402
FXCA20 KWBC 171229
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
828 AM EDT WED MAY 17 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY
17/12UTC: IN THE MID-LEVELS...A RIDGE CENTERS OVER THE SOUTHEAST
CARIBBEAN/NORTH COAST OF VENEZUELA AND EXTENDS OVER THE ENTIRE
EASTERN CARIBBEAN. THE GREATER ANTILLES ARE LOCATED NORTH OF THIS
RIDGE...IN A REGION OF DEEP-LAYER WESTERLIES THAT EXTEND DOWN TO
600 HPA. A MOIST PLUME IS PRESENT NEAR AND NORTH OF THE GREATER
ANTILLES...WHERE PRECIPITABLE WATER ESTIMATIONS SHOW VALUES OF
45-50MM. THIS ENVIRONMENT IS FAVORABLE FOR ROBUST AFTERNOON
CONVECTION AND MODERATE RAINFALL RATES. THE SAN JUAN SOUNDING
CONFIRMS HIGH VALUES OF MOISTURE IN THE ENTIRE COLUMN. IT ALSO
SHOWS A WEAK TRADE WIND CAP PRESENT NEAR 750 HPA. THE CAP IS YET
WEAK AND PRONE TO BE OVERCOME BY DEVELOPING AFTERNOON CONVECTION.
THE TRADES ARE WEAK...IN THE 05-10KT RANGE AND FROM THE
EAST-SOUTHEAST. SATELLITE IMAGERY CONFIRMS WEAK TRADES FROM THE
SOUTHEAST AND POCKETS OF SHALLOW CONVECTION PRODUCING ISOLATED
PRECIPITATION MOSTLY OFF THE SOUTH COAST OF PUERTO RICO AND IN THE
EASTERN VI.
MODELS CONTINUE RESOLVING THE MID-LEVEL RIDGE MEANDERING WESTWARD
INTO CENTRAL AMERICA BY FRIDAY. AS THE RIDGE WEAKENS ACROSS THE
NORTHEAST CARIBBEAN...EXPECT AN ASSOCIATED DESTABILIZATION OF THE
MID-LEVELS. A LARGE AND ROBUST POLAR TROUGH IS FORECAST TO DEEPEN
WHILE ENTERING THE BAHAMAS ON SATURDAY. THE TROUGH WILL BE
PROGRESSIVE AND ARRIVE INTO PUERTO RICO SOMETIME ON SUNDAY/MONDAY.
THE TIMING AFTER SUNDAY IS STILL UNCERTAIN IN THE GUIDANCE...BUT
THE TROUGH WILL LIKELY FAVOR A SIGNIFICANT INCREASE IN THE
COVERAGE OF CONVECTION ACROSS HISPANIOLA AND PUERTO RICO ON
SATURDAY AND SUNDAY.
IN THE MEAN TIME...EXPECT AFTERNOON CONVECTION ON A DAILY BASIS
PRODUCING MODERATE AND LOCALLY HEAVY ACCUMULATIONS...GIVEN THE
PRESENCE OF ABOVE-NORMAL VALUES OF AVAILABLE MOISTURE. ON
WEDNESDAY...WEAK SOUTHEASTERLY TRADES WILL FAVOR AFTERNOON
CONVECTION IN MOST OF NORTHERN PUERTO RICO. A WEAK WESTERLY
COMPONENT IN 700 HPA WILL FAVOR MODERATE AMOUNTS EXTENDING INTO
THE SAN JUAN METRO...WHERE EXPECT MAXIMA OF 0.5-1 INCH. ON
THURSDAY...A DEEPER LAYER OF EASTERLY FLOW WILL RELOCATE MAXIMA TO
NORTHWEST PUERTO RICO...WHERE EXPECT AMOUNTS OF 1-2 INCHES. ON
FRIDAY...EXPECT ONCE AGAIN MAXIMA OF 1-2 INCHES IN NORTHWEST
PUERTO RICO. ENHANCED MOISTURE CONVERGENCE ASSOCIATED WITH THE
TRADES WILL FAVOR AN AN INCREASE IN ACCUMULATION IN EASTERN PUERTO
RICO AND THE WESTERN VI OVERNIGHT...TO FAVOR MAXIMA OF 0.5-1 INCH.
AS THE UPPER TROUGH APPROACHES...EXPECT WETTER CONDITIONS ON
SATURDAY...WHERE SCATTERED AMOUNTS OF 0.5-1 INCH IN
EASTERN...WESTERN AND NORTHERN PUERTO RICO...AND ISOLATED MAXIMA
OF 1.5-2 INCHES IN FAR NORTHWEST PUERTO RICO. SUNDAY LOOKS WET AS
WELL...BUT THERE IS STILL UNCERTAINTY ON THE LOCATION OF THE RAIN
PRODUCING SYSTEMS. AT THE MOMENT...THE FORECAST SHOWS MAXIMA OF
1-1.25 INCHES IN NORTHWEST PUERTO RICO...AND MAXIMA OF 0.5-1 INCH
IN THE WESTERN VI...BUT GENERALLY AMOUNTS OVER 0.15 INCHES IN THE
ENTIRE ISLAND.
GALVEZ/ACOSTA...WPC (USA)
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