297  
FXCA20 KWBC 171819  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
218 PM EDT TUE OCT 17 2017  
 
TROPICAL DISCUSSION FROM OCT 17/12 UTC: STRONG POLAR TROUGH  
EXITING THE EAST COAST OF THE UNITED STATES IS SUSTAINING A  
SURFACE FRONT AND A SHEAR LINE THAT WILL CONTINUE ENHANCING  
ACTIVITY IN NORTHERN CENTRAL AMERICA/SOUTHERN MEXICO. ON  
TUESDAY...THE FRONT IS FORECAST TO BECOME STATIONARY NORTH OF THE  
BAHAMAS AND EXTEND ACROSS FLORIDA INTO THE NORTHERN/CENTRAL GULF  
OF MEXICO. AN ILL-DEFINED SHEAR LINE IS FORECAST TO EXTEND OVER  
THE NORTHERN BAHAMAS/WESTERN CUBA AND THE YUCATAN PENINSULA AREA.  
AT THIS TIME...THE POLAR TROUGH AT THE UPPER LEVELS WILL BE AT A  
POSITION FAVORABLE FOR ENHANCED CONVECTION OVER THE EASTERN GULF  
OF MEXICO...IN A REGION WITH HIGH PRECIPITABLE WATER CONTENT WHERE  
VALUES EXCEED 55MM. IN ASSOCIATION WITH THE SYSTEM...A NORTHERLY  
WIND SURGE IN THE SOUTHERN GULF OF MEXICO WILL CONTINUE TO SUPPORT  
MODERATE PRECIPITATION AMOUNTS OVER SOUTHERN MEXICO AIDED BY  
OROGRAPHIC UPLIFT. THIS WILL LEAD TO LOCALIZED AMOUNTS OF  
15-30MM/DAY AND MAXIMA OF 35-70MM IN SOUTHERN VERACRUZ ON  
TUESDAY-WEDNESDAY. IN THE YUCATAN PENINSULA...SHEAR LINE  
CONVECTION WILL LEAD TO AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-30MM. BY WEDNESDAY-THURSDAY...OROGRAPHIC ENHANCEMENT WILL LEAD  
TO 15-20MM/DAY AND MAXIMA OF 25-50MM. ALTHOUGH THE SHEAR LINE WILL  
LOSE DEFINITION BY THEN...AN ARRIVING TROPICAL WAVE WILL SUSTAIN  
SUFFICIENT MOISTURE CONVERGENCE TO PRODUCE 10-15MM/DAY AND MAXIMA  
OF 20-30MM/DAY IN THE EASTERN YUCATAN PENINSULA/NORTHERN  
BELIZE...AND IN WESTERN CUBA AND THE NORTHERN BAHAMAS. BY  
THURSDAY-FRIDAY...THE FRONT WILL ENHANCE PRECIPITATION IN THE  
NORTHERN BAHAMAS...WHERE IT WILL LEAD TO 10-15MM/DAY AND ISOLATED  
MAXIMA OF 20-35MM. SIMILAR AMOUNTS ARE EXPECTED IN THE  
CENTRAL/SOUTHEASTERN BAHAMAS. IN NORTHERN CENTRAL AMERICA...WHILE  
TRADES REMAIN FROM THE NORTHEAST...EXPECTING CONTINUED OROGRAPHIC  
UPLIFT TO SUSTAIN AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM  
FROM SOUTHERN VERACRUZ/CHIAPAS/TABASCO...INTO CENTRAL GUATEMALA  
AND SOUTHERN BELIZE. IN THE YUCATAN PENINSULA AND CUBA EXPECTING  
ISOLATED AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.  
 
