, or because of a continuous
layer of lower clouds.

No Cirrus, Cirrostratus or Cirrocu-
mulus.

Cirrus in the form of filaments,
strands or hooks, not progressively
invading the sky.

Dense Cirrus in patches or entangled
sheaves which usually do not in-
crease and sometimes seem to be
the remains of the upper parts of
Cumulonimbus; or Cirrus with
sproutings in the form of small tur-
rets or battlements or Cirrus having
the appearance of cumuliform tufts.

Dense Cirrus often in the form of an
anvil, being the remains of the
upper parts of Cumulonimbus.

Cirrus in the form of hooks or fila-
ments or both, progressively invad-
ing the sky; they generally become
denser as a whole.

Cirrus, often in bands converging to-
wards 1 point or 2 opposite points
of the horizon and Cirrostratus, or
-Cirrostratus alone; in either case
they are progressively invading the
sky, and generally growing denser
as a whole, but the continuous veil
does not reach 45° above the
horizon.

Cirrus, often in bands converging to-
wards | point or 2 opposite points
of the horizon, and Cirrostratus, or
Cirrostratus alone; in either case
they are progressively invading the
sky, and generally growing denser
as a whole; the continuous veil ex-
tends more than 45° above the
horizon, without the sky being
completely covered.

Veil of Cirrostratus covering the
celestial dome.

Cirrostratus not progressively invad-
ing the sky, and not completely
covering the celestial dome.

Cirrocumulus alone, or Cirrocumulus
accompanied by Cirrus or Cirro-
stratus or both, but Cirrocumulus is
predominant.

No Cirrus, Cirrostratus or Cirrocumu-
lus visible owing to darkness, fog,
blowing dust or sand, or other
similar phenomena, or more often
because of the presence of a con-
tinuous layer of lower clouds.

80 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

8370. CLOUD GROUP NpCy;hCyCy. Instructions for tre coding of the
individual symbols of this group are contained in §8320-8360. These are
entered on WB Form 615-5 in columns 19-23.

Example: The coded cloud group 51406 is decoded as follows:

Description Meaning

Fraction of celestial dome Five-eighths of sky
covered by Cy, cloud (or covered with the Cy,
Cy when no Cy cloud is type cloud (Cumu-
present). lus).

Predominant type of Cy, Cumulus type clouds
cloud. with little vertical

development.

Height of lowest cloud of Height of the base of

types Cr or Cyr: the lowest cloud is
between 1,000 and
2,000 feet above the

sea,

Predominant type of Cy No clouds of type
cloud. Cy present.

Predominant type of Cy Cirrus and Cirro-
cloud. stratus gradually
spreading over sky
with the layer ex-
tending more than
45° above the horizon.

_
Fs

CHAPTER IX. WAVES

CONTENTS

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WMDSeErVaAtlO epee en sy cue ce sel ee ata ere! ite vel! el es Ss) weit) Geet ge vemen | vem
Wiawie mein t se race ene ster Gace) std: sale ster 8a. gan ciNel Seine! dole oe, ae telis a a) ee Hse
Generale cae. Nolet he tree alk Eel hid 8, USNS) oe Gu es a, cee Boae Om eal Ghs, ej
Meter in atvOMmive, aes <twel Soe: Seine feud A oon sigbi en Ss doe: we Rie oie, Ores A
Coding and Entries of Wave Data on Form 615-5 .............
Genes alia wc wold, oc ey 0s, Sh. ckieleuta te. woe natced oP acs meme, vo or yel anil Bae Gi! atte
BERSCULONM (Cl Cy) aerate aise, «lee! aha aide) St ews RG a oe Yet Te
Eve NGC (oagp) cae vines Site: VelSi ancy cl an Gina: Sia “araaee arte wh ie eget wean wh aA: Eble
Ie OIA GEL 7) erettatie ston Sixth Sate Aw mine 4o-ay@ cele Gh di toad ie alls fetes a eect
NVViCm GICOUP mem smem otmee ious SNe gy eclohie ce Je) eps, eetbee ane aes Gate een ad coeaeey

CODE TABLES

Code Table 4. Symbol dydy --Direction from Which Waves

PE Cl G OMITINE ma cache, eth ieee ete eMedia

Code Pabie 17. Symbol Py,=-Period of Waves w.2056 5s toe eae

Codewiable 1d. symbol MH. =-Heipht of Waves ..2:..5 o. 4 2 eee
FIGURES

Figure 11. --Section of a Trace from a Wave Recorder ........
Bigtre We -Wave Length and Height . 49.24 250 sess 6 oe oOo es

81

87
88
89

83
85

83

CHAPTER IX. WAVES
9000. GENERAL

9010. The wave group of the weather message, as entered on Form
615-5, consists of the direction of movement, period, and height of the
waves on the surface of the sea. When more than one wave system is
present (sea and swell), the direction, period, and height of the waves in
each system will be observed and recorded as if they existed alone.

9020. The wave record section (columns 34-47) of W. B. Form 615-5
consists of two parts, one section for entry of sea and swell data similar
to a "rough log'' and one section for ''smooth'" data. The first section
(columns 34-39) is grey andis used for later transcription to punched cards;
the second wave section is white and is used for radio transmission when
authorized. Both the grey and white sections refer to the same waves,
that is, columns 34-36 and 41-43 are for the same observation of sea
waves, columns 37-39 and 45-47 for the swell waves. Additional wave
data may be recorded under column 48, ''Remarks."

9030. Waves in the same system usually occur in a sequence of a few,
large, well-formed waves followed by an interval in which only small and
poorly formed waves appear, then another series of large, well-formed
waves, etc. (see Fig. 11). To obtain uniform waves data from all ships,
observers will record only the larger, well-formed waves, and omit en-
tirely the low and poorly formed waves.

TaN TAS JIN

Six Second Intervals

Figure 11. -- Section of a trace from an automatic wave recorder il-
lustrating the up-and-down movement of a small object floating on the
surface of the sea. In accordance with §9020, the height and period of
only the well-defined waves (A) of each group will be determined.

84 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS
9040. Distinction between SEA and SWELL.

9041. The system of waves raised by the local wind blowing at the
time of observation is usually referred to as ''SEA,"

9042. Those waves not raised by the local wind blowing at the time of
observation, but due either to winds blowing at a distance or to winds
that have ceased to blow, are known collectively as 'SWELL."

9043. Usually one swell train dominates the rest, but occasionally two
swell trains crossing at an angle may be observed. These are referred
to as "CROSS SWELLS."

9050. For additional wave observation techniques, see W.B. Training
Paper No, 14, "Observing and Reporting Sea and Swell."

9100. WAVE DIRECTION

9110. Wave direction, like wind direction, is the direction from which
the waves are coming. The wave direction is determined with reference
to true north (360°), and is recorded to the nearest ten degrees in tens of
degrees; e.g., 237° is recorded as 24,

9120. Wave direction may be determined by eye observation or, more
accurately, by sighting from a compass along the wave crests and adding
or subtracting 90°. Ship's heading canalso be used as a guide to determine
the direction from which the waves are approaching. The higher the
observation point, the easier it is to determine wave direction. The
average of several observations should be used as the reported wave
direction,

9200. WAVE PERIOD

9210. GENERAL, The wave period is the interval in seconds between
the passage of two successive crests of well-formed waves past a fixed
point (see Fig. 11). The interval can be timed with a stop watch or an
ordinary watch with a second hand.

9220. OBSERVATION, Determine the period as follows:

9221. Select a distinctive patch of foam or a small floating object at
some distance from the ship. Select a new patch of foam from time to
time as the old one falls astern.

9222. Note the elapsed time tothe nearest second between the moments
when the object is on the crest of the first and of the last well-formed
wave in the group. Also note the number of crests that pass under the

WAVES 85

object during the interval. Continue the observation until at least 15
well-formed waves have been timed.

9223. Add the elapsed times of the various groups together and divide
the total by the number of waves to obtain the average period.

Example: The observer might make the following observation to
determine the wave period:

Number of Time
Wave group No. well-formed elapsed
waves (seconds)

Average period, . 252 divided by 17= 14.8 seconds

The wave period should be recorded to the nearest second, e.g., as
15 seconds.

9300. WAVE HEIGHT

9310. GENERAL. The height of a wave is the vertical distance
between a crest and the troughs on either side of it (see Fig. 12). The
wave height, as recorded on Form 615-5, is the average of the estimated
heights of the larger, well-formed waves (see $9002).

mre

Figure 12, --Wave length and height.

(1) The wave length (L) is the horizontal distance between successive
crests, or troughs,

(2) The height (H) is the vertical distance between crest and trough,

(3) The wave speed is the distance traveled by a wave in a unit of time,

(4) The period is the interval of time which elapses between the passage of
any two successive crests past a fixed point; that is, each crest ad-
vances one wave length in a time equal to one period. It is the wave
length divided by the wave speed,

86 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

9320. DETERMINATION. In general, the wave height should be esti-
mated from the best available point on the ship that permits the height of
the waves to be compared to the height of the ship. If the observer is free
to move about the vessel, the wave height should be determined in accord-
ance with the following paragraphs.

9321. When the wave length is the same as or less than the length of
the ship, the height of the waves should be observed and estimated from a
low point on the ship, if possible. The point of observation should be chosen
amidships, where the pitching of the vessel is ata minimum. The wave
height should be estimated when the shipison an even keel in the following
manner:

9321.1. The height of the waves from troughto crest may be estimated
against the side of another ship when in company.

9321.2. Look over the side and compare the height of waves with known
points on the side of the ship.

9322. When the wave length is greater than the length of the ship, an
observation may be made as follows:

9322.1. When in a trough of a wave and the ship is on even keel, the
observer may move up and down (if possible) on the ship's structure until
wave crests appear momentarily on a horizontal plain with the height
of the eye. The wave height is then equal to the height of the observer's
eyes above the water line.

9322.2. When in company with another ship and the observer's ship is
on even keel, determine the amount of the observed ship that is obscured
When it is in a trough. The height of the waves may be estimated by
judging the size of the ship and the height of her bridge above the water
line.

9323. When both sea and swell or two systems of swell are present at
the same time, observations will be more difficult. Estimate the higher
system of waves first, then repeat the process for the lower system.

9400. ENTRIES AND CODING OF WAVE DATA ON WBFORM 615-5

9410. GENERAL. Two sections are provided for the entry of wave
data on Form 615-5; one section (grey incolor) is for the entry of "rough"
data, the other section (white in color) is for "smooth" data. Each
section provides for both sea and swell information.

9411. When more inan one wave system can be distinguished at
observation time, the sea wave data will be entered in columns 34-36 and
41-43; swell wave information will be e. tered in columns 37-39 and

WAVES 87

45-47, Enter additional groups, if any, under column 48, ''Remarks"'
(see §1253.1).

9420. DIRECTION (dywdy). Select the code figure from Code Table 4
corresponding to the direction from which the sea waves came and enter
the value in column 34 of Form 615-5. Similarly, the direction of the
swell waves will be entered in column 37,

Code Table 4

SYMBOL d,,d,,.--Direction, in 10's of degrees, FROM which
waves are coming

Code Code
figure Direction figune Direction

Calm. 205° to 2142;

5° to 14°. PAM Ia h2 10) PAPE

Too stor 242: 2292 to. 234°"

25° toa4e. 235° to 244°,

35° to 44°, 245° to 254°.

45° to 54°, 255° to 264°.

55° to 64°. 265° to 274°.

65° to 74°. 275° to 284°,

75° to 84°, 285° to 294°.

85° to 94°, 2952 to 304°,

95° to 104° 305° to 314°.

105° to 114°. 315° to 324°.

Ito toml 242% 325° tOnoose,

1252 to 134°: 335° to 344°.

135° to 144°. 345° to 354°.

145° to 154°. 350° to 4°.

15 52° tomMib42,

W652 ton li42. Waves confused,

175° to 184°. direction indeterminate

185° to 194°.

195° to 204°. Waves confused,
direction indeterminate,
but higher than
14 feet (4-1/2 meters).

664508 O - 62-7

88 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

9421. When the directions of the sea and swell waves have been entered
in columns 34 and 37 and the wave heights are less than 15 feet, the di-
rections will be entered similarly in column 41 for sea and column 45 for
swell.

9421.1. If the wave height for either sea or swell is above 15 feet,
50 will be added to the coded wave direction, e.g., the direction of the sea
coming from 320° with a height of 20 feet would be entered in column 34
as 32 and in column 41 as 82 (32 + 50).

9430. PERIOD (P,,). Enter the period of the sea waves in seconds
directly in column 35 and the period of swell waves in column 38.

9431. Select the code figure from Code Table 17 corresponding to the
average sea wave period incolumn 35 andenter the coded figure in column 42.

9432. Select the code figures from Code Table 17 corresponding to the
average swell wave period in column 38 and enter the coded figure in column 46.

Code Table 17
SYMBOL P,,. --Period of waves

Period

5 seconds or less.
6 to 7 seconds.

8 to 9 seconds.

10 to 11 seconds.
12 to 13 seconds.
14 to 15 seconds.
16 to 17 seconds.
18 to 19 seconds.
20 to 21 seconds.
Over 21 seconds.
Calm, or period indeterminate.

2
3
4
H)
6
7
8
9
0
1
x

9440. HEIGHT (H,,). Enter the height of the sea waves in half meter
units directly in column 36 and the height of the swell waves in column 39.
That is, for a height of 9 feet (3 meters) there will be 3 x 2 or 6 one-half
meter units and the value 6 will be entered in the appropriate column.
These correspond to the values found in Code Table 18.

9441. Select the code value from Code Table 18 corresponding to the
average sea wave height and enter it in column 43,

9442. Select the code value from Code Table 18 corresponding to the
average swell wave height and enter it in column 47.

0
1
2
3
4
5
6
8
9
x

ODN DURWNH OC

WAVES 89

Code Table 18
SYMBOL Hy. --Height of waves

Less than 1 foot (1/4 meter).

1-1/2 feet (1/2 meter).

3 feet (1 meter).

5 feet (1-1/2 meters).

6-1/2 feet (2 meters).

8 feet (2-1/2 meters).

9-1/2 feet (3 meters).

11 feet (3-1/2 meters).

13 feet (4 meters).

14 feet (4-1/2 meters).

Height impossible to determine.

(When 50 is added to dydy the height
of waves is as follows):

16 feet (5 meters).

17-1/2 feet (5-1/2 meters).

19 feet (6 meters).

21 feet (6-1/2 meters).

22-1/2 feet (7 meters).

24 feet (7-1/2 meters).

25-1/2 feet (8 meters).

27 feet (8-1/2 meters).

29 feet (9 meters).

30-1/2 feet (9-1/2 meters).

Height impossible to determine.

Each code figure except ''zero'' covers a range of 1/2 meter;
e.g., code figure 1 = 1/4 meter to 3/4 meter, code figure
2 = 3/4 meter to 1-1/4 meters.

If the wave height is exactly between the heights corresponding
to two code figures, the lower code figure is reported.

For wave heights greater than 31 feet (9-3/4 meters), the
code figure 9 for 30-1/2 feet (9-1/2 meters) is reported,
followed by the words "SEA WAVES" or "SWELL WAVES"
and the actual height of the waves in feet or meters; e.g.,
"SEA WAVES" or "SWELL WAVES 37" depending on whether
sea or swell waves are greater than 30-1/2 feet.

90 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

9450. WAVE GROUP. The symbols for the direction (dyd,,), period
(Pw), and height (Hy) of the waves combine to form the wave group
"IdywdwPwHwy,'' where "1" is the group indicator.

Example: The coded wave group ''12768" is decoded as follows:

il Group indicator.

27 Waves are coming from the west (270°).
6 Wave period of 12 to 13 seconds.
8 Wave height of 13 feet.

9451. When more than one wave system is observed, code each system
separately:

Example: The coded wave groups '12939 and 12157" are decoded as
follows:

(a) Sea waves group:

1 Group indicator.

29 The sea is from 290°.
3 Period of sea waves is 6 seconds.
2 Height of sea waves is 14 feet.

(b) Swell group:

1 Group indicator,

2 Swell direction is from 210°.
5 Period of swell is 10 seconds.
7 Height of swell is 12 feet.

9452. When the sea is CALM, or when no waves are present, the wave
group is coded (100X0) as follows:

(a) Calm sea.

i Group indicator.
00 Calm, wind direction indeterminate.

x Period of waves calm, or indeterminate.
0 Height of waves less than 1 foot.

a

CHAPTER X. ICE

CONTENTS
Genet alligi., chiat f face SiGe sre ae Oe ee pe) EE ae Say Sea caver ais! Se ei
EC CROOSCE VALIONN. 6. lS stee ba 9's aes 2S be we See Be ee we we, ee
Ge nencal ens cites) oo neyo ysh ey ee hs) stents, Cate cree oe ap eae tcl ence eee cneeece
ISSTET CI CL UC CR aren excepto toa to ene ye oe eu ee muses ea et OS cgee ee ee
Beane - Distance, and Onientation. « ..0 <.« <0. <)enelesse 6 aes
Coding and Entry of Ice Data on Form 615-5................
MEETS Thal epee asia) ep ee es oy os evanal Woe 4nd wGeiews eh et etacisit arco Gr wee es UE eet
STIG UE oa pee tetee ue Gi vse yi tite che AO ie oh ae ap ae ce a, etl
eitectton INavicatton. (IX). 4 <a. 6 «ats 4.0.4 7 bg sree Swed
earimexorice-teumit(Ds)e gion 6 anaes a eats a eo oie Fae ee A
Distance to Ice-Limit from Reporting Ship (r)............
Orientation of Ice=Limit (ec) >. 24446 aw eae eee ee nee eas
PGPOrtine ICEDELESs wis ace aye ek a Se oe ewe wwe ee eS
ECS CEGOUD te Suse less ao: owe ne oe we le ew lee oe se ae
CODE TABLES
Code Table lo. —-=Symbol c9-—Description of Kind of Ice. 7. ....;
Code Table 20. --Symbol K--Effect of Ice on Navigation........
@Code Table 212 —=Symbol D;=-Bearing of Ice=Limit . ....<. 54.4:

Code Table 22. --Symbol r--Distance to Ice from Reporting Ship. .
Code Table 23. --Symbol e--Orientation of Ice-Limit..........

oil

95
95
96
97
98

93

CHAPTER X. ICE
10000. GENERAL

10010. The presence of ice at sea, including icebergs, is recorded as
part of the weather observation on Form 615-5 when ice is visible, or has
been observed at a point within adistance of 30 miles from the ship's position
at the time of the weather observation.

10020. The reporting of icebergs or sea-ice in connection with the
weather report is not to take the place of the reporting of sea-ice and ice-
bergs according to the International Convention for the Safety of Life at Sea.
Reports requested by the United States Hydrographic Office, Coast Guard,
etc., will be submitted in addition to the weather report.

10100. ICE OBSERVATION

10110. GENERAL. The ice observation includes determination of the
kind of ice, the effect of the ice on navigation, the bearing of the ice-limit,
the distance to the ice-limit, and the orientation of the ice-limit.

10120. KIND OF ICE. Ice is observed in terms of the most important
or prominent of the following conditions:

10121. Ice-blink. When observed, determine the bearing of the blink.
Ice-blink is the white or yellowish-white glare on the sky produced by the
reflection of considerable areas of sea-ice or land-ice, which may be beyond
the range of vision.

10122. New-Ice. A general term which includes the following types:

10122.1. Ice-crystals (frazil-crystals) are fine spicules or plates of ice
suspended in water.

10122.2. Slush (sludge) is an accumulation of ice-crystals which remain
Separate or only slightly frozen together. It forms a thin layer and gives
the sea surface a grayish or leaden-tinted color. With light winds no ripples
appear,

10122.3, Pancake-ice is composed of pieces of newly formed ice, usually
approximately circular, about 30 cm. (11.8 in.) to 3 m. (9.84 ft.) across,
and with raised rims, due to the pieces striking against each other, as the
result of wind and swell.

