352
FXCA20 KWBC 201243
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
842 AM EDT TUE JUN 20 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUN
20/12UTC: TROPICAL STORM BRET IS ADDING CONSIDERABLE UNCERTAINTY
TO THE RAINFALL FORECAST LATE THIS WEEK...ESPECIALLY FRIDAY INTO
SATURDAY. THE WIND FLOW DIRECTION AND SPEED WILL ALSO BE AFFECTED
AS BRET MOVES THROUGH THE CARIBBEAN. THE FORECAST WILL BE ADJUSTED
EACH DAY SHOWING THE LATEST OFFICIAL FORECAST FROM THE NATIONAL
HURRICANE CENTER REGARDING THE CURRENT TROPICAL STORM BRET.
A SURFACE HIGH PRESSURE WILL REMAIN OVER THE CENTRAL ATLANTIC FOR
THE NEXT FEW DAYS AS IT WEAKENS...BUT ANOTHER SURFACE HIGH
PRESSURE WILL MOVE IN TO THE NORTHWESTERN ATLANTIC LATE IN THE
WEEK...WHICH WILL KEEP AN EASTERLY WIND FLOW THROUGH 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 SHORT WAVE
TROUGH WILL POSITION ITSELF JUST WEST OF PUERTO RICO ON
WEDNESDAY...THEN IT WILL 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 IS CURRENTLY BELOW
NORMAL...BUT MOISTURE IS EXPECTED TO INCREASE ON WEDNESDAY...AND
MOISTURE IS EXPECTED TO REMAIN NEAR NORMAL LEVELS THROUGH THE REST
OF THE WEEK...THOUGH COULD INCREASE SIGNIFICANTLY LATE INT HE WEEK
INTO THE WEEKEND DEPENDING ON THE TRAJECTORY OF BRET.
FOR TODAY...THE DRIER THAN NORMAL MOISTURE WILL LIMIT THE SHOWER
ACTIVITY OVER PR/USVI. THE MODEL GUIDANCE IS SUGGESTING MINIMAL
AMOUNTS OF RAIN ACROSS THE LOCAL ISLANDS. FOR THAT REASON...A MAX
OF NEAR A QUARTER OF AN INCH OF RAIN IS EXPECTED ACROSS EASTERN
PR...WHILE UNDER A HALF AN INCH OF RAIN IS FORECAST FOR
NORTHWESTERN PR. THE USVI IS FORECAST TO HAVE UNDER A TENTH OF AN
INCH OF RAIN TODAY. BECAUSE THE MOISTURE INCREASES ON
WEDNESDAY...AND THE UPPER TROUGH IS EXPECTED TO BE JUST WEST OF
PR...THE CHANCES OF SIGNIFICANT RAIN INCREASES ON WEDNESDAY. THE
AFTERNOON CONVECTION ON WEDNESDAY IS EXPECTED TO CAUSE OVER AN
INCH OF RAIN ACROSS NORTHWESTERN PR...WHILE EASTERN PR COULD HAVE
AMOUNTS OF AROUND 0.75 INCHES IN GENERAL. THE USVI WOULD HAVE
AROUND A TENTH OF AN INCH OF RAIN ON WEDNESDAY...WITH SLIGHTLY
HIGHER AMOUNTS POSSIBLE FOR THE NORTHERN ISLANDS. THURSDAY IS
EXPECTED TO HAVE A SIMILAR RAINFALL PATTERN AS WEDNESDAY...BUT
WITH LESS AMOUNTS OF RAIN DUE TO THE UPPER TROUGH HAVING MOVED
EAST BY THEN. HOWEVER...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 AND THUNDERSTORM POTENTIAL WOULD BE
EXPECTED OVER THE AREA. THEREFORE...AN INCREASE IN RAINFALL TOTALS
OF OVER AN INCH ACROSS EASTERN PR IS FORECAST FOR FRIDAY AND
SATURDAY.
THE FIVE-DAY FORECAST TOTALS INDICATE MAXIMA OF AROUND 3 INCHES IN
EASTERN PUERTO RICO...AND NEAR 2.5 INCHES ACROSS NORTHWESTERN PR.
TOTALS OF OF 0.25 TO 0.50 INCHES ACROSS THE USVI. ISOLATED HIGHER
AMOUNTS ARE POSSIBLE.
ALAMO/GALVEZ/ACOSTA...WPC (USA)
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