300
FXCA20 KWBC 181239
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
838 AM EDT THU MAY 18 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY
18/12UTC: A MID-LEVEL RIDGE CENTERS IN THE SOUTHERN CARIBBEAN AND
EXTENDS INTO THE GREATER ANTILLES. HOWEVER...THE ISLANDS LIE IN
THE PERIPHERY OF THE RIDGE...WHICH MEANS A WEAKER TRADE WIND CAP
AND THE PRESENCE OF SHORT WAVE PERTURBATIONS IN THE MID-LEVEL
WESTERLIES. PRECIPITABLE WATER REMAINS ABOVE AVERAGE...WITH VALUES
NEARING 50MM. THIS ENVIRONMENT IS FAVORABLE FOR ROBUST AFTERNOON
CONVECTION AND MODERATE TO LOCALLY HEAVY RAINFALL ACCUMULATIONS.
ON THURSDAY MORNING...SATELLITE IMAGERY SHOWS GENERALLY FAIR
WEATHER CONDITIONS ACROSS PUERTO RICO WITH THE EXCEPTION OF A FEW
POCKETS OF SHALLOW TRADE WIND CONVECTION IN SOUTHERN PUERTO RICO
AND IN PORTIONS OF THE VI. THE TRADES ARE FROM THE SOUTHEAST AT
10-15KT...WHICH WILL CONTINUE FAVORING AFTERNOON DEVELOPMENT IN
NORTHERN AND ESPECIALLY NORTHWEST PUERTO RICO.
THE SYSTEM OF INTEREST IS A POTENT UPPER TROUGH CURRENTLY OVER THE
SOUTHERN USA. THE TROUGH IS FORECAST DEEPEN AS IT MOVES ACROSS
FLORIDA INTO THE NORTHWEST CARIBBEAN ON FRIDAY. MODELS SUGGEST A
PROGRESSIVE SYSTEM...REACHING MAXIMUM AMPLITUDE DURING SATURDAY
AND SUNDAY...STARTING TO LIFT TO THE NORTHEAST ON MONDAY. AS IT
INTERACTS WITH THE CURRENT MOIST PLUME...THIS WILL FAVOR PERIODS
OF HEAVY RAINFALL ACROSS HISPANIOLA AND PUERTO RICO...PARTICULARLY
ON SATURDAY AND SUNDAY. ON THURSDAY...EXPECT AFTERNOON MAXIMA IN
NORTHWEST PUERTO RICO REACHING 1-2 INCHES. THIS INCREASES TO 2-2.5
INCHES ON FRIDAY...WHILE ENHANCED SOUTHEASTERLY TRADE MOISTURE
CONVERGENCE FAVORS MAXIMA OF 0.5-1 INCH IN EASTERN PUERTO RICO AND
THE WESTERN VI. ON SATURDAY...EXPECT MAXIMA OF 2-2.5 INCHES IN
NORTHWEST PUERTO RICO...BUT MODERATE AMOUNTS ARE EXPECTED ACROSS
THE ENTIRE ISLAND. THESE ARE FORECAST TO REACH 0.5-1 INCH IN
EASTERN PUERTO RICO AND THE CORDILLERA...0.2-0.4 INCHES IN
SOUTHERN PUERTO RICO AND 0.2-0.6 INCHES IN THE VI. ON SUNDAY...THE
BULK OF THE HEAVY PRECIPITATION STIMULATED BY THE UPPER TROUGH
WILL LIKELY FOCUS WELL TO THE NORTH OF THE ISLANDS. YET...A FEEDER
BAND-TYPE STRUCTURE TILL FAVOR ENHANCED ONSHORE FLOW IN SOUTHERN
PUERTO RICO...WHICH WILL SCATTERED AMOUNTS OF 0.5-1 INCH ACROSS
MOST OF SOUTHERN PUERTO RICO AND THE VI. MODERATE AMOUNTS ARE ALSO
EXPECTED ON MONDAY...BUT MOSTLY FOCUSING ACROSS THE VI AND FAR
NORTHERN PUERTO RICO...THE LATTERN IN AFTERNOON CONVECTION.
GALVEZ/ACOSTA...WPC (USA)
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