10122.4,. Ice-rind is a thin, elastic, shining crust of ice, formed by the
freezing of slush (sludge) on a quiet sea surface. Thickness less than

94 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

5 cm. (1.97 in.), It is easily broken by wind or swell, and makes a tinkling
noise when passed through by a ship.

10123. Fast-Ice. Observe whether the amount is unusually great (heavy).
Fast-ice is a sea-ice which remains fast, generally in the position where
originally formed, and which may attain a considerable thickness. It is
found along coasts, where it is attached tothe shore, or over shoals, where it
may be held in position by islands, grounded icebergs or grounded polar-ice.
Subdivisions are Winter fast-ice and Polar fast-ice.

10124, Drift-Ice. Observe whether -the amount is unusually great (heavy).
Drift-ice (Pack-ice) is a term used in a wide sense to include any area of
sea-ice, other than fast-ice, no matter what form it takes or how disposed.

10125. Packed (compact) slush, or packed strips of hummocked-ice.
Note that this condition involves drift-ice (pack-ice), and more than that,
the condition of the ice being packed intoa compact mass, under the influence
of wind, swell, or current. When hummocked-ice is run together in the
foregoing manner to form a long narrow area of pack-ice, about 1 km.
(0.54 nautical mile) or less in width, it is also termed a strip (stream or
string).

10126. Presence of leads near the shore. A lead (lane) is a navigable
passage through drift-ice. It may be sonamedeven if covered with young-ice.

10127. Hummocked ice. Hummocked ice refers to ice piled haphazardly,
one piece over another.

10128. Ice jamming. This term refers to the action of ice that is being
squeezed or crowded together into a compact mass.

10129. Icebergs. An iceberg is a large mass of floating or stranded
ice, more than 5 m,. (16.4 ft.) above sea level, which has broken away
either from a glacier or from a shelf-ice formation.

10130. BEARING, DISTANCE, AND ORIENTATION. When ice is present,
estimate the distance to the nearest part of the ice (ice-limit) and determine
the bearing to 8 points of the compass. When the ice-field is so arranged
that a fairly definite edge is seen, determine the orientation of the nearest
edge, i.e., whether the edge lies in a northeast to southwest direction, etc.

10200. CODING AND ENTRY OF ICE DATA ON FORM 615-5

10210. GENERAL. Ice observed at sea is coded and entered on Form
615-5 in 'Remarks,."

10220. KIND (c9). Select the code figure from Code Table 19 that most
nearly corresponds with the predominant kind of ice observed, and enter the
figure in the ''Remarks" column.

ICE 95

Code Table 19
SYMBOL co. --Description of kind of ice.

Code
figure Description

No ice. (''0'' will be used to report "Ice blink, "
and then a direction must be reported. )

New ice.

Fast ice.

Pack ice/drift ice.

Packed (compact) slush or sludge.

Shore lead.

Heavy fast ice.

Heavy pack ice/drift ice.

Hummocked ice.

Icebergs.

DCOANDoUrhWNH

10230. EFFECT ON NAVIGATION (K). Select the code figure from
Table 20 that most accurately describes the effect of the ice on navigation,
and enter the figure in "Remarks" after cy (§10220).

Code Table 20
SYMBOL K. --Effect of ice on navigation

Code
figure Description

Navigation unobstructed.

Navigation unobstructed for steamers; difficult
for sailing ships.

Navigation difficult for low-powered steamers;
closed to sailing ships.

Navigation possible only for powerful steamers.

Navigation possible only for steamers constructed
to withstand ice pressure.

Navigation possible with the assistance of
icebreakers.

Channel open in the solid ice.

Navigation temporarily closed.

Navigation closed.

Navigation conditions unknown (e.g., owing to

bad weather).

96 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

10240. BEARING OF ICE-LIMIT (Dj). Select the code figure from Code
Table 21 corresponding to the bearing ofthe nearest part of the ice, and enter
the figure in ''Remarks" after 'K''(§10230). Ifan ice-blink was recorded under
"Kind (cg), '' report the bearing of the blink. When more than one area of
ice is observed, record code figure '9" unless one area is of outstanding im-
portance to navigation, in which case the bearing of the ice-limit for that area
only will be recorded.

Code Table 21

SYMBOL D. --Bearing of ice-limit

No ice limit can be stated.

Ice limit towards NE.

Ice limit towards E.

Ice limit towards SE.

Ice limit towards S.

Ice limit towards SW.

Ice limit towards W.

Ice limit towards NW.

Ice limit towards N.

Ice limit in several directions.

Code
figure

DOONDUKhWNH CO fe

NOTE. --If more than 1 ice limit can be stated, the nearest or most
important is reported.

ICE 97

10250. DISTANCE TO ICE-LIMIT FROM REPORTING SHIP (r). Select
the code figure from Code Table 22 corresponding to the distance from the
ship to the edge of the ice (bearing given as Dj), and enter the figure in
"Remarks" after ''Dj" (J10240).

Code Table 22

SYMBOL r. --Distance to ice-limit from reporting ship.

Distance

Up tov! mule:

1 to 2 miles.

2 to 4 miles.

4 to 6 miles.

6 to 8 miles.

8 to 12 miles.

12 to 16 miles.

16 to 20 miles.

More than 20 miles.
Unspecified or no observations.

0
1
2
3
4
5
6
7
8
9

Note. --If the exact bounding distance for the ice limit corresponds to
2 code figures, the lower code figure is reported.

98 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

10260. ORIENTATION OF ICE-LIMIT (e). Select the code figure from
Code Table 23 corresponding to the orientation of the edge of the ice (the
same edge as reported in Dj; and r), and enter the figure in ''Remarks"
after '"'r'' (§10250).

Code Table 23

SYMBOL e. --Orientation of ice-limit

Orientation of ice-limit

Orientation of ice-limit impossible to estimate--ship
outside the ice.

Ice-edge lying in a direction NE. to SW. with ice
situated to the NW.

Ice-edge lying in a direction E. to W. with ice situated
to the northward.

Ice-edge lying in a direction SE. to NW. with ice
situated to the NE.

Ice-edge lying in a direction S. to N. with ice situated
to the eastward.

Ice-edge lying in a direction SW. to NE. with ice
situated to the SE.

Ice-edge lying in a direction W. to E. with ice situated
to the southward.

Ice-edge lying in a direction NW. to SE. with ice
situated to the SW.

Ice-edge lying in a direction N. to S. with ice situated
to the westward.

Orientation of ice-limit impossible to estimate --ship
inside the ice.

ICE 99

10270. REPORTING ICEBERGS. When icebergs are observed, record
their size and height above the sea in the column headed ''Remarks."

10280. ICE GROUP. The symbols for the kind (co), effect (K), bearing
(D;), distance (r), and orientation (e) of the ice combine to form the ice
group "ICEcyKDjre," where "ICE" is the group indicator.

Example: The coded group "ICE 10423" is decoded as follows:

ICE Group indicator.

1 New ice present.

0 Navigation unobstructed.

4 Ice- limit toward south.

2 Ice-limit 2 to 4 miles away (south).

3 Ice-limit lying in a direction SE. to NW. with the
ice situated to the NE.

+33

101

CODE TABLES

Code Table No. Page
I tSyVAaalfoyoul 3 SIDE Colt qdlals WWI 5 Bo Hen Ges. g nes bsdoG oo Go coe 102
Zee yinbol @r-i@ctant onthe: Globei. a ewsiere cnc a ns sack Oz
3 Symbol N - Fraction of the Celestial Dome Covered by

ClOUGS att ao HS men enc omen earn icy wre s</neet aie chee New ena 102
Symbol Nj - Fraction of Celestial Dome Covered by
Type of Cloud Reported for Cy (or Cy)) iS Gs Perce eee 102
4 Symbol dd - True Direction from Which Wind is Blowing. . 103
Symbol dd, - Direction from Which Waves Come...... 103
MES VIVOO ls Va i VESUDULIE Vora oe 8! oes can Viton Gite ow er ha ee al Bee tene a 103
CR OVInbOl Wwe resent Wicabhet wa-i ie. susie emsmeicee! scheme omens 104
i jayMabol W = Past Weather. & .. Grd. ale eae tens Apel miareccmbaens 106
o ~oymbol PPP = Corrected Barometric Pressure .. 2: «4. 107
9 Symbol Cy; - Clouds of Types Stratocumulus, Stratus,
(Chehanpwillns etaiol (Cibbaakbilyoyautianoeles. 5 455555 00 bu eo a oe 108
10 Symbol Cy - Clouds of Types Altocumulus, Altostratus,
Onde NimMbOSEPALUS? (2 %o26. a salad ado. So de, Siesta oe Be enol ae 109
11 Symbol Cy, - Clouds of Types Cirrus, Cirrostratus, and
Gshereofe, shoe hit: Pau eee a ee ace ea eee a ar oe 110
12 Symbolh - Height of Base of Lowest Cy, ( or Cy) Cloud
PMD OWE FOC Arete aiken Geiyacic as Seas Oemevete os Shee cue ates ee op eee Et
Loe oyviMnboO) Wa-— ship's COUPSe: e.6 opie oe dm ieee ea sa ean italal
Ife Symbols. = Snip S. Speed. 20. 65 wie era aloe oS ree ye © s ila tal
15 Symbol a - Barometer Change Characteristics in the Last
SHOU Se ae eRe lee Sa: Asa al 2m doyet ioe ows tbe ge ae aware ens 112
16 Symbol pp - A-- ck ot Barometric Change in Last 3 Hours 113
ieee ye Ol tre ee rrOd Ol WAVES 2 a0. i a)al ist Siete) ae ee 114
iGmoympon Hun HeEToht Ol Waves? on 2s.) ee > 9 G2 8 suas 114
i eaymbol ¢5 = Description of Kind of Ice 2. 2). ssw - = we 115
20> oymmbol K = Eiteet of Ice on Navigation. .....%2 22.5.5. 115
21 Symbol D; = bearing Ol PcG =Lamit. 2s es ee ea eae ene ee 115
22 Symbol r - Distance to Ice from Reporting Ship........ 116
20) oymbole = Orientation of Ice—Limit. . 40% 266 os e266 116
MISCELLANEOUS TABLES
Table No.
24 Celsius (Centigrade to Fahrenheit Temperatures....... 117
Zoe heIMmperature o: Dew Poimt in Degrees Celsius... 2... =< 119
ZG stianrenheit tO Celsius Temperatures 2 sss es aa fe es 127
27 Correction of Mercurial Barometer for Temperature .... 129
28 Reduction of Barometric Reading to Mean Sea Level..... 130
29 Reduction of Mercurial Barometer to Standard Gravity... 130
ZO eOV eters: sO. WiGtHbAts: 4. 41s soc ae ane 2 os ws Oa Baw Se 130
JU @=Code sionals (Selected) oi aucun. kh 4.003 oa wee es BO a iLSyal

102 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 1

SymroLt Y.— Day of the week

Code
Day figure

RVULTT CS yt ate er ate ee
Monda yeas 5 en eee
Muesday eon 22a Ss le Seen eae
Wednesda y2a 2225 eee ee eee

NOoupwnre

CODE TABLE 2
SymMBoL Q.—Octant of the globe

Longitude ae

North latitude:

O° 8Wiito 902 Wile se ae 0

O0SMW.to 180 ce Wines 1

180° Es to'90° B_-__-_-=__-____ 74

O022H tol lsh ae eee eee 3
South latitude:

0° W. to 90° W_____--_-----.-.- 5

902° Wa. to? 18023 Wiles = eee 6

18O0S he toL90e Wes ee eee eee = E 7

OOSSE StolOSs beeen ee = ee ees ee 8 |

CODE TABLE 3
SymBot N—Fraction of the celestial dome covered by clouds

SymBou N,—Fraction of celestial dome covered by type of
cloud reported for Cy (or Cy if no Cy cloud present)

Cloud amount
Code | (eighths of sky
8 covered)
0 None
1 1]
32 2
3 3
4 4
5 5
6 6
“f 27
8 8
9 Sky obscured 3

Notes.—(1) ‘‘Fragments of clouds’ are coded as 1.
(2) “Overcast but with openings” is coded as 7. (3) Sky
obscured by fog, rain, snow, smoke or other phenomena
or obstruction except clouds, or cloud amount cannot
be estimated.

Sympou dd.—True direction,

TABLES

CODE TABLE 4

in 10's of degrees, FROM which wind is blowing (00-86)

SymBou dydy.— Direction, in 10’s of degrees, FROM which waves are coming

01 5° to 14°.

02 15° to 24°.
03 25° to 34°.
04 35° to 44°.
05 45° to 54°.
06 55° to 64°.
07 65° to 74°.
08 75° to 84°.
09 85° to 94°.
10 95° to 104°.
11 105° to 114°.
12 115° to 124°.
13 125° to 134°.
14 135° to 144°.
15 145° to 154°.
16 155° to 164°.
17 165° to 174°.
18 | 175° to 184°.

sie Direction i ae Direction
00 Calm. 19 185° to 194°.

20 195° to 204°.
21 205° to 214°.
22 215° to 224°.
23 225° to 234°.
24 235° to 244°.
25 245° to 254°.
26 255° to 264°.
27 265° to 274°.
28 275° to 284°.
29 285° to 294°.
30 295° to 304°.
31 305° to 314°.
32 315° to 324°.
33 325° to 334°.
34 335° to 344°.
35 345° to 354°.
36 355° to 4°.

Used only with d,d,

terminate.

49 Waves confused, direction inde- 99

Waves confused, _ direction
indeterminate, but
higher than 14 feet (4%
meters).

Norte.—In case the true wind speed exceeds 99 knots, 50 will be added to ‘‘dd’”’ and only

the wind speed in excess of 100
and speed =121 knots, the wind

knots will be coded.
will be coded as ‘‘6621”’ (dd=16+50; ff=121—100).

CODE TABLE 5
Symrot VV.—Vistbility

Visibility range!

Less than 50 yards (50 meters).

50 yards (50 meters).

200 yards (200 meters).

¥ nautical mile (500 meters).

¥ nautical mile (1,000 meters).

1 nautical mile (2,000 meters).

2 nautical miles (4,000 meters).

5 nautical miles (10 kilometers).

10 nautical miles (20 kilometers).

25 nautical miles (50 kilometers) or more.

For example, if the direction= 163°

664508 O - 62-8

1. In case the observed visibility is between two
of the distances given in the table, the code figure
for the lesser distance will be reported, e. g., when
the visibility is between 50 and 200 yards, code the
visibility as 91.

103

104 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 6

Symbol ww—Present weather
ww=00-49 NO PRECIPITATION AT THE STATION AT THE TIME OF OBSERVATION

00-19: No PRECIPITATION, FOG, 1CE FOG, DUSTSTORM, SANDSTORM, DRIFTING OR
BLOWING SNOW AT THE STATION (OR SHIP) AT THE TIME OF OBSERVATION,
EXCEPT FOR 09 AND 17, OR DURING THE PRECEDING HOUR.

00 Cloud development not observed
01 Clouds generally dissolving or becoming less| Characteristic change of
developed the state of sky during

02 State of sky on the whole unchanged the past hour.

03 Clouds generally forming or developing

04 Visibility reduced by smoke, e.g., from veldt or forest fires, industrial

smoke, or volcanic ashes.

05 Haze.

Widespread dust in suspension in the air, not raised by wind at or near

the station (or ship) at the time of observation.

07 Dust or sand raised by wind at or near the station (or ship) at the time

of observation, but no well developed dust whirl(s) or sand whirl(s)

and no duststorm or sandstorm seen..

08 Well developed dust whirl(s) or sand whirl(s) seen at or near the station

(or ship) within last hour, but no duststorm or sandstorm.

09 Duststorm or sandstorm within sight of station (or ship) or at station

(or ship) at time of observation or during the last hour.

10 Light fog, visibility 1,000 meters (1,100 yards) or more.

11 Patches of___)Shallow fog or ice fog at the station (or ship) not deeper

12 More or less| than about 2 meters (6% feet) on land or 10 meters
continuous (33 feet) at sea (visibility less than 1,000 meters (1,100

yards)).

13 Lightning visible, ho thunder heard.

14 Precipitation within sight, but not reaching ground or surface of the sea.

15 Precipitation within sight, reaching ground or surface of the sea, but
distant [i.e., estimated to be more than 5 kilometers (3 miles) from
station (or ship)].

16 Precipitation within sight, reaching ground or surface of the sea, near to
but not at the station (or ship).

17 Thunderstorm, but no precipitation at the time of observation.

18 Squall(s) lab sight during the past

19 Funnel cloud(s)* (tornado or waterspout)f hour.

20-29: PRECIPITATION, FOG oR ICE FoG OR THUNDERSTORM AT THE STATION
(OR SHIP) DURING THE PRECEDING HOUR BUT NOT aT THE TIME OF
OBSERVATION.

20 Drizzle (not freezing) or snow grains

21 Rain (not freezing)

22 Snow not falling as showers.
23 Rain and snow or ice pellets. (See fig. 79.)

24 Freezing drizzle or freezing rain

25 Shower(s) of rain.

26 Shower(s) of snow, or of rain and snow.

27 Shower(s) of hail, or of hail and rain.

28 Fog or ice fog (visibility less than 1,000 meters (1,100 yards)).

29 Thunderstorm (with or without precipitation).

30-39: DustTsToRM, SANDSTORM OR DRIFTING OR BLOWING snow.

30 Slight or moderate duststorm or
sandstorm

31 Slight or moderate duststorm pane appreciable change during the pre-
sandstorm ceding hour.

32 Slight or moderate duststorm gees begun or increased during the pre-

Haze, dust, sand or smoke. See note 2.
Ss
rod

\has decreased during the preceding hour.

sandstorm ceding hour.
33 Revere uc taborm oThas decreased during the preceding hour.
34 Se eee orlkno appreciable change during preceding hour.
ae Bevorn dustetonn ortnas begun or increased during the preceding hour.

36 Slight or moderate drifting pacha aes ar snow 10 meters (33 ft.) or be-
37 Heavy drifting snow low at sea.
38 Slight or moderate blowing aad areas snow above 10 meters (33 ft.)
39 Heavy blowing snow at sea.
40-49: Foc oR ICE FOG AT THE TIME OF OBSERVATION (visibility less than 1,000
meters (1,100 yards)).
40 Fog or ice fog at a distance at the time of observation, but not at the
station (or ship) during the last hour, the fog extending to a level above
that of the observer.

TABLES 105

41 Fog or ice fog in patches.

42 Fog or ice fog, sky discernible hare become thinner during the preced-
43 Fog or ice fog, sky not discerniblef ing hour.

44 Fog or ice fog, sky discernible as appreciable change during the pre-
45 Fogor ice fog, sky not discernibleJ ceding hour.

46 Fog or ice fog, sky discernible tae begun or has become thicker during
47 Fog orice fog, sky not discerniblef the preceding hour.

48 Fog, depositing rime, sky discernible.

49 Fog, depositing rime, sky not discernible.

50-59 PRECIPITATION AT THE STATION (OR SHIP) AT THE TIME OF OBSERVATION

50-59: DrizzLE AT TIME OF OBSERVATION.
50 Drizzle, not freezing, intermittent
51 Drizzle, not freezing, continuous
52 Drizzle, not freezing, intermittent
53 Drizzle, not freezing, continuous
54 Drizzle, not freezing, intermittent
55 Drizzle, not freezing, continuous
56 Drizzle, freezing, slight.

57 Drizzle, freezing, moderate or heavy (dense).
58 Drizzle and rain, slight.
59 Drizzle and rain, moderate or heavy.

60-69: RAIN AT TIME OF OBSERVATION.

