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FXCA20 KWBC 191217
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
816 AM EDT WED JUL 19 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
19/12UTC: SAHARAN DUST WILL PREVAIL OVER PR/USVI THROUGH THE REST
OF THE WEEK AND INTO THE WEEKEND. THE AVAILABLE MOISTURE WILL BE
BELOW NORMAL THROUGH SATURDAY...INCREASING SLIGHTLY INTO THE
NORMAL LEVELS ON SUNDAY. THE PRECIPITABLE WATER WILL BOTTOM OUT AT
AROUND 1.2 INCHES ON THURSDAY AND FRIDAY AFTERNOON...WHICH IS NEAR
2 STANDARD DEVIATIONS BELOW NORMAL. THIS MEANS THAT FAIR WEATHER
IS TO BE EXPECTED THROUGH SATURDAY WITH HAZY SKIES. THAT
SAID...THERE IS A CHANCE OF BRIEF SHOWERS THAT COULD AFFECT
EASTERN PR/USVI IN THE MORNINGS AND OVERNIGHT...WITH WESTERN PR
HAVING LIMITED AFTERNOON CONVECTION. SINCE THE MOISTURE IS
EXPECTED TO INCREASE SLIGHTLY ON SUNDAY INTO MONDAY...AND THE
SAHARAN DUST CONCENTRATION IS EXPECTED TO DECREASE BY THEN...THE
RAINFALL FORECAST SUGGESTS HIGHER RAINFALL ACCUMULATIONS ON
SUNDAY. THERE WILL BE A TROPICAL WAVE THAT COULD MOVE IN ON
MONDAY.
A WEAK SFC HIGH PRESSURE OVER THE WEST CENTRAL ATLANTIC WILL KEEP
E-ESE INTO THE EARLY WEEKEND...THEN A STRONG SURFACE HIGH PRESSURE
ACROSS THE CENTRAL ATLANTIC WILL MAINTAIN THE EASTERLY WINDS FROM
SUNDAY ONWARD. A MID LEVEL HIGH PRESSURE IS FORECAST TO MOVE FROM
THE CENTRAL ATLANTIC TO WESTERN ATLANTIC BY FRIDAY INTO
SATURDAY...THEN A WEAK MID LEVEL TROUGH WILL MOVE INTO THE
SOUTHWESTERN ATLANTIC THIS WEEKEND. THE UPPER LEVEL WINDS WILL BE
FROM THE WEST THROUGH TONIGHT...THEN AN UPPER LOW AND ASSOCIATED
TROUGH MOVES INTO THE NORTH NORTHEAST OF THE LOCAL ISLANDS. BY
LATE SATURDAY...AN UPPER LOW DEVELOPS OVER THE NORTHERN
CARIBBEAN...CAUSING WEAK SOUTHERLY WINDS LOCALLY. THE LATEST
GUIDANCE CONTINUES TO SUGGEST A TRADE WIND INVERSION AT AROUND
850HPA FOR THE REST OF THE WORKWEEK...WEAKENING THIS WEEKEND.
OVERALL...THE DRIER THAN NORMAL AIR MASS WITH SAHARAN DUST AND
TRADE WIND INVERSION WILL CAUSE DRY CONDITIONS OVER PR/USVI
THROUGH AT LEAST SATURDAY. ALTHOUGH THERE IS A SLIGHT CHANCE OF
BRIEF SHOWERS...THERE WOULD BE MINIMAL IF ANY RAINFALL
ACCUMULATIONS. THE REST OF THE WORKWEEK IS EXPECTED TO BE FAIRLY
DRY...SUNDAY COULD BE THE DAY WITH BEST RAINFALL CHANCES...AND
EVEN THEN THE MAX RAINFALL FORECAST IS UNDER A HALF AN INCH. THAT
SAID...SUNDAY IS A BIT FAR INTO THE FORECAST PERIOD SO THERE IS
SOME UNCERTAINTY FOR SUNDAY. THE 5-DAY RAINFALL ACCUMULATION
FORECAST HAS MAX VALUES BETWEEN 0.75 AND 1 INCH ACROSS
NORTHEASTERN AND NORTHWESTER PR...WHILE AROUND A QUARTER OF AN
INCH OR LESS ACCUMULATIONS FOR THE USVI.
ALAMO...WPC (USA)
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