171  
FXCA20 KWBC 141119  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
718 AM EDT SAT OCT 14 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE VI FROM OCT 14/06  
UTC: A TROPICAL WAVE LIES AT 60W. THE WAVE HAS AMPLIFIED UNDER THE  
INFLUENCE OF A WEAK TUTT LOW LOCATED AT 16N 53W. THE INTERACTION  
BETWEEN THE TUTT AND THE WAVE HAS ALSO GENERATED A POOL OF  
MOISTURE AND ENHANCED CONVECTIVE INSTABILITY TO THE EAST OF THE  
WAVE AXIS. SCATTERED DEEP CONVECTION IS OCCURRING IN THIS MOISTURE  
POOL WHICH LIES TO THE EAST OF 59W.  
 
MODELS ARE STRUGGLING RESOLVING THE EVOLUTION AFTER THE WAVE  
CROSSES THE ISLANDS. THE DISCREPANCIES ON THE FLOW AND POSITIONING  
OF MOISTURE POOLS IS VERY DIFFERENT FROM MONDAY AND ON. THERE IS  
BETTER AGREEMENT...HOWEVER...ON THE ARRIVAL OF THE WAVE...WHICH IS  
FORECAST TO CROSS PUERTO RICO ON SUNDAY MORNING. THIS WILL LEAD TO  
A MARKED SHIFT IN THE TRADES FROM NORTH EASTERLIES ON SATURDAY  
INTO EARLY SUNDAY TO SOUTH EASTERLIES ON SUNDAY. AS CONVECTIVE  
INSTABILITY INCREASES FROM EAST TO WEST...AND ENTERS IN PHASE WITH  
THE PEAK IN THE DIURNAL CYCLE OF MARINE CONVECTION...WE EXPECT  
MODERATE SHOWERS AND THUNDERSTORMS TO DEVELOP IN THE VIRGIN  
ISLANDS DURING EARLY SUNDAY. STRONGEST CONVECTION IS EXPECTED TO  
THE NORTH OF THE VIRGIN ISLANDS...YET...ACCUMULATIONS NEAR OR  
SLIGHTLY ABOVE 2 INCHES ARE POSSIBLE FROM EARLY SUNDAY THROUGH  
NOON TIME. CONVECTION IS TO FLARE UP DURING SUNDAY NIGHT INTO  
EARLY MONDAY IN THE VIRGIN ISLANDS AGAIN...TO PRODUCE RAINFALL TO  
PRODUCE AMOUNTS OF 1-1.5 INCHES.  
 
IN PUERTO RICO...UNDER NORTHEASTERLY TRADES ON  
SATURDAY...EXPECTING THUNDERSTORM DEVELOPMENT IN THE SOUTHWESTERN  
PORTION OF THE ISLANDS ON THE AFTERNOON...TO PRODUCE ISOLATED  
MAXIMA OF NEAR 2 INCHES. DURING SUNDAY...LARGEST AMOUNTS WILL  
CLUSTER IN EASTERN PUERTO RICO...TO PRODUCE MAXIMA OF 1.5-2  
INCHES. ON MONDAY...LARGEST ACCUMULATIONS WILL CLUSTER IN BOTH  
SOUTHEASTERN AND NORTHWESTERN PUERTO RICO. IN SOUTH EASTERN PUERTO  
RICO...EARLY MORNING CONVECTION WILL LEAD TO MAXIMA OF 1.5  
INCHES...WHILE AFTERNOON THUNDERSTORMS IN NORTHWESTERN PUERTO RICO  
WILL LEAD TO MAXIMA OF NEAR 2 INCHES. A SIMILAR EVOLUTION IS  
EXPECTED ON TUESDAY...ALTHOUGH CONFIDENCE DECREASES FOR THIS  
PERIOD.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
GALVEZ...WPC (USA)  

 
 
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