60 Rain, not freezing, intermittent
61 Rain, not freezing, continuous
62 Rain, not freezing, intermittent
63 Rain, not freezing, continuous
64 Rain, not freezing, intermittent
65 Rain, not freezing, continuous
66 Rain, freezing, slight.

67 Rain, freezing, moderate or heavy.

68 Rain or drizzle and snow, slight.

69 Rain or drizzle and snow, moderate or heavy.

70-79: SoLID PRECIPITATION NOT IN SHOWERS AT TIME OF OBSERVATION.
70 Intermittent fall of snowflakes
71 Continuous fall of snowflakes
72 Intermittent fall of snowflakes
73 Continuous fall of snowflakes
74 Intermittent fall of snowflakes
75 Continuous fall of snowflakes
76 Ice prisms (with or without fog).

77 Snow grains (with or without fog).

78 Isolated starlike snow crystals (with or without fog).

79 ioe pellets (i.e., frozen raindrops or largely melted and refrozen snow-
akes).

80-99: SHOWERY PRECIPITATION, OR PRECIPITATION WITH CURRENT OR RECENT

THUNDERSTORM.

80 Rain shower(s), slight.

81 Rain shower(s), moderate or heavy.

82 Rain shower(s), violent.

83 Shower(s) of rain and snow mixed, slight.

84 Shower(s).of rain and snow mixed, moderate or heavy.

85 Snow shower(s), slight.

86 Snow shower(s), moderate or heavy.

87 Shower(s) of snow pellets or ice pellets* with or without rain on light
rain and snow mixed SAN

88 Shower(s) of snow pellets or ice pellets* with or with-
out rain or rain and snow mixed

89 Shower(s) of hail with or without rain or rain and snow mixed, light
not associated with thunder Sayer

90 Shower(s) of hail, with or without rain or rain and
snow mixed, not associated with thunder

91 Slight rain at time of observation

92 Moderate or heavy rain at time of observation

93 Slight snow or rain and snow mixed or hail*
at time of observation

94 Moderate or heavy snow, or rain and snow
mixed or hail* at time of observation

95 Thunderstorm, slight or moderate, without hail
but with rain and/or snow at time of observation

96 Thunderstorm, slight or moderate, with hail* at
time of observation ‘

97 Thunderstorm, heavy, without hail* but with rain thunderstorm at time
and/or snow at time of observation of observation.

**98 Thunderstorm combined with duststorm or sand-

storm—at time of observation

99 Thunderstorm, heavy, with hail* at time of observation

\slight at time of observation.
\moderate at time of observation.

}neavy (dense) at time of observation.

}stight at time of observation.
\moderate at time of observation.

}neavy at time of observation.

\slight at time of observation.
}moderate at time of observation.

\heavy at time of observation.

}moderate or heavy.

}moderate or heavy.

thunderstorm during the
preceding hour but not
at time of observation

*Hail, ice pellets, i.e., pellets of snow encased in a thin layer of ice: snow pellets.
**In reporting code figure 98, the observer is allowed considerable latitude in the presumption that pre-
cipitation is or is not occurring if it is not actually visible.

106

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 7

Symbol W—Past weather

Description

Cloud covering ¥ or less of the sky through-
out period.

Snow or rain and snow mixed or ice pellets.
Shower(s).
Thunderstorm(s) with or without precipitation

1 Cloud covering more than 4 of sky during
part of period, and less than % during part
of period.

2 Cloud covering more than % of sky through
out period.

3 Sandstorm or duststorm or blowing snow.

4 Fog or ice fog or thick haze.

5 Drizzle.

6 Rain. k

7

8

)

Notes

1. In 0000, 0600, 1200 and 1800 G. C. T. reports ‘‘Past Weather’’ covers the
preceding 6-hour period while in 0300, 0900, 1500, and 2100 G. C. T. reports, ‘‘W”’
covers the preceding 3-hour period.

2. The code figure for ‘‘W”’ is selected in order that ‘‘W”’ and ‘‘ww’”’ together
give as complete a description as possible of the weather in the time interval
concerned. For example, if the type of weather undergoes a complete change
during the time interval concerned, the code figure selected for ‘‘W”’ will describe
the weather prevailing before the type of weather indicated by ‘“‘ww” began. If
however more than one code figure may be given to W with regard to past weather,
the higher code figure is reported.

TABLES

CODE TABLE 8

SymBoLt PPP.—Corrected barometer reading

(Code in “‘tens,”’ ‘‘units,’’ and “‘tenths” of millibars, omit initial 9 or 10}

1 inch=33.86395 mb. 1 mb.=0.02952993 inch] !

|

in. mb. in. mb. in. mb, in. mb.

27. 50! 931. 3] 28.00 948. 2] 28. 50) 965. 1) 29. 00! 982. 1
27. 51) 931. 6] 28. 01) 948. 5] 28. 51) 965. 5} 29. 01; 982. 4
27. 52) 931. 9) 28. 02, 948. 9) 28. 52) 965. 8) 29. 02) 982. 7
27. 53| 932. 3] 28. 03) 949. 2] 28. 53] 966. 1) 29. 03) 983. 1
27. 54| 932. 6] 28. 04 949. 5] 28. 54) 966. 5) 29. 04) 983. 4
27. 55) 933. 0] 28. 05) 949. 9} 28. 55) 966. 8] 29. 05) 983. 7
27. 56) 933. 3] 28. 06 950. 2} 28. 56) 967. 2] 29. 06) 984. 1
27. 57| 933. 6} 28. 07; 950. 6] 28. 57| 967. 5] 29. 07) 984. 4
27. 58) 934. 0} 28. 08) 950. 9] 28. 58) 967. 8] 29. 08) 984. 8
27. 59) 934. 3] 28. 09) 951. 2} 28. 59) 968. 2] 29. 09) 885. 1
27. 60 934. 6] 28. 10) 951. 6} 28. 60) 968. 5] 29. 10] 985. 4
27. 61' 935. 0} 28. 11) 951. 9} 28. 61) 968. 8] 29. 11) 985. 8
27. 62; 935. 3) 28. 12) 952. 3] 28. 62) 969. 2) 29. 12) 986. 1
27. 63, 935. 7) 28. 13) 952. 6] 28. 63) 969. 5} 29. 13) 986. 5
27. 64| 936. 0] 28. 14) 952. 9] 28. 64] 969. 9} 29. 14! 986. 8
27. 65 936. 3] 28. 15] 953. 3] 28. 65) 970. 2) 29. 15) 987. 1
27. 66 936. 7} 28. 16) 953. 6] 28. 66) 970. 5) 29. 16) 987. 5
27. 67 937. 0} 28. 17] 953. 9] 28. 67| 970. 9} 29. 17) 987. 8
27. 68 937. 4] 28. 18) 954. 3] 28. 68] 971. 2) 29. 18) 988. 2
27. 69| 937. 7] 28. 19] 954. 6] 28. 69] 971. 6] 29. 19] 988. 5
27. 70| 938. O} 28. 20] 955. O} 28. 70} 971. 9] 29. 20) 988. 8
27. 71 938. 4] 28. 21) 955. 3} 28. 71) 972. 2} 29. 21) 989. 2
27. 72 938. 7| 28. 22) 955. 6] 28. 72) 972. 6] 29. 22) 989. 5
27. 73 939. 0} 28. 23] 956. 0} 28. 73) 972. 9] 29. 23) 989. 8
27. 74 939. 4) 28. 24) 956. 3] 28. 74) 973. 2] 29. 24) 990. 2
27. 75, 939. 7| 28. 25) 956. 7] 28. 75) 973. 6] 29. 25] 990. 5
27. 76 940. 1] 28. 26) 957. 0} 28. 76) 973. 9] 29. 26) 990. 9
27. 77 940. 4] 28. 27| 957. 3} 28. 77| 974. 3] 29. 27) 991. 2
27. 78 940. 7] 28. 28) 957. 7| 28. 78] 974. 6] 29. 28) 991. 5
27. 79| 941. 1] 28. 29] 958. O| 28. 79] 974. 9] 29. 29) 991. 9
27. 80 941. 4] 28. 30) 958. 3} 28. 80) 975. 3] 29. 30) 992. 2
27. 81 941. 8] 28. 31] 958. 7} 28. 81] 975. 6] 29. 31) 992. 6
27. 82 942. 1} 28. 32) 959. 0} 28. 82) 976. O} 29. 32) 992. 9
27. 83 942. 4] 28. 33) 959. 4] 28. 83] 976. 3] 29. 33] 993. 2
27. 84 942. 8} 28. 34] 959. 7| 28. 84] 976. 6] 29. 34) 993. 6
27. 85 943. 1} 28. 35} 960. 0] 28. 85] 977. 0] 29. 35) 993. 9
27. 86, 943. 4] 28. 36) 960. 4] 28. 86] 977. 3] 29. 36) 994. 2
27. 87| 943. 8| 28. 37) 960. 7| 28. 87| 977. 7} 29. 37) 994. 6
27. 88 944. 1] 28. 38) 961. 1] 28. 88} 978. 0} 29. 38) 994. 9
27. 89 944. 5} 28. 39) 961. 4| 28. 89] 978. 3] 29. 39) 995. 3
27. 90) 944. 8] 28. 40} 961. 7) 28. 90} 978. 7] 29. 40) 995. 6
27. 91) 945. 1) 28. 41) 962. 1) 28. 91) 979. 0} 29. 41) 995. 9
27. 92) 945. 5) 28. 42) 962. 4] 28. 92) 979. 3] 29. 42) 996. 3
27. 93) 945. 8] 28. 43) 962. 8] 28. 93] 979. 7] 29. 43) 996. 6
27. 94| 946, 2] 28. 44) 963. 1] 28. 94) 980. 0] 29. 44) 997. 0
27. 95) 946. 5] 28. 45) 963. 4] 28. 95) 980. 4] 29. 45] 997. 3
27. 96) 946. 8] 28. 46) 963. 8} 28. 96} 980. 7] 29. 46) 997. 6
27. 97, 947. 2] 28. 47 964. 1] 28. 97| 981. 0} 29. 47) 998. 0
27. 98 947. 5] 28. 48 964. 4] 28. 98 981. 4] 29. 48 998. 3
27. 99) 947. 9] 28. 49 964. 8] 28. 99) 981. 7] 29. 49) 998. 6

. 50
. 51
. 52)
. 53
. 54
. 55
. 56
. 57
. 58
. 59

. 61
. 62
. 63

. 67,
. 68)
. 69)

ZO
La
es
. 73
. 74
. 75
. 76)
eee
. 78)
A}

. 80
. 81
. 82
. 83
. 84
. 85)
. 86
. 87
. &8)
b iste]

. 90
OW
. 92
. 93
. 94
. 95

. 98

999.

his)

999!
1000.
1000.
1000.
1001.
1001.
1001.
1002.

. 60/1002.
1002.
1003.
1003.
. 64/1003.
. 65/1004.
. 66 1004.
1004.
1005.
1005.

1005.
1006.
1006.
1006.
1007.
1007.
1007.
1008.
1008.
1008.

1009.
1009.
1009.
1010.
1010.
1010.
1011.
1011.
1011.
1012.

1012.
1012.
1013.
1013.
1013.
1014.
. 96 1014.
. 971014.
1015.
. 99)1015.

ANOANOCUNO NOON WON wUre

COMH ONO RHO Pewee AR OTR ONWOAWO

. 39

. 40
. 41

. 47
. 48
. 49

mb,

1015.
1016.
1016.
1016.
1017.
1017.
1018.
1018.
1018.
1019.

1019.
1019.
1020.
1020.
1020.
1021.
1021.
1021.
1022.
/1022.

|1022.
|1023.
1023.
1023.
1024.
1024.
1024.
1025.
1025.
1025.

1026.
1026.
1026.
1027.
1027.
1027.
1028.
1028.
1028.
1029.

1029.
1029.
1030.
1030.
1030.
1031.
1031.
1031.
1032.
1032.

NRE NRONFON RPRONWONWOODW ASDAWOMWOAWSO

HOO PH OO RH CORE

Orbs 00 Ord 00 Ore Or

in.

| mb.

in.

. 60
. 61
. 62
. 63
. 64
. 65
. 66
. 67
. 68
. 69

. 70
gal
. 72
. 73]
. 74
. 75]
. 76
tad
. 78
. 79

. 80
. 81

. 82!
. 83
. 84
. 85

. 87
. 88
. 89

. 90
. 91
. 92
. 93
. 94
. 95
. 96
BASIC
. 98
. 99

. 50
. 51
. 52
. 53 |
. 54
. 55)
. 56
. 57,
. 58
. 59

86

' Based on standard gravity of 980.665 cm./sec.?

1032.
1033.
1033.
1033.
1034.
1034.
1034.
1035,
1035.
1035.

1036.
1036.
1036.
1037.
1037.
1037.
1038.
1038.
1038
1039.

1039.
1040.
1040.
1040.
1041.
1041.
1041.
1042.
1042.
1042.

1043.
1043.
1043.
1044.
1044,
1044.

1045.

1045.
1045.
1046.

1046.
1046.
1047.
1047.
1047.
1048.
1048.
1048.
1049.
1049.

On SCOnNoanNnoaws

eNPONRONWO NWONWORDWODM WODWORAWS

Ore! CO ee OO Re

|
. 00)
01
. 02
. 03
. 04
. 05|
. 06
. 07|
. 08)
09

. 10
polka
. 12)
wld
.14
-15
a6
wlle4
. 18
» It]

. 20
Al
. 22
Bes
. 24
me
. 26
nad
. 28
. 29)

. 80
. 31

hoe
. 33
. 34
. 35
. 86
. 37
. 88
. 39

. 40
41
42
. 43
44
45
- 46)
47
48
49

107

mb.

1049.
1050
1050.
1050.
1051.
1051,
1051.
1052.
1052.
1052

1053.
1053.
1053.
1054.
1054.
1054.
1055.
1055. }
1055.
1056,

1056.
1056,
1057.
1057.
1057.
1058.
1058.
1058.
1059.
1059.

1059.
1060.
1060.
1061.
1061.
1061.
1062.
1062.
1062.
1063.

1063.
1063.
1064.
1064.
1064.
1065.
1065.
1065.
1066.
1066.

DWN Wor — 00 Or 00

tw

Nounmoenw rie

RONRONWONW ONWAOMWODWH lore e)

108 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

ures

CODE TABLE 9

Symbol C,—Clouds of types Stratocumulus, Stratus, Cumulus,

and Cumulonimbus

Technical language specifications

Plain language specifications

No Gr. cloudsS === === =a

Cumulus humilis, or Cumulus
fractus other than of bad
weather, or both.

Cumulus mediocris or congestus,
with or without Cumulus of
species fractus or humili§, or
Stratocumulus; all having their
bases at the same level.

Cumulonimbus calvus, with or
without Cumulus, Stratocumu-
lus or Stratus.

Stratocumulus cumulogenitus_ _ __

Stratocumulus other than Strato-
cumulus cumulogenitus.

Stratus nebulosus or Stratus frac-
tus other than of bad weather,
or both.

Stratus fractus or Cumulus frac-
tus of bad weather or both
(pannus) usually below Alto-
stratus or Nimbostratus.

Cumulus and Stratocumulus,
other than Stratocumulus cu-
mulogenitus, with bases at dif-
ferent levels.

Cumulonimbus capillatus (often
with an anvil), with or without
Cumulonimbus calvus, Cumu-
lus, Stratocumulus, Stratus or
pannus,

Clouds Cy not visible owing to
darkness, fog, blowing dust or
sand, or other similar phe-
nomena.

No Cumulus, Cumulonimbus, Strato-
cumulus or Stratus.

Cumulus with little vertical extent
and seemingly flattened, or ragged
Cumulus other than of bad weather,
or both.

Cumulus of moderate or strong verti-
cal extent generally with protuber-
ances in the form of domes or
towers, either accompanied or not
by other Cumulus or by Strato-
cumulus; all having their bases at
the same level.

Cumulonimbus the summits of which,
at least partially, lack sharp out-
lines, but are neither clearly fibrous
(cirriform), nor in the form of an
anvil; Cumulus, Stratocumulus or
Stratus may be present.

Stratocumulus formed by the spread-
ing out of Cumulus; Cumulus may
also be present.

Stratocumulus not resulting from the
spreading out of Cumulus.

Stratus in a more or less continuous
sheet or layer, or in ragged shreds
or both, but no Stratus fractus of
bad weather.

Stratus fractus of bad weather or
Cumulus fractus of bad weather
or both (pannus) usually below
Altostratus or Nimbostratus.

Cumulus and Stratocumulus, other
than those formed from the spread-
ing out of Cumulus; the base of
Cumulus is at a different level than
that of the Stratocumulus.

Cumulonimbus, the upper part of
which is clearly fibrous (cirriform)
often in the form of an anvil; either
accompanied, or not by Cumulo-
nimbus without anvil or fibrous
upper part, by Cumulus, Strato-
cumulus, Stratus, or pannus.

No Cumulus, Cumulonimbus, Strato-
cumulus or Stratus visible owing to
darkness, fog, blowing dust or
sand, or other similar phenomena.

Note: ‘Bad Weather’ denotes the conditions which generally exist during
precipitation and a short time before and after.

TABLES

CODE TABLE 10

Symbol Cy—Clouds of types Altocumulus, Altostratus, and Nimbostratus

Code
fig-
ures

Technical language specifications

Plain language specifications

No Cm clouds________-----------

Altostratus translucidus__-_____-_-

Altostratus opacus or Nimbo-
stratus.

Altocumulus translucidus at a
single level.

Patches of Altocumulus translu-
cidus (often lenticular), contin-
uously changing and occurring
at one or more levels.

Altocumulus translucidus — in
bands, or one or more layers
of Altocumulus translucidus or
opacus progressively invading
the sky; these Altocumulus
clouds generally thicken as a
whole.

Altocumulus cumulogenitus (or
cumulonimbogenitus).

Altocumulus’translucidus — or
opacus in 2 or more layers, or
Altocumulus opacus in a single
layer, not progressively invad-
ing the sky, or Altocumulus
with Altostratus or Nimbo-
stratus.

Altocumulus castellanus or floc-
cus.

Altocumulus of a chaotic sky,
generally at several levels.

Clouds Cm not visible owing to
darkness, fog, blowing dust or
sand, or other similar phe-
nomena, or because of a con-
tinuous layer of lower clouds.

No Altocumulus, Altcstratus or Nim-
bostratus.

Altostratus, the greater part of which
is semitransparent; through this
part the sun or moon may be
weakly visible as through ground
glass.

Altostratus, the greater part of which
is sufficiently dense to hide the sun
(or moon), or Nimbostratus.

Altocumulus, the greater part of which
is semitransparent; the various
elements of the cloud change only
slowly and are all at a single level.

Patches (often in the form of almonds
or fishes) of Altocumulus, the
greater part of which is semitrans-
parent; the clouds occur at one or
more levels and the elements are
continually changing in appearance.

Semitransparent Altocumulus in
bands or Altocumulus in one or
more fairly continuous layers (semi-
transparent or opaque) progres-
sively invading the sky; these Alto-
cumulus clouds generally thicken
as a whole.

Altocumulus resulting from the
spreading out of Cumulus (or Cu-
mulonimbus).

Altocumulus in two or more layers
usually opaque in places and not
progressively invading the sky; or
opaque layer of Altocumulus not
progressively invading the sky; or
Altocumulus together with Alto-
stratus or Nimbostratus.

Altocumulus with sproutings in the
form of small towers or battle-
ments, or Altocumulus having the
appearance of cumuliform tufts.

Altocumulus of a chaotic sky gen-
erally at several levels.

No Altocumulus, Altostratus or Nim-
bostratus visible owing to darkness,
fog, blowing dust or sand, or other
similar phenomena, or more often
because of the presence of a con-
tinuous layer of lower clouds.

