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FXCA20 KWBC 041220
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
819 AM EDT THU MAY 04 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY
04/12UTC: ON THURSDAY MORNING...A MID-LEVEL RIDGE CENTERS NEAR 23N
45W AND EXTENDS AN AXIS INTO THE NORTHEAST CARIBBEAN. THIS IS
HIGHLIGHTING THE TRADE WIND CAP...SETTING NEAR 850 HPA AS
INDICATED BY THE SAN JUAN SOUNDING AND THE TRADE WIND INVERSION
ALGORITHM FROM THE WPC INTERNATIONAL DESKS. A VERY DRY AIR MASS
LIES OVER THE CAP...WHICH REFLECTS IN PRECIPITABLE WATER VALUES
NEARING 30MM. THE TRADES ARE FROM THE SOUTHEAST WITH SPEEDS OF
05-10KT. SATELLITE IMAGERY IS CONSISTENT WITH THE PRESENCE OF THE
CAP AND SOUTHEASTERLY TRADES...AND IT SHOWS ISOLATED SHALLOW
CONVECTION IN PORTIONS OF SOUTHERN PUERTO RICO AND TO THE
NORTHWEST OF THE VI...WHILE SCATTERED STRATIFORM CLOUD DECKS ARE
PRESENT IN INTERIOR PORTIONS OF PUERTO RICO...PRIMARILY OVER THE
THE CORDILLERA AND IN MOUNTAINOUS REGIONS OF SOUTHEASTERN AND
EASTERN PUERTO RICO.
UNDER CURRENT UPPER CONVERGENT MJO CONDITIONS AND BELOW-AVERAGE
VALUES OF PRECIPITABLE WATER...EXPECT GENERALLY LIGHT RAINFALL
ACCUMULATIONS IN THE NEXT FEW DAYS. OF RELEVANCE...AN UPPER TROUGH
CURRENTLY EXTENDING ACROSS THE BAHAMAS INTO NORTHEAST NICARAGUA IS
FORECAST TO SLOWLY MEANDER EASTWARD...ENTER PUERTO RICO/THE MONA
PASSAGE EARLY ON SATURDAY...WHERE IT IS FORECAST TO PERSIST
THROUGH MONDAY WHILE SHORT WAVE TROUGHS PROPAGATE ALONG ITS
PERIPHERY. IN THE MEAN TIME...A SURFACE FRONT IS FORECAST TO
APPROACH FROM THE NORTH BUT ONLY REACH 22N WHILE THE SHEAR LINE
ENTERS HISPANIOLA DURING SATURDAY AND SUNDAY. GIVEN A FLARE UP OF
CONVECTION WITH THE FRONT AND A DRIER AIR MASS TO ITS
SOUTH...EXPECT THE CURRENT DRY PATTERN TO CONTINUE INTO SUNDAY. ON
THURSDAY AND FRIDAY...EXPECT AFTERNOON CONVECTION TO CLUSTER IN
NORTHWEST/NORTH-CENTRAL PUERTO RICO TO PRODUCE ISOLATED MAXIMA OF
0.2-0.5 INCHES. LESSER ACCUMULATIONS ARE EXPECTED ON SATURDAY AND
SUNDAY...WHERE MAXIMA WILL LIKELY APPROACH 0.2 INCHES.
THE FORECAST BECOMES CHALLENGING AFTER THIS PERIOD. UNDER THE
INFLUENCE OF THE SLOW-MOVING UPPER TROUGH TO THE NORTH...EXPECT
SOME DESTABILIZATION ACROSS THE ISLANDS AND OVER THE EASTERN
CARIBBEAN TO THE SOUTH. THE TROUGH TO THE NORTH WILL LIKELY FAVOR
LOWER PRESSURES OVER AND NORTH OF THE ISLANDS...WHICH IS
CONSISTENT WITH THE PREDOMINANCE OF SOUTHEASTERLY TRADES.
YET...MODELS HAVE VERY DIFFERENT SOLUTIONS REGARDING THE DEGREE OF
DESTABILIZATION AND MOISTENING OF THE TROPOSPHERE TO THE SOUTH OF
THE ISLANDS. THE GFS IS THE WETTEST MODEL...SHOWING THE ARRIVAL OF
A MOIST PLUME LATE ON SUNDAY/EARLY ON MONDAY...FAVORING SCATTERED
PRECIPITATION ACROSS PUERTO RICO AND ESPECIALLY THE VI DURING THE
ENTIRE DAY ON MONDAY. OTHER MODELS ARE MORE CONSERVATIVE...SHOWING
A MUCH DRIER SOLUTION. UNDER THE CURRENT SCENARIO...THE FORECAST
LIES IN THE MIDDLE...SHOWING AN INCREASE IN CONVECTION AND
PRECIPITATION STARTING LATE ON SUNDAY/EARLY ON MONDAY
MORNING...PRODUCING ACCUMULATION IN THE ORDER OF 0.2-0.5 INCHES
ACROSS SOUTHEASTERN AND EASTERN PUERTO RICO AND ALL OF THE VI.
AFTERNOON CONVECTION IN INTERIOR PORTIONS OF THE NORTHWEST SHOULD
FAVOR MAXIMA OF 0.4-0.7 INCHES. NOTE THAT THIS FORECAST IS SUBJECT
TO ADJUSTMENTS AS CONFIDENCE INCREASES.
GALVEZ/ACOSTA/ALAMO...WPC (USA)
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