CHAPTER 12 THE SYNOPTIC CODE DETAILED DESCRIPTION

1 Amendmentnoi~ ,theobserverwillfindthatthepreparationof theSynopticmessageis simplifiediftheappropriateentriesforline sandcolumnsIto42aonForm63 9028,TablesforSynopticCode,willassistthe min 2322aregivenin is thefirstgroupof thesecondlineof themessageheader.(M1M1M~M~isencodedBBXX forsy-nopticreportsfromshipstations.) thesecondlineof themessageheaderofa Dayofthemonth(UTC).GG Houroftheobservation(UTC). ~ Windindicator, fori~, ptionofspecifyinga3or 4,dependingonwhetheror ~ Stationnumber, , Thissymbolis anindicatorto showwhetheror nottheprecipitationgroup6 RRRtRis includedinthemessageand,ifincluded,inwha tSectionof :iR0inSections1and3includedinbothSection sinSection1included2inSection3included3i n noneof thetwosectionsomitted(precipitationland3 amount=0)4innoneof thetwosectionsomitted(precipitationIand3 amountnotavailable) ,itisincludedinSectionI, andiRis astationwhichtrans-mitsintermediatesynop ticreports,anditoccursbetweenamainsynopt ichourandthesubsequentintermedi-atesynop tichour,the6 RRRtRgroupwillbeincludedintheintermediat esynopticreport, ,~ Thissymbolindicateswhetherthesynopticmes sagehasoriginatedfromamannedoranauto-mat icstationandsecondly,whetherornotthepres entandpastweathergroup.

2 W2or7wawaWalWa2operationstaffedincluded2 staffedomitted(nosignificantphenomenonto report)3staffedomitted(notobserved,datan otavailable)4automaticincludedusingCodet ables4677and45615automaticomitted(nosign ificantphenomenonto report)6automaticomitted(notobserved,dat anotavailable)7automaticincludedusingCod etables4680and4531 Note:Currentautomaticstationsdonotuseind icatori,~=4;theynormallyuseindicatori,~= 5,6, aredefinedin height, , ,h iscodedwithreferenceto theheightof :WhenCHcloudsareobservedwithoutCLor CMcloudsbeingpresent, (HourlyReports)h0 OtolessthanSOm0,1IS0mtolessthanlOOm2,32l 00mtolessthan200m4,5,63200mtolessthan300 m7,8,94300m tolessthan600m10tol95600mtolessthanlOOOm 20to336l000mtolessthan1500m34to4971500mt olessthan2000m50to6682000mto lessthan2500m67to839 Greaterthan2500mGreaterthan83ornocloud(o rnocloud)/Skycompletelyobscured, codedcloudheightsinthehourlyreportdonotf itwithintheadjacentrangeofmetricheightsb ecauseofrounding,giveprecedencetotheactu alcloudheightinselectingthecodeforh, ,cloudheight290m:codeas10inhourlyreport.

3 Codehas3in theskyis partiallyobscuredbyfogor otherobscuringphenomena,h refersto thebaseofthelowestcloudobserved, ,hisrecordedasX;however,iftheskyis completelyob-scuredandcloudsarevisiblebe lowtheobscuration, ,iftheskyis com-pletelyobscuredbysnowinwhichtheverti calvisibilityis300m and1/10of Thehorizontalvisibility( )shallbecodedusingthefollowingtable:WMOC ode4377 MilesCodeMilesCodeFigureVVCodeVisibility FigurevV761 Lessthan55yards901/80286255yards,butless than220911/404964220yards,butlessthan550 923/8061066550yards,butlessthan1100931/2 0811671100yards,butlessthan2200945/81012 692200yards,butlessthan4400( )953/41213704400yds.,butlessthan11,000( ) , thesametimeandtheentrymore89inColumn31is 15+, , ,20milesshallbecodedas80; Thissymbolgivesthefractionofthecelestial domecoveredbyclouds, ,01oktasorless,butnotzero2/10 3/104/105/106/107/10and8/109/10ormorebut not10/1010/10butnotzero2 oktas3oktas4 oktas5oktas6 oktas7 oktasormore,butnot8oktas8oktasSkycomplet elyobscuredbyasurface ,or, r isnormallyusedonlyin theentryinColumn26(TotalAmount).

4 However,becauseofsomedifferencesinthepro ceduresforcodingHourlyandSynopticObserva tionssomeexceptionsarenecessaryasindicat edbelow:(a)Whenblueskyor starsareseenthroughalayerof fogor otherobscuringphenomenonwith-outanytrace ofcloudabovethislayer,N 6(b)If ,partialobscurationsmaybedisregardedandN is determinedbyconsideringthatportionofthes kywhichis :Example1:Referto notconcealedthereareequalpartsofblueskya ndcloud;thecodeforNwouldbe4(4oktas)in eachcase, ,incodingN theskyis consideredto ~CO~o-~I~rrrM~ILII(I,p).a~~. ~3 ENOWNAO~L~PGS~Zt2O 1A70 AkPd-~ 270 AKN-y 30 AKNI7 OtO~UOOVIO--~&1[21i--~.~0 StT~OSA~T9 OSCT-~Example2:Referto partiallyconcealedor theskyis 20%clearand80% theskyisconsideredto be80%coveredbycloud, :Referto ,butsincecloudispresentthecodeforN wouldbe0, ,incod-ingN theskyisconsideredto ,NhandN5(maybeusedwhentheskyispartiallyo bscured)AMOUNTOFSKYOBSCURED(TENTHS) (ACorSCperlucidus), ,eventhoughthesecloudsextendoverthewhole celestialdome,thetotalamountshallberepor tedbyN=7 shallbereportedwhentheskyiscompletelycon cealedbyanobscuringphenomenoneithersurfa ce :(a)Cloudscoverpartof theskybelowtheverticalvisibilityorbelowa nobscuringlayeraloft.]