109

110

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 11

Symbol Ca—Clouds of types Cirrus, Cirrostratus, and Cirrocumulus

Code
fig-
ures

Technical language specifications

Plain language specifications

0
i

iw)

INO Cr ClOUdS =a a oes

Cirrus fibratus, sometimes un-
cinus, not progressively invad-
ing the sky.

Cirrus spissatus, in patches or en-
tangled sheaves, which usually
do not increase and sometimes
seem to be the remains of the
upper part of a Cumulonimbus;
or Cirrus castellanus or floccus.

Cirrus spissatus cumulonimbo-
genitus.

Cirrus uncinus, or fibratus, or
both, progressively invading
the sky; they generally thicken
as a whole.

Cirrus, often in bands, and Cirro-
stratus, or Cirrostratus alone,
progressively invading the sky;
they generally thicken as a
whole, but the continuous veil
does not reach 45° above the
horizon.

Cirrus, often in bands, and Cirro-
stratus, or Cirrostratus alone,
progressively invading the sky;
they generally thicken as a
whole, but the continuous veil
extends more than 45° above
the horizon, without the sky
being totally covered.

Cirrostratus covering the whole
sky.

Cirrostratus not progressively in-
vading the sky, and not entirely
covering it.

Cirrocumulus alone, or Cirrocu-
mulus predominant among the
cirriform clouds.

Clouds Cy not visible owing to
darkness, fog, blowing dust or
sand or other similar phenom-
ena, or because of a continuous
layer of lower clouds.

No Cirrus, Cirrostratus or Cirrocu-
mulus,

Cirrus in the form of filaments,
strands or hooks, not progressively
invading the sky.

Dense Cirrus in patches or entangled
sheaves which usually do not in-
crease and sometimes seem to be
the remains of the upper parts of
Cumulonimbus; or Cirrus’ with
sproutings in the form of small tur-
rets or battlements or Cirrus having
the appearance of cumuliform tufts.

Dense Cirrus often in the form of an
anvil, being the remains of the
upper parts of Cumulonimbus.

Cirrus in the form of hooks or fila-
ments or both, progressively invad-
ing the sky; they generally become
denser as a whole.

Cirrus, often in bands converging to-
wards 1 point or 2 opposite points
of the horizon and Cirrostratus, or
Cirrostratus alone; in either case
they are progressively invading the
sky, and generally growing denser
as a whole, but the continuous veil
does not reach 45° above the
horizon.

Cirrus, often in bands converging to-
wards | point or 2 opposite points
of the horizon, and Cirrostratus, or
Cirrostratus alone; in either case
they are progressively invading the
sky, and generally growing denser
as a whole; the continuous veil ex-
tends more than 45° above the
horizon, without the sky being
completely covered.

Veil of Cirrostratus covering the
celestial dome.

Cirrostratus not progressively invad-
ing the sky, and not completely
covering the celestial dome.

Cirrocumulus alone, or Cirrocumulus
accompanied by Cirrus or Cirro-
stratus or both, but Cirrocumulus is
predominant.

No Cirrus, Cirrostratus or Cirrocumu-
lus visible owing to darkness, fog,
blowing dust or sand, or other
similar phenomena, or more often
because of the presence of a con-
tinuous layer of lower clouds.

TABLES 111

CODE TABLE 12

SymBou h.—Height of base of lowest cloud (Cy or Cy) above sea ? 8

ss Height in feet Approximate height in meters
0? QO 149 O- 49. |
1 150— 299 50- 99.
2 300— 599 100— 199
33 600— 999. 200— 299.
4 1000-1999. 300— 599.
5 2,000 to 3,500- 600 to 1,000.
6 | 3,500 to 5,000. 1,000 to 1,500.
7 5,000 to 6,500. 1,500 to 2,000.
8 6,500 to 8,000. 2,000 to 2,500.
9 8,000 or higher or no 2,500 or higher or

clouds.

! For the purpose of the shi
27 When the sky is obscur
otherwise, disregard the obscuring phenomena an

y f
31f the h

NOTES

g.
eight of the cloud base cannot be reported owing to darkness or any reason not covered by Note 2 an X is reported for ‘‘h”’.

no clouds.

code used in this manual (FM 21A), symbol ‘‘h” from WMO Code Table 43 has the meaning shown in this table.
by rain, snow, fog, smoke, or other phenomena so that cloud cannot be observed, ‘‘h’’ is coded as 0 and ‘‘Ny”’ as 9;
code h as observed—e. g., use code figure 9 if no clouds are observable even though half the sky is

CODE TABLE 13

SymBo. D,.—Ship’s course (true) made good in 3 hours preceding the time of observation

Code Code
| figure True course figures True course
0 Ship hove to. 5 SW.
1 NE. 6 W.
2 Ee 7 ae
3 SE. 8 P
4 | S. 9 No information.

CODE TABLE 14

SyMBOL v,.—Ship’s average speed made good during 3 hours preceding the time

of observation

Code Code
figure euced figures Speed
0 Ship stopped. 5 13 to 15 knots.
1 1 to 3 knots. 6 16 to 18 knots.
2 4 to 6 knots. 7 19 to 21 knots.
3 7 to 9 knots. 8 22 to 24 knots.
4 10 to 12 knots. 9 More than 24 knots.

112 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 15

SymBou a.—Barometer change characteristics in the last 3 hours

lower

Code Bags
Trace figures Description
tf 0 Fusing then falling. Barometer the same or higher than
ours ago.
1 Rising, then steady; or rising then rising more slowly.
ae
as 2 Rising, steadWy or unsteadily. Barometer now higher
a 3 aling or steady, then rising; or rising then rising more] than 3 hours ago.
quickly.
me 4 Steady. Barometer the same as 3 hours ago.
Nv 5 Falling, then rising. Barometer the same or lower than 3
hours ago.
6 Falling, then steady; or falling then falling more slowly.
~S Barometer now
XY tf Falling, steadily or unsteadily. than 3 hours ago.
ANY 8 Steady or rising, then falling; or falling, then falling more
quickly.

SYMBOLS "pp" and "ppp. ''--Amount of barometric change

TABLES

Code Table 16

Amount of rise or fall

Code Inches of P Code
figure mercury Millibars figure

00 0. 000 0.0

02 . 005 avd 52
03 . 010 3 54
05 - O15 -5 56
07 . 020 Sef 58
08 . 025 -8 59
10 . 030 1.0 61
12 . 035 1.2 63
14 . 040 1.4 64
15 . 045 1.5 66
17 . 050 Led 68
19 . 055 1.9 69
20 . 060 2.0 71
22 - 065 2.2 73
24 . 070 2.4 75
25 . 075 2.5 76
27 - 080 2.7 78
29 - 085 2.9 80
30 . 090 3. 0 81
32 . 095 3. 2 83
34 . 100 3.4 85
36 - 105 3.6 86
37 - 110 3.7 88
39 115 3.9 90
41 - 120 4.1 91
42 - 125 4.2 93
44 - 130 4.4 95
46 - 135 4.6 97
47 . 140 4.7 98
49 - 145 4.9

51 150 5.1 199

Inches of Code
mercury Millibars figure

iis}
in the last 3 hours
ppp
Inches of | Minibars || code | Inches of | Millibars
100 0. 295 10. 0
0. 155 52 102 . 300 10. 2
160 5.4
165 5. 6 103 . 305 10.3 154 0. 455 15. 4
170 5. 8 105 . 310 10. 5 156 460 15. 6
175 5. 9 107 . 315 10.7 157 465 15. 7
108 . 320 10. 8 159 470 15.9
. 180 6.1 110 . 325 11.0 161 475 16. 1
185 6. 3
190 6. 4 112 . 330 11.2 163 480 16. 3
195 6. 6 113 . 335 11.3 164 485 16. 4
. 200 6.8 115 . 340 11.5 166 490 16. 6
117 . 345 11.7 168 495 16. 8
205 6.9 119 . 350 11.9 169 500 16. 9
210 (hil
215 1633 120 . 355 12.0 171 505 17.1
220 Ups 122 . 360 12. 2 173 510 17.3
228 7.6 124 . 365 12.4 174 515 17.4
125 . 370 1255 176 520 17. 6
230 7.8 127 375 L2N7. 178 525 17.8
235 8.0
°240 8&1 129 . 380 12.9 179 530 17.9
245 8.3 130 . 385 13. 0 181 535 18. 1
250 8.5 132 . 390 ps 4 183 540 18.3
134 . 395 13. 4 185 545 18.5
255 8.6 135 . 400 13. 5 186 550 18. 6
. 260 8.8
265 9.0 137 . 405 13. 7 188 555 18.8
270 9.1 139 . 410 13.9 190 560 19.0
275 9.3 141 - 415 14.1 191 565 19.1
142 . 420 14.2 193 570 19. 3
280 9.5 144 . 425 14.4 195 575 19.5
285 9: 7
290 9.8 146 . 430 14.6 196 580 19. 6
295 10. 0 147 - 435 14. 7 198 585 19.8
300 10. 2 149 . 440 14.9 200 590 20. 0
etc. etc. 151 . 445 15. 1 201 595 20. 1
152 . 450 15. 2 203 600 20. 3

1 When the amount of the barometric pressure change equals or exceeds 9.9 millibars, the group “‘99ppp” should be inserted in the message followin,
the “D,v.eapp” group. The ‘‘99” is the group identifier, and “‘ppp”’ is the total amount of the pressure change (in tens, units, and tenths of millibars,
’'group. Forezample: If the total amount

during the preceding 3 hours. When the group is inserted

. ‘‘99’’ should be reported for ‘“‘pp’’ in the ‘‘ D.vea

of the pressure change is 13.4 millibars, the groups should be coded ‘‘D,v.a99 99134.’ If the amount is 9.9 mili

(“‘D,v.a"’ should be given appropriate valucs.)

ars, the groupsare coded ‘‘D.v.899 99.0099.""

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 17
Symbol P,.—Pervod of waves

Code
figures

5 seconds or less.
6 to 7 seconds.

8 to 9 seconds.

10 to 11 seconds.
12 to 13 seconds.
14 to 15 seconds.
16 to 17 seconds.
18 to 19 seconds.
20 to 21 seconds.
Over 21 seconds.
Calm or period unable to be determined.

eR OOONMUOP HDD

CODE TABLE 18

SymBot H,.—Height of waves

Code

figure Height

Less than 1 foot (% meter).

1% feet (4% meter).

3 feet (1 meter).

5 feet (1% meters).

6% feet (2 meters).

8 feet (2% meters).

9% feet (3 meters).

11 feet (3% meters).

13 feet (4 meters).

14 feet (4% meters).

Height impossible to determine.

(When 50 is added to d,, d., the height
of waves is as follows):

16 feet (5 meters).

1714 feet (514 meters).

19 feet (6 meters).

21 feet (6% meters).

22% feet (7 meters).

24 feet (7% meters).

2514 feet (8 meters).

27 feet (814 meters).

29 feet (9 meters).

30% feet (9% meters).
Height impossible to determine.

Notes

Mh ODNAURWNHHO

OWONBWUIPLWNHr OS

ta

1. Each code figure except ‘‘zero’”’ covers a range of
¥% meter: e. g., code figure 1=% meter to % meter, code
figure 2=% meter to 1% meters.

2. If the wave height is exactly between the heights
corresponding to two code figures, the lower code fig-
ure is reported.

3. For wave heights greater than 31 feet (9% meters)
the code figure for 30% feet (914 meters) is reported
followed by the word ‘‘WAVES” and the actual height
of the waves in feet or meters; e. g., ““WAVES 37.”

TABLES HEIRS)

CODE TABLE 19

SYMBOL ¢).— Description of kind of ice

sae Description
) Noice. (“‘0” will be used to report “ice blink,” and then a direction
must be reported.)
1 New ice.
2 Fast ice.
3 Pack ice/drift ice.
a Packed (compact) slush or sludge.
5 Shore lead.
6 Heavy fast ice.
7 Heavy pack ice/drift ice.
8 Hummocked ice.
9 | Icebergs.

CODE TABLE 20

Sympou K.—Effect of ice on navigation

Code

figures Description

Navigation unobstructed.

Navigation unobstructed for steamers;
difficult for sailing ships.

Navigation difficult for low-powered
steamers; closed to sailing ships.

Navigation possible only for powerful
steamers.

Navigation possible only for steamers
constructed to withstand ice pressure.

Navigation possible with the assistance

| of icebreakers.

Channel open in the solid ice.
Navigation temporarily closed.
Navigation closed.

Navigation conditions unknown (e. g.,
owing to bad weather).

=

COND w Be WwW bw

CODE TABLE 21

Sympot D;.—Bearing of ice-limit

|
Code

figure Description

No ice limit can be stated.
Ice-limit toward NE.
Ice-limit toward E.

Ice-limit toward SE.
Ice-limit toward 8S.

Ice-limit toward SW.
Ice-limit toward W.

Ice-limit toward NW.
Ice-limit toward N.

Ice-limit in several directions.

OW-IDNRWN—O

|
|
|

Nore.—If more than one ice-limit can be stated,
the nearest or most important is reported.

116 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

CODE TABLE 22

SymBot r.—Distance to ice-limit Jrom reporting ship

cae Distance
0 0 to 1 mile.
1 1 to 2 miles.
2 2 to 4 miles.
3 4 to 6 miles.
4 6 to 8 miles.
5 8 to 12 miles.
6 12 to 16 miles.
o | 16 to 20 miles.
8 More than 20 miles.
9 Unspecified or no observations.

Nore.—lIf the exact bounding distance for the ice-
limit corresponds to two code figures, the lower code
figure is reported.

CODE TABLE 23

SymBou e.—Orientation of ice-limit

Orientation of ice-limit

0 Orientation of ice-limit impossible to
estimate—ship outside the ice.

1 Ice-edge lying in a direction NE to
SW with ice situated to the NW.
Ice-edge lying in a direction E to W

with ice situated to the northward.
Ice-edge lying in a direction SE to
NW with ice situated to the NE.
Ice-edge lying in a direction S to N
with ice situated to the eastward.
Ice-edge lying in a direction SW to
NE with ice situated to the SE.
Ice-edge lying in a direction W to E
with ice situated to the southward.
Ice-edge lying in a direction NW to
SE with ice situated to the SW.
Ice-edge lying in a direction N to 8
with ice situated to the westward.
Orientation of ice-limit impossible to

estimate—ship inside the ice.

co monn oon +, WO WD

TABLES

TABLE 24.—Celsius (centigrade) to Fahrenheit temperatures

alent

1

cc: 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

°F. SFA °F AF ee oF. cr. oF. °F. oF; che
+45 [4113.0 |+113. 2 |+113. 4 |+113.5 |+113. 7] 4113.9 | +114.1 |} +114.3 | +114. 4 |+114.6
44 111.2 111.4 111.6 A 7 111.9 112.1 112.3 112.5 112. 6 112.8
43 109. 4 109. 6 109. 8 109. 9 110. 1 110. 3 110. 5 110. 7 110. 8 111.0
42 107. 6 107. 8 108. 0 108. 1 108. 3 108. 5 108. 7 108. 9 109. 0 109. 2
41 105. 8 106. 0 106. 2 106. 3 106. 5 106. 7 106. 9 107. 1 107. 2 107. 4
+40 |+104.0 |+104. 2 |+104. 4 |+ 104.5 |+ 104.7 | +104.9 | +105.1 | +105. 3 | +105. 4 |+ 105.6
39 102. 2 102. 4 102. 6 102. 7 102. 9 103. 1 103. 3 103. 5 103. 6 103. 8
38 100. 4 100. 6 100. 8 100. 9 101-1 101.3 101.5 101.7 101.8 102. 0
37 98. 6 98. 8 99. 0 99. 1 99. 3 99. 5 99. 7 99. 9 100.0 | 100. 2
36 96. 8 97.0 97. 2 97.3 97. 5 97.7 97.9 98. 1 98. 2 98. 4
+35 +95.0} +95.2 | +95.4 | +95.5 | +95.7 +95. 9 +96. 1 +96. 3 +96.4 | +96. 6
34 93. 2 93. 4 93. 6 93. 7 93. 9 94.1 94.3 94.5 94.6 94. 8
33 91.4 91.6 91.8 91.9 92.1 92. 3 92. 5 92. 7 92.8 93.0
32 89. 6 89. 8 90. 0 90. 1 90. 3 90. 5 90. 7 90. 9 91.0 91.2
31 87.8 88. 0 88. 2 88.3 88. 5 88. 7 88. 9 89. 1 89. 2 | 89. 4
+ 30 +86.0 |} +86.2 | +86.4 | +86.5 | +86.7 + 86. 9 +87. 1 +87. 3 +87.4 | +87.6
29 84. 2 84. 4 84. 6 84. 7 84.9 85. 1 85. 3 85. 5 85. 6 85. 8
28 82. 4 82. 6 82.8 82.9 83. 1 83. 3 83. 5 83. 7 83. 8 84.0
27 80. 6 80. 8 81.0 81.1 81.3 81.5 81.7 81.9 82.0 82. 2
26 78. 8 79.0 79. 2 79. 3 79. 5 79. 7 79.9 80. 1 80. 2 80. 4
+25 +77.0 | +77.2 | +77.4 |) +77.5 | +77.7 ar Ute) +78. 1 +78. 3 +78.4 | +78.6
24 75. 2 75.4 75. 6 75. 7 75. 9 TAg, al 76.3 76. 5 76. 6 | 76. 8
23 73. 4 73. 6 73. 8 73.9 74. 1 74.3 74.5 74.7 74. 8 | 75. 0
22 (AEG 7i. 8 72.0 72. 1 72. 3 72. 5 72. 7 72.9 73. 0 73. 2
21 69. 8 70. 0 70. 2 70. 3 70. 5 (AWN 6 70.9 Colle al 71. 2 || 71.4
+20 +68.0 | +682] +684] +685 | +687 +68. 9 +69. 1 +69. 3 +69.4 | +69.6
19 66. 2 66. 4 66. 6 66. 7 66. 9 (Veal 67.3 67. 5 67.6 | 67. 8
18 64. 4 64. 6 64.8 64.9 65. 1 65. 3 65. 5 65. 7 65. 8 66. 0
17 62. 6 62. 8 63. 0 63. 1 63. 3 63. 5 63. 7 63. 9 64. 0 | 64. 2
16 60. 8 61.0 61. 2 61.3 61.5 61.7 61.9 62. 1 62. 2 | 62. 4
+15 +59.0] +59.2 | +59.4 | +59.5 | +59.7 +59. 9 +60. 1 +60. 3 +60. 4 | +60. 6
14 57. 2 57. 4 57. 6 57. 7 57.9 58. 1 58. 3 58. 5 58. 6 58. 8
13 55. 4 55. 6 55. 8 55. 9 56. 1 56. 3 56. 5 56. 7 56. 8 57.0
12 53. 6 53. 8 54. 0 54. 1 54. 3 54. 5 54. 7 54. 9 55. 0 55. 2
11 51.8 52. 0 52. 2 52. 3 52. 5 52.7 52.9 53. 1 53. 2 53. 4
+10 +50.0 | +50.2 | +50.4 | +50.5 | +50.7 +50. 9 sols 1 +51.3 +51.4 | +51.6
9 48. 2 48.4 48.6 48.7 48.9 49. 1 49. 3 49.5 49. 6 49.8
8 46. 4 46. 6 46.8 46. 9 47.1 47. 3 47.5 47.7 47. 8 48.0
7 44.6 44.8 45. 0 45. 1 45. 3 45.5 45.7 45.9 46. 0 46. 2
6 42.8 43 0 43. 2 43.3 43.5 43.7 43.9 44.1 44.2 44.4
+5 +41.0} +41.2 | +41.4 ] +41.5 | +417 +41.9 +42. 1 +42. 3 +42.4 | +42.6
4 39. 2 39. 4 39. 6 39. 7 39. 9 40. 1 40. 3 40.5 40. 6 40. 8
3 37.4 37. 6 37. 8 37.9 38. 1 38. 3 38. 5 38. 7 38.8 39. 0
2 35. 6 35. 8 36. 0 36. 1 36. 3 36.5 36. 7 36. 9 37.0 | 37. 2
1 33. 8 34. 0 34. 2 34.3 34.5 34.7 34.9 35. 1 35. 2 35. 4
0 32.0 32. 2 32. 4 32.5 32.7 32. 9 33. 1 | 33. 3 33. 4 33. 6

u |

Lal:

