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FXCA20 KWBC 131453
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
952 AM EST FRI DEC 13 2024
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI DEC 13/14UTC:
THE MADDEN-JULIAN OSCILLATION (MJO) IS CURRENTLY IN AN UPPER
CONVERGENT PHASE OVER THE NORTHEAST CARIBBEAN. HOWEVER, THE CFS
MODEL SUGGESTS A GRADUAL TRANSITION TO AN UPPER DIVERGENT PATTERN
BY THE END OF NEXT WEEK.
IN THE UPPER LEVELS...A LOW-PRESSURE SYSTEM CENTERED NEAR 20N/56W
IS FORECAST TO WEAKEN THROUGHOUT THE WEEKEND. FOLLOWING THIS...AN
UPPER RIDGE IS EXPECTED TO DEVELOP AND PERSIST THROUGH THE WEEK.
UPPER-LEVEL WINDS WILL STRENGTHEN LATE MONDAY INTO TUESDAY.
CONCURRENTLY...A MID-LEVEL LOW NEAR 20N/58.5W IS ALSO EXPECTED TO
WEAKEN DURING THE WEEKEND...LEAVING BEHIND A SOMEWHAT WEAK TROUGH
OVER THE AREA...BUT INCREASED MI-LEVEL VORTICITY IS FORECAST BY
LATE MONDAY INTO TUESDAY NEAR PR/USVI. BY MIDWEEK...THE AXIS OF
THIS TROUGH WILL SHIFT EASTWARD...ALLOWING PR/USVI TO COME UNDER
THE INFLUENCE OF A MID-LEVEL RIDGE.
AT THE SURFACE...A LOW-PRESSURE SYSTEM NEAR 22.5N/62W IS CURRENTLY
PRODUCING NORTHERLY WINDS. THIS LOW IS FORECAST TO MOVE WEST
TOWARD HISPANIOLA ON SATURDAY...RESULTING IN A SHIFT TO SOUTHERLY
WINDS ACROSS PR AND THE USVI EARLY SATURDAY. BY SATURDAY
AFTERNOON...SOUTHEASTERLY WINDS ARE EXPECTED TO
PREVAIL...CONTINUING THROUGH MONDAY. ADDITIONALLY, A SURFACE
TROUGH MAY DEVELOP OVER THE USVI BY LATE MONDAY INTO
TUESDAY...POTENTIALLY INDUCED BY THE MID-LEVEL TROUGH FORECAST TO
LINGER IN THE REGION DURING THAT TIME. AVAILABLE MOISTURE WILL
INCREASE RAPIDLY TODAY...REACHING ABOVE-NORMAL LEVELS BY SATURDAY
AND PERSISTING THROUGHOUT THE FOLLOWING WEEK. RELATIVE HUMIDITY IN
THE LOWER TO MID-LEVELS WILL ALSO REMAIN ELEVATED FROM SATURDAY
ONWARD. RAINFALL DISTRIBUTION ACROSS PR AND THE USVI WILL DEPEND
ON WIND FLOW...WITH NORTHERN PR EXPECTED TO RECEIVE THE MAJORITY
OF THE RAINFALL TODAY...DUE TO THE PREVAILING NORTHERLY WINDS.
GLOBAL MODELS SEEM TO BE A BIT SHY WITH THEIR RAINFALL SOLUTIONS
FOR THE NEXT FIVE DAYS...SUGGESTING A 5-DAY MAXIMUM ACCUMULATION
OF APPROXIMATELY 1 INCH...THOUGH THEY ARE IN AGREEMENT...GENERALLY
FAVORING NORTHERN PR. HOWEVER...HIGH-RESOLUTION MODELS SUGGEST
ISOLATED AREAS COULD RECEIVE UP TO 1 INCH OF RAINFALL EACH DAY
TODAY AND TOMORROW. TAKING BOTH GLOBAL AND HIGH-RESOLUTION MODELS
INTO ACCOUNT...THE 5-DAY RAINFALL TOTAL COULD BE CLOSER TO 3-4
INCHES...PARTICULARLY ACROSS NORTHERN AND EASTERN PR...WITH LESSER
AMOUNTS ELSEWHERE. FOR THE USVI...TOTAL RAINFALL ACCUMULATION OVER
THE NEXT FIVE DAYS IS ESTIMATED AT AROUND 2 INCHES.
ALAMO...WPC (USA)
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