TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
847 AM EDT THU JUN 22 2023

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUN
22/12UTC: THE NATIONAL HURRICANE CENTER HAS TROPICAL STORM BRET
PASSING OVER 200 MILES SOUTH OF PR/USVI FRIDAY EVENING.
HOWEVER...A GRADUAL INCREASE IN MOISTURE IS FORECAST ON FRIDAY
INTO SATURDAY. THE SHOWER ACTIVITY IS ALSO EXPECTED TO INCREASE
ACROSS THE AREA...WITH EASTERN PR HAVING THE HIGHEST RAINFALL
ACCUMULATION. THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES
ON THE NEWLY FORMED TROPICAL DEPRESSION FOUR. ON THE FORECAST
TRACK...TD FOUR WILL PASS OVER 250 MILES NORTHEAST OF ST JOHN ON
MONDAY MORNING. ON THE FORECAST TRACK...LIGHTER WINDS COULD BE
EXPECTED...AND A LINE OF DEEP MOISTURE COULD MOVE INTO THE LOCAL
ISLANDS EARLY NEXT WEEK.

A SURFACE HIGH PRESSURE IS MOVING INTO THE CENTRAL
ATLANTIC...WHICH WILL KEEP A GENERAL EASTERLY WIND FLOW THROUGH
THE REST OF THE WEEK...THOUGH THE WIND COULD BE SLIGHTLY STRONGER
THIS EVENING INTO EARLY FRIDAY AS BRET PASSES SOUTH OF THE LOCAL
AREA. AN UPPER TROUGH IS PASSING THROUGH THE AREA TODAY AND
FRIDAY...AND ITS AXIS IS FORECAST TO BE EAST OF PR BY
SATURDAY...THEN AN UPPER LEVEL RIDGE WILL MOVE IN LATE IN THE
WEEKEND INTO EARLY NEXT WEEK. HOWEVER...ANOTHER TROUGH COULD
DEVELOP EAST OF PR BY MIDWEEK. THE PRECIPITABLE WATER IS EXPECTED
TO DECREASE TODAY...AS SOME DRY AIR AND SAHARAN DUST IS
PRESENT...BUT WILL INCREASE GRADUALLY ON FRIDAY...REMAINING NEAR
NORMAL THROUGH THE WEEKEND...ONLY BECAUSE THERE IS A NARROW BAND
OF RELATIVELY DRY AIR NORTH OF TS BRET THAT IS FORECAST TO PERSIST
OVER THE LOCAL ISLANDS. A SMALL SHIFT NORTH OF THE MOISTURE FIELD
WOULD CAUSE PR/USVI TO HAVE ABOVE NORMAL MOISTURE THIS WEEKEND.
THE PRECIPITABLE WATER IS EXPECTED TO DECREASE BY MONDAY
AGAIN...THEN ANY INCREASE IN MOISTURE COULD DEPEND ON THE
TRAJECTORY OF THE CURRENT TD 4.

FOR TODAY...DUE TO THE MOISTURE DECREASE AND SAL...THE RAINFALL
ACTIVITY IS EXPECTED TO BE A BIT MORE MODEST...WITH UNDER A HALF
AN INCH OF RAIN ACROSS EASTERN PR...AND ONLY A SMALL AREA OF
WESTERN PR HAVING A CHANCE OF SIGNIFICANT RAINFALL...WITH OVER ONE
INCH OF RAIN IN THE FORECAST ACROSS AN ISOLATED SECTION. THE USVI
IS EXPECTED TO HAVE MINIMAL RAIN TODAY. AS BRET MOVES SOUTH OF THE
LOCAL ISLANDS...THE UNCERTAINTY IN THE RAINFALL FORECAST
INCREASES...BUT AN INCREASE IN SHOWER ACTIVITY IS STILL EXPECTED
ON FRIDAY AND THIS WEEKEND.

THE FIVE-DAY FORECAST TOTALS INDICATE MAXIMA OF OVER 3 INCHES IN
EASTERN AND WESTERN PUERTO RICO...MOST OF THAT RAINFALL OCCURRING
FROM FRIDAY INTO SUNDAY. TOTALS BETWEEN 0.5 AND 1 INCH ARE
FORECAST ACROSS THE USVI. ISOLATED HIGHER AMOUNTS ARE POSSIBLE.

ALAMO...WPC (USA)