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FXCA20 KWBC 271250
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
849 AM EDT FRI OCT 27 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI OCT 27/12UTC:
A MULTI-DAY WET SPELL IS STILL EXPECTED ACROSS PR/USVI FROM TODAY
INTO THE WEEKEND. THE AVAILABLE MOISTURE IS NOW ABOVE NORMAL AND
WILL REMAIN ABOVE NORMAL THROUGH AT LEAST MONDAY. MOISTURE COULD
BE AS MUCH AS TWO STANDARD DEVIATIONS ABOVE NORMAL THIS WEEKEND.
IN TERMS OF PRECIPITABLE WATER...THE VALUES WILL RANGE BETWEEN 2.3
AND 2.6 INCHES FROM TODAY THROUGH MONDAY...BUT COULD DECREASE TO
2.1 INCHES OR SO ON TUESDAY.
IN THE UPPER LEVELS...AN UPPER TROUGH WILL REMAIN TO THE WEST AND
NORTHWEST OF PR FOR THE NEXT FEW DAYS...MOVING TO THE WEST
NORTHWEST AS IT WEAKENS. AN UPPER LEVEL HIGH PRESSURE IS EXPECTED
OVER PR/USVI BY SUNDAY. A MID LEVEL TROUGH THAT IS ALSO LOCATED TO
THE WEST AND NORTHWEST OF PR/USVI IS CAUSING ENHANCED VORTICITY
TODAY AND SATURDAY. IN ADDITION...THERE IS A TROPICAL WAVE THAT
COULD MOVE IN THIS WEEKEND...WITH IS AXIS OVER PR ON SATURDAY
NIGHT...WHICH WOULD KEEP THE AREA WITH DEEP MOISTURE AND COMBINE
WITH THE REMAINING INSTABILITY OF THE UPPER TROUGH BEFORE THE
UPPER LEVEL HIGH PRESSURE MOVES IN DURING THE DAY ON SUNDAY.
ADDING TO THAT...THE TROPICAL WAVE THAT WOULD PASS OVER THE LOCAL
ISLANDS LATE SATURDAY...IS EXPECTED TO MOVE NORTHWEST AND CONTINUE
TO CAUSE SOUTHEASTERLY WINDS AND PULL MOISTURE OVER THE LOCAL
ISLANDS INTO EARLY NEXT WEEK. GIVEN THE NUMBER OF FACTORS
CONTRIBUTING TO ENHANCED MOISTURE AND INSTABILITY OVER THE LOCAL
AREA...SEVERAL DAYS OF SHOWERS AND THUNDERSTORMS OVER PR/USVI
WOULD BE EXPECTED. THE EGDI ALGORITHM AGREES...SUGGESTING THE RISK
OF SCATTERED THUNDERSTORMS FOR THE NEXT FEW DAYS INTO EARLY NEXT
WEEK. THAR BEING SAID...THE PERIOD WITH MOST INSTABILITY AND UPPER
LEVEL DIVERGENCE APPEAR TO BE LATE TODAY INTO SUNDAY. ANOTHER
THING TO NOTE IS THAT THE NOW EXTRATROPICAL CYCLONE FORMERLY KNOWN
AS TAMMY...IS EXPECTED TO BECOME A TROPICAL CYCLONE ONCE AGAIN
LATER TODAY...BUT IS EXPECTED TO REMAIN WELL TO THE NORTH OF PR.
THE 5-DAY RAINFALL TOTAL OVER PR/USVI IS FORECAST TO BE NEAR 8
INCHES...WITH EASTERN PR...VIEQUES...CULEBRA AND THE USVI
RECEIVING THE HIGHEST AMOUNTS. WESTERN PR IS FORECAST TO OBSERVE
ABOUT 2-4 INCHES. THIS FORECAST IS BETWEEN THE GFS AND ECMWF
GLOBAL MODELS. THE 00Z GFS WAS SUGGESTING MAX TOTALS ACROSS
E-PR/USVI NEARING 6-8 INCHES ACROSS ISOLATED SPOTS...WHILE THE
ECMWF WAS SUGGESTING ABOUT 3-5 INCHES TOTAL. HOWEVER...THE HI-RES
ECMWF WAS VERY AGGRESSIVE WITH THE RAINFALL IN THE SHORT TERM.
ALAMO...WPC (USA)
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