I

|
COUNAPM PWWHO

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TABLE 24.—Celsius (centigrade) to Fahrenheit temperatures—Continued

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Pde a oF: yo °F. ee ky oe Woe pls
+31.8 |+31.6 |431.5 |+31.3 +o. 1 +30.9 |+30.7 +30. 6 +30. 4
30. 0 29. 8 29. 7 29. 5 29. 3 29. 1 28.9 28. 8 28. 6
28. 2 28.0 27.9 27.7 27.5 27.3 27.1 27.0 26.8
26. 4 26. 2 26. 1 25. 9 25. 7 25. 5 25. 3 25. 2 25. 0
24. 6 24. 4 24.3 24,1 23. 9 23.7 23. 5 23. 4 23. 2
+22.8 |4+22.6 |4+22.5 |+22.3 +22. 1 +21.9 |421.7 +21.6 +21. 4
21.0 20. 8 20. 7 20. 5 20. 3 20. 1 19.9 19. 8 19. 6
19. 2 19.0 18.9 18. 7 18.5 18. 3 18. 1 18.0 17.8
17,4 17. 2 Vie 16. 9 16.7 16.5 16. 3 16. 2 16.0
15. 6 15. 4 15. 3 15. 1 14.9 14.7 14.5 14.4 14. 2
+13.8 |413.6 |+13.5 |+13.3 +13. 1 +12.9 |412.7 +12. 6 +12. 4
12.0 11.8 abe ¢f 11.5 11.3 11.1 10. 9 10. 8 10. 6
10. 2 10. 0 ong 9.7 9.5 9.3 Or 9.0 8.8
8. 4 8. 2 8.1 bY) Weak 7.5 7.3 7.2 7.0
6. 6 6. 4 6. 3 6. 1 5. 9 5.7 5.5 5. 4 5. 2
+4.8 46 +45 +43 Sea +3.9 +3.7 +3. 6 +3. 4
+3.0 +2. 8 apeh tf +2.5 +2.3 +2. 1 ie lao +1.8 =16
12 12.0 aes) +0.7 +0.5 +0.3 =O —On0) —0. 2
=O (ec —OnS AY ie E58} nO =k af las —2.0
—2.4 —2.6. | —2.7 —2.9 hal —3.3 —3.5 —3.6 —3.8
—4,2 —4.4 —45 Sth Aa) —5.1 —5.3 —5.4 —5.6
6. 0 6. 2 6. 3 6.5 6. 7 6. 9 (bal 7. 2 7.4
7.8 8.0 8.1 8.3 8.5 8.7 8.9 9.0 9. 2
6) 9.8 9.9 10. 1 10. 3 10. 5 10. 7 10. 8 110
11.4 11.6 17 11.9 12. 1 12.3 12.5 12. 6 12.8
—13.2 |—13.4 |—13.5 |—13.7 —13.9 —14.1 |-143 —14.4 —14.6
15.0 15, 2 15. 3 15.5 15.7 15.9 16. 1 16. 2 16. 4
16. 8 17.0 ly ak 17.3 17.5 We 17.9 18.0 18. 2
18. 6 18.8 18. 9 eral 19. 3 19.5 1 ON 19.8 20. 0
20. 4 20. 6 20. 7 20. 9 21.1 21.3 21.5 21. 6 21.8
— 22. 2 22.4 22.5 22.7 — 22.9 —23.1 |—23.3 — 23. 4 — 23. 6
24.0 24.2 24.3 24. 5 24. 7 24.9 25. 1 25, 2 25. 4
25. 8 26.0 26. 1 26. 3 26. 5 26. 7 26.9 27.0 27. 2
27. 6 27.8 27.9 28. 1 28. 3 28.5 28. 7 28.8 29. 0
29. 4 29. 6 29. 7 29.9 30. 1 30. 3 30. 5 30. 6 30. 8
—31.2 |—31.4 |—31.5 |—31.7 —31.9 —32.1 |—32.3 — 32. 4 — 32. 6
33. 0 33. 2 33. 3 33. 5 33. 7 33. 9 34. 1 34. 2 34. 4
34.8 35. 0 35. 1 35. 3 35. 5 35. 7 35. 9 36. 0 36. 2
36. 6 36. 8 36. 9 37. 1 37. 3 37.5 37.7 37.8 38. 0
38. 4 38. 6 38. 7 38. 9 39. 1 39. 3 39. 5 39. 6 39. 8
40, 2 40.4 |—40.5 |—40.7 — 40.9 —41.1 |—41.3 —41.4 — 41.6
42.0 42.2 42.3 42.5 42.7 42.9 43. 1 43. 2 43. 4
43. 8 44.0 44. 1 44.3 44.5 44.7 44.9 45. 0 45, 2
45. 6 45. 8 45.9 46. 1 46. 3 46.5 46. 7 46. 8 47.0
47. 4 47. 6 47.7 47.9 48. 1 48. 3 48.5 48. 6 48. 8

TABLES Lally,

TABLE 25.— Temperature of the dew point in degrees Celsius
(Tabular values are dew points with respect to water ]

Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

0.0) 0.1) 0.2) 0.3 |;0.4/0.5/0.6)0.7/0.8/0.9)1.0]1.1]1.2)1.3)1.4]1.5]1.6)1.7/1.8)1.9

. OF —33) —35) —37} —40)—44/—51

— 22) —22| —23| —24)—25)— 26|— 27|— 28)— 29|—30|—32|—34|— 36|— 38] — 41|— 46
231 22 23 23|— 24| — 25] — 26] — 27| — 28] — 29] — 31]— 32] — 34] — 36] — 39| — 42) — 48

21 21 22 23} — 23] — 24) — 25) — 26] — 27) — 28] — 30/— 31] — 33] — 34] —37| — 39) — 43] —49
—20| —21| —21| —22)/—23)—24|—24|— 25)— 26|— 27|— 28]— 30|—31|—33|—35|—37|— 40|}— 44/— 50
— 20} —20 21 21|— 22] — 23) — 24| — 25] — 25|— 26] — 27/— 29] — 30] —31| —33]—35|— 37| — 40] — 44/51
—19) —20) —20) —21)—21|—22)—23|— 24|— 25|— 25] — 26|— 27| — 29|—30)—31|—33]—35|—37|—40|— 44
—18) —19} —20) —20/—21|—21|—22)—23)— 24|— 25|— 25|— 26] — 27| — 29] 30] —31|— 33] —35|—37|— 40
—18} —18} —19| —20|—20)—21|—21]—22)— 23) — 24| — 25|— 25) — 26|— 27| — 29] —30| —31|—33|— 35|— 37
—17; —18) —18) —19/—20)—20/—21|— 21] — 22|— 23] — 24|— 24) — 25| — 26| — 27| — 28] 30| —31|— 33] —35

Ng) algd) alts) 18] — 19] — 19] — 20) — 21] — 21] — 22) — 23] — 24| — 24|— 25| — 26) — 27/28) —30|—31|—33
—16| —17) —17) —18|—18|/—19|—19|—20|—21|— 21) —22|— 23) — 23)}— 24|— 25|— 26|— 27|— 28 — 29|— 31
—16) —16) —17} —17/—18]/—18/—19/—19]—20}—20|—21]|— 22)— 22|— 23] — 24|— 25] — 26|— 27|— 28|— 29
Wo — Lo 16 UG} 14 17) —= 1318) =19|—20| 20 |= 21 = 22 |= 22|— 23 | — 24 — 2 5|— 26 |— 2728

— 14 14 15 15|—16}— 16|—17|—17|—18/—18|—19|— 19} — 20] — 20)— 21| — 22| — 22|— 23) —24|— 25
ay} Saale! 14 15) 15) —-16| 16) 16 | = 14 4 = 18/18! 19|— 20/20! — 21 = 21 | 22) 2324

13 13 14 14)—14)—15|—15)— 16) —16|—17|—17|—18]—18]—19/—19|— 20} — 20|— 21) — 22)—22
— 12) 13) =13) —13|— 14|—14|—15|—15| —15|— 16] —16|—17| —17|—18|—18|— 19] — 19) —20|—21|\— 21
—12) —12} —13] —13/—13/—14)/—14]—14)—15|—15|— 16]— 16|—17|—17|;—18|—18/—19]— 19] 20|— 20

|
iw)
i)
|
bo
w
|
to
css
|
bo
on
|
Li)
ez)
|
bo
i
|
bo
oo
|
bo
©
|
w
S
|
w
to
|
Ww
wo
|
w
ao
|
w
Qo
|
rs
-
|
rs
oO

lil) iy 12 12) = 13) >13|= 13 |= 14|— 14)\— 14) — 15) 15|—16|— 16|—17|— 1 7|— 18) = 18) 191 — 9
= 1) ad ual 12 | 2) 3 | 3 | 3) 4a 4) 1) 15 | 5G) 16) — 174 7 | 18s
= 10) — 10) 0 2) 2 — 2 13) 13 ||— 13 |= 14 | — 14) 15) 5 — 15 | — 16|— 16 | 4

10 10 10 10) —11)—11}—11) —12)— 12] —12/—13|—13|/—14)—14|14|—15|—15)— 16; 16|—16
—9} —9} —10); —10)—10)—10)—11]—11}—11]—12)—12|—12|—13]—13/—14/— 14|—14;—15|— 15|]—16

0

9.5

9.0

5

0

.5| —8} —9| —9| —9|—10/—10|—10]/—10|—11/—11/—11|—12|—12|—12|—13]—13]—13|—14/—14|—15
.o| —8| —s8| —8| —9} —9} —9/—10/—10/—10/—10|—11]—11)—11/—12|—12]/—12/—13|—13/—13|—14
. 5] —7/ —8| —8} —s| —8| —9| —9| —9| —9/—10/—10/—10|—11]—11/—11]—12/—12/—12|—13/—13
.0o| —7}/ —7| —7} —8| —8| —8} —8| —9| —9] —9| —9/—10|—10|—10)/—11]—11]—11/—11]—12/-12
. 5] —6| —6| —7/ —7| —7| —7| —8| —8} —8| —8} —9| —9} —9|—10|/—10/—10/—10/—11]—11/-11
.o| —6| —6| —6| —6] —7| —7| —7| —7} —8| —8| —8] —8} —9| —9| —9]} —9/—10/—10)—-10/—11
.5| —5| —5| —6| —6] —6| —6| —6| —7| —7| —7| —7| —8| —8| —8| —8| —9| —9] —9] —9/—-10
.0o| —5| —5| —5| —5| —5| —6] -6| —6| —6| —7/ —7| —7/ —7| —7| —8} —8| —8] —8| —9] —9
5} —4) —4| —4) —5| —5| —5| —5| —5]/ —6| —6| —6] —6] —7) —7| —7| —7} —7| —8| —8| —8
of —3}| —4| —4} —a| —4] —4] —5] —5] —5] —5) —5! —6] —6| —6| —6| —7| —7| —7| —7] —8
5} —3| —3/ —3] —3| —4| —4] —4] —4] —4] —5] —5! —5]} —5| —5| —6| —6] —6) —6| —7| —7
oj} —2) —2| —3)/ —3] —3] —3} —3] —4] —4} —4] —4] —4] —5] —5| —5] —5| —5] —6] —6] —6
5] —2) —2| —2| —2} —2) —3/ —3] —3/ —3] —3| —4! —4] —4] —4| —4] —5] —5] —5] —5] —5
oj —1) —1/ —2) —2| —2| —2} —2) —2) —3/ —3/ —3}) —3] —3] —3| —4} —4] —4] —4] —4] —5
. 51 —1] —1) —1} —11 —1] —1] —2| —2} —2| —al —al —2| —3/ —3] —3| —3] —3| —4] —4] —4

664508 O - 62-9

120 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TABLE 25.— Temperature of the dew point in degrees Celsitus—Continued
{Tabular values are dew points with respect to water]

Wet- Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)
bulb
tem-
pera-
ae 0.0); 01)02) 03 )0.4/0.5)0.6/0.7/ 0.8/0.9) 1. 0]/1.1]1.2]1.3]1.4)1.5/1.6]1.7)/1 8/19
(2C)
0. 0} 0 0 Oo} —1) —1) —-1) -1 1 1 1 2 2 2 2} —2| —2) —3] —3} —3) —3
0.5 1 0 0 0 0 0 0} —1} —1} —1} —l} —1] —1} —2} —2} —2) —2) —2]) —2) —3
120 1 1 1 1 0 0 0 0 0 0 1 1 1 1 1 1} —1) —2| —2) —2
eo 2 1 1 1 1 1 1 1 0 0 0 0 0 0} —1) —1) —1) —1) —-1] —-1
2.0 2 2 2 2 2 1 1 1 1 1 1 1 0 0 0 0 0 0) —1; -—1
2. § 3 2 2 2 2 2 2 2 1 1 1 1 1 1 1 0 0 0 0 0
3. 0 3 3 3 3 3 2 2 2 2 2 2 2 1 1 1 il 1 1 1 0
3.5 4 3 3 3 3 3 a 3 3 2 2 2 2 2 2 2 1 1 1 il
4.0 4 4 4 4 4 3 3 3 3 3 3 3 3 2 2 2 2 2 2 2
4.5 5 4 4 4 4 4 4 4 4 3 3 3 3 3 3 3 3 2 2 2
5. 0) 5 5 5 5 5 4 4 4 4 4 4 4 4 4 3 3 3 3 3 3
5. 5) 6 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 3 3
6. 0) 6 6 6 6 6 6 5 5 5 5 5 5 5 i) 5 4 4 4 4 4
6. 5 ff 6 6 6 6 6 6 6 6 6 6 5 5 5 5 5 5 5 5 5
7. 0 7 7 di di Gi 7 6 6 6 6 6 6 6 6 6 6 5 5 5 5
73 8 qi Ul 7 i 7 i u 7 7 7 6 6 6 6 6 6 6 6 6
8.0 8 8 8 8 8 8 a 7 iC 7 {| if 7 (4 7 7 i 6 6 6
8. 5 9 8 8 8 8 8 8 8 8 8 8 8 A @ 1 7 7 7 7 Lf
9. 0 9 9 9 9 9 9 9 8 8 8 8 8 8 8 8 8 8 8 i 7
9.5 10 9 9 9 9 9 9 9 9 9 9 9 9 8 8 8 8 8 8 8
10. 0 10 10 10 10} 10; 10} 10 9 9 9 9 9 9 9 9 9 9 9 9 8
10. 5 i 10 10 10} 10; 10) 10; 10; 10) 10; 10) 10; 10 9 9 9 9 9 9 9
11.0 1 11 ita 11; 11; 11; 11} 10} 10) 10) 410; 10) 10; 10) 410; 410) 10) #410} 10) #10
11. 5 12 11 1a 11) 11) 11{ 11) 11) 11) 11) 11) 11) 121) 11) 10) 10} 10) 10) 10) 10
12. 0 12 12 2 12)) 12) 22) 12) Lah TT) 1D) 0) 1) 2) a) 1)
12.5 13 12 12 12; 12) 12) 12) 12) 12) 12) 2) 12) 12) 12) 2) a ae
13. 0 IS 13 13 13] 13) 13) 13) 13; 12) 12) 12) 12) 12) 12) 12) 12) 12) 12) 12) 12
13.5 14 13 13 13; 13} 13) 13] 13] 13) 18) 13] 13) 138) 13) 13) 13; 412) 12) 12) #12
14. 0 14 14 14 14, 14 14 14 14) #14) 13) 13) 13) 13) 13) 13) 13) 13) 13) 13) 138
14. 5 15 14 14 14, 14; 14 #14) #14| #14) #14) #14] #14) #14) #14) #14) #14) #14) #13) #13) 13
15. 0 15 15 15 15} 15) 15) 15) 15) 15) 14) 14) #14) #14) #14) #14) #14) #14) #14) #14) #14
15. 5 16 15 15 15} 15) 15) 15) 15) 15) 15 15) 15) 15) 15) 15) 15) 15) 14) 14) 14
16. 0 16 16 16 16) 16] 16; 16) 16; 16) 16; 15) 15} 15) 15) 15) 15) 15) 15) 15) 15
16. 5 ily 16 16 16| 16) 16) 16) 16] 16; 16; 16; 16] 16) 16) 16] 16) 16; 16) 15) 15
17.0 ily 17 iy/ 17; 17) 17; #17; #17; #17) #17; #16] 16; 16) 16) 16} 16) 16) 16) 16) 16
17.5 18 17 17 1d Vib 4 ies Bed a Bd a Ud Ed Eid hed Vs fd Pa bd Fe Ed a yA I Ed Rs Ee at bed 1K)
18. 0 18 18 18 18} 18} 18) 18) 18) 18) 18} 18) 17) 17) #17; #17) #17; #17] #17) #17) «+417
18. 5 19 18 18 18; 18} 18) 18) 18) 18) 18 18) 18} 18) 18) 18 18) 18} 18 18) 18
19. 0 19 19 19 19) 19) 19) 19) 19) 19} 19) 19) 18} 18 18) 18; 18} 18} 18 18 18
19. 5 20 20 19 19} 19) 19) 19) 19) 19) 19) 19) 19) 19) 19} 19) 19) 19; 19) 19) 19
20. 0} 20 20 20 20} 20) 20} 20) 20) 20; 20) 20] 20; 19) 19) 19) 19) 19) 19) 19} 19
20. 5) 21 21 20 20; 20) 20) 20) 20) 20; 20; 20) 20) 20/) 20) 20] 20; 20; 20} 20; 20
21.0 21 21 21 21; 21) 21) 21) 21); 21) 21] 21] 21] 21]; 20] 20) 20) 20} 20) 20) 20
21.5 22 22 21 21; 21) 21) 21) 21) 21) 21) 21] 21) 21) 21) 21) 21) 21) 21) 21), 21
22. 0 22 22 22 22} 22) 22) 22) 22) 22) 22) 22) 22) 22) 21) 21); 21) 21) 21] 21) 21
22.0 23 23 22 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22
23..0 23 23 23 23) 23) 23) 23) 23) 23) 23) 23) 23) 23) 23) 22) 22) 22) 22) 22) 22
23. 5 24 24 23 23] 23) 23) 23) 23) 23) 23) 23] 23) 23) 23) 23) 23) 23) 23) 23) 23
24. 0 24 24 24 24; 24) 24) 24) 24) 24) 24) 24) 24) 24) 24] 24) 23) 23) 23) 23) 23
24. 5) 25 25 24 24; 24) 24) 24) 24) 24) 24) 24) 24) 24) 24) 24) 24) 24) 24) 24) 24
25. 0 25 25 25 25) 25) 25) 25) 25) 25) 25) 25) 25) 25) 25) 25) 24) 24) 24) 24) 24
25. 5 26 26 25 25; 25) 25) 25) 25) 25) 25) 25] 25) 25) 25) 25) 25) 25) 25) 25) 25
26. 0 26 26 26 26} 26) 26; 26) 26) 26) 26) 26] 26) 26) 26) 26) 26) 25) 25) 25) 25
26. 5) 27 Pah 26 26} 26) 26; 26) 26] 26; 26) 26] 26) 26) 26) 26) 26) 26) 26) 26) 26
27. 0 27 27 27 27| 27| 27| 27| 27) 27) 27| 27] 27) 27| 27) 27) 27) 27) 26) 26) 26
27. 5 28 28 26 27| 27| 27) 27| 27| 27) 27) 27) 27| 27) 27) 27) 27) 27) 27 27) 27
28. 0 28 28 28 28} 28) 28) 28) 28) 28) 28] 28] 28) 28) 28] 28) 28) 28) 28) 27) 27
28. 5) 29 29 28 28) 28) 28! 28) 28) 28) 28) 28) 28) 28) 28) 28) 28) 28 28) 28) 28
29. 0 29 29 29 29; 29) 29) 29) 29) 29} 29) 29] 29) 29} 29] 29) 29) 29) 29) 29) 28
29. 5 30 30 29 29 291 291 29! 29! 29! 291 291 29] 29) 29! 29] 29! 29], 29] 29) 29

TABLES 121

TABLE 25.—Temperature of the dew point in degrees Celsius—Continued
[Tabular values are dew points with respect to water]

Wet- Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

bulb

tem-

pera-

ate 00/01);02)]03/)04/0.5/0.6/0.7/0.8)0.9]1.0]1.1)1.2)1.3]1.4)1.5)1.6/1.7])1.8/1.9

(°C.)
30. 0 30 30 30 30} 30; 30) 30) 30; 30) 30 30} 30) 30) 30) 30) 30) 30} 30} 30
30. 5 31 31 30 30} 30} 30] 30) 30) 30) 30 30} 30} 30) 30) 30) 30; 30) 30) 30
31.0 31 31 31 31; 31} 31) 31) 31) 31] 31 31) 31} 31) 31) 31) 31) 31) 31) 31
31.5 32 32 31 31) 3} 32) 31) 31) 31) 31 31; 31] 31) 31) 31) 31) 31) 31) 31
32. 0 32 32 32 32! 32) 32] 32) 32) 32) 32 32) 32) 32) 32) 32) 32) 32! 32) 32
32. 5 33 33 33 S2ieeo2| O2eeos|) o2|eeo2| eos 32) 32) 32) 32) 32) 32) 32) 32) 32
33. 0 33 33 33 33] 33) 33) 33) 33) 33) 33 33] 33] 33) 33) 33) 33] 33) 33) 33
33. 5 34 34 34 33} 33] 33) 33) 33) 33] 33 33] 33} 33) 33) 33) 33] 33) 33) 33
34. 0 34 34 34 34) 34) 34! 34] 34) 34) 34 34; 34) 34) 34) 34] 34) 34) 34) 34
34.5 35 35 35 34) 34) 34] 34] 34) 34) 34 34; 34] 34) 34) 34; 34) 34) 34! 34
35. 0 35 35 35 35] 35} 35) 35) 35} 35) 35 35} 35) 35) 35) 35) 35) 35) 35) 35

Nore.—Table computed by means of Professor Ferrel’s formula; e=e’ —[(t —t’) (KP) (1+0.00095t’)].

