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FXCA20 KWBC 281256
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
855 AM EDT TUE MAR 28 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAR
28/12UTC: GENERALLY FAIR WEATHER IS EXPECTED TODAY...ONLY LIGHT
AND BRIEF SHOWERS EXPECTED IN THE MORNING...BUT IMPROVING AS THE
MORNING PROGRESSES. A BETTER CHANCE OF SHOWERS IS EXPECTED ON
WEDNESDAY AND THURSDAY DUE TO INCREASING MOISTURE...BUT MOISTURE
MAY BE BELOW NORMAL FROM FRIDAY INTO THE WEEKEND. HOWEVER...THERE
IS SOME DISCREPANCY IN THE MODEL GUIDANCE FOR THIS WEEKEND. THE
LATEST GUIDANCE IS STILL SUGGESTING A FAIRLY DRY ATMOSPHERE FOR
THE REST OF THE DAY. PRECIPITABLE WATER WILL BE NEAR 2 STANDARD
DEVIATIONS BELOW NORMAL TODAY...BUT WILL INCREASE ON WEDNESDAY TO
NEAR NORMAL LEVELS...PERSISTING UNTIL THURSDAY...DECREASING FRIDAY
INTO THE WEEKEND.
AT THE SURFACE THERE IS A HIGH PRESSURE NORTH OF THE AREA THAT
WILL BE MOVING EAST...AND SHOULD BE IN THE EASTERN ATLANTIC BY
WEDNESDAY. THEN A SURFACE LOW PRESSURE WILL MOVE INTO THE WESTERN
ATLANTIC...WEAKENING THE LOCAL PRESSURE GRADIENT UNTIL LATE
THURSDAY WHEN ANOTHER SURFACE HIGH PRESSURE STARTS TO MOVE IN THE
THE WESTERN ATLANTIC ONCE AGAIN. ACROSS THE MID LEVELS THERE IS A
HIGH PRESSURE NORTH OF PR/USVI...BUT WILL ALSO MOVE EAST ON
WEDNESDAY...THEN ANOTHER MID LEVEL HIGH PRESSURE WILL MOVE IN LATE
FRIDAY. THERE WILL BE AN TRADE WIND CAP INVERSION TODAY THROUGH
WEDNESDAY...THEN THE INVERSION WILL WEAKEN SIGNIFICANTLY ON
THURSDAY INTO FRIDAY...BUT WILL RETURN LATE FRIDAY INTO THE
WEEKEND. ACROSS THE UPPER LEVELS...A WEAK UPPER TROUGH WEST OF THE
LOCAL ISLANDS IS FORECAST TODAY...BUT WILL FLATTEN BY WEDNESDAY.
BY LATE THURSDAY INTO FRIDAY...AN UPPER TROUGH MAY BE MOVING IN
FROM THE WEST...THE AXIS WILL MOVE THROUGH PR/USVI ON FRIDAY INTO
SATURDAY. HOWEVER...THE MODEL SOLUTIONS DO NOT DO MUCH IN TERMS OF
RAINFALL OR CONVECTION BEING ENHANCED BY THIS UPPER TROUGH MOVING
THROUGH...POSSIBLY DUE TO THE MID LEVEL HIGH PRESSURE AND TRADE
WIND INVERSION EXPECTED ON FRIDAY INTO SATURDAY.
WITH THIS PATTERN...BRIEF TRADE WIND SHOWERS ARE EXPECTED FOR
PR/USVI TODAY...BUT CAUSING VERY MINIMAL ACCUMULATIONS IF
ANY...INCREASING ACTIVITY ON WEDNESDAY ONWARD. THAT
SAID...CONFIDENCE IS LOW AT THIS TIME...ESPECIALLY FOR FRIDAY INTO
THE WEEKEND. THE ECMWF AND GFS MODELS DIFFER SLIGHTLY ON THE
TIMING AND LOCATION OF A FRONTAL BOUNDARY AND A PREFRONTAL TROUGH
THAT COULD BE APPROACHING THE LOCAL ISLANDS FROM THE NORTH.
THEREFORE THE MOISTURE PLUME AND THE RAINFALL THAT WOULD BE
ASSOCIATED WITH IT DIFFERS IN EACH MODEL SOLUTION.
ALAMO...WPC (USA)
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