902
FXCA20 KWBC 271214
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
714 AM EST TUE DEC 27 2022
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM DEC
27/12UTC: IN THE UPPER LEVELS...A TROUGH EXTENDS OVER THE TROPICAL
ATLANTIC FROM A LOW NEAR 18N 52W INTO THE CENTRAL LESSER ANTILLES.
IN THE MEAN TIME...A MID-LEVEL RIDGE EXTENDS FROM A HIGH IN THE
NORTH ATLANTIC NEAR 33N 50W INTO THE NORTHEAST CARIBBEAN. THE
INFLUENCE OF THE RIDGE IS LIMITING THE EFFECTS OF THE UPPER TROUGH
ON TRADE WIND CONVECTION...WHICH IS FAVORING SHALLOW DEVELOPMENT
ACROSS THE EASTERN CARIBBEAN. A FEATURE OF INTEREST IN THE
LOW-LEVELS IS A TRADE WIND SURGE ACROSS THE TROPICAL NORTH
ATLANTIC...WHICH HAS LED TO AN ELONGATED REGION OF ENHANCED TRADE
WIND CONVERGENCE AND INSTABILITY THAT EXTENDS FROM 14N 50W INTO
THE WATERS EAST OF LEEWARD ISLANDS OR NEAR 19N 60W. SATELLITE
IMAGERY EVEN SHOWS THE PRESENCE OF THUNDERSTORMS ALONG THIS
BOUNDARY. THE SYSTEM IS PROPAGATING RAPIDLY WESTWARD EMBEDDED IN
AN ENVIRONMENT OF FAST 25-35KT TRADES...AND IS FORECAST TO ENTER
THE NORTHEAST CARIBBEAN LATER ON TUESDAY.
THE DOMINANT FEATURE ON TUESDAY WILL BE THE PLUME OF ENHANCED
CONVECTION MOVING INTO THE LEEWARD ISLANDS FROM TROPICAL ATLANTIC.
AS THIS PLUME APPROACHES PUERTO RICO AND THE VI...MODELS CONTINUE
BEING CONSISTENT ABOUT A DECREASE IN ORGANIZATION OF THE
CONVECTION OBSERVED ALONG THE BOUNDARY ON TUESDAY MORNING. BASED
ON MODEL SOLUTIONS...THE BULK OF THE ACTIVITY WITH THIS PLUME WILL
LIKELY FOCUS IN THE CENTRAL LESSER ANTILLES...WHILE MORE DISCRETE
ENHANCEMENT OCCURS IN PUERTO RICO. GIVEN THE PRESENCE OF FAST
25-35KT TRADES AS THE FEATURE STREAMS IN FROM THE EAST ON TUESDAY
EVENING...EXPECT THE LARGEST ACCUMULATIONS TO CLUSTER IN THE VI
AND EASTERN PUERTO RICO OVERNIGHT. EXPECT MAXIMA OF 0.3-0.4 INCHES
ACROSS THE VI WHILE ENHANCED MOISTURE CONVERGENCE IN EASTERN
PUERTO RICO TRIGGERS MAXIMA OF 0.6-0.8 INCHES.
AFTER THE PLUME PASSES BY...THE VARIABILITY OF PRECIPITATION WILL
CONTINUE TO BE PRIMARILY CONTROLLED BY PERTURBATIONS STREAMING
FROM THE EAST AND NORTHEAST EMBEDDED IN THE TRADES. IN THE UPPER
LEVELS...THE TROUGH LOCATED TO THE EAST OF THE LESSER ANTILLES IS
FORECAST TO PERSIST THROUGH THE FORECAST CYCLE. THIS WILL CONTINUE
TO ENHANCE VERTICAL DEVELOPMENT IN TRADE WIND CONVECTION EAST OF
THE CARIBBEAN...YET...THE PREVALENCE OF THE MID-LEVEL RIDGE ACROSS
THE GREATER ANTILLES WILL COUNTERACT THIS...RESULTING IN
CONSERVATIVE RAINFALL ACCUMULATION THROUGH THE CYCLE. MODELS
SUGGEST THE TRADES BACKING FROM EAST-SOUTHEASTERLIES ON
TUESDAY...TO EASTERLIES ON WEDNESDAY...TO EAST-NORTHEASTERLIES ON
THURSDAY AND THEREAFTER. THIS WILL SET UP LIGHT NOCTURNAL/EARLY
MORNING TRADE WIND SHWOERS ALONG NORTHERN PUERTO RICO FROM LATE
THURSDAY INTO SUNDAY. LARGEST AMOUNTS ARE EXPECTED IN NORTHEAST
PUERTO RICO...WHERE ENHANCED TRADE WIND CONVERGENCE WILL RESULT IN
MAXIMA OF 0.4-0.7 INCHES ON THURSDAY-FRIDAY AND FRIDAY-SATURDAY. A
DECREASE IN AVAILABLE MOISTURE AND INSTABILITY SHOULD FAVOR A
DECREASE IN MAXIMA TO 0.3-0.4 INCHES ON NEW YEAR'S EVE/NEW YEAR'S
MORNING.
GALVEZ...WPC (USA)
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