859  
FXCA20 KWBC 111234  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
834 AM EDT THU MAY 11 2023  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY  
11/12UTC: THE DOMINANT FEATURE CONTINUES BEING A MID-LEVEL RIDGE  
LOCATED OVER THE CENTRAL CARIBBEAN AND ESTENDING INTO THE EEWARD  
ISLANDS. THIS IS ENHANCING THE TRADE WIND CAP OVER THE  
ISLANDS...WHICH SITS VERY LOW...NEAR 925 HPA. THE FEATURES IN  
SATELLITE IMAGERY ARE CONSISTENT WITH A SHALLOW MOIST LAYER AND  
WITH PLENTY OF DRY AIR IN THE REGION. THE SAN JUAN SOUNDING  
CONFIRMS THAT THERE IS VERY LITTLE MOISTURE ABOVE THE MARINE  
LAYER. ALSO OF RELEVANCE...A MOIST PLUME IS PROPAGATING ACROSS THE  
CENTRAL LESSER ANTILLES. YET...THE BULK OF THE FEATURE IS FORECAST  
TO PASS SOUTH OF THE ISLANDS...WHICH WILL CONTINUE TO FAVOR  
LIMITED COVERAGE OF PRECIPITATING CONVECTION THROUGH THE FORECAST  
CYCLE.  
 
MODELS CONTINUE STRUGGLING RESOLVING THE STRUCTURE OF PRECIPITABLE  
WATER PLUMES IN THE TRADES AND ON HOW THESE WILL EVOLVE OVER  
PUERTO RICO THROUGH THE FORECAST CYCLE. THIS HAS AN IMPACT ON THE  
DAY-TO-DAY QPF VARIABILITY. IN TERMS OF THE EVOLUTION OF SYNOPTIC  
SYSTEMS...THERE IS AGREEMENT ON A MID AND UPPER RIDGE PATTERN TO  
DOMINATE DURING THE NEXT FEW DAYS. THIS GENERALLY ASSOCIATES WITH  
ENHANCED SINKING MOTION AND DRIER CONDITIONS OVER THE ISLANDS.  
GIVEN THAT THE CARIBBEAN IS STILL IN THE TAIL END OF THE UPPER  
CONVERGENT/DRY MJO...THERE ARE MANY POINTERS TOWARDS A DRIER  
FORECAST. GIVEN THE TIME OF THE YEAR AND LOCAL AVAILABILITY OF  
HEAT AND MOISTURE...MODERATE AMOUNTS ARE STILL EXPECTED IN  
AFTERNOON CONVECTION ACROSS WESTERN AND NORTHWESTERN PUERTO  
RICO...BUT IN AN ISOLATED MANNER.  
 
ON THURSDAY...A SHORT WAVE TROUGH IS FORECAST TO CROSS HISPANIOLA.  
THE TROUGH WILL BE TOO FAR TO ENHANCE AFTERNOON CONVECTION IN  
PUERTO RICO...WHICH WILL LIKELY LIMIT AFTERNOON MAXIMA TO 1-1.25  
INCHES IN WESTERN PUERTO RICO. ON FRIDAY...THE MOIST PLUME IS  
FORECAST TO PROPAGATE WESTWARD TO THE SOUTH OF THE  
ISLANDS...LEAVING PUERTO RICO AND THE VI IN THE DRY SLOT. THIS  
WILL FAVOR SIMILAR AMOUNTS IN AFTERNOON CONVECTION. MODELS  
CONTINUE SHOWING A GRADUAL MOISTENING STARTING ON SATURDAY. UNDER  
THE INFLUENCE OF EAST-SOUTHEASTERLY TRADES...MAXIMA WILL CLUSTER  
ONCE AGAIN IN NORTHWEST PUERTO RICO. EXPECT AMOUNTS OF 1-1.5  
INCHES IN MAXIMA ON SATURDAY AND SUNDAY. MODELS DISAGREE ON  
MONDAY...YET THE SYNOPTIC PATTERN IS MORE CONSISTENT WITH THE  
ECMWF SOLUTION WHICH FAVORS DRIER CONDITION. ACCORDINGLY...WE ARE  
REFLECTING A DECREASE IN MAXIMA TO 0.5-0.75 INCHES...SUBJECT TO  
ADJUSTMENTS.  
 
GALVEZ/ACOSTA...WPC (USA)  

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page