673  
FXCA20 KWBC 241939  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
238 PM EST WED JAN 24 2018  
 
TROPICAL DISCUSSION FROM JAN 24/12 UTC: A SURFACE COLD FRONT AND  
SHEAR LINE WILL CONTINUE STIMULATING PRECIPITATION IN THE GULF OF  
MEXICO/NORTHERN CENTRAL AMERICA...AND LATER INTO CUBA AND THE  
BAHAMAS. BY WEDNESDAY EVENING THE FRONT WILL EXTEND FROM SOUTHERN  
FLORIDA...JUST TO THE NORTH OF THE YUCATAN PENINSULA...INTO  
CENTRAL VERACRUZ/SOUTHERN GULF OF CAMPECHE. BY THURSDAY EVENING  
THE BOUNDARY WILL MEANDER ACROSS THE NORTHERN BAHAMAS...NORTHERN  
CUBA... WHILE THE TAIL OF THE FRONT STARTS LOSING DEFINITION OVER  
THE SOUTHERN GULF OF MEXICO. BY FRIDAY EVENING...THE FRONT WILL  
EXTEND ACROSS THE CENTRAL BAHAMAS...NORTHERN CUBA...WITH AN  
ILL-DEFINED TAIL EXTENDING INTO THE CENTRAL GULF. AS THE POLAR  
HIGH MEANDERS FROM TEXAS ON WEDNESDAY...SURFACE PRESSURES OVER THE  
GULF OF MEXICO WILL REMAIN SUFFICIENTLY HIGH TO CONTINUE  
SUSTAINING A TEHUANTEPECER JET. THE JET IS FORECAST TO REACH PEAK  
INTENSITY THROUGH THURSDAY MORNING...WHEN IT IS FORECAST TO REACH  
50-55KT...TO WEAKEN RAPIDLY AFTER. A SHEAR LINE HAS ALSO  
FORMED...AND BY WEDNESDAY EVENING IT WILL EXTEND ACROSS THE  
NORTHERN BAHAMAS...CENTRAL-NORTHERN CUBA...BELIZE. BY THURSDAY  
EVENING THE SHEAR LINE WILL EXTEND ACROSS EASTERN HISPANIOLA INTO  
NORTHEASTERN NICARAGUA. BY FRIDAY EVENING...THE SHEAR LINE WILL  
EXTEND ACROSS NORTHERN PUERTO RICO...SOUTHEASTERN  
HISPANIOLA...LOSING DEFINITION ACROSS THE NORTH-CENTRAL CARIBBEAN.  
 
