606
FXCA20 KWBC 191238
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
837 AM EDT TUE SEP 19 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI SEP 19/12UTC:
LOCALLY INDUCED SHOWERS AND THUNDERSTORMS ARE EXPECTED FOR THE
NEXT SEVERAL DAYS OVER PR...MAINLY OVER CENTRAL TO WESTERN
PR...BUT SOME AREAS OF NORTHEASTERN PR INTO THE SAN JUAN METRO
COULD OBSERVE SIGNIFICANT RAIN TODAY. THE USVI IS FORECAST TO
OBSERVE ISOLATED TO SCATTERED BRIEF SHOWERS OVER THE FORECAST
PERIOD...WHICH COULD LEAD TO A FEW HUNDREDTHS OF AN INCH OF RAIN
EACH DAY...THOUGH NEAR A QUARTER OF AN INCH OF RAIN IS POSSIBLE
FROM LATE THURSDAY INTO FRIDAY. PRECIPITABLE WATER IS EXPECTED TO
BE SLIGHTLY BELOW NORMAL THIS MORNING...BUT IT IS INCREASING
SLOWLY INTO NORMAL LEVELS BY THIS EVENING...THEN IT WILL DECREASE
ON WEDNESDAY...ONLY TO GRADUALLY INCREASE AGAIN ON THURSDAY...AS A
TROPICAL WAVE REACHES THE AREA...PEAKING IN MOISTURE EARLY FRIDAY
WITH A VALUE OF NEAR 2.0 INCHES.
EVEN THOUGH THE AVAILABLE MOISTURE IS EXPECTED TO BE NEAR OR
SLIGHTLY BELOW NORMAL TODAY...THERE IS A GOOD POTENTIAL FOR
SHOWERS AND THUNDERSTORMS ACROSS PR...DUE TO OROGRAPHIC LIFTING
AND SEA BREEZE CONVERGENCE...COMBINED WITH A SHORTWAVE TROUGH IN
THE UPPER LEVELS. ONCE AGAIN THE HI-RES GUIDANCE IS MORE
AGGRESSIVE WITH THE RAINFALL AMOUNTS OVER PR COMPARED TO THE
GLOBAL MODELS...AND OUR FORECAST REFLECTS 1-2 INCHES OF RAIN
ACROSS SEVERAL SECTORS OF PR...BUT ISOLATED HIGHER AMOUNTS ARE
POSSIBLE. THE U.S. VIRGIN ISLANDS ARE NOT EXPECTED TO OBSERVE AS
MUCH RAIN...AND ONLY A FEW HUNDREDTHS ARE FORECAST. ON
WEDNESDAY...THE SEA BREEZE CONVERGENCE AND LOCAL EFFECTS WILL
CAUSE SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS PORTIONS OF
CENTRAL TO WESTERN PR ONCE AGAIN...WHILE NOT AS MUCH RAIN IS
FORECAST FOR THE EASTERN HALF OF PR. THE GLOBAL MODELS START BEING
A BIT MORE AGGRESSIVE WITH THE COVERAGE AND AMOUNTS OF RAIN ON
THURSDAY AND PARTICULARLY ON FRIDAY. THIS IS BECAUSE A TROPICAL
WAVE COULD BE APPROACHING THE LOCAL ISLANDS LATE THURSDAY INTO
FRIDAY...WHICH WOULD CAUSE AN INCREASE IN MOISTURE AND IN LOWER
LEVEL RELATIVE VORTICITY. THE EGDI ALGORITHM CONTINUES TO INDICATE
THE POSSIBILITY OF ISOLATED TO SCATTERED THUNDERSTORMS OVER THE
LOCAL ISLANDS LATE THURSDAY INTO FRIDAY. THEREFORE...FRIDAY COULD
BE A DAY WITH GOOD RAINFALL COVERAGE NOT ONLY FOR PR BUT ALSO FOR
THE USVI. AFTER THE TROPICAL WAVE PASSES...SCATTERED SHOWERS ARE
EXPECTED ACROSS THE AREA THROUGH THE WEEKEND...WITH LOCALIZED
AREAS WITH OVER A HALF AN INCH OF RAIN...THOUGH MAINLY ACROSS
CENTRAL TO WESTERN PR.
THE 5-DAY RAINFALL TOTAL IS FORECAST TO BE AROUND 6.5 INCHES
ACROSS THE WESTERN INTERIOR OF PR...EASTERN PR IS FORECAST BETWEEN
2 AND 2.5 INCHES...WHILE THE USVI IS FORECAST BETWEEN 0.50 AND
0.75 INCHES.
ALAMO...WPC (USA)
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