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FXCA20 KWBC 141603
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1102 AM EST THU NOV 14 2024
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI NOV 14/12UTC:
LARGE SCALE CONDITIONS SUGGEST THAT THE CURRENT UPPER DIVERGENT
MJO PULSE IS RAPIDLY FADING ACROSS THE CARIBBEAN REGION. UNDER THE
LACK OF ROBUST KELVIN WAVES FORECAST TO ARRIVE FROM THE EAST...THE
LARGE SCALE PATTERN SEEMS TO BE BECOMING LESS FAVORABLE FOR
SIGNIFICANT PRECIPITATION EVENTS DURING THE NEXT TWO WEEKS.
A POTENT UPPER TROUGH IN THE NORTHWEST ATLANTIC IS SUSTAINING A
LONG SURFACE FRONT THAT EXTENDS ALONG 20N 60W...19N 66W...19N 70W
IN NORTHERN HISPANIOLA. THE FRONT IS RAPIDLY WEAKENING AS IT
PROPAGATES INTO PUERTO RICO AND THE VI...WHICH SHOULD YIELD TO
CONSERVATIVE RAINFALL AMOUNTS ON THURSDAY. GIVEN PREDOMINANTLY
DEEP-LAYER WESTERLY WINDS DURING THE AFTERNOON...EXPECT
PRECIPITATION TO DEVELOP PRIMARILY IN EASTERN PUERTO RICO AND THE
VI.
THE SETUP OF THE DRIER POST FRONTAL AIR MASS WILL YIELD TO
GENERALLY FAIR WEATHER AND VERY LIGHT ACCUMULATION ON FRIDAY. THE
NEXT SYSTEM OF INTEREST IS AN APPROACHING UPPER TROUGH...FORECAST
TO START TO AFFECT THE AREA LATE ON SATURDAY. THIS WILL LIKELY
OPEN A WINDOW FOR MODERATE PRECIPITATION FROM SATURDAY EVENING
INTO MIDDAY SUNDAY. MODELS DO DISAGREE WITH THE DETAILS OF THIS
EVOLUTION. HOWEVER...BASED ON THE DIURNAL CYCLE OF CONVECTION AND
INTERACTION BETWEEN THE MOIST PLUME TO THE EAST AND UPPER TROUGH
DYNAMICS...EXPECT A HIGHER CHANGE FOR MODERATE PRECIPITATION TO
DEVELOP OVER THE VI AND FAR EASTERN PUERTO RICO OVERNIGHT INTO THE
MORNING. IN TERMS OF ACCUMULATION...WE EXPECT MAXIMA ON THE
20-35MM/DAY RANGE.
AFTER MIDDAY SUNDAY...EXPECT A RAPID DRYING TREND. TRADE WINDS ARE
EXPECTED TO SHIFT TO NORTH-NORTHEASTERLIES SOMETIME DURING SUNDAY
AFTERNOON-EVENING. ALTHOUGH THE MID AND UPPER TROPOSPHERE WILL
REMAIN UNFAVORABLE FOR ASCENT THROUGH THE REST OF THE FORECAST
CYCLE...THE NORTHEASTERLY TRADES WILL FAVOR SUFFICIENT COLD
ADVECTION TO DEVELOP SHALLOW INSTABILITY AND FAVOR THE DEVELOPMENT
OF VERY LIGHT TRADE WIND SHOWERS OVERNIGHT INTO THE EARLY MORNING.
THESE WILL LIKELY FAVOR VERY LIGHT ACCUMULATIONS IN NORTHERN AND
NORTHEAST PUERTO RICO ON A DAILY BASIS.
ON TUESDAY...SOME MODELS ARE SUGGESTING THE ORGANIZATION OF A
SHEAR LINE ACROSS THE NORTH ATLANTIC INTO THE ISLAND.
HOWEVER...THERE IS LIMITED CONFIDENCE ON THIS EVOLUTION AND ON THE
ASSOCIATED WEATHER. GIVEN AN UNFAVORABLE UPPER FLOW PATTERN FOR
SIGNIFICANT PRECIPITATION...WE ARE LEANING TOWARDS CONSERVATIVE
PRECIPITATION AMOUNTS IN ASSOCIATION WITH THIS DEVELOPMENT.
GALVEZ...WPC (USA)
JACKMAN... BMS (BARBADOS)
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