541
FXCA20 KWBC 261300
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
859 AM EDT THU OCT 26 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI OCT 26/12UTC:
A MULTI-DAY WET SPELL IS EXPECTED ACROSS PR/USVI FOR THE NEXT FEW
DAYS INTO THE WEEKEND...WHICH IS NOT PARTICULARLY UNCOMMON FOR
THIS TIME OF YEAR. THE AVAILABLE MOISTURE WILL INCREASE STEADILY
TODAY AND FRIDAY...THEN STAYING AS MUCH AS TWO STANDARD DEVIATIONS
ABOVE NORMAL AT LEAST THROUGH THE WEEKEND. IN TERMS OF
PRECIPITABLE WATER...THE VALUES WILL INCREASE FROM AROUND 1.9
INCHES THIS MORNING TO ABOUT 2.4 - 2.6 INCHES FOR THE WEEKEND.
IN THE UPPER LEVELS...THERE IS AN UPPER TROUGH THAT WILL REMAIN TO
THE WEST AND NORTHWEST OF PR FOR THE NEXT FEW DAYS. THE UPPER
TROUGH WOULD WEAKEN AND LIFT BY MONDAY. THIS UPPER TROUGH CAUSED A
SFC INDUCED TROUGH THAT WILL SLOWLY MOVE WEST AND OVER PR/USVI.
THERE IS A MID LEVEL TROUGH THAT IS ALSO LOCATED TO THE WEST AND
NORTHWEST OF PR/USVI...CAUSING ENHANCED VORTICITY ON FRIDAY INTO
THE WEEKEND. IN ADDITION...THERE IS A TROPICAL WAVE THAT COULD
MOVE IN THIS WEEKEND...WHICH WILL COMBINE WITH THE REMAINING
INSTABILITY OF THE MID AND UPPER LEVEL TROUGHS. ADDING TO
THAT...POST TROPICAL CYCLONE TAMMY IS EXPECTED TO REMAIN WELL TO
THE NORTH OF PR...BUT WOULD CAUSE THE DEEP MOISTURE TO POOL OVER
THE LOCAL AREA THIS WEEKEND INTO EARLY NEXT WEEK. SO CONSIDERING
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 FROM THIS
AFTERNOON ONWARD FOR THE NEXT SEVERAL DAYS INTO EARLY NEXT WEEK.
THAR BEING SAID...THE PERIOD WITH MOST INSTABILITY AND UPPER LEVEL
DIVERGENCE APPEAR TO BE LATE FRIDAY INTO SUNDAY.
THE 5-DAY RAINFALL TOTAL OVER PR/USVI IS FORECAST TO BE OVER 8
INCHES...WITH EASTERN PR...VIEQUES...CULEBRA AND THE USVI
RECEIVING THE HIGHEST AMOUNTS. WESTERN PR IS FORECAST TO OBSERVE
ABOUT 3-4 INCHES OVER THE NEXT 5 DAYS. HAVING SAID THAT...THE
FORECAST IS ACTUALLY IN BETWEEN THE GLOBAL MODELS. THE 00Z GFS WAS
SUGGESTING MAX TOTALS ACROSS E-PR/USVI NEARING 10 INCHES ACROSS
ISOLATED SPOTS...WHILE THE ECMWF WAS SUGGESTING ABOUT 3-5 INCHES
TOTAL. HOWEVER...GIVEN EVERYTHING THAT IS GOING TO AFFECT THE
LOCAL AREA COMBINED WITH THE LOCAL EFFECTS...THE FORECAST IS
CLOSER TO THE GFS MODEL IN TERMS OF AMOUNTS OF RAIN.
ALAMO/ACOSTA...WPC (USA)
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