482
FXCA20 KWBC 191243
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
742 AM EST TUE DEC 19 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI DEC 19/12UTC:
THERE IS A STATIONARY FRONT ACROSS WESTERN HISPANIOLA THAT EXTENDS
NORTH THROUGH THE WESTERN ATLANTIC...BECOMING A COLD FRONT NORTH
OF 30N. THE STATIONARY PORTION OF THIS FRONTAL BOUNDARY WILL
GRADUALLY WEAKEN OVER THE NEXT FEW DAYS...BUT A SFC HIGH PRESSURE
ACROSS THE SW ATLANTIC WILL PUSH THE COLD FRONT TO THE
SOUTH...THOUGH REMAINING NORTH OF THE LOCAL ISLANDS BY LATE
THURSDAY INTO FRIDAY. THIS PATTERN WILL ALSO CAUSE A PATCH OF DRY
AIR TO MOVE IN TODAY BUT MOISTURE WILL INCREASE SIGNIFICANTLY BY
THIS EVENING...THEN STABILIZE WITH NEAR TO SLIGHTLY ABOVE NORMAL
MOISTURE FOR THE LATTER PART OF THE WEEK AS THE COLD FRONT
REMAINS NORTH OF THE LOCAL ISLANDS.
THE MODEL GUIDANCE HAS NOT CHANGED THAT MUCH COMPARED TO PREVIOUS
RUNS. A WEAK SURFACE LOW PRESSURE ACROSS THE CENTRAL TROPICAL
ATLANTIC IS STILL EXPECTED TO SLOWLY MOVE WEST OVER THE NEXT FEW
DAYS...POSSIBLY BEING ABSORBED BY ANOTHER SURFACE LOW THAT WILL
DEVELOP OVER THE NORTHWESTERN ATLANTIC BY LATE THURSDAY. IN THE
MID LEVELS...A BROAD THROUGH WILL PASS TO THE NORTH OF THE LOCAL
ISLANDS THROUGH THE WEEK...CAUSING WESTERLY WINDS IN THE MID
LEVELS. IN THE UPPER LEVELS...A RIDGE WILL BE PRESENT
TODAY...WHILE STRONGER WINDS AND WESTERLY FLOW WOULD BE EXPECTED
ON WEDNESDAY ASSOCIATED WITH AN UPPER TROUGH ACROSS THE WESTERN
ATLANTIC. HOWEVER...AN UPPER TROUGH WILL MOVE INTO THE CENTRAL
CARIBBEAN BY FRIDAY AND STRONG SOUTHWESTERLY WINDS AFFECT THE
LOCAL ISLANDS IN THE UPPER LEVELS. THE AXIS OF THE UPPER TROUGH
COULD BE OVER HISPANIOLA BY LATE FRIDAY INTO SATURDAY...WITH
STRONG WINDS ON THE EAST SIDE OF THE AXIS CAUSING SOME DIVERGENCE
ALOFT.
THIS OVERALL PATTERN WOULD PROMOTE GENERALLY FAIR WEATHER WITH
BRIEF MOMENTS OF VERY SHALLOW SHOWER ACTIVITY TODAY AND WEDNESDAY.
THE TWIN ALGORITHM STILL SUGGESTS AN INVERSION THROUGH WEDNESDAY
AT ABOUT THE 800 MB LEVEL...ERODING BY LATE WEDNESDAY INTO
THURSDAY. THE THE UPPER LEVEL TROUGH APPROACHES ON FRIDAY INTO
SATURDAY...THERE WOULD BE A SLIGHT CHANCE OF THUNDERSTORMS THIS
WEEKEND. THE EGDI ALGORITHM DOES SUGGEST A SLIGHT RISK FOR
ISOLATED THUNDERSTORMS. GIVEN THE COMBINATION OF THE NEAR TO
SLIGHTLY ABOVE NORMAL MOISTURE EXPECTED FROM FRIDAY ONWARD AND THE
UPPER LEVEL TROUGH APPROACHING...LATE FRIDAY THROUGH EARLY SUNDAY
MAY BE THE PERIOD WITH THE MORE WIDESPREAD RAINFALL COVERAGE AS
WELL AS WITH A SLIGHT CHANCE OF THUNDERSTORMS.
ALTHOUGH RAINFALL IS EXPECTED TO BE LIMITED OVER THE NEXT COUPLE
OF DAYS...WITH RAINFALL MAXIMA AT 0.25 INCHES OR LESS TODAY AND
WEDNESDAY...THURSDAY ONWARD ARE FORECAST TO BE WETTER. THE 5-DAY
RAINFALL TOTAL FORECAST IS SUGGESTING OVER AN INCH OF RAIN ACROSS
NORTH COASTAL AND NORTHEASTERN PUERTO RICO. BETWEEN 0.5 TO AROUND
0.75 INCHES FOR THE NORTHERN USVI...AND BETWEEN 0.25 TO 0.50
INCHES FOR ST. CROIX.
ALAMO...WPC (USA)
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