5 (b)Cloudsarepresentbelowtheextentof verticalvisibilityinasurface basedlayerwhichhasa summationopacityof10 ~, ,o~~~*..ainn~ ~ ~ 0 .~.1A &~~~AAOOBS~ .G0~.-~rnS~CSCTA/SX023456789(a)(b)12 , Winddirection(true).The10 minutemeanwinddirectionshallbecodedto thenearesttende-grees(01 36) ~204o200050014001205o~2I4o21 NNE015~ 024~02215o~224o22025o~034o03035o~044o04S W225a~234o235a~244o2324NE045o~O54o055o~0 64o0506245o~254o255o~264o2526 ENEO65o~074oO75Q~084o0708W265~ 274~275o~284o2728EO85o~0940095010400910 WNW285o~294o2950~30402930 ESE105o~I14o11305o~3I4o31115~ 124~12NW3I5o~324o32 SESSEI250~I3401350~I44o145o~1540I550~I64 0I650~17401314151617 NNWN325o~3340335034403450354035500040333 435361750~I8401850~19401819 Winddirectionvariable99 Note:dd= 9 Amendmentn013 October1994ffTheWindSpeedinKnots(lOMinut eMean).

6 Thefollowingtableis *100 Knots09172635435261707887101827364453627 0792345 Knots23101119202829363745465455636371728 081 Knots34121321223030383947485656646573748 283 :l0mph=9knots11mph=l0knots34mph=30knots3 5mph=30knots*110mph=(87knots+9knots)= (OOfft)Thissupplementarygroupis includedinallsynopticreportswhenthewinds peed,intheunitsindicatedbyis.,,,, ,whenrequired, ,thefffof theO0fffgroupshallcontaintheactualwindsp eedandtheff southwindof 99knotsshallbecodedN ~ ~2s~ Signof ;usecodefigure1if DryBulbTemperatureintenthsof a thetemperatureforITFasread,fillingina :Temperatures~TITls~ ~ Signof ifthedew ;usecodefigure1ifthedew pointtemperatureis Dew , :Dew pointTemperature5~ Indicatorfigureof , ,codeP0P0P0P0byomittingthethousandsdigit andrecordthehundreds,tens,units,andtenth sdigitsdirectly, :Stationpressure= SeaLevelPressureinTenthsof a ,referto thevaluerecordedonLine22, 1000hPaormore,omitthethousandsdigitandre cordthehundreds,tens,units, hourCharacteristicshallbeobtainedfromthe barographchartandcodedin accordancewiththefollowingtable:GRAPHICR EPRESENTATION il--LI-I-i/-iCHARACTERISTICI ncreasing,thendecreasing;Increasing,then steady;orincreasing,thenincreas-ingmores lowly;Increasing(stead-ilyor unsteadily);Decreasingorsteady,thenincre asing;orincreasing,thenincreasingmorerap idlySteadyDecreasing,thenincreasing;Decr easing,thensteady.

7 Ordecreasing,thendecreasingmoreslowly;.9 Decreasing(steadilyorunsteadily);-Steady orincreasingthendecreasing;or,decreasing , ~ ~Lowerthan3 a Amountof PressureTendencyDuringtheThreeHoursPrece dingtheTimeofObserva-tion,ExpressedinTen thsof ,( )andcodedirectlyforpppinsertingazeroin theplaceof thetensdigitiftheamountis lessthan10hPaandtwozerosintheplacesofthe tensandunitsdigitsif :Net3 mainandintermediatesynopticreportsifprec ipitationhasoccurredsincethepreviousmain synopticobservation.( thesymboliR.) Amountofprecipitationwhichhasfallendurin gtheperiodprecedingthetimeofobservation, themainsynopticobservationandathreehourp eriodat ;threehouramountsshallbeobtainedfromanin termediatereadingofthestandardraingauge( ). (notused) (notusedinCanada) ,thenthe6 , , ,codefigures2to ,the6-groupshallbeincluded,usingcodefigu res5to 9 therehasbeennoprecipitation,the6 group,includingtR, groupisomittedwhenweatherofnosignificanc eis observed;thatis whenwwmaybecoded00,01,02,or03andpastweat hercodefigures0, WeatherandObstructionsto Vision (Column32)shallusuallybecodedfor ww ,howeverconsiderationshallalsobegivento anyrelatedinformationthatmayberecordedun derNotes, :wwCodes00 49inclusiveareusedto codepresentweatherwhenthereisnoprecipita tionat thestationat 99inclusiveareusedto codepresentweatherwhenprecipitationisocc ur-ringat thestationat 99areusednotonlyto indicatethetypeof precipitationbutalsotheintensity(light,m oderateor heavy),andthecharacter(continuous,interm ittentorshowery).

