448
FXCA20 KWBC 271150
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
749 AM EDT THU JUL 27 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
27/12UTC: ON THURSDAY MORNING...A TUTT CENTERS NEAR 24N 68W.
ASCENT ALONG ITS SOUTHERN FLANK IS FAVORING THE DEVELOPMENT OF
HIGH CLOUDS ALONG ITS SOUTHERN PERIPHERY. IN THE MID AND LOW
TROPOSPHERE...A TROPICAL WAVE IS PROPAGATING WESTWARD ACROSS
HAITI. PUERTO RICO AND THE VI ARE ALREADY UNDER THE DRIER AIR MASS
TRAILING BEHIND THE WAVE. MIMIC TPW SHOWS VALUES OF
40-45MM...WHICH IS CLOSE TO AVERAGE FOR THIS TIME OF THE YEAR. OF
RELEVANCE...A WEAK TROPICAL WAVE IS PROPAFATING ALONG 50W. THIS
WAVE ASSOCIATES WITH A NARROW BAND OF 48-52MM OF PRECIPITABLE
WATER. IT WILL THUS PRODUCE VERY TRANSIENT ENHANCEMENT OF
PRECIPITATION ON SATURDAY.
REGARDING THE FORECAST...THE VARIABILITY OF PRECIPITATION IS BEING
LARGELY MODULATED BY TROPICAL WAVES. THE NEXT WAVE CROSSING IS
EXPECTED FOR SATURDAY MORNING...FOLLOWED BY A POTENTIAL WAVE
CROSSING ON TUESDAY OR WEDNESDAY. THE NHC IS MONITORING THE
LATTER...BUT MODEL CONFIDENCE IS QUITE LOW AT THIS TIME. ASIDE
FROM TROPICAL WAVES...DIURNAL HEATING WILL ALSO PLAY A ROLE IN
MODULATING CONVECTIVE DEVELOPMENT. UNDER PREDOMINANT
EAST-SOUTHEASTERLY TRADES THROUGH THE FORECAST CYCLE...EXPECT
AFTERNOON DEVELOPMENT IN NORTHWEST PUERTO RICO...AND LIGHT LATE
NIGHT/EARLY MORNING SHOWERS IN EASTERN PR. THURSDAY WILL BE THE
DRIEST DAY...YET STILL EXPECT MAXIMA NEAR 0.5 INCHES IN NORTHWEST
PUERTO RICO AND MAXIMA NEAR 0.2 INCHES IN EASTERN PR AND THE
STREAMER FROM EL YUNQUE. DIURNAL PRECIPITATION IS FORECAST TO
GRADUALLY INCREASE THROUGH SATURDAY...WHEN EXPECT MAXIMA OF 1-1.5
INCHES IN FAR NORTHWEST PUERTO RICO IN AFTERNOON CONVECTION...AND
MAXIMA OF 0.5-0.75 IN EASTERN PR. A DECREASE FOLLOWS.
ON SUNDAY...EXPECT AFTERNOON MAXIMA NEAR 0.5 INCHES IN NORTHWEST
PUERTO RICO AND MAXIMA NEAR 0.25 INCHES IN EASTERN PUERTO RICO AND
EL YUNQUE STREAMER. UNCERTAINTY INCREASES ON MONDAY. YET...WEAKER
TRADES SHOULD FAVOR A DECREASE IN THE INFLUENCE OF STREAMER AND
OROGRAPHICALLY INDUCED ASCENT...FAVORING AFTERNOON CONVECTION IN
THE CENTRAL CORDILLERA. UNDER AN ENVIRONMENT WITH NEAR-NORMAL
AVAILABLE MOISTURE...EXPECT MAXIMA OF 0.5-0.75 INCHES IN AFTERNOON
CONVECTION...BUT LOCALLY HIGHER AMOUNTS ARE POSSIBLE.
GALVEZ...WPC (USA)
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