527  
FXCA20 KWBC 021117  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
616 AM EST FRI FEB 02 2018  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM FEB 02/06  
UTC: A 500 HPA HIGH OVER THE YUCATAN/CAMPECHE SOUND EXTENDS A  
RIDGE EAST ACROSS THE GREATER ANTILLES TO THE EASTERN CARIBBEAN.  
THIS SUSTAINS A FAIRLY STRONG TRADE WINDS CAP ACROSS THE FORECAST  
AREA. MID LEVEL RIDGE PATTERN IS TO GENERALLY HOLD THROUGH THE  
MEDIUM RANGE PERIOD...TO CONTINUE TRAPPING SHALLOW MOISTURE TO THE  
LOW LEVELS OF THE ATMOSPHERE. AT LOW LEVELS...A RIDGE OVER THE  
CENTRAL ATLANTIC FAVORS BRISK EASTERLY TRADES ACROSS THE EASTERN  
CARIBBEAN ISLES...WITH 850 HPA WINDS PEAKING AT 20-25KT. PATCHY  
CLOUD CLUSTERS EMBED IN THIS FLOW...STREAMING ACROSS THE FORECAST  
AREA FROM TIME-TO-TIME...MEANWHILE FAVORING LIGHT RAINFALL AMOUNTS  
IN PASSING SHOWERS. FARTHER EAST...A TUTT INDUCED PERTURBATION  
MEANDERS OVER THE TROPICAL ATLANTIC ALONG 51W...WITH MOISTURE  
CLUSTERING ALONG AND EAST OF THIS AXIS.  
 
AT MID LEVELS...A POLAR TROUGH EXITING THE EASTERN USA EARLY IN  
THE CYCLE IS TO RAPIDLY LIFT ACROSS THE CENTRAL ATLANTIC. LACKING  
UPPER LEVEL SUPPORT...THE ASSOCIATED FRONTAL BOUNDARY BOTTOMS OUT  
NORTH OF 27N/28N. ALTHOUGH THE FRONT IS NOT TO REACH THE FORECAST  
AREA...THIS FRONT AND A POST FRONTAL POLAR RIDGE WILL INDUCE A  
WIND SHIFT TO THE NORTHEAST LATER THIS EVENING. IN A FRESH  
NORTHEASTERLY FLOW EXPECTING COOL ADVECTION ACROSS THE FORECAST  
AREA AND SOMEWHAT HIGHER INCIDENCE OF TRADE WIND SHOWERS ON  
SATURDAY THROUGH SUNDAY MORNING. THE SHOWERS ARE TO PESTER  
NORTHERN PUERTO RICO AND THE NORTHERN VIRGIN ISLES DURING THE  
MORNING HOURS...WITH WEATHER CONDITIONS GENERALLY IMPROVING DURING  
THE LATE MORNING/EARLY AFTERNOON HOURS. LATE AFTERNOON CONVECTION  
IS TO THEN BUILD ALONG THE CORDILLERA/WESTERN INTERIOR PORTIONS OF  
PUERTO RICO...BUT THESE ARE TO MAINLY FAVOR LIGHT RAINFALL  
AMOUNTS. PREVAILING EASTERLY TRADES ARE TO THEN RETURN DURING THE  
DAY ON SUNDAY...ENHANCING MOISTURE CONVERGENCE ACROSS EL YUNQUE  
RAINFOREST AND WESTERN PORTIONS OF PUERTO RICO.  
 
EMBEDDED IN THIS FLOW...REMNANTS OF THE TUTT INDUCED PERTURBATION  
MEANDER WEST ACROSS THE NORTHERN LEEWARD ISLES LATER ON  
SUNDAY...REACHING THE VIRGIN ISLES/EASTERN PUERTO RICO ON MONDAY  
MORNING. PWAT CONTENT WITH THIS FEATURE IS EXPECTED TO RANGE  
BETWEEN 1.25-1.50 INCHES...WITH THE DEEPER MOISTURE CLUSTERING  
JUST SOUTH OF THE FORECAST AREA. IN ASSOCIATION WITH THIS FEATURE  
THE MODELS AGREE ON LIGHT TO MODERATE RAINFALL AMOUNTS...WITH THE  
UKMET IN PARTICULAR SHOWING MOST ACTIVE CLUSTERING OVER WESTERN  
INTERIOR PORTIONS OF PUERTO RICO IN AFTERNOON CONVECTION. THE GFS  
AND ECMWF INSTEAD FAVOR MOST ACTIVE CONVECTION AFFECTING THE  
VIRGIN ISLES-NORTHEAST/NORTHERN PUERTO RICO. IN AN EAST-SOUTHEAST  
STEERING FLOW IT LOOKS LIKE THE GFS/ECMWF SOLUTION MIGHT HAVE A  
BETTER CHANCE OF VERIFYING.  
 
GORDON...NMS (BELIZE)  
NIXON...BDM (THE BAHAMAS)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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