669
FXCA20 KWBC 201219
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
818 AM EDT WED SEP 20 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI SEP 20/12UTC:
LOCALLY INDUCED SHOWERS AND THUNDERSTORMS ARE STILL EXPECTED TO BE
THE MAIN CONTRIBUTOR OF SIGNIFICANT RAIN FOR THE NEXT SEVERAL DAYS
OVER PR...PARTICULARLY OVER CENTRAL TO WESTERN PR...THOUGH 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...EXCEPT ON
LATE THURSDAY INTO FRIDAY WHERE NEAR A QUARTER OF AN INCH OF RAIN
IS POSSIBLE. PRECIPITABLE WATER IS EXPECTED TO BE BETWEEN 1.8 AND
2.1 INCHES THROUGH FRIDAY...DECREASING TO 1.6 INCHES ON SATURDAY
BUT THEN INCREASING AGAIN TO AROUND 2.1 INCHES BY SUNDAY EVENING.
THERE IS GOOD POTENTIAL FOR SHOWERS AND THUNDERSTORMS ONCE AGAIN
TODAY ACROSS PR...DUE TO OROGRAPHIC LIFTING AND SEA BREEZE
CONVERGENCE...COMBINED WITH SOME TROUGHINESS IN THE UPPER LEVELS
TO THE WEST OF PR. OUR FORECAST INDICATED 1-2 INCHES OF RAIN
ACROSS SEVERAL SECTORS OF PR...BUT THE HI-RES GUIDANCE INDICATES
THAT ISOLATED HIGHER AMOUNTS...AS MUCH AS 3 INCHES ARE POSSIBLE.
THE U.S. VIRGIN ISLANDS ARE NOT EXPECTED TO OBSERVE AS MUCH RAIN
TODAY...AND ONLY A FEW HUNDREDTHS ARE FORECAST WITH THE EXPECTED
BRIEF SHOWERS. DURING THE DAY ON THURSDAY...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. HOWEVER...AN APPROACHING TROPICAL WAVE LATE ON THURSDAY WILL
CAUSE AN INCREASE IN MOISTURE AND IN SHOWER ACTIVITY...WHICH WILL
GIVE THE USVI...VIEQUES...CULEBRA AND EASTERN PR SCATTERED TO
LOCALLY NUMEROUS SHOWERS OVERNIGHT THURSDAY INTO FRIDAY. THE EGDI
ALGORITHM INDICATES POSSIBLE ISOLATED THUNDERSTORMS THIS
AFTERNOON...AND ISOLATED TO SCATTERED THUNDERSTORMS THURSDAY
AFTERNOON AND FRIDAY. SATURDAY LOOKS A BIT DRIER...WITH
PRECIPITABLE WATER DECREASING AS WELL AS LOWER MID LEVEL RELATIVE
HUMIDITY...WHICH WOULD CAUSE LIMITED SHOWER ACTIVITY ACROSS THE
ISLANDS. THE EGDI ALSO HAS LITTLE TO NO INDICATION OF THUNDERSTORM
POTENTIAL ON SATURDAY. HOWEVER...AVAILABLE MOISTURE IS EXPECTED TO
INCREASE ON SUNDAY...AND THE EGDI INDICATES A GOOD CHANCE OF
THUNDERSTORMS SUNDAY AFTERNOON.
THE 5-DAY RAINFALL TOTAL IS FORECAST TO BE AROUND 6.5 INCHES
ACROSS THE WESTERN INTERIOR OF PR...EASTERN PR IS FORECAST BETWEEN
2.5 AND 3.5 INCHES...WHILE THE USVI IS FORECAST BETWEEN 0.50 AND
0.75 INCHES.
ALAMO...WPC (USA)
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