194
FXCA20 KWBC 181233
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
832 AM EDT TUE APR 18 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR
18/12UTC: THE LOCAL AND DIURNAL EFFECTS WILL BE THE MAIN REASON
FOR THE DEVELOPMENT OF SHOWERS ACROSS THE INTERIOR TO WESTERN PR
EACH AFTERNOON THROUGH THURSDAY. A SURFACE HIGH PRESSURE OVER THE
ATLANTIC WILL KEEP EASTERLY WINDS THROUGH FRIDAY.,..THOUGH IT WILL
BE VERY WEAK BY FRIDAY. THEN A SURFACE LOW PRESSURE WILL CAUSE
VERY WEAK WINDS LOCALLY WITH A SOUTHEASTERLY COMPONENT BY
SATURDAY. IN THE MID AND UPPER LEVELS... THERE WILL BE RIDGES THAT
WILL INHIBIT VERY DEEP CONVECTION LOCALLY. BY FRIDAY...THERE WILL
BE A MID LEVEL TROUGH THAT WILL APPROACH THE LOCAL AREA. A WEAK
UPPER LEVEL TROUGH WILL MOVE JUST NORTH OF THE NORTHEAST CARIBBEAN
FOR FRIDAY INTO SATURDAY. ALTHOUGH THE UPPER TROUGH IS BROAD...IT
HAS STRONG WINDS AND 70KT WINDS OR HIGHER COULD BE OBSERVED OVER
PR/USVI ON FRIDAY INTO THE WEEKEND...CAUSING VENTILATION AND
DIVERGENCE...PROMOTING PERSISTENT SHOWERS. THE PRECIPITABLE WATER
WILL REMAIN NEAR NORMAL OVER THE NEXT SEVERAL DAYS...GENERALLY
FLUCTUATING BETWEEN 1.3 AND 1.6 INCHES THROUGH THURSDAY.
HOWEVER...THE PRECIPITABLE WATER IS FORECAST TO PEAK ON FRIDAY
EVENING INTO SATURDAY MORNING...WITH VALUES UP TO 1.7 INCHES.
IN TERMS OF EXPECTED RAINFALL TOTALS...THE HIGHEST ACCUMULATIONS
ARE EXPECTED ACROSS THE INTERIOR INTO THE NORTHWESTERN QUADRANT OF
PUERTO RICO THIS AFTERNOON....WHERE RAINFALL MAXIMA SURPASSING 1.5
INCHES IS POSSIBLE ACROSS ISOLATED SECTIONS. ON WEDNESDAY
ONWARD...THE AFTERNOON CONVECTION COULD ONCE AGAIN AFFECT THE
INTERIOR...WESTERN AND NORTHWESTERN PUERTO RICO...WITH RAINFALL
MAXIMA THAT COULD SURPASS 0.50 INCHES EACH AFTERNOON. LOWER
RAINFALL AMOUNTS ARE EXPECTED ON THURSDAY...WHILE SOME UNCERTAINTY
REMAINS FOR FRIDAY DUE TO THE CHANGES IN MODEL GUIDANCE OUTPUT
FROM ONE DAY TO THE NEXT AND THE PRECISE LOCATION OF THE MID AND
UPPER LEVEL TROUGHS.
ALAMO/ACOSTA...WPC (USA)
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