8 Detailedinstructionsre-gardingprecipitat iontypes,characterandintensityaregivenin PartA, Durationofperiodofreferenceforamountofpr ecipitation(RRR),Codeendingatthetimeofre portFigureTotalprecipitationduringthe6 hoursprecedingtheobservation2 Totalprecipitationduringthe12hourspreced ingtheobservation3 Totalprecipitationduringthe18hourspreced ingtheobservation4 Totalprecipitationduringthe24hourspreced ingtheobservation5 Totalprecipitationduringthe1hourprecedin gtheobservation6 Totalprecipitationduringthe2 hoursprecedingtheobservation7 Totalprecipitationduringthe3hoursprecedi ngtheobservation8 Totalprecipitationduringthe9 hoursprecedingtheobservation9 Totalprecipitationduringthe15hourspreced ingtheobservation12 , (ww)codesrequiresacompleteknowledgeof:(a ) DefinitionsandDescriptionsof Meteors asgivenin theInternationalCloudAtlas,and,(b) AtmosphericPhenomena instructionsanddefinitionsasgiveninChapt er3of thewwcodecorrespondsto thetenprincipalcategoriesof ,thedecademostsuitableto thegeneralstateof theweatherischosen;then,fromthatdecade,t hecodefigureischosenwhichbestdescribesth eweatheratthetimeof observationor(wherespecificallymentioned inthecode) ,onedoesnottakeintoaccountmeteorological phenomenawhichhavebeenexperiencedmoretha nonehourbeforetheofficialtimeof observingtheweather(withtheoneexceptiono f thunder,whichmay havebeenheardupto 1 94.)

9 Morethanonespecificationofthewwcodesisap plicable,thehighestcodefigureischo-sen,e xceptthatcode17shallbegivenpreferenceove rcodes20 :If a tornadois at orwithinsightof a stationat thetimeofobservationor withinthepasthour,theplainlanguagewordTO RNADO shallberecordedandtransmittedasthelastgr oupof tor-nadomayalsobereportedinthe7 groupsimultaneouslyifww= , ,inwhichpriorityis indicatedbytherelativepositionoftheblock ,maybeusedto 16 CHARTFORASSISTINGINTHESELECTIONOFTHEPRES ENTWEATHERCODEPRESENTWEATHER[IIINote:Whe nmixedprecipitationisoccuring,thecodefig ureformixedprecipitationshallbeselectedr atherthanthecodefigureforeitheroftheindi vidualtypesof :lightrainandlightsnowareoccuringtogethe r codefigure68shallbeusedratherthancodefig ure71(lightsnow)orcodefigure61(lightrain ).*Note:If codefigure17isapplicabletogetherwithoneo rmoreof wwcodes20 49,codefigure17shalltakePrecipitationNOT occuringat thestationat thestation*ww=17 PrecipitationISoccuringat thestationat imeofobservationVsby1/2mileorless*ww~=4O 49 Dustorm,sandstorm,blowingsnow,ordrifting snow*ww=30 39 Thunderstormwithpcpnattimeofobservationw w=95-99 IIIPepo,fog,or thunderstormduringpasthour,butnotattimeo f observation ww=20 29 Funnelcloudsightedinpasthourorattimeof observationww=19 Pcpnintheformofshowers,ie,RW,SW,IPW,SP,A ww=80-90 Pcpnat timeof observationandthunderstormduringthepasth ourww=91-94 ISquall(s)experiencedinpasthourorattimeo fobservationww=18 Thunderheardinpast15mm.]

10 ,orrainandsnowmixed,ordrizzleandsnowmixe d,notinshowersww= , thestationww=14-16 Drizzle,ordrizzleandrainmixedww=50-59 IIIIL ightningseeninpast15mm., ,notdeeperthan2mww=IIor12 IMist,(fog)visibility5 ,haze,dustorsprayww=04-4)9 Noweatherotherthancloudsww= WMOCODE4677 DetailedDescriptionNoteI: Throughoutthesedetaileddescriptions,thet erm slight whenreferringtoprecipitationintensity, :Codefigures00,01,02, ,combinedwitha codefigureof2 orlessforpastweather(W1W2),thenwwis :Codefigures00,01, (shownbyincreasingverticalextentorthicke ning)ordissolution(shownbydecreasingvert icalextentor thinning) lessimportantandshouldbeusedasthecriteri onwhenthereis nogeneraldevelopmentordissolutionobserva ble;ww= 00,01and02caneachbeusedwhentheskyisclear atthetimeof :00 whentheprecedingconditionsarenotknown;01 whenthecloudshavedissolvedduringthepasth our;02 :ww=00,01,02,03,18,19,20-28,30 35,and40 :Al