495
FXCA20 KWBC 111140
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
740 AM EDT TUE APR 11 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR
11/12UTC: IN THE UPPER LEVELS...A CELL OF THE SUBEQUATORIAL RIDGE
IS BUILDING ACROSS NORTHERN SOUTH AMERICA INTO THE NORTHERN
CARIBBEAN. THIS IS ENTERING IN PHASE WITH A MID-LEVEL RIDGE THAT
CENTERS OVER NORTHERN VENEZUELA ON TUESDAY MORNING...EXTENDING
NORTH INTO THE NORTHEAST CARIBBEAN. THE SAN JUAN SOUNDING SHOWS A
TRADE WIND CAP NEAR 750 HPA...AND PLENTY OF DRY AIR ABOVE
ASSOCIATED WITH WESTERLY WINDS. IN THE LOW-LEVELS...THE TRADES ARE
WEAK FROM THE SOUTHEAST...WITH SPEEDS NEAR 5KT. SATELLITE IMAGERY
SHOWS VERY LITTLE CLOUDINESS ACROSS THE ISLANDS THIS MORNING.
IN THE MID AND UPPER LEVELS...THE CURRENT RIDGE PATTERN IS
FORECAST TO HOLD THROUGH THE FORECAST CYCLE...FAVORING THE
PRESENCE OF A WEAK TRADE WIND CAP. THIS WILL BE SUFFICIENT TO
DELAY THE ONSET OF DIURNAL CONVECTION AND LIMIT COVERAGE BUT NOT
SUFFICIENT TO FULLY INHIBIT VERTICAL DEVELOPMENT. THE MID-LEVEL
RIDGE ROLLS WESTWARD ON THURSDAY AND FRIDAY...FAVORING TAN UPPER
TROUGH OVER AND EAST OF THE LEEWARD ISLANDS BY THE WEEKEND. THIS
WILL DESTABILIZE TRADE WIND CONVECTION EAST OF THE
CARIBBEAN...ALLOWING FOR DEEPER CELLS ENTERING THE BASIN BY THE
WEEKEND. IN THE MEAN TIME...THE MOST SIGNIFICANT FEATURE WILL BE A
SURFACE FRONT THAT IS FORECAST TO STALL NEAR 22-24N BY FRIDAY.
PRE-FRONTAL NORTHEASTERLY TRADES WILL DEVELOP ON THURSDAY...WHICH
WILL DEVELOP SHALLOW CONVECTIVE INSTABILITY AND ASSOCIATED LIGHT
RAIN SHOWERS ACROSS MOST OF NORTHERN PUERTO RICO AND THE VI. THE
TRADES ARE FORECAST TO ACQUIRE A MORE EASTERLY COMPONENT ON FRIDAY
AND SATURDAY.
IN TERMS OF ACCUMULATIONS...TUESDAY AND WEDNESDAY WILL SEE THE
LARGEST ACCUMULATIONS FROM AFTERNOON CONVECTION IN THE CENTRAL AND
WESTERN CORDILLERA. EXPECT MAXIMUM AMOUNTS OF 0.5-0.75 INCHES. ON
THURSDAY EXPECT MAXIMA NEAR 0.1 INCHES ALONG MOST OF
NORTHERN...EASTERN PUERTO RICO AND THE VI. IN THE SOUTHWEST
CORDILLERA EXPECT AFTERNOON MAXIMA OF 0.2-0.3 INCHES. ON FRIDAY
AND SATURDAY...ACTIVITY WILL CLUSTER MOSTLY IN THE WESTERN
CORDILLERA...WHERE EXPECT MAXIMA OF 0.4-0.5 INCHES. TRADE WIND
CONVERGENCE WILL FAVOR MAXIMA OF 0.1-0.2 INCHES IN EASTERN PUERTO
RICO IN MORNING CONVECTION. NOTE POTENTIALLY WETTER CONDITIONS ON
SATURDAY IN RESPONSE TO INCREASED VERTICAL DEVELOPMENT IN TRADE
WIND CONVECTION ARRIVING FROM THE LEEWARD ISLANDS...WHERE THE
UPPER TROUGH WILL BE PRESENT.
GALVEZ/ALAMO...WPC (USA)
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