463
FXCA20 KWBC 101218
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
817 AM EDT WED MAY 10 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY
10/12UTC: A MID-LEVEL RIDGE CONTINUES STRENGTHENING ACROSS THE
EASTERN CARIBBEAN...WHILE ROLLING WESTWARD. ON WEDNESDAY
MORNING...THE RIDGE CENTERED NEAR 16N 69W...AND COVERED THE ENTIRE
EASTERN CARIBBEAN. THE RIDGE IS STRENGTHENING THE CAP RAPIDLY
WHILE FAVORING A QUICK DRYING IN THE 850-700 HPA LAYER. THIS IS
RESULTING IN LOWER PRECIPITABLE VALUES THAN PREVIOUSLY
ANTICIPATED. ALL MODELS HAVE MADE CORRECTIONS AS WELL AND ARE
SHOWING LOWER PRECIPITABLE WATER VALUES...WHICH WILL HAVE AN
IMPACT IN RAINFALL AMOUNTS. MIMIC TPW SUGGESTS AMOUNTS OF 30-35MM
THIS MORNING. THIS IS CONSISTENT WITH VERY LITTLE CLOUDINESS
OBSERVED IN SATELLITE IMAGERY. THE TRADES ARE FROM THE
SOUTH-SOUTHEAST...WHICH IS FAVORING A FAIR WEATHER CUMULUS CLOUD
FIELD IN SOUTH-CENTRAL...SOUTHEASTERN AND EASTERN PUERTO RICO.
REGARDING THE FORECAST...CORRECTIONS HAVE MADE TO LOWER RAINFALL
TOTALS ON WEDNESDAY...WHEN ISOLATED AFTERNOON DEVELOPMENT IS
EXPECTED IN FAR NORTHWEST PUERTO RICO...TO FAVOR MAXIMA OF 0.3-0.6
INCHES. A STRONGER CAP WILL LIKELY DELAY THE ONSET OF AFTERNOON
CONVECTION. ON THURSDAY...THE TRADES ARE FORECAST TO BACK FROM
SOUTHEASTERLY TO EASTERLY...WHICH WILL FAVOR A REPOSITIONING OF
AFTERNOON CONVECTION MAXIMA TO INTERIOR PORTIONS OF WESTERN PUERTO
RICO. AN UPPER TROUGH APPROACHING FROM THE WEST WILL PROVIDE
SUFFICIENT LIFT TO BREAK THE CAP AND FAVOR ISOLATED MODERATE
ACCUMULATION...FORECAST TO REACH 1-1.5 INCHES.
MODELS HAVE ALSO MADE SOME IMPORTANT CORRECTIONS AFTER
THURSDAY...PARTICULARLY ON THE POSITIONING OF THE MOIST PLUME
FORECAST TO ARRIVE ON FRIDAY. THEY NOW AGREE VERY WELL ON
RESOLVING THE MOIST PLUME PASSING WELL TO THE SOUTH OF PUERTO RICO
AND THE VI DURING FRIDAY AND SATURDAY. THIS MEANS MUCH DRIER
CONDITIONS DURING FRIDAY AS A DRY SLOT OF 28-32 MM OF PRECIPITABLE
WATER MOVES THROUGH THE ISLANDS FROM EAST TO WEST. BASED ON THIS
AND ON THE CONVERGENT TIER OF THE UPPER TROUGH OVER THE ISLANDS ON
FRIDAY...THE FORECAST HAS BEEN ADJUSTED TO REFLECT LESSER
ACCUMULATIONS AND COVERAGE OF AFTERNOON CONVECTION. EXPECT MAXIMA
THE 0.5-0.75 IN RANGE CLUSTERING IN FAR NORTHWEST PUERTO RICO.
SATURDAY AND SUNDAY STILL LOOK WETTER AS THE TRADE WIND CAP
WEAKENS AND THE LARGE SCALE PATTERN BECOMES GRADUALLY LESS UPPER
CONVERGENT IN ASSOCIATION WITH THE MJO. UNDER THE INFLUENCE OF
SOUTHEASTERLY TRADES...EXPECT MAXIMA CLUSTERING IN NORTHWEST
PUERTO RICO RANGING FROM 1.25-1.75 INCHES ON BOTH DAYS.
GALVEZ...WPC (USA)
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