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FXCA20 KWBC 211242
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
842 AM EDT WED JUN 21 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUN
21/12UTC: TROPICAL STORM BRET CONTINUES TO ADD SOME UNCERTAINTY TO
THE RAINFALL FORECAST FROM FRIDAY INTO SUNDAY. THE RAINFALL
FORECAST WILL BE ADJUSTED EACH DAY SHOWING THE LATEST OFFICIAL
FORECAST FROM THE NATIONAL HURRICANE CENTER REGARDING TROPICAL
STORM BRET.
A SURFACE HIGH PRESSURE WILL REMAIN OVER THE CENTRAL ATLANTIC
TODAY WHILE IT WEAKENS...BUT ANOTHER SURFACE HIGH PRESSURE WILL
MOVE IN TO THE NORTHWESTERN ATLANTIC ON THURSDAY...WHICH WILL KEEP
AN EASTERLY WIND FLOW THROUGH THE REST OF THE WEEK...THOUGH THE
WIND FLOW COULD BE IMPACTED BY BRET AS IT PASSES THROUGH THE
CARIBBEAN. A BROAD MID LEVEL RIDGE WILL REMAIN OVER THE ATLANTIC
FOR THE NEXT SEVERAL DAYS. AN UPPER LEVEL TROUGH IS EXPECTED JUST
WEST OF PUERTO RICO TODAY...THEN IT WILL SLOWLY MOVE EAST ON
THURSDAY...GIVING WAY TO AN UPPER LEVEL HIGH PRESSURE THAT WILL
MOVE OVER HISPANIOLA...CAUSING NORTH TO NORTHWESTERLY WINDS IN THE
UPPER LEVELS OVER PR/USVI INTO THE WEEKEND. THE PRECIPITABLE WATER
INCREASE SIGNIFICANTLY TODAY TO NEAR 2 INCHES BY THIS
AFTERNOON...AND MOISTURE IS EXPECTED TO REMAIN NEAR NORMAL LEVELS
THROUGH THE REST OF THE WEEK...WITH A BRIEF DIP TO BELOW NORMAL
MOISTURE ON FRIDAY AFTERNOON. THAT SAID...PRECIPITABLE WATER COULD
INCREASE TO ABOVE NORMAL THIS WEEKEND DEPENDING ON THE PATH THAT
BRET ACTUALLY TAKES...BUT THE GLOBAL MODEL GUIDANCE DOES SHOW
MOISTURE INCREASING FOR THE WEEKEND TO ABOVE NORMAL LEVELS.
FOR TODAY...DUE TO THE MOISTURE INCREASE COMBINING WITH THE UPPER
TROUGH...THE CHANCES OF SIGNIFICANT RAIN AND THE POTENTIAL FOR
THUNDERSTORMS INCREASES. THE EGDI ALGORITHM SHOWS THE POTENTIAL
FOR ISOLATED THUNDERSTORMS THIS AFTERNOON ACROSS NORTHWESTERN
PUERTO RICO...WHICH COULD CAUSE OVER 1.5 INCHES OF RAIN...WHILE
EASTERN PR COULD HAVE AMOUNTS OF AROUND 0.75 INCHES TO ONE INCH.
THE USVI WOULD HAVE AROUND A TENTH OF AN INCH OF RAIN...WITH
SLIGHTLY HIGHER AMOUNTS POSSIBLE FOR THE NORTHERN ISLANDS.
THURSDAY IS EXPECTED TO HAVE A SIMILAR RAINFALL PATTERN AS
WEDNESDAY...BUT WITH LESSER AMOUNTS OF RAIN DUE TO THE UPPER
TROUGH HAVING MOVED EAST BY THEN. HOWEVER...THE AFTERNOON
CONVECTION COULD BE MORE FOR WESTERN PR RATHER THAN NORTHWESTERN.
THE DAYS WITH THE MOST UNCERTAINTY ARE FRIDAY AND SATURDAY AS
TROPICAL STORM BRET MOVES THROUGH THE CARIBBEAN. THE CURRENT
FORECAST TRACK BY THE NATIONAL HURRICANE CENTER HAS BRET MOVING
SOUTH OF PR/USVI...WITH MOST OF THE CONVECTION ASSOCIATED WITH IT
OVER THE CARIBBEAN WATERS. THAT SAID...AN INCREASE IN MOISTURE IS
EXPECTED OVER THE AREA...AND THE GLOBAL MODELS SUGGEST AN INCREASE
IN RAINFALL TOTALS FROM FRIDAY THROUGH SUNDAY.
THE FIVE-DAY FORECAST TOTALS INDICATE MAXIMA OF OVER 4 INCHES IN
EASTERN PUERTO RICO...AND NEAR 3 INCHES ACROSS NORTHWESTERN PR.
TOTALS OF OF NEAR 1 INCH ARE FORECAST ACROSS THE USVI. ISOLATED
HIGHER AMOUNTS ARE POSSIBLE.
ALAMO/GALVEZ/ACOSTA...WPC (USA)
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