466  
FXCA20 KWBC 301035  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
634 AM EDT MON OCT 30 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM OCT 30/06  
UTC: A MID LEVEL HIGH TO THE NORTH OF PUERTO RICO ANCHORS A  
BUILDING RIDGE OVER THE WESTERN ATLANTIC. CONSISTENT WITH PREVIOUS  
FORECASTS...THE RIDGE IS TO REACH MAXIMUM AMPLITUDE ON  
TUESDAY/EVENING-EARLY WEDNESDAY MORNING. THIS IS TO THEN  
STRENGTHEN THE TRADE WINDS CAP WHILE SUSTAINING EROSION OF  
AVAILABLE MOISTURE. MEANWHILE...PLUME OF DEEP TROPICAL MOISTURE IS  
TO MEANDER ACROSS THE FORECAST AREA DURING THE NEXT DAY OR  
SO...WITH PWAT CONTENT OF TWO INCHES. AS THE TRADE WINDS CAP  
STRENGTHENS ON WEDNESDAY...PWAT CONTENT DECREASES TO AN INCH. IN  
RESPONSE TO ENVIRONMENTAL CHANGES...THE GFS GDI FORECAST INITIALLY  
SHOWS MODERATE INSTABILITY AND POTENTIAL FOR ISOLATED  
THUNDERSTORMS ACROSS THE NORTHERN VI AND PORTIONS OF PUERTO RICO.  
LATER ON TUESDAY...AS THE RIDGE STRENGTHENS ITS FOOTHOLD...A  
CONVECTIVELY STABLE AIR MASS IS TO THEN ENVELOP THE FORECAST AREA.  
EVOLVING PATTERN WILL THEN RESULT IN A DECREASE IN DIURNAL  
CONVECTION ACROSS THE ENTIRE FORECAST AREA.  
 
AT 700 HPA...A HIGH CLOSES OVER THE TURKS/SOUTHEAST BAHAMAS EARLY  
THIS AFTERNOON. THIS IS TO THEN FAVOR A LONG FETCH NORTHEASTERLY  
FLOW ACROSS THE WESTERN ATLANTIC TO THE EASTERN CARIBBEAN. THIS  
FLOW IS TO PERSIST THROUGH THE END OF THE WEEK. AT 850 HPA LIGHT  
MEANDERING WINDS ARE TO INITIALLY PREVAIL. ON TUESDAY...THE FLOW  
BECOMES SOMEWHAT BETTER ORGANIZED WITH EAST-TO-NORTHEAST WINDS TO  
PERSIST THROUGH THE END OF THE WEEK. AS THE WINDS SHIFT TO THE  
NORTHEAST...A COOL ADVECTIVE PATTERN IS TO ESTABLISH ACROSS THE  
NORTHEAST CARIBBEAN ISLES. THIS...IN INTERACTION WITH WARM SEA  
SURFACE TEMPERATURES NORTH OF THE ISLANDS...WILL FAVOR GENERATION  
OF EARLY MORNING SHOWERS AND LIGHT RAINFALL AMOUNTS ALONG THE  
NORTH/NORTHEAST COAST OF PUERTO RICO. UNDER THE INFLUENCE OF THE  
NORTHEAST STEERING FLOW...SHALLOW CONVECTION IS TO THEN CLUSTER  
OVER SOUTHWEST PUERTO RICO DURING THE MIDAFTERNOON HOURS.  
OTHERWISE... FAIR WEATHER CONDITIONS WILL PREVAIL.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  

 
 
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