122

WOMONNOSOMN PPWWONNE EOS

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TABLE 25—Temperature of the dew point in degrees Celstus—Continued

{Tabular values are dew points with respect to water]

Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

5.0/5. 2/5. 4] 5.6] 5.8/6.0] 6. 2

2.0) 2.2)2.4/2.6/2.8/3.0/3.2/3.4/3.6/3.8/4.0/4.2/4.4/4.6)4 8

= Oil

—44

—40)—51

— 37|— 44

—34|—40)—49

— 32|—36|—42

— 30) —34|—38]— 46

— 29) — 32) —35|—41

— 27) —30|—33]—37|— 43

— 26] — 28] — 30) — 34) —38]—47

— 24] — 26) — 29) — 31] 35] —40)— 51

— 23] — 25] — 27| — 29] — 32) — 36) — 42

— 22) — 24) — 25) — 27| — 30] — 33] —37|— 44

— 21] — 22) — 24) — 26) — 28] — 30) — 34) — 38) — 46

— 20] — 21) — 23) — 24) — 26) — 28) — 31] — 34] — 39] — 48

— 19) — 20) — 21) — 23] — 24) — 26) — 28) — 31] — 35] — 40) —50

— 18]—19]— 20} — 21] — 23] — 24] — 26) — 29] —31| — 35] — 40) 52

—17]—18)—19]— 20] — 21] — 23} — 25] — 26] — 29) —31)—35}—41

— 16)—17/—18]—19]—20|— 21] — 23] — 25] — 26| — 29] — 32/—35)— 41

—15}—16|—17|—18]—19]—20]— 21] — 23] — 25] — 26] — 29] — 31] 35] — 40

—14/—15]—16)—17|—18|—19}— 20)—21]—23|— 24] — 26| —28/—31/—35]—40)—51

—13}]—14]—15]—16]—17/—18/—19]— 20) — 21] — 23) — 24|— 26] — 28] —31|—34|]—39)—49

—12/—13]—14]—15|]—16]—17|—18]—19|—20]—21|— 22/—24|— 26] — 28) — 30) —34| —38|— 47

— 12)—12)—13]—14]—15]—15]—16|—17|—18|—19|—21|—22|— 24] — 25] —27|—30| —33]—37

—11]—12]—12|—13]}—14]—14]—15|—16|—17|—18]— 19) — 20) — 22) — 23) — 25] — 27| — 29] — 32

—10}—11]—11)—12/—13]—13]—14|}—15]—16] —17}—18]—19)—20|—21|— 23) —24|— 26)—28

—9)—10)—10}—11]}—12/—12/—13]—14|—15]—16|—16|/—17|— 18|— 20) —21| —22)—24|— 26

—9) —9]—10}—10}—11}—11]—12|—13]—14]—14|—15]—16|—17]— 18) —19|—20| —22/— 23
8} —8 9 9) — 10] — 11] — 11] —12/—12|—13]—14]—15|— 16) —17/—18}—19/—20)—21

—7| —8| —8} —9} —9}—10]—10)—11]—11]—12|—13]}—14|/— 14|— 15) —16)—17|—18|—19

—6| —7| —7| —8} —8] —9} —9}—10]/—10}—11]—12/—12/—13)—14)—15]—16|—16|—17

—6| —6) —6) —7} —7} —8| —8) —9) —9)/—10)—11}—11]}—12/—13)—13]—14)—15/—16

—5| —5| —6) —6| —7} —7| —8] —8] —9} —9}—10/—10]/—11/—12)—12)/—13/—14/—14

—4| —5) —5| —5} —6) —6) —7} —7| —8] —8} —9} —9/—10}—10)/—11]—12)/—12/—13

—3| —4| —4]) —5) —5| —5} —6) —6] —7| —7| —8} —8| —9) —9/—10)/—10/—11/—12

—3) —3)/ —4} —4| —4| —5) —5) —6) —6} —6) —7| —7| —8} —8 —9}—10)—10)—11

—2;| —3) —3| —3) —4| —4| —4| —5) —5) —6) —6 7 uf 8 8 }) 9) =)

—2) —2) —2) —3! —3) —3 4 4 4 5 5 6; —6| —7| —7| —8 —8| —9

—1)| —1) —2} —2} —2) —3] —3} —3) —4) —4| —5) —5) —5| —6) —6) —7} —7| —8
0} —1) —1} —1} —2] —2) —2} —3) —3) —3] —4| —4) —5) —5} —5) —6] —6 —7
0 0 0} —1} —1} —1} —2) —2} —2) —3} —3] —3) —4]) —4) —5| —5|) —5} —6
1 1 0 0 0 1 ileal 2 2 2 3] —3] —3) —4) —4; —5) —5
2 1 1 1 0 0 oj) —1) —1} —1) —2} —2) —2) —3} —3) —3] —4| —4
2 2 2 1 1 1 0 0 0} —1} —1); —1} —2} —2) —2) —3]) —3) —3
3 2 2 2 2 1 1 il 0 0 oj —1) —1) —1] —1) —2| —2| —3
3 3 3 2 2 2 2 1 1 1 1 0 0 0} —1) —1]; —1| —2
4 4 3 3 3 3 2 2 2 2 1 1 1 0 0 Oe
4 4 4 4 3 3 3 3 2 2 2 2 1 1 1 1 0 0
5 5 5 4 4 4 4 3 3 3 3 2 2 2 1 1 1 1
6 5 5 5 5 4 4 4 4 3 3 3 3 2 2 2 2 1
6 6 6 5 5 5 5 5 4 4 4 4 3 3 3 3 2 2
7 6 6 6 6 6 5 5 5 5 5 4 4 4 4 3 3 3
Uf 7 7 7 6 6 6 6 6 5 5 5 5 4 4 4 4 4
8 8 7 iq 7 rf 7 6 6 6 6 6 5 5 5 5 4 4

— 44
—36|— 42

—31|}—35)—40)—50
— 28] — 30] — 33/—38
— 25|— 27| — 29) —32
— 22) — 24) — 26) 28
— 20| — 22) — 23) — 25
— 18]— 20|—21)—22
—17|/—18)—19)—20
—15)—16)—17/—18
—14]/—15)—15)— 16

—12)/—13)—14)—-15
—11)—12)/—13/—13
—10}—11)—12/—12
—9}—10)—10|—11
—8s —9| —9|/—10

—i7| —8| —8
—6| —7| 7%
— 09) —O6/5—6
—5) —5| —5
—4) —4) —5
—3} —3} —4
—=2| —2| —3
—1) —2) —2
—1; —1; —1
0 0 0
1 1 1
2 2 1
3 2 2
3 3 3
4 4 3

==(!)

TABLES

TABLE 25.—Temperature of the dew point in degrees Celsius—Continued

(Tabular values are dew points with respect to water]

123

So monmounononeo nounoenenened momononono nonononons nNononoens ne

Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

2.4/2.6] 2.8)3.0/3.2/3.4]/3.6]3.8/4.0]/4 2/4. 4/4 6/4 8/5.0)5. 2)5.4/5.6)5.8)6.0
8 8 8 7 th U6 if U 6 6 6 6 6 5 5 5 5 4 4
9 8 8 8 8 8 U iG df ti i 6 6 6 6 6 5 5 5
9 9 9 a 8 8 8 8 8 i 7 7 iG 7 6 6 6 6 6
10 9 9 @} 9 9 9 8 8 8 8 8 7 7 7 Ui 7 6 6
10; 10) 10; 10) 10 i 9 9 9 9 8 8 8 8 8 8 7 7 7
11} 11) 10) 10; 10; 10) 10) 10 9 i) 9 9 ) ) 8 8 8 8 8
11) 11) 11) 11) 11) 11) 10; 10) 10; 10; 10) 10 w) () ) 9 ) 8 8
12} 12) 12) 1) 11) 11] 11) 11) 11] 10; 10) 10) 10; 10) 10 9 gy) 9 9
12) 12) 12) 12) 12) 12) 12) 11) 12; 121; 121; 11; 11) 10; 10) 10) 10) 10; 10
13} 13) 13] 13) 12) 12) 12) 12) 12) 42); 12) 11) 21) 21): 11) 12) 11) 10) 10
14, 13} 13) 13) 13) 13) 13) 138) 12) 12) 12) 12) 12) 12) 12) 21} 11) 121) 11
144 14, 14) 14) 14) 13) 13) 13) 13) 13) 13) 13) 12) 12) 12) 12) 12) 12) 12
15) 14) 14) 14) 14) #14) #14) 14) 14 13) 13) 13) 13) 13) 13) 13) 12) 12) 12
15} 15) 15) 15) 15) 15] 14) 14) 14) 14] 14) 14) 14) 13) 13) 13) 13] 13) 138
16} 16) 15) 15) 15) 15} 15) 15) 15) 15] 14) 14) 14) 14) 14) #14) 14) 14) 13
16) 16] 16) 16) 16] 16) 15) 15) 15) 15) 15) 15) 15) 15) 15) 14) 14) 14) 14
17} 17} 17] 16) 16} 16) 16) 16; 16; 16) 16) 15; 15) 15) 15) 15) 15) 15) 15
17/ 17) #17} #17; #17) #17; #17; #17] 16) 16) 16] 16; 16) 16) 16; 16; 15) 15) 15
18} 18] 18} 17); 17; #17) #17; #17) #17] #17; #17; #+17/ +16) 16) 16) 16) 16; 16) 16
18} 18} 18) 18) 18) 18] 18) 18) 18) 17) #17); #17) #17} #17) #17) #17) #17) #17) «16
19} 19} 19; 19) 18) 18} 18} 18) 18) 18) 18) 18) 18} 18) -17| 17) 17; #17) #17
19} 19} 19] 19} 19} 19) 19} 19} 19) 19) 18) 18} 18) 18) 18) 18) 18) 18) 18
20) 20} 20} 20; 20) 19) 19) 19) 19} 19) 19} 19) 19) 19) 19} 18 18) 18) 18
20} 20) 20) 20} 20; 20) 20) 20} 20) 20) 20; 19) 19) 19) 19; 19) 19) 19) 19
21; 21] 21) 21) 21} 21) 20) 20) 20) 20) 20; 20} 20) 20; 20) 20) 20) 19) 19
22} 21{ 21) 21) 21) 21) 21) 21) 21) 21) 21) 21) 20) 20) 20) 20] 20) 20) 20
22) 22) 22) 22) 22) 22) 22) 21) 21) 21) 21) 21) 21) 21) 21) 21) 21) 21) 20
23] 23) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22; 21; 21; 21) 21) 21) 21
23| 23] 23] 23] 23) 23) 23) 23) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22) 22
24; 24) 23) 23) 23) 23) 23) 23] 23) 23) 23) 23) 23) 23) 23) 22) 22) 22) 22
24| 24] 24) 24) 24| 24) 24) 24/ 24) 23) 23) 23) 23) 23) 23] 23) 23) 23) 23
25| 25} 25} 24) 24) 24) 24) 24) 24| 24) 24) 24) 24) 24) 24) 24) 23) 23) 23
25| 25) 25) 25) 25) 25) 25) 25} 25) 25) 24) 24) 24) 24) 24| 24) 24) 24) 24
26/ 26} 26] 26} 25) 25) 25) 25) 25) 25) 25} 25) 25) 25) 25) 25) 25) 24) 24
26] 26] 26) 26] 26) 26) 26} 26] 26) 26) 26) 25) 25) 25) 25) 25) 25) 25) 25
27| 27} 27} 27| 27| 26) 26) 26) 26) 26) 26) 26) 26) 26) 26) 26} 26) 26) 26
27| 27) 27) 27) 27) 27) 27) 27) 27; 27) 27) 27) 26) 26) 26) 26) 26) 26) 26
28] 28} 28] 28/ 28) 27) 27) 27) 27| 27) 27) 27) 27) 27) 27); 27) 27) 27) 27
28] 28/ 28) 28) 28] 28) 28) 28] 28) 28] 28) 28) 28] 28) 27) 27) 27) 27) 27
29| 29} 29} 29} 29) 29) 28) 28} 28] 28) 28) 28) 28) 28) 28] 28) 28) 28) 28
29] 29} 29] 29) 29} 29) 29) 29} 29) 29) 29} 29) 29} 29) 29) 28] 28) 28) 28
30} 30} 30} 30} 30] 30) 30) 29} 29} 29) 29) 29) 29) 29) 29} 29) 29; 29) 29
30} 30} 30) 30} 30) 30) 30} 30) 30) 30} 30) 30; 30) 30) 30} 30) 29) 29) 29
31] 31) 31) 31) 31) 31) 31) 31) 30) 30) 30} 30) 30; 30) 30) 30} 30) 30; 30
31] 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31) 30
32) 32) 32) 32) 32) 32) 32) 32] 32) 31) 31) 31) 31) 31) 31) 31) 31) 31) 31
32) 32! 32) 32) 32) 32) 32) 32] 32) 32) 32) 32) 32) 32) 32) 32) 32) 32) 32
33] 33) 33] 33) 33) 33] 33] 33]/ 33) 33) 32) 32) 32) 32) 32) 32] 32) 32) 32
33} 33] 33) 33] 33) 33) 33) 33] 33} 33) 33) 33) 33) 33) 33) 33) 33) 33) 33
34, 34) 34) 34) 34) 34) 34) 34) 34! 34] 34] 33} 33) 33] 33) 33) 33] 33) 33
35] 34) 34) 34] 34) 34) 34] 34] 34] 34) 34) 34) 34) 34) 34) 34) 34) 34) 34

>
Ne)

OCOWONNOMOS

10

124 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TABLE 25.—Temperature of the dew point in degrees Celsius—Continued
[Tabular values are dew points with respect to water]

Wet- Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

bo

ture |6.4/6.6/6.8 7.2/7. 4/7. 6/7. 8/8 0)/8 2/8 4/8 6/8 8/9.0/9. 2/9. 4/9. 6/9. 8]10. 0/10. 2/10. 4

NI
o

0.

0.

1.

Ue

2.

2. 5)

