919
FXCA20 KWBC 211132
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
731 AM EDT THU MAR 21 2024
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI MAR 21/12UTC:
A SURFACE FRONT IS APPROACHING THE REGION WHILE EXTENDING ALONG
20N 65W...19N 67.5W...FAR EASTERN HISPANIOLA. TO THE SOUTHEAST OF
THE FRONT...FAIR WEATHER AND LIMITED CLOUDINESS ARE
PRESENT...COVERING MOST OF PUERTO RICO AND THE VI. WINDS ARE WEAK
FROM THE EAST AND WEAKENING...AS THE FRONTAL TROUGH APPROACHES THE
ISLANDS.
AS THE FRONTAL TROUGH AND DEVELOPING SHEAR LINE MOVE ACROSS THE
ISLANDS ON THURSDAY...EXPECT AN INCREASE IN AVAILABLE MOISTURE AND
IN MOISTURE CONVERGENCE. MODELS SUGGEST PRECIPITABLE WATER
INCREASING TO 40-45MM...WHICH IS FAVORABLE FOR MODERATE RAINFALL
AMOUNTS...PARTICULARLY GIVEN THE POTENTIAL FOR ENHANCED DIURNAL
HEATING DUE TO LIMITED CLOUDINESS DURING MORNING HOURS. GIVEN THE
PREVALENCE OF NORTHEASTERLY TRADES...ESPECIALLY IN THE AFTERNOON
AND AFTER...EXPECT THE LARGEST ACCUMULATION TO CLUSTER IN SOUTHERN
AND SOUTHWEST PUERTO RICO...WHERE EXPECT MAXIMA OF 1-1.5 INCHES.
A DECREASING TREND IS EXPECTED AFTER DUE TO A STRENGTHENING OF THE
MID-LEVEL RIDGE. THIS WILL FAVOR SOME AFTERNOON CONVECTION IN THE
CORDILLERA ON FRIDAY PRODUCING ISOLATED MAXIMA UNDER 0.75
INCHES...BUT DURING THE WEEKEND PRECIPITATION WILL BE LIGHT AND
WILL PRIMARILY CLUSTER IN REGIONS OF EARLY MORNING TRADE WIND
CONVERGENCE...PRIMARILY IN EASTERN AND SOUTHEASTERN PUERTO RICO.
THE NEXT SYSTEM OF INTEREST IS EXPECTED EARLY NEXT WEEK. AS
SURFACE PRESSURES GRADUALLY DECREASE TO THE NORTH OF THE
ISLANDS...EXPECT THE TRADES TO VEER TO SOUTHEASTERLIES BY SUNDAY
AND SOUTHERLIES BY MONDAY. THE VEERING OF THE TRADES WILL FAVOR AN
INCREASE IN LIGHT MORNING SHOWERS ALONG SOUTHERN PUERTO RICO ON
SUNDAY. ON MONDAY...THE INFLUENCE OF A POTENT UPPER TROUGH WILL
LIKELY TRIGGER DEEP CONVECTION AND MODERATE AMOUNTS IN NORTHERN
PUERTO RICO...WHERE THE CURRENT FORECAST CALLS FOR MAXIMA IN THE
0.4-0.7 INCH RANGE. UNCERTAINYY WITH MONDAY'S EVOLUTION EXISTS. AT
THE CURRENT TIME...WE ARE LEANING TOWARDS A FASTER SYSTEM...MORE
CONSISTENT WITH THE ECMWF MODEL SOLUTION...GIVEN THAT THE GFS
SEEMS TO BE UNDERFORECASTING THE SPEED OF SYSTEMS TRIGGERED BY
PERTURBATIONS IN THE MID-UPPER WESTERLIES.
GALVEZ/ACOSTA...WPC (USA)
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