200
FXCA20 KWBC 121251
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
750 AM EST THU JAN 12 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JAN
12/12UTC: A POTENT UPPER TROUGH IS CROSSING THE CENTRAL UNITED
STATES ON THURSDAY MORNING. THIS ASSOCIATES WITH A ROBUST SURFACE
FRONT THAT IS FORECAST TO REACH AND CROSS THE ISLANDS ON SUNDAY.
IN THE MEANTIME...A MOIST PLUME CONTINUES EXTENDING OVER THE
NORTHEASTERN GREATER ANTILLES AND OVER AREAS TO THE NORTH
SUSTAINING UNSEASONABLY WET CONDITIONS. PRECIPITABLE WATER VALUES
ARE NEAR 40MM IN THE ISLANDS. A FRONT AND A SHEAR LINE EXTEND
FROMT HE NORTH ATLANTIC INTO THE DOMINICAN REPUBLIC...SPARING
PUERTO RICO FROM DEEP CONVECTION ON THURSDAY MORNING. THE TRADES
REMAIN WEAK FROM THE EAST...BUT THEY ARE STARTING TO ACCELERATE TO
SPEEDS OVER 10KT. EASTERLY WINDS EXTEND UP TO 700 HPA IN A LAYER
OF LITTLE WIND SHEAR. BUT FROM 500 HPA AND ABOVE...WESTERLIES ARE
PRESENT.
THE SYSTEM OF INTEREST IS A POTENT COLD FRONT THAT IS FORECAST TO
ENTER THE ISLANDS ON SUNDAY...AND CROSS THEM RAPIDLY TO EXTEND
ACROSS THE LEEWARD ISLANDS AND INTO THE CENTRAL CARIBBEAN BY
MONDAY. THE FAST PROGRESSION OF THIS SYSTEM WILL LIMIT POTENTIAL
RAINFALL ACCUMULATIONS. YET...SCATTERED PRECIPITATION IN MOST OF
THE NORTHERN THIRD OF PUERTO RICO ON SUNDAY MORNING...WITH
FORECAST ACCUMULATION OF 0.5 TO 1 INCHES ALONG THE COASTAL
PLAIN...AND 0.25-0.5 INCHES INLAND. PRECIPITATION IS EXPECTED TO
DECREASE RAPIDLY DURING THE DAY ON SUNDAY AS THE DRIER
POST-FRONTAL AIR MASS SETS IN. YET...GIVEN THE PERSISTENCE OF
NORTHERLY LOW-LEVEL WINDS...EXPECT LIGHT PRECIPITATION TO DEVELOP
OVERNIGHT ALONG THE NORTH COAST OF PUERTO RICO...TO PRODUCE TRACE
ACCUMULATIONS INTO MONDAY MORNING.
IN THE MEAN TIME...MODERATE AND LOCALLY HEAVY PRECIPITATION IS
STILL EXPECTED ON THURSDAY GIVEN CURRENT VALUES OF MOISTURE AND
INSTABILITY. MAXIMA IS FORECAST TO CLUSTER IN THE WESTERN
CORDILLERA AND TO REACH VALUES OF 2-2.5 INCHES. SCATTERED
CONVECTION IS EXPECTED IN MOST OF NORTHERN AND CENTRAL PUERTO
RICO...WHERE MAXIMA WILL LIKELY BE MORE CONSERVATIVE AND REMAIN IN
THE 0.2-0.4 RANGE. MUCH DRIER CONRIDIONS ARE EXPECTED ON
FRIDAY...WHEN SOUTHEASTERLY TRADES WILL CLUSTER AFTERNOON
CONVECTION IN EXTREME NORTHWEST PUERTO RICO. ON SATURDAY...EXPECT
ONCE AGAIN CONSERVATIVE AMOUNTS UNDER THE INFLUENCE OF DRIER
SOUTHERLY TRADES. CONDITIONS SHOULD START TO DETERIORATE LATE ON
SATURDAY NIGHT AS THE FRONT APPROACHES AND REACHES THE ISLAND ON
SUNDAY MORNING.
GALVEZ/ACOSTA...WPC (USA)
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