3. 0} —8) —9) —9/—10]—11]—11]—12/—13]—13]—14]—15]—16]}—17]—18]—19]—20|—21|— 23/—24]— 26] 28
3.5 if 8 8 ) 9]— 10}—11)—11]—12|—13)—13]— 14|—15]— 16]—17|—18]— 19|— 20|— 21]— 23]—24
4,0} —6| —7| —7 8 8 9 9} — 10}— 11]—11}—12)—12)—13)/— 14)—15)— 16]—17/—18/—19]— 20]}—21
4. 5} —5| —6) —6) —7| —7 8 8 9) —9}—10)—10}—11]—12}/—12/—13]—14/—15}— 16|— 16)—17/—18
5. 0} —4| —5) —5} —6; —6) —7|/ —7| —8) —8] —9} —9/—10]—10}—11]—12/—12/—13]—14]/—15}—15]—16
5. 5 4 4 4 5 5 6 (| Ag) 7 u 8 8 9|—10|— 10|—11|—11| —12|—13]/—13]—14
6. 0} —3; —3) —3) —4} —4] —5) —5} —5} —6) —6} —7| —7| —8| —8 9 9/—10)— 11-11) — 12) as
6. 5} —2 2 3 3 3 4 4| —4| —5) —5| —6; —6] —7} —7| —8 —8! —9} —9/—10/—10/—11
7. OQ} —1) —1} —2} —2) —2) —3) —3} —3} —4]| —4) —5) —5) —5]} —6 6 7 7 8 i] —E)}) 9)
7.5 0 0} —1}; —1} —1} —2] —2) —2) —3}) —3} —4} —4] —4) —5) —5) —6} —6} —7|/ —7| —8] —8
8. 0 1 0 0 0; —1; —1}| -1 2 2 2 3 3 Bi 2! 4 5 5 5 6) — 6a
8. 5) 1 1 1 1 0 0 0} —1; —1; —1) —2) —2; —2; —3) —3) —3) —4) —4| —5|] —5] —5
9. 0 2 2 2 1 1 1 1 0 0 0} —1; —1) —1) —2) —2 2 3 3 4 4) —4
9. 5) 3 3 2 2 2 2 1 1 il 1 0 0 Ot a) a yp) ai) = 3)
10. 0 4 3 3 3 3 2 2 2 2 1 1 1 1 0 0 QO} —1; —1) —1) —2) =2
10. 5) 4 4 4 4 4 3 3 3 3 2 2 2 1 1 1 1 0 0 0) =i
11.0 5 5 5 4 4 4 4 4 3 3 3 3 2 2 2 1 1 1 1 0 0
11.5 6 6 5 5 5 5 5 4 4 4 4 3 3 3 3 2 2 2 2 1 1
12. 0 i 6 6 6 6 6 5 5 5 5 4 4 4 4 3 3 3 3 2 2 2
12.5 a 7 id 7 6 6 6 6 6 5 5 5 5 5 4 4 4 4 3 3 3
13. 0} 8 8 8 7 7 7 7 tf 6 6 6 6 6 5 5 5 5 4 4 4 4
13. 5 3) 8 8 8 8 8 7 i Ui Ul U 6 6 6 6 6 5 5 5 5 5
14.0 9 9 9 9 ) 8 8 8 8 8 it uf ra 7 a 6 6 6 6 6 5
14.5) 10) 10) 10 9 9 9 ) g) 9 8 8 8 8 8 7 ts 7 a if 6 6
15. 0} 11) 10} 10) 10) 10) 10) 10 0 9 9 9 9 9 8 8 8 8 8 i 7 7
15.5} 11) 11} 11] 11) 11) 10} 10} 10) 10) 10) 10 9 9 9 9 9 9 8 8 8 8
16.0) 12) 12) 12) 11) 11) 11} 11) 11] 11) 10) 10} 10) 10} 10) 10 3) ¢) Y) 9 g) i)
16.5) 12) 12) 12) 12) 12) 12) 12) 11) 11) 11) 11) 11) 11) 11] 10) 10] 10} 10} 10] 10 ©)
17.0} 13) 13) 13) 13} 13) 12) 12) 12) 12) 12) 12) 12) 11) 11] 11) 11] 11) 11) 10] 10) 10
17. 5{ 14) 14) 13) 13] 18) 13) 18) 13) 13] 12) 12) 12) 12} 12) 12) 12) 11) 11) 11] 11) 11
18.0) 14) 14) 14) 14) 14) 14) 14) 13) 13] 13] 13} 13] 13) 13) 12} 12) 12) 12) 12) 12) 12
18.5) 15) 15) 15} 15) 14 14) 14) 14] 14) 14) 14) 14) 13) 13) 13) 13} 13] 13) 13) 12) 12
19.0] 16) 15) 15} 15) 15) 15) 15) 15] 15) 14) 14) 14) 14] 14) 14) 14) 14] 13] 13] 13) 13
19.5) 16) 16} 16; 16) 16) 16) 15) 15) 15) 15} 15} 15) 15) 15} 14) 14] 14) 14) 14) 14) 14
20. 0} 17) 17) 17; 16) 16] 16} 16} 16) 16] 16} 16) 15] 15} 15] 15) 15} 15} 15] 15] 14] 14
20.5) 17) 17; 17) #17|/ #17} 17) 17} 17] +16) 16) 16) 16) 16) 16) 16} 16} 16) 15) 15} 15) 15
21.0} 18) 18) 18} 18) 18) 17} 17} 17] #17] #17) #17; #17] 17] #17] 16) 16} 16] 16) 16) 16) 16
21.5) 19) 18) 18) 18} 18) 18} 18} 18) 18] 18} 17/ 17] 17} 17| 17] #17} 17| 17] #17] 16) 16
22.0) 19) 19) 19} 19) 19) 19} 19} 18] 18] 18} 18] 18] 18} 18] 18] 18} 17] 17] 17} 17} 17
22.5) 20) 20; 20) 19) 19} 19} 19} 19) 19) 19} 19} 19) 19] 18] 18] 18] 18] 18] 18] 18] 18
23. 0} 20) 20) 20) 20) 20) 20} 20} 20) 20) 19} 19} 19) 19] 19} 19} 19) 19) 19} 19} 18] 18
23. 5 21) 21) 21} 21) 20) 20} 20} 20) 20) 20; 20) 20] 20]; 20) 20) 19} 19} 19] 19] 19} 19
24.0) 21) 21) 21} 21) 21) 21) 21) 21) 21) 21) 21) 20) 20] 20) 20) 20) 20; 20) 20) 20} 20
24.5) 22) 22) 22) 22) 22) 22) 21) 21) 21) 21] 21) 21) 21! 21) 21] 21) 21) 21] 20) 20) 20

TABLES

TABLE 25.—Temperature of the dew point in degrees Celsius—Continued
(Tabular values are dew points with respect to water]

125

Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

6. 8| 7.0} 7. 2
22) 22) 22
23) 23) 23
24); 23) 23
24; 24) 24
25) 25) 25
25) 25) 25
26) 26) 26
26} 26) 26
27| 27| 27
27) 27| 27
28) 28) 28
29} 29) 28
29) 29} 29
30) 30) 30
30} 30) 30
31) 31} 31
31) 31) 31
32} 32) 32
32) 32] 32
33} 33] 33

7.4/7.6/7.8
22) 22) 22
23} 23} 23
23} 23) 23
24; 24) 24
24) 24) 24
25) 25) 25
26) 26) 25
26; 26) 26
27| 27) 27
27| 27) 27
28) 28) 28
28} 28} 28
29} 29) 29
30) 29) 29
30} 30; 30
31) 31) 30
31} 31} 31
32} 32) 32
32} 32) 32
33) 33} 33
33} 33] 33

8.0} 8. 2
22| 22
22) 22
23) 23
24) 24
24) 24
25) 25
25} 25
26) 26
27| 26
27| 27
28) 28
28) 28
29) 29
29} 29
30) 30
30) 30
31) 31
32) 31
32} 32
33) 33
33] 33

8.4

8.6/8.8) 9.0/9. 2/9. 4] 9.6/9. 8/10. 0/10. 2/10. 4
22) 22) 21) 21; 21) 21) 21) 21) 21) 21
22} 22) 22) 22) 22) 22) 22) 22) 22) 21
23) 23) 23) 23) 23) 22) 22) 22) 22: 22
23) 23) 23) 23) 23) 23) 23) 23] 23) 23
24) 24; 24) 24) 24) 24) 24) 23) 23) 23
25) 25) 24) 24) 24) 24) 24) 24) 24) 24
25} 25) 25) 25) 25) 25) 25) 25) 25) 25
26) 26) 26) 26) 25) 25) 25) 25) 25) 25
26) 26} 26) 26) 26) 26) 26) 26) 26; 26
27) 27) 27) 27) 27) 27; 26) 26) 26) 26
27; 27) 27) 27) 27) 27) 27) 27) 27) 27
28) 28) 28] 28) 28) 28) 28) 28) 28) 27
29} 29} 28] 28) 28) 28) 28] 28) 28! 28
29; 29} 29) 29) 29} 29) 29) 29} 29) 29
30} 30} 30] 30) 29) 29) 29) 29) 29) 29
30} 30} 30) 30) 30) 30) 30) 30) 30; 30
31) 31} 31) 31) 31) 31) 31) 30; 30) 30
31) 31} 31) 31) 31) 31) 31) 31) 31) 31
32) 32) 32) 32) 32) 32) 32) 32] 32) 31
32) 32) 32) 32) 32) 32) 32) 32) 32) 32
33} 33] 33) «33; 33) 33) 33) 33) 33) «33

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TABLE 25.— Temperature of the dew point in degrees Celsius—Continued

(Tabular values are dew points with respect to water]

Depression of the wet-bulb thermometer (dry-bulb minus wet-bulb)

11, 4/11. 6/11. 8/12. 0

126

Wet-

bulb

tem-

pera-

ture {10. 6/10. 8/11. 0/11. 2

(°C.)
10. 0} —2. 3 3 4 4
10. 5} —1} —2}) —2} —2) —3] —3
1750 0} —1} —1) —1} —2} —2
11.5 1 0 0 o| —1; —1
12.0 2 1 1 1 0 0
12. 5 3 2 2 2 i} 1
13. 0 3 3 3 3 2 2
13. 5) 4 4 4 4 3 3
14.0 5 5 5 4 4 4
14.5) 6 6 6 5 5 5
15. 0) if 7 6 6 6 6
15. 5) 8 a tf if 7 7
16. 0 8 8 8 8 8 if
16.5 9 9 9 9 8 8
17.0} 10) 10) 10 9 9 9
17.5) 11) 11); 10) 10) 10) 10
18.0} 11) 11); 11) #11) 12) #11
18.5) 12) 12); 22) 12) 2) Jl
19.0; 13) 13) 13) 12) 1 12
19. 5) 14) 13) 13) 13) 13) 138
20 O} 14, #14, #14, #+%14 «+414 «#214
20. 5} 15) 15) 15) 15) 14, 14
21.0] 16) 15) 15) 15) 15) 15
21. 5] 16) 16) 16; 16) 16; 16
22.0] 17) #17; +417; +417) #+16) 16
22.5) 18) 7) 7} 17) 17) «(17
23.0] 18) 18 18) 18) 18) 18
23. 5} 19; 19) 19) 19) 18) 18
24.0] 19; 19) 19) 19) 19) 19
24. 5} 20; 20) 20) 20) 20) 20
25.0} 21); 21) 21) 20) 20) 20
25. 5) 21) 21) 21) 21) 21) 21
26. O| 22) 22) 22) 22) 22) 22
26. 5| 23) 23) 22) 22) 22)| 22
27.0] 23) 23) 23) 23) 23) 23
27. 5] 24) 24) 24) 24) 24) 23
28.0] 24) 24) 24) 24) 24) 24
28. 5, 25) 25) 25) 25) 25) 25
29.0} 26) 26) 25) 25) 25) 25
29. 5} 26) 26) 26) 26) 26] 26
30. 0}. 27| 27) 27) 27| 27) 26
30. 5] 27) 27) 27| 27) 27| 27
31.0] 28) 28} 28) 28) 28) 28
31.5} 29) 28) 28) 28) 28] 28
32.0} 29) 29} 29) 29) 29) 29
32. 5} 30) 30} 30) 30) 29} 29
33. 0} 30} 30; 30} 30) 30) 30
33.0] 31] 31) 31) 31) 321i) 31
34.0] 31); 31) 31) 31) 31) 31
34. 5] 32) 32) 32) 32) 32) 32
35. O| 33) 32) 32) 32) 32) 32

12. 2

OE |
OOWNAT PWN OR NWHA

12. 4/12. 6/12. 8
=i) tl) =e
— tj} st}, =)
—3} —4) —4
—2\e—3|—3
Sia) 4

0 Oat
1 1 0
2 2 2
3 3 3
4 4 4
5 5 4
6 6 5
u 6 6
8 Uf if
8 8 8
9 9 )
10| 10) 10
11) 11; 10
12} 11) 11
12) 12) 12
13) 13) 13
14, 14) 13
14, 14) 14
15) 15) 15
16} 16) 16
17; 16; 16
17} 17) 17
18) 18! 18
19} 18) 18
19} 19) 19
20} 20} 20
21) 20) 20
21} 21); 21
22) 22) 22
22} 22) 22
23) 23} 23
24) 24; 24
24, 24) 24
25) 25) 25
26) 26) 25
26} 26) 26
27| 27) 27
27| 27) 27
28] 28) 28
29} 29} 28
29} 29} 29
30} 30) 30
30} 30) 30
31); 31] 31
32} 31} 31
32} 32} 32

13. 0/13. 2/13. 4
=f) =) Sy
— 6) 6/7
=), —4]) —@
=| —4// —4
— 4) 0) ai
— al

0 Oj
1 1 1
2 2 2
3 3 3
4 4 4
5 5 5
6 6 6
7 7 7
8 8 7
9 8 8
9 ) 9
10; 10; 10
1 i Ua
12} 12) 12
13} 12) °12
13} 13) 13
14, 14) 14
15] 15) 15
16} 15) 15
16) 16) 16
U7 dl lia
18) 17) 17
18; 18) 18
19) 19) 19
20) 20) 19
20; 20) 20
21; 21) 21
22) 22) 21
22) 22) 22
23) 23) 23
24) 23) 23
24, 24) 24
25) 25) 25
25) 25) 25
26) 26) 26
27| 27) 26
27; 27) 27
28} 28] 28
28) 28} 28
29; 29) 29
30} 30} 29
30} 30) 30
31) 31] 31
31); 31} 31
32} 32) 32

13. 6/13. 8}14 0/14. 2/14. 4/14. 6/14. 8
—9|—=10|— 10) 1 2 a2 as
—7| —8| —8| —9)—10)\—10) al
—=6| =6| = 7) =A Sie sia
—5|| —5| —0|)— 656 aes,

3 4 4 4, —5 5} —6
—2| —2| —3| —di) —3|) 4 ee
a ey] 8)

0 0 0} 1) el

1 1 1 1 0 0 0

2 2 2 2 1 1 1

3 3 3 3 2 2 2

4 4 4 4 4 3 3

5 5 5 5 5 4 4

6 6 6 6 5 5 5

7 U C 7 6 6 6

8 8 8 8 7 7 Ul

9 9 9 8 8 8 8

10) 10 9 9 9 9 9

11; 10; 10; 10} 10) 10) 10

11) 1) FN) Ya) OE a LO

12; 12) 12) 12) 12) 11) 11

13} 13} 13} 12) 12) 12) 12

14; 14) 13) 13} 13) 13) 13

14, 14; 14) 14; 14) #14) 14

15} 15; 15} 15) 15) 15) 14

16} 16; 16) 16; 15; 15) 15

17; 16} 16; 16] 16) 16) 16

1d i yd es rs eee bd bd shee

18} 18} 18) 18} 18} 17) 17

19} 19} 18) 18} 18) 18) 18

19/0) 19) 19) 19) 1S ae eek)
20; 20} 20] 20) 20) 20) 19
21{ 21) 20) 20) 20} 20) 20
21} 21) 21) 21) 21) 21) 21
22) 22) 22) 22) 22) 22) 21
23) 23) 22) 22) 22) 22) 22
23} 23) 23] 23) 23) 23) 23
24, 24) 24) 24) 24) 24) 23
25) 24) 24) 24) 24) 24) 24
25| 25) 25) 25) 25) 25) 25
26} 26] 26) 26) 25) 25) 25
26] 26} 26) 26) 26) 26) 26
27) 27) 27) 27 27) “27s e2e
28) 28) 27) 27; 27) 27) 27
28] 28} 28) 28) 28) 28) 28
29| 29] 29) 29) 29) 29) 28
29] 29; 29) 29) 29) 29) 29
30} 30} 30} 30) 30) 30; 30
31| 31} 30) 30) 30) 30) 30
31] 31) 31) 31) 31) 31) 31
32) 32} 32) 32) 32) 32) 31

TABLES ILPATE
TasLE 26.—Fahrenheit to Celsius Temperatures
hae oe 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
oC: AGE, SCe o“. aCe ee i OF na OF Or oC;
+100 +37. 8 +37. 8 +37. 9 +37. 9 +38. 0 +38. 1 +38. 1 +38. 2 +38. 2 +38. 3
99 37. 2 37.3 37.3 37.4 37. 4 37.5 37. 6 37. 6 Sint 37.7
98 36. 7 36. 7 36. 8 36. 8 36. 9 36. 9 37.0 37, 1 Bye 1 37. 2
' 97 36. 1 36. 2 36. 2 36. 3 36. 3 36. 4 36. 4 36. 5 36. 6 36. 6
96 35. 6 35. 6 35. 7 35. 7 35. 8 35. 8 35. 9 35. 9 36. 0 36. 1
+95 +35. 0 +35. 1 +35. 1 +35. 2 +35. 2 +35. 3 +35. 3 +35. 4 +35. 4 +35. 5
94 34. 4 34.5 34. 6 34. 6 34. 7 34.7 34. 8 34. 8 34. 9 34.9
93 33. 9 33. 9 34. 0 34. 1 34. 1 34. 2 34. 2 34. 3 34. 3 34. 4
92 33. 3 33. 4 33. 4 33. 5 33. 6 33. 6 33. 7 33. 7 33. 8 33. 8
91 32. 8 32. 8 32. 9 32.9 33. 0 33. 1 33. 1 33. 2 33. 2 33. 3
+90 +32. 2 +32. 3 +32. 3 +32. 4 +32. 4 +32. 5 +32. 6 +32. 6 +32. 7 +32. 7
89 31.7 31.7 31.8 31.8 31.9 31.9 32. 0 32. 1 32. 1 32. 2
88 31.1 31. 2 31.2 31.3 31.3 31.4 31.4 31.5 31.6 31.6
87 30. 6 30. 6 30. 7 30. 7 30. 8 30. § 30. 9 30. 9 31.0 31. 1
86 30. 0 30. 1 30. 1 30. 2 30. 2 30. 3 30. 3 30. 4 30. 4 30. 5
+85 +29. 4 +29. 5 +29. 6 +29. 6 +29. 7 +29. 7 +29. 8 +29. 8 +29. 9 +29. 9
84 28. 9 28. 9 29. 0 29. 1 29. 1 29. 2 29. 2 29. 3 29. 3 29. 4
83 28. 3 28. 4 28. 4 28. 5 28. 6 28. 6 28. 7 28. 7 28. 8 28. 8
82 27.8 27.8 27.9 27.9 28. 0 28. 1 28. 1 28. 2 28. 2 28. 3
81 27. 2 27.3 27. 3 27.4 27. 4 27.5 27.6 27. 6 27. 7 27.7
+80 +26. 7 +26. 7 +26. 8 +26. 8 + 26. 9 +26. 9 +27.0 +27. 1 +27. 1 +27. 2
79 26. 1 26. 2 26. 2 26. 3 26. 3 26. 4 26. 4 26. 5 26. 6 26. 6
78 25. 6 25. 6 25. 7 25. 7 25. 8 25. 8 25. 9 25. 9 26. 0 26. 1
77 25. 0 25. 1 25. 1 25. 2 25. 2 25. 3 25. 3 25. 4 25. 4 25. 5
76 24.4 24. 5 24. 6 24. 6 24.7 24.7 24. 8 24. 8 24.9 24.9
+75 +23. 9 +23. 9 +24. 0 +24. 1 +24. 1 424. 2 +24. 2 +24. 3 +24. 3 +24. 4
74 23. 3 23. 4 23. 4 23. 5 23. 6 23. 6 23. 7 23. 7 23. 8 23. 8
73 22. 8 22. 8 22.9 22.9 23. 0 23. 1 23. 1 23. 2 23. 2 23. 3
72 22. 2 22. 3 22. 3 22. 4 22. 4 22. 5 22. 6 22. 6 22. 7 22. 7
71 21.7 21.7 21.8 21.8 21.9 21.9 22.0 22. 1 22. 1 22. 2
+70 +21.1 +21. 2 +21. 2 +21.3 +21.3 4+21.4 4+21.4 +21.5 +21.6 +21.6
69 20. 6 20. 6 20. 7 20. 7 20. 8 20. 8 20. 9 20. 9 21.0 21.1
68 20. 0 20. 1 20. 1 20. 2 20. 2 20. 3 20. 3 20. 4 20. 4 20. 5
67 19. 4 19.5 19. 6 19. 6 19.7 19. 7 19. 8 19.8 19.9 19. 9
66 18. 9 18. 9 19. 0 19 19. 1 19. 2 19. 2 19. 3 19.3 19. 4
+65 +18. 3 +18. 4 +18. 4 +18. 5 +18. 6 +18. 6 +18. 7 +18. 7 +18. 8 +18. 8
64 17.8 17.8 17.9 17.9 18. 0 18. 1 18. 1 18. 2 18. 2 18. 3
63 17. 2 17. 3 173 17. 4 17. 4 17.5 17. 6 17.6 Wes 17.7
62 16. 7 16. 7 16. 8 16. 8 16. 9 16. 9 17.0 te 1 17.1 17:2
61 16. 1 16. 2 16. 2 16. 3 16. 3 16. 4 16. 4 16. 5 16. 6 16. 6

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

128

TABLE 26.—Fahrenheit to Celsius Temperatures—Continued

FIM HO MENSCH WMAHOMD MPNORID BHOMKR NOAM ONKNRMO HWHMAO
= OSI Hivos BAA i SAA HW MRNeCSH dHHHAN ABHSS SHAAN Sordid
3S ° OW als arama) ule lt (elke teckel) dal

~ ~ +

SCHAMO AMTOD HAMON MHOOH AMON~E FBOOHH KRNANDMH toon
oo Ow sitios BANA SSAOHH YPKSSH HtinGN ANHHSS SHHANN Hits
* 4 al
3 a ee ar 7. as a ce staat le Vesle wlll Slee 1)