IN THE CARIBBEAN...A REGION OF INTEREST IS THE EASTERN TIER AND  
THE NORTHERN ANTILLES. CURRENTLY...THE WET PATTERN IN THE EASTERN  
CARIBBEAN ASSOCIATES WITH AN ITCZ DISPLACED TO THE NORTH OF ITS  
CLIMATOLOGICAL POSITION...AND ONE TROPICAL WAVE APPROACHING.  
YET...NOTE THAT UNDER THE INFLUENCE OF AN APPROACHING TRADE WIND  
SURGE...THE CURRENT WET PATTERN WILL EVOLVE INTO A MUCH DRIER ONE  
DURING WEDNESDAY THROUGH FRIDAY. AS THE TRADE WIND SURGE ENTERS  
THE BASIN...IT WILL LIMIT LARGEST ACCUMULATIONS TO THE WINDWARD  
ISLANDS...WHERE AN ACTIVE ATLANTIC ITCZ IS FORECAST TO MEANDER  
DURING THE NEXT SEVERAL DAYS. IN THE MEAN TIME...HOWEVER...THE  
TROPICAL WAVE (SEE BELOW) AND ENHANCED LOW-LEVEL CONVERGENCE AHEAD  
OF THE TRADE WIND SURGE WILL SUSTAIN MODERATE PRECIPITATION  
AMOUNTS. THROUGH EARLY WEDNESDAY...LARGEST AMOUNTS ARE EXPECTED IN  
THE LESSER ANTILLES...AS TRAILING PLUME BEHIND THE TROPICAL WAVE  
AND CONVERGENCE AHEAD OF THE TRADE WIND SURGE INTERACT. THIS WILL  
LEAD TO 15-20MM/DAY AND MAXIMA OF 30-60MM. IN  
HISPANIOLA...PRE-FRONTAL TROUGH IN INTERACTION WITH THE MOISTURE  
PLUME WILL SUSTAIN 15-20MM/DAY AND MAXIMA OF 25-50MM. IN PUERTO  
RICO/VI EXPECTING MAXIMA OF 20-35MM. IN JAMAICA...EXPECTING  
ISOLATED AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. BY  
WEDNESDAY-THURSDAY...EXPECTING LARGEST ACCUMULATIONS IN THE  
SOUTHERN DOMINICAN REPUBLIC...WHERE THE TROPICAL WAVE/MOIST PLUME  
WILL FAVOR 15-30MM/DAY AND ISOLATED MAXIMA OF 40-80MM. THE TRADE  
WIND SURGE WILL LEAD TO FAIR CONDITIONS IN THE NORTHEASTERN  
ANTILLES...YET...ITCZ MOISTURE CONVERGENCE IN THE WINDWARD  
ISLANDS/NORTH EASTERN VENEZUELA WILL LEAD TO 15-30MM/DAY AND  
MAXIMA OF 35-70MM. BY THURSDAY-FRIDAY...LARGEST AMOUNTS WILL  
CLUSTER ONCE AGAIN IN THE SOUTHERN WINDWARDS AND NORTHEASTERN  
VENEZUELA/NORTHERN GUYANA...WHERE EXPECTING 15-20MM/DAY AND MAXIMA  
OF 25-50MM.  
 
IN NORTHWESTERN SOUTH AMERICA AND SOUTHERN CENTRAL  
AMERICA...ACCUMULATIONS WILL BE MODULATED BY A TRAVERSING TROPICAL  
WAVE AND ITS INTERACTIONS WITH THE PANAMANIAN LOW. AS THE WAVE  
CROSSES PANAMA ON TUESDAY...IT WILL CONTINUE ENHANCING CONVECTION  
TO PRODUCE AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM IN PANAMA  
AND WESTERN COLOMBIA. ISOLATED HIGHER AMOUNTS ARE EXPECTED IN  
EASTERN NICARAGUA AND COSTA RICA...WHERE EXPECTING 15-20MM/DAY AND  
MAXIMA OF 30-60MM. BY WEDNESDAY-THURSDAY...EXPECTING 10-15MM/DAY  
AND MAXIMA OF 20-40MM IN EASTERN NICARAGUA/EASTERN HONDURAS.  
ELSEWHERE IN SOUTHERN CENTRAL AMERICA EXPECTING MAXIMA OF 15-25MM.  
BY THURSDAY-FRIDAY...LARGEST AMOUNTS ARE EXPECTED IN EASTERN  
NICARAGUA AND COSTA RICA...WHERE EXPECTING 10-15MM/DAY AND MAXIMA  
OF 20-35MM. IN COLOMBIA...ITCZ/NET CONVERGENCE AND WESTERLIES  
ALONG THE PACIFIC BASIN WILL SUSTAIN AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-35MM ON A DAILY BASIS.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
62W 64W 67W 69W 72W 74W 76W 78W TW 17N  
81W 83W 85W 87W 90W 92W 93W 94W TW 18N  
 
TROPICAL WAVE INITIALIZED AT 62W WILL CONTINUE STIMULATING  
CONVECTION AS IT PROPAGATES WEST ACROSS THE CARIBBEAN BASIN. THE  
WAVE WILL STIMULATE CONVECTION IN PUERTO RICO/VI AND CENTRAL  
VENEZUELA ON TUESDAY...HISPANIOLA AND WESTERN VENEZUELA ON  
WEDNESDAY...AND NORTHERN COLOMBIA AND JAMAICA ON THURSDAY. NOTE  
THAT MODELS ARE SUGGESTING MODERATE RAINFALL AMOUNTS IN JAMAICA  
DURING FRIDAY...AS TROPICAL WAVE AND MOIST PLUME INTERACT WITH THE  
ISLAND. IN THE MEAN TIME...EXPECTING ISOLATED AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY.  
 
A TROPICAL WAVE INITIALIZED AT 81W IS ORGANIZING AS IT APPROACHES  
SOUTHERN CENTRAL AMERICA. THE WAVE IS FORECAST TO ENTER COSTA  
RICA/NICARAGUA LATE ON TUESDAY/EARLY WEDNESDAY. BY  
WEDNESDAY-THURSDAY...IT WILL ENHANCE CONVECTION IN  
HONDURAS/EASTERN YUCATAN...AND BY THURSDAY-FRIDAY...IT WILL  
ENHANCE ACTIVITY SLIGHTLY ACROSS GUATEMALA/CHIAPAS.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
GALVEZ...WPC (USA)  

 
 
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