778  
FXCA20 KWBC 171208  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
807 AM EDT TUE OCT 17 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE VI FROM OCT 17/06  
UTC: CURRENT WET AND WINDY WEATHER PATTERN IN PUERTO RICO AND THE  
VIRGIN ISLANDS IS TO LAST THROUGH WEDNESDAY AFTERNOON...TO THEN  
GIVE IN INTO MUCH DRIER CONDITIONS THAT ARE TO PERSIST AT LEAST  
INTO EARLY NEXT WEEK.  
 
UPPER TROUGH EXTENDS ALONG 70-71W AND TO THE NORTH OF HISPANIOLA.  
THIS UPPER TROUGH IS BEING DRAWN TO THE NORTHEAST BY THE LARGE  
POLAR TROUGH EXITING THE UNITED STATES EAST COAST. THE UPPER  
TROUGH IS INTERACTING WITH A MOISTURE POOL LOCATED TO THE NORTH OF  
THE ISLANDS...WHERE STRONGEST CONVECTION IS OCCURRING. SOME DEEP  
CONVECTION IS ALSO OCCURRING IN SOUTHEASTERN PUERTO RICO AND IN  
THE VIRGIN ISLANDS THIS MORNING. ALSO OF INTEREST...ANOTHER  
TROPICAL WAVE IS APPROACHING AS IT EXTENDS ALONG 61W. THIS WAVE IS  
INTERACTING WITH THE ITCZ AND IS PRODUCING NUMEROUS SHOWERS AND  
THUNDERSTORMS IN THE LESSER ANTILLES.  
 
THE TROPICAL WAVE IS FORECAST TO CROSS THE ISLANDS LATE ON  
TUESDAY. AS THE TROPICAL WAVE APPROACHES AND THE UPPER TROUGH WILL  
MEANDERS TO THE EAST...THEY WILL INTERACT POSITIVELY ON TUESDAY  
NIGHT/EARLY MORNING TO SUSTAIN NOCTURNAL DEEP CONVECTION IN THE  
VIRGIN ISLANDS AND EASTERN PUERTO RICO INTO TUESDAY MORNING. THIS  
WILL SUSTAIN ACCUMULATIONS OF 1-2 INCHES AND ISOLATED MAXIMA OF 3  
INCHES BETWEEN LATE TUESDAY AND NOON ON WEDNESDAY. DURING THE DAY  
ON WEDNESDAY...UNDER 20-25KT SOUTHEASTERLY TRADES...EXPECTING A  
FEW SHORT-LIVED AND FAST MOVING THUNDERSTORMS TO DEVELOP IN  
EXTREME NORTHWESTERN PUERTO RICO...AND NUMEROUS TRADE WIND SHOWERS  
TO CONTINUE DOTTING SOUTHERN AND EASTERN PUERTO RICO. AS THE TRADE  
WIND SURGE ARRIVES ON WEDNESDAY EVENING...EXPECTING AN INCREASE IN  
WIND SPEEDS AND THE ESTABLISHMENT OF MUCH DRIER CONDITIONS DURING  
WEDNESDAY NIGHT INTO EARLY THURSDAY.  
 
IN THE MEAN TIME...DURING TUESDAY...WHILE 15-25KT SOUTHEASTERLY  
TRADES CONTINUE...EXPECTING LARGEST ACCUMULATIONS IN EASTERN AND  
SOUTHEASTERN PUERTO RICO WITH DAILY MAXIMA OF 2-4 INCHES...WHILE  
SHORT-LIVED AFTERNOON CONVECTION IN EXTREME NORTHWESTERN PUERTO  
RICO WILL PRODUCE MAXIMA NEAR 1 INCH.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
GALVEZ...WPC (USA)  

 
 
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