THE BULK OF PRECIPITATION WITH THE FRONT/SHEAR LINE SYSTEM WILL  
OCCUR ALONG THE GULF OF CAMPECHE AND NORTHERN CENTRAL AMERICA. IN  
VERACRUZ/TABASCO/NORTHERN CHIAPAS...ACTIVE CONVECTION WILL PERSIST  
THROUGH THE CYCLE. LARGEST ACCUMULATIONS ARE EXPECTED THROUGH  
THURSDAY...WHEN AMOUNTS WILL REACH 15-20MM/DAY AND MAXIMA OF  
35-70MM. THIS IS TO GRADUALLY DECREASE TO 10-15MM/DAY AND MAXIMA  
OF 20-35MM BY FRIDAY-SATURDAY. ACTIVE CONVECTION WILL CONTINUE  
ACROSS NORTHWESTERN HONDURAS/SOUTHERN BELIZE INTO CENTRAL  
GUATEMALA. MODELS AGREE ON MOISTURE POOL BUILDING DUE TO CONTINUED  
TRADE WIND CONVERGENCE...AND AID FROM AN UPPER TROUGH APPROACHING  
FROM THE WEST. THIS WILL LEAD TO PRECIPITABLE WATER VALUES OF  
45-50MM BY THURSDAY THROUGH SATURDAY. RAINFALL TOTALS WILL REACH  
15-20MM/DAY AND MAXIMA OF 25-50MM THROUGH FRIDAY. BY FRIDAY  
THROUGH SATURDAY...THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF  
20-40MM. ACTIVE CONVECTION IS ALSO EXPECTED IN INLAND PORTIONS OF  
THE YUCATAN PENINSULA. THROUGH EARLY THURSDAY...EXPECTING  
05-10MM/DAY AND MAXIMA OF 15-20MM. THIS WILL INCREASE TO  
05-10MM/DAY AND MAXIMA OF 15-25MM BY THURSDAY-FRIDAY. AS THE  
DYNAMIC FORCING DECREASES...AMOUNTS WILL DECREASE ON  
FRIDAY-SATURDAY TO 05-10MM/DAY AND MAXIMA OF 15MM. FRONT/SHEAR  
LINE ACTIVITY WILL ALSO STIMULATE ACCUMULATIONS IN CUBA...WHERE  
EXPECTING 05-10MM/DAY AND MAXIMA OF 15MM THROUGH FRIDAY  
MORNING...CONCENTRATING GENERALLY IN NORTHERN CUBA. FRONTAL  
CONVECTION WILL INCREASE IN EAST-CENTRAL CUBA...TO PRODUCE  
05-10MM/DAY AND MAXIMA OF 15-25MM. IN THE BAHAMAS...LARGEST  
ACCUMULATIONS ARE EXPECTED THROUGH FRIDAY...TO REACH 05-10MM/DAY  
AND ISOLATED MAXIMA OF 15-20MM. BY FRIDAY-SATURDAY THIS IS TO  
DECREASE TO MAXIMA OF 15MM...WHILE ACTIVITY SHIFTS TO THE  
CENTRAL-SOUTHERN BAHAMAS. IN HISPANIOLA...SHEAR LINE CONVECTION  
WILL COMBINE WITH FAST TRADES OF 25-35KT. THIS WILL ENHANCE THE  
OROGRAPHIC FORCING IN NORTHEASTERN PORTIONS OF THE  
ISLAND...ESPECIALLY BY THURSDAY-FRIDAY...WHEN TOTALS WILL REACH  
10-15MM/DAY AND MAXIMA OF 20-30MM. OTHERWISE...EXPECTING ISOLATED  
MAXIMA OF 15-20MM ON A DAILY BASIS. NOTE THAT AMOUNTS ARE LIKELY  
TO INCREASE ONCE AGAIN BY SATURDAY-SUNDAY DUE TO A BUILDUP OF  
PRECIPITABLE WATER AS THE FAST TRADES CONTINUE. SHEAR LINE  
CONVECTION IN PUERTO RICO WILL LEAD TO 05-10MM/DAY AND ISOLATED  
MAXIMA OF 15-25MM BY FRIDAY-SATURDAY...MOSTLY ALONG THE NORTHERN  
AND EASTERN COASTS. AMOUNTS WILL BE ENHANCED BY SHALLOW CONVECTIVE  
INSTABILITY/COLD ADVECTIVE PATTERN FROM THE NORTHEASTERLY TRADES.  
 
IN THE CENTRAL AND EASTERN CARIBBEAN...SEASONALLY DRY CONDITIONS  
CONTINUE ESTABLISHING. THE MID-LEVEL RIDGE WILL BE PRESENT THROUGH  
THE FORECAST CYCLE...WITH ITS CENTER MEANDERING NORTH OF PUERTO  
RICO AND HISPANIOLA. WHILE THE RIDGE COVERS MOST OF THE EASTERN  
AND CENTRAL CARIBBEAN...ACTIVITY IN THESE REGIONS WILL OCCUR  
MOSTLY IN THE FORM OF TRADE WIND SHOWERS. ACCUMULATIONS WILL BE  
LIKELY UNDER 10MM. ISOLATED HIGHER AMOUNTS ARE EXPECTED ON THE  
CENTRAL LESSER ANTILLES ON WEDNESDAY...IN ASSOCIATION WITH THE  
TRAILING MOISTURE BEHIND A WEAK TUTT-INDUCED TROUGH IN THE TRADES  
(SEE BELOW).  
 
