848
FXCA20 KWBC 181242
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
841 AM EDT MON SEP 18 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI SEP 18/12UTC:
LOCALLY INDUCED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE THE
MAIN REASON FOR SIGNIFICANT PRECIPITATION ACROSS PR OVER THE NEXT
5 DAYS. 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. THE PRECIPITABLE WATER IS
EXPECTED TO BE SLIGHTLY BELOW NORMAL TODAY...BUT THEN EXPECTED TO
INCREASE TO NEAR NORMAL LEVELS FROM TUESDAY THROUGH
THURSDAY...THEN A FURTHER INCREASE IN MOISTURE IS POSSIBLE ON
FRIDAY.
EVEN THOUGH THE AVAILABLE MOISTURE IS EXPECTED TO BE NEAR OR
SLIGHTLY BELOW NORMAL OVER THE NEXT FEW DAYS...THE SEA BREEZE
CONVERGENCE...DIURNAL HEATING...AND OROGRAPHIC LIFTING WILL CAUSE
SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS PORTIONS OF CENTRAL TO
WESTERN PR EACH AFTERNOON. THE MAX RAINFALL AMOUNTS ARE FORECAST
TO SURPASS ONE INCH EACH AFTERNOON...WITH SOME AREAS POSSIBLY
OBSERVING AROUND 2 INCHES. THE GLOBAL MODELS ARE SUGGESTING MUCH
LOWER AMOUNTS OF RAIN COMPARED TO THE HI-RES MODELS...BUT THIS IS
TO BE EXPECTED CONSIDERING THAT THE SHOWER ACTIVITY IS EXPECTED TO
BE LOCALLY INDUCED...WHICH MAY BE DIFFICULT FOR THE GLOBAL MODELS
TO CAPTURE. 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 ON FRIDAY...WHICH WOULD CAUSE AN INCREASE IN
MOISTURE AND IN THE LOWER LEVEL RELATIVE VORTICITY. THE EGDI
ALGORITHM INDICATES THE POSSIBILITY OF ISOLATED TO SCATTERED
THUNDERSTORMS OVER THE LOCAL ISLANDS ON FRIDAY. THEREFORE...EVEN
THOUGH SIGNIFICANT RAIN COULD BE OBSERVED EACH AFTERNOON ACROSS
ISOLATED AND LOCALIZED AREAS IN CENTRAL TO WESTERN PR...THE LATEST
GUIDANCE INDICATES THAT FRIDAY COULD BE A DAY WITH MORE RAINFALL
COVERAGE. THAT BEING SAID...ONE MUST CONSIDER THAT FRIDAY IS A BIT
FAR INTO THE FORECAST PERIOD TO BE TOO CONFIDENT.
THE 5-DAY RAINFALL TOTAL IS FORECAST TO BE AROUND 6 INCHES ACROSS
THE WESTERN INTERIOR OF PR...EASTERN PR IS FORECAST BETWEEN 1.5
AND 2 INCHES...WHILE THE USVI IS FORECAST BETWEEN 0.25 AND 0.50
INCHES.
ALAMO...WPC (USA)
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