349  
FXCA20 KWBC 181130  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
730 AM EDT WED OCT 18 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE VI FROM OCT  
18/06UTC: TROPICAL WAVE EXTENDS ALONG 65W AND IS ABOUT TO CROSS  
PUERTO RICO. AS ANTICIPATED...DEEP CONVECTION HAS FLARED UP IN  
EASTERN PUERTO RICO AND THE WESTERN VIRGIN ISLANDS EARLY THIS  
MORNING. TRADE WINDS ARE FROM THE EAST-SOUTHEAST...AT  
15-25KT...WHICH IS FAVORING EARLY MORNING MOISTURE CONVERGENCE IN  
EASTERN PUERTO RICO AND THE VIRGIN ISLANDS. ALSO OF INTEREST...A  
TRADE WIND SURGE EXTENDS ITS FRONTAL BOUNDARY ALONG 63W. THIS  
FEATURE IS ASSOCIATED WITH TRADE WINDS EXCEEDING 30KT AND A STRONG  
SUBSIDENCE CAP SITTING NEAR 900 HPA. AT UPPER LEVELS...A RIDGE  
EXTENDS AN AXIS FROM 28N 60W SOUTHWEST INTO THE VIRGIN ISLANDS. TO  
THE WEST...THE REMNANTS OF AN UPPER TROUGH AT 70W ARE BEING LIFTED  
NORTHEASTWARD BY A LARGE POLAR TROUGH THAT HAS EXITED THE EASTERN  
COAST OF THE UNITED STATES.  
 
INITIALLY...AS THE TROPICAL WAVE CROSSES THE ISLAND ON WEDNESDAY  
MORNING...NUMEROUS SHOWERS AND THUNDERSTORMS ARE TO PRODUCE  
MODERATE RAINFALL AMOUNTS IN EASTERN PUERTO RICO. EXPECTING  
ACCUMULATIONS REACHING AMOUNTS NEAR 1 INCH...YET MAXIMA IN REGIONS  
OF ENHANCED OROGRAPHIC UPLIFT WILL REACH 2-2.5 INCHES. ALSO DURING  
WEDNESDAY...ISOLATED MAXIMA NEAR 1 INCH IS EXPECTED IN EXTREME  
NORTHWESTERN PUERTO RICO IN THE FORM OF ISOLATED AFTERNOON  
THUNDERSTORMS.  
 
DURING WEDNESDAY EVENING...AS THE TRADE WIND SURGE PROPAGATES  
ACROSS THE ISLANDS AND THE SUBSIDENCE CAP ESTABLISHES...EXPECTING  
A SHARP DECREASE IN PRECIPITATION AND RAINFALL ACCUMULATIONS. FROM  
THIS PERIOD AND INTO EARLY NEXT WEEK...EXPECTING FAIR CONDITIONS  
ACROSS THE ISLANDS. PRECIPITATION WILL CLUSTER IN EASTERN PUERTO  
RICO...WHERE ENHANCED CONVERGENCE OF LIGHT AND ISOLATED TRADE WIND  
SHOWERS WILL LEAD TO TRACE AMOUNTS. NOTE THAT WINDY CONDITIONS ARE  
TO PREVAIL THROUGH EARLY NEXT WEEK...AS MODELS ARE INDICATING  
EAST-SOUTHEASTERLY TRADE WIND SPEEDS OF 20-25KT ON WEDNESDAY AND  
THURSDAY DECREASING TO 15-20KT EASTERLIES FROM LATE THURSDAY INTO  
EARLY NEXT WEEK.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
GALVEZ...WPC (USA)  

 
 
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