AS THE MID-LEVEL RIDGE PATTERN DOMINATES THE CARIBBEAN...A  
MID-LEVEL TROUGH IS FORECAST TO PERSIST IN CENTRAL AMERICA. THE  
TROUGH WILL EVOLVE FROM AN ELONGATED TROUGH FROM THE PACIFIC COAST  
OF CENTRAL AMERICA ON WEDNESDAY...TO EXTEND ACROSS NORTHERN  
GUATEMALA-PANAMA BY FRIDAY. THIS TROUGH WILL CONTINUE AIDING  
CURRENT PATTERN OF ACTIVE CONVECTION IN THE REGION...EVEN IN AREAS  
TO THE SOUTH OF THOSE INFLUENCED BY THE FRONT AND SHEAR LINE.  
THROUGH FRIDAY...EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM  
EXTENDING FROM NORTHEASTERN HONDURAS TO NORTHERN COSTA RICA. THIS  
IS TO DECREASE TO 05-10MM/DAY AND MAXIMA OF 15-20MM/DAY IN  
NICARAGUA AND COSTA RICA. IN HONDURAS...UNDER THE INFLUENCE OF  
CONTINUED MOISTURE CONVERGENCE DUE TO 25-35KT EASTERLY  
TRADES...EXPECTING RAINY PATTERN TO EXTEND INTO THE EARLY WEEKEND.  
BY FRIDAY-SATURDAY EXPECTING 10-15MM/DAY AND MAXIMA OF 20-40MM.  
 
IN NORTHERN SOUTH AMERICA...LARGEST ACCUMULATIONS WILL CONTINUE  
CLUSTERING IN WESTERN COLOMBIA WHILE THE PACIFIC ITCZ REMAINS TO  
THE NORTH OF ITS CLIMATOLOGICAL POSITION. MODELS ARE  
CONFIDENT...HOWEVER...ON THE ITCZ MEANDERING SOUTHWARD THROUGH THE  
CYCLE. THIS WILL LEAD TO A GRADUAL DRYING IN PANAMA/DARIEN...WHILE  
ACTIVITY PERSISTS IN SOUTHWESTERN COLOMBIA/CAUCA VALLEY. EXPECTING  
05-10MM/DAY AND MAXIMA OF 15-20MM THROUGH THE CYCLE.  
OTHERWISE...EXPECTING DIURNAL CONVECTION TO CONSTRAIN TO THE  
SOUTHERN AMAZON...AND ISOLATED AND LIGHT DIURNAL SHOWERS IN PARTS  
OF THE ANDES. WHILE THE ATLANTIC ITCZ REMAINS IN NORTHERN  
BRAZIL...EXPECTING LIGHT ACCUMULATIONS IN THE GUIANAS THROUGH THE  
CYCLE.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
SOF  
61W 65W 69W 73W 77W DISSIPATED TUTT INDCD  
15N  
75W 79W 82W 87W 91W DISSIPATED EW22N  
 
A TUTT-INDUCED WAVE IS INITIALIZED AT 61W. THIS WAVE IS EXITING  
THE LESSER ANTILLES...YET TRAILING MOIST PLUME WILL LEAD TO  
05-10MM/DAY AND MAXIMA OF 15MM IN THE CENTRAL LESSER ANTILLES ON  
WEDNESDAY. ELSEWHERE...THE EFFECTS OF THIS WAVE WILL BE LIMITED  
UNDER THE PRESENCE OF DRY MID-LEVELS....AND THE WAVE IS FORECAST  
TO DISSIPATE BY FRIDAY.  
 
AN EASTERLY WAVE IS INITIALIZED AT 75W. THIS WAVE HAS AN  
ILL-DEFINED SIGNATURE ACROSS THE NORTHERN CARIBBEAN/SOUTHERN  
CUBA/SOUTHERN BAHAMAS. AS THE WAVE INTERACTS WITH SHEAR  
LINE/FRONTAL SYSTEM...IT WILL LOSE DEFINITION THROUGH FRIDAY WITH  
LITTLE EFFECTS ON PRECIPITATION.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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