280  
FXCA20 KWBC 311057  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
657 AM EDT TUE OCT 31 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM OCT 31/06  
UTC: MID LEVEL HIGH TO THE NORTH OF THE DOMINICAN REPUBLIC ANCHORS  
A RIDGE OVER THE WESTERN ATLANTIC/NORTHERN CARIBBEAN ISLES. UNDER  
INFLUENCE OF THIS FEATURE A STRONG TRADE WINDS CAP IS TO SET LATER  
THIS AFTERNOON. THIS WILL BE ACCOMPANIED BY EROSION OF AVAILABLE  
MOISTURE...WITH PWAT CONTENT ACROSS PUERTO RICO AND THE USVI TO  
DROP FROM 2.0 INCHES TO AROUND 1.0-1.25 LATER TODAY. THE STRONG  
RIDGE PATTERN IS TO PERSIST THROUGH WEDNESDAY EVENING...WITH  
MODELS THEN SHOWING ITS GRADUAL COLLAPSE ON FRIDAY-SATURDAY AS  
SUCCESSIVE POLAR PERTURBATIONS STREAMING ACROSS THE EASTERN USA  
LIFT OVER THIS AXIS. ALTHOUGH THE RIDGE IS TO GRADUALLY  
WEAKEN...THE TRADE WINDS CAP AND LOW MOISTURE CONTENT IS EXPECTED  
TO HOLD THROUGH THE END OF THE WORKWEEK. AS A  
RESULT...ENVIRONMENTAL CONDITIONS ARE TO REMAIN HOSTILE TO  
ORGANIZED DEEP CONVECTION. AT LOW LEVELS...A LOW TO MID LEVEL  
RIDGE OVER THE WESTERN ATLANTIC SUSTAINS A LIGHT EAST TO  
NORTHEASTERLY FLOW ACROSS THE FORECAST AREA. EMBEDDED IN THIS  
FLOW...A TUTT INDUCED PERTURBATION IS TO APPROACH FROM THE  
NORTHEAST... REACHING THE NORTHEAST CARIBBEAN ON WEDNESDAY  
AFTERNOON. THIS IS TO THEN STREAM ACROSS THE VIRGIN ISLES LATER IN  
THE DAY...AND ACROSS PUERTO RICO EARLY ON THURSDAY MORNING. AS THE  
WAVE PRESSES AGAINST THE RIDGE TO THE WEST...THE GRADIENT WILL  
TIGHTEN. IN RESPONSE...THE 800-700 HPA WINDS INCREASE TO 15-20KT.  
THE STRONGER TRADES WILL THEN FAVOR A COOL ADVECTIVE PATTERN ON  
WEDNESDAY-FRIDAY MORNING...AND ARE LIKELY TO FAVOR GENERATION OF  
STREAMERS ACROSS THE VIRGIN ISLES THAT ARE TO AFFECT EASTERN  
PUERTO RICO FROM TIME-TO-TIME.  
 
AS THE PATTERN EVOLVES...THE GLOBAL MODELS FAVOR A DRYING TREND  
ACROSS THE NORTHEAST CARIBBEAN. MOST ACTIVE CONVECTION IS EXPECTED  
TODAY...WITH MODERATE CONVECTION CLUSTERING ACROSS  
WESTERN-SOUTHWESTERN PORTIONS OF PUERTO RICO DURING THE EARLY  
AFTERNOON HOURS. THE TUTT INDUCED WAVE ENTERING THE NORTHEAST  
CARIBBEAN ISLES ON WEDNESDAY IS GOING TO HAVE A HARD TIME  
OVERCOMING NEGATIVE INFLUENCE OF MID LEVEL RIDGE PATTERN. AS A  
RESULT...IT IS TO ONLY FAVOR LIGHT CONVECTION AS IT STREAMS ACROSS  
THE VIRGIN ISLES-EASTERN PUERTO RICO LATER ON WEDNESDAY-THURSDAY  
MORNING. IN A COOL ADVECTIVE PATTERN...THE BRISK NORTHEASTERLY  
TRADES ARE TO TRIGGER LIGHT EARLY MORNING SHOWERS ACROSS NORTHERN  
PUERTO RICO-VIRGIN ISLES. MEASURABLE RAINFALL AMOUNTS ARE TO  
GENERALLY CONFINE TO WESTERN INTERIOR PORTIONS OF PUERTO RICO IN  
LATE AFTERNOON CONVECTION.  
 
ON SATURDAY...BUILDING RIDGE OVER MEXICO WILL THEN INDUCE THE  
SOUTHWARD AMPLIFICATION OF A TROUGH ACROSS THE BAHAMAS-CUBA TO THE  
WESTERN CARIBBEAN. UNDER PRESSURE...THE RIDGE TO THE EAST  
COLLAPSES AND THE TRADE WINDS CAP RELAXES ITS FOOTHOLD ACROSS THE  
FORECAST AREA. THIS WILL THEN ALLOW FOR A SLIGHT INCREASE IN  
PRECIPITABLE WATER CONTENT...WITH ENVIRONMENTAL CONDITIONS  
BECOMING SOMEWHAT MORE FAVORABLE FOR DEEP CONVECTION TO DEVELOP.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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