+ + +

QD Hoomr NoOonmwMmaD HOOMIr~N Omid HH WOmr~NO FIL DHA I~ 0D CO HOD MMA OND~
N OU 1936 xi sind BAAS SSSH6HG KKSHH HHHGN NAHSSS SHAAN Sxidiidis
: Sono] Soaion! I
So a = sraraeae lato ae

° + + +

DMNON~E BAOOHHR MON~H OOHRM WDANRTAO CHAMN OMAHO OAKRNOD
oO O1818 HH tiod SAAS SAA WO NNO Hit Aa AHSSS Sra os siiisis
. aioe entation Renton]

S AF ar Spararar A A lh aha
o + 7 +

DWOMr-NO BANPHO MNO WRHHOM KBMNODD ABAHOMM DHMH ONNMOO
1 O18 16 vi vied BAS SAB Wo NOCH wits A BHSSS SH Sais
S An a geararar NW tb te alt

° + ~ 4

OAMABOH SCOAMMO ALHOSO HPHRMON PRHADOH AMONM AHOSH KHRNDMS
H US 18 wi vied SAAS SIABOHGH MSSHH didi GAN GHSSS Sains od tisis
Ss oe ate amen ih © il ab Well St Aaa 4

° + + +

NORD AHAHOM~E NOGMND HOMrN ONANAH OMRAH BDNAON BMMOHD
a) OSS Hi tied AAS SSSGO~ NESHG HHHAN FHHASSS SHrins Sidi
: onl rt Lon Lol |
—) ale aie Seaman) et Je ele ie ah

o + + +

SAO OY AMON~E BOOHHR MONRH OOHRM WONA~KAH CORN DMANHSO
a O19 18 wi vid AGS SSGOr~r KOESHGH HHHAN FHHSSS FBHANS SH
* coal ion! ol
S cea aD tp ampere in ibe ay ib th We iy

+ ~ +

Ona OWMr~NO TLD > =H OO COI NO if) O> =H 00 oD eNO mip mONM~ OD (- oor an]
4 O1818 sed od ANS SAH Wr NOSIS HHGAN FBHSSS FHA orididd
S ote ar arama) MM a a

° + ~ +

OOAAMD OANA OH COHAMD APTOS HWHRMON RwHOOD ARNDOM BHOOR
oO OWS ANKHS SSHHK NSSIHH HASAN FHHSSS SHdins Sd
S Se eee eres ee pene Me aE a Sete ee a

+ 7 ~
é SDBWOMr~OOD WHONF CODOMO WHOA OBONMO NMHMNDT CAMRDO NAMAH
& Ow wii DAH AD A AQ ALI HHHAH HAH Won MINIM DANNN ANNAN
: ~ + + 7 + + + +

TABLES 129
TABLE 27.—Correction of mercurial barometer for temperature (English measures)
ADD
Observed reading (inches) Observed reading (inches)
Temperature Temperature
(C195) | @ BE)

28.5 | 29.0 | 29.5 | 30.0 | 30.5 28.5 | 29.0 | 29.5 | 30.0 | 30.5
(ee >--| 0:07 | 0: 08 | 0: 08 | (0:08 | 0:08 || 16-.-_-.._--__. 0.03 | 0.03 | 0.03 | 0.03 | 0.04 |
hee ___| .07 .07 . 07 . 08 HOGS || ildpes see . 03 .03 | .03 . 03 . 03
la SE eee S28 nO O07 00 207 O(a |S ae ee ee ee . 03 . 03 . 03 . 03 . 03
SOS eee es .07 .07 207 207 1095 | | flO ee ye weet . 02 .02 | .03 03 . 03
te Perey ces . 06 . 06 . 07 .07 UY! Ae ee e Se . 02 . 02 -02 . 02 502
5. Bi 06 . 06 . 06 . 06 AYE ee oe eS . 02 = 02 . 02 . 02 . 02
(ae eee eee . 06 . 06 . 06 . 06 008 |S 228ee ee eeee see 202 . 02 . 02 . 02 . 02
Ve 2 \s206 . 06 . 06 . 06 a (Olah I) PRI = eee eee | . 02 .02 | .02 . 02 . 02
Sieers ee aa 705 . 05 . 06 . 06 OG8| M242 oes eee oe e011 OLS iO .01 .01
OR eee. . 05 . 05 . 05 . 05 05: ||| 255-_---_.-_-_- .01 OT .01 .01 .01
iI ¢ eA cae eae . 05 . 05 . 05 . 05 SODg| 26295-22220 02. .01 alin .01 .01 .01
) ee ee . 05 . 05 . 05 . 05 abi Oye oe Se aoe cee Eh eaee lle ae a
Dee ee . 04 . 04 . 04 . 04 05: || 28_.._.--.-.--_ AC 2 ae
Th ae eae . 04 . 04 . 04 . 04 O4))|| 20 Nee es ee eee
i ae eae . 04 . 04 . 04 . 04 O04) ||sa0422 see | =| oe
Topas 2204 . 04 . 04 . 04 . 04 | |

|
SUBTRACT
Observed reading (inches) Observed reading (inches)
Temperature Temperature
(@10)) (Gata) |

28.5 | 29.0 | 29.5 | 30.0 | 30.5 28.5 | 29.0 | 29.5 | 30.0 | 30.5
Sill eee ee 0.01 | 0: 01 || 0: OL || 0: OF |, 0. 01 ||| 66. _---___-_ 0.10 | 0.10} 0.10 | 0.10 | 0. 10
32. bees .01 .O1 . 01 .O1 ROU G fener eee .10 . 10 . 10 . 10 .1l
Soe es 2 .01 .O1 .01 . 01 SAUDE |) Gis = eS .10 . 10 = 10 Sil vit
RY hee a eer . Ol . Ol -O1 . 02 028] |969 eee - 10 11 Peli a all el
Soe eee . 02 . 02 . 02 . 02 mOZ (Obese = oe 11 11 ahi Jalil ald
SG ee . 02 . 02 . 02 . 02 OZ) ||Petise. 222 ae 11 11 stil 12 12
Slee et . 02 . 02 . 02 . 02 S02 Ai 2 see eS 11 11 12 12 12
SR . 02 . 02 . 02 . 03 SLO com dick ee eer ee ee 11 Sale +12 12 12
|! gr apelin . 03 . 03 . 03 . 03 SURYA IS¢ Sree pos Seens 12 12 pall? 12 12
40__ 5/303 . 03 . 03 . 03 HOST 0n See eee 12 12 el2 13 Sal}
7) . 03 . 03 . 03 . 03 (0B yal boyd oh ere eee ee 12 12 .138 213 aS
7 ea el Se . 04 . 04 . 04 . 04 OA Rite eee eee 2 sas 13 3118) + 118}
218 Yaa Spal . 04 . 04 . 04 . 04 OSH eS oe ee ee . 13 .13 = 1183 5 1} .14
CV a ee . 04 . 04 . 04 . 04 LLU Bel At A hes nce en ee . 13 «13 .14 .14 14
4 aes See . 04 . 04 . 04 . 04 04> /|5802_ 222 == =e -13 wil 14 .14 14
AG ieee eee . 04 . 05 . 05 - 05 ODs Pol eseeeeees see .14 14 14 lk 14
YY (orale a . 05 . 05 . 05 . 05 OS! ||; 82002202245 5-2 14 14 14 14 15
| oe . 05 . 05 . 05 . 05 ODM Saas ates eee pale! .14 14 15 15
4 eee se . 05 . 05 . 05 . 06 . 06 a ee ere 14 14 15 15 15
50s See | 506 . 06 . 06 . 06 065| |e Soseessee sees 2 Altes 15 15 15 16
Ol eee eee . 06 . 06 . 06 . 06 JOG ||S62.2e5 ee 15 = 14S) 15 16 16
Doe see . 06 . 06 . 06 . 06 mOGE |RSiaeo===e eae 15 215 . 16 16 16
ia (es Nee . 06 . 06 . 06 . 07 Os MSS aee2 eee s= ee 15 716 . 16 16 16
Dae renee . 06 . 07 . 07 . 07 BOM NGSOS2 22a 16 mG 16 16 17
D0 meee ee nO’ . 07 “07 aUUYA UGH WU ee 16 16 16 a lvs = ile
{ise Sls aie acme . 07 . 07 . 07 . 07 2708" || HO) ese Se eee 16 . 16 17 ilt¢¢ Piles
iY (aaa Aly Are . 08 . 08 . 08 OSs || Olen See ae 16 Raye 17 ily 18
082s22 22 _| .08 . 08 . 08 . 08 Ue} PB eee es ae 8 al? Sf nally elit 18
{| eee ee eee . 08 . 08 . 08 . 08 308))||/ 9422 2a eae males al? A ile .18 .18
60___- aoa 5 We . 08 . 08 . 08 O98 || 95 2meere seen 2 es ales aS 18 .18
Gee es) 08 . 08 . 09 . 09 OO) || ROGu 2 sen ee a 1R/ .18 .18 .18 .19
62ers . 09 . 09 . 09 . 09 09) || O fe ce et eee 118 . 18 . 18 .18 19
LR ee se eens . 09 . 09 . 09 . 09 eLO) ||RO82 22222222. = +18 . 18 .18 19 19
64____ e2-\) 2109 . 09 .10 10 LOU |p 09 sae sae. eee . 18 .18 .19 19 19
65___- 222|\" 09 10) 210 . 10 ol) ||) WO ee ee .18) .19 .19 .19 20

130 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

TaBLE 28.—Reduction of barometric reading to mean sea level

(Reading, 30 inches. The correction is always to be added.]

Temperature of air (dry bulb)
Height
in feet
0° 10° 20° 309 40° 50° 60° 70° 80° 90°
5 0. O1 0. 01 0 Ol 0. 01 0. O1 0. 01 0. 01 fe eee
10 . Ol OL S01 01 OL OL VOL 0x01 0. 01 0. 01
15 . 02 . 02 . 02 . 02 02 . 02 . 02 02 . 02 . 02
20 . 02 . 02 202 02 . 02 . 02 . 02 . 02 . 02 . 02
25 B03 . 03 . 03 03 . 03 . 03 . 03 . 03 . 03 203
30 . 04 . 04 . 04 04 . 03 . 03 03 . 03 . 03 . 03
35 . 64 . 04 . 04 04 . 04 . 04 . 04 . 04 . 04 . 04
40 . 05 . 05 205 05 . 04 . 04 . 04 . 04 . 04 . 04
45 . 06 . 05 = (05) 05 . 05 . 05 . 05 . 05 .05 . 05
50 . 06 . 06 . 06 06 . 06 . 06 £05 . 05 705) 7) 05
55 07 500 . 06 . 06 . 06 . 06 . 06 . 06 .06 | .06
60 107 07 200 07 07 .07 . 06 . 06 .06 | .06
65 . 08 . 08 . 08 08 . 07 07 s0u . 07 07 07
70 . 09 . 08 . 08 08 . 08 . 08 . 08 . 07 .07 } 07
aD . 09 . 09 . 09 09 . 08 . 08 . 08 . 08 .08 | .08
80 .10 .10 . 09 09 . 09 . 09 . 09 . 08 .08 | .08
85 .10 710 .10 10 .10 .10 . 09 . 09 .09 | .09
90 Salil .1l .11 10 .10 Fil) .10 .10 . 09 . 09
95 2 5 lal = lal 11 aalil lal .10 .10 .10 .10
100 212 . 12 anil, 12 slat Ul a ilal ul 10 10
TaBLE 29.—Reduction of the mercurial barometer to standard gravity (45°) (30 inches)
Lat. Cor. Lat. Cor. Lat. Cor. Lat. Cor.
2 Inch 2 Inch 2 Inch 2 Inch
0 —0. 08 25 —0. 05 45 0. 00 70 +0. 06
5 —. 08 30 —. 04 50 +.01 rh) +.07
10 —. 08 35 —. 03 55 +. 03 80 +. 08
15 —.07 40 —.01 60 +. 04 85 +. 08
20 —. 06 45 0. 00 65 +. 05 90 +. 08
=|
Table 29A —Millimeters to millibars
Mm 0 1 2 3 4 5 6 7 8
Mb. Mb. Mb. Mb. Mb. Mb. Mb. Mb. Mb. Mb
690 919.9 921.3 922. 6 923. 9 925. 3 926. 6 927.9 929. 3 930. 6 931
700 933. 3 934. 6 935. 9 937. 3 938. 6 939. 9 941.3 942. 6 943. 9 945,
710 946. 6 947.9 949. 3 950. 6 951.9 953. 3 954. 6 955. 9 957. 3 958
720 959. 9 961. 3 962. 2 963. 6 965. 3 966. 6 967. 9 969. 3 970. 6 971
730 973. 3 974. 6 975.9 977.3 978. 6 979. 9 981.3 982. 6 983. 9 985
740 986. 6 987.9 989. 3 990. 6 991.9 993. 3 994. 6 995. 9 997.3 998
750 999. 9 {1,001.3 /1, 002. 6 |1, 003. 9 |1, 005. 3 | 1, 006. 6 | 1,007.9 | 1,009.3 | 1,010.6 | 1,011
760 |1, 013.3 |1, 014. 6 |1, 015. 9 |1, 017. 2 /1, 018.6 | 1,019.9 | 1,021.2 | 1,022.6 | 1,023.9 1) 025
770 |1, 026. 6 |1, 027. 9 |1, 029. 2 /1, 030. 6 /1, 031.9 | 1,033. 2 | 1,034.6 | 1,035.9 | 1,037.2] 1, 038
780 1, 039. 9 |1, 041. 2 |1, 042.6 /1, 043.9 /1, 045.2 | 1,046.6 | 1,047.9 | 1,049.2 | 1,050.6 | 1,051
790 }1, 053. 2 |1, 054. 6 |1, 055. 9 /1, 057. 2 /1, 058.6 | 1,059.9 | 1,061.2 | 1,062.6 | 1,063.9 | 1, 065.

NOCAOND AWOoMmwe

Meteorological Q-code signals are reproduced below as a guide to ship’s officers in furnishing meteorological
data when requested by aircraft. Note that when these signals are used in replies, the message may require some
additional (supplementary) information to convey clearly meteorological data that cannot be presented in the

TABLES

CODE TABLE 30
Meteorological Q-Code Signals

order, units, ete., specified in the following list.

Signal Question Reply

QAM What is the latest available meteoro- | Meteorological observation made at ___ (place) at __-
logical observation for ___ (place)? hours was as follows ___

When the reply is presented in the Q-code form, the
sequence of information is to be, as far as practicable,
that pertaining to the Q-signal sequence QAN, QBA,
QNY, QMU. When presented in this sequence, it is
not necessary to precede each type of datum with the
corresponding Q-signal.

QAN What is the surface wind direction (in | The surface wind direction and speed at ___ (place)
degrees relative to MAGNETIC at ___ hours is ___ (direction) ___ (speed figures and
North, unless otherwise indicated in units).
the question) and speed at —_-_- Nore.—Unless otherwise indicated in the question,
(place)? answer (or advice), surface wind direction is given in

degrees relative to MAGNETIC North.

QAO What is the wind direction in degrees | The wind direction and speed at ___ (position or zone/s)
TRUE and speed at ___ (position or at the following heights above ___ (datum) is:
zone/s) at each of the ___ (figures) _-- (vertical distance in figures and units)

__- (units) levels above ___ (datum)? _-- degrees TRUE __~ (speed in figures and units)
Note.—Merchant ships can be ex- --- (vertical distance in figures and units)

pected to furnish wind data only for _-- degrees TRUE ~~~ (speed in figures and units).

the level near the SURFACE (sea

level).

QBA What is the horizontal visibility at _._ | The horizontal visibility at ___ (place) at ___ hours
(place)? is ___ (distance figures and units).

QFC What is the amount, the type, and the | At ___ (place, position, or zone) the base of the cloud
height above ___ (datum) of the base is ___ eighths ___ type at ___ (figures and units)
of the cloud at ___ (place, position height above ___ (datum).
or zone)? Notre.—If several cloud layers or masses are

present, the lowest is reported first.

QFF [At --- (place)] what is the present | At --- (place) the atmospheric pressure converted
atmospheric pressure converted to to mean sea level in accordance with meteorological
mean sea level in accordance with practice is (or was determined at ___ hours to be)
meteorological practice? __- tenths of millibars (e. g., 9237 for 923.7 millibars).

QFY Please report the present meteorological | The present meteorological landing conditions at ___
landing conditions [at ___ (place)]. (place) are ___. When the reply is prepared in the

Q-code form, the sequence of information is to be, as
far as practicable, that pertaining to the Q-signal
sequence QAN, QBA, ONY, QMU. When presented
in this sequence, it is not necessary to precede each
type of datum with the corresponding Q-signal.

QMU What is the surface temperature at ___ | The surface temperature at ___ (place) at ___ hours
(place) and what is the dew-point is ___ degrees and the dew-point temperature at that
temperature at that place? time and place is ___ degrees.

QNY What is the present weather and the | The present weather and intensity thereof at ___ (place,
intensity thereof at ___ (place, position, or zone) at ___ hours is ___ (duststorm, sand-
position, or zone)? storm, rain, snow, hail, thunderstorm, etc., or if no

such phenomena as these is present, signal QN Y NIL).

QTI What is your TRUE track? My TRUE track is ___ degrees.

QUB Can you give me, in the following order, | Here is the information requested ___.
information concerning — visibility,
height of clouds, direction and veloc-
ity of ground wind at ___ (place of
observation)?

QUH Will you give me the present baro- | The present barometric pressure at sea level is ___ (units).
metric pressure at sea level?

QUK Can you tell me the condition of the | The sea at ___ (place or co-ordinates) is ___.

sea observed at ___ (place or co-
ordinates)?

132

CODE TABLE 30 (Continued)
Meteorological Q-Code Signals—Continued

MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS

Signal

Question

QUL

QUN!

|

Can you tell me the swell observed | The swell at
at _._ (place or co-ordinates)?

Num-
ber

CONMWMILWNeE SO

Reply

_-- (place or co-ordinates) is

Complete the answer, information or advice form by the
use of the following numbered alternatives:

Length of swell

Average
hon gee ee ee
Confused

Height

Low.
Do.
Moderate.

Additionally, indicate the direction of swell by the use

of the appropriate cardinal or intermediate
ee (abbreviation where appropriate), e. g.,
ve

uadran-

ORTH,

E, SE, ete., following the numbered alternative

for indicating swell condition.

The descriptions in

the above-numbered alternatives are as follows:

Short:

Length of swell
0-100 meters (0-300 feet).

Average: 100-200 meters (300-600 feet).

Long:

Over 200 meters (600 feet).
Height of swell

Low: Below 1.75 meters (below 6 feet).

Moderate: 1.75 to 3.75 (6 to 12 feet).

Heavy: Above 3.75 meters (above 12 feet).

Will vessels in my immediate vicinity
[(or in the vicinity of __- latitude --__
longitude) (or of ___)] please indi-
cate their position, TRUE course
and speed?

My position, TRUE course and speed are --_-.

! Allstations of the international aeronautical telecommunication service will interpret this signal as referring to TRUE TRACK. English-speaking
stations of the maritime mobile service may interpret this signal as referring to TRUE HEADING. When communicating with the latter it is recom-
mended that supplementary use be made of the signal QTI to avoid any misunderstanding.

"T LuvHO

“‘WOOU UBEUT YOIMUIIH 0} Zurpuodsassoo aut} [BoO] BYy SOAIZ IBY Sty J,

TABLES

PORES cee
|v | | tT At | ets!

eter Hie
abl CT LT | Ra |S
ial PHN Le IAL
dew | | TING ge]
jsf | | dete] ||
cw | | LT NT

| awl | | Leet | |

dnl ry ESET
PME sak

GE le |
eet
ey ERS

U.S. GOVERNMENT PRINTING OFFICE : 1962 O - 664508

133

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