905
FXCA20 KWBC 201218
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
818 AM EDT THU APR 20 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR
20/12UTC: THE AVAILABLE MOISTURE WILL BE NEAR TO BELOW NORMAL
THROUGH FRIDAY...INCREASING TO NEAR THE 75TH PERCENTILE ON
SATURDAY...THEN DROPPING TO NEARLY 2 STANDARD DEVIATIONS BELOW
NORMAL ON SUNDAY NIGHT INTO MONDAY MORNING...AS SUGGESTED BY THE
LATEST MODEL GUIDANCE. AN UPPER LEVEL RIDGE WILL BE OVER PR/USVI
TODAY...WHILE MOVING EAST...BUT AN UPPER LEVEL TROUGH IS
APPROACHING THE AREA FROM THE WEST. THE TROUGH AXIS IS STILL
FORECAST TO PASS ACROSS PR/USVI ON SATURDAY. THE APPROACHING
TROUGH WILL CAUSE RELATIVELY STRONG WINDS ALOFT...POSSIBLY OVER
70KT...CAUSING UPPER LEVEL DIVERGENCE. A MID LEVEL RIDGE IS ALSO
PRESENT OVER THE LOCAL AREA AND IS MOVING EAST...WHILE A MID LEVEL
TROUGH ALSO APPROACHES THE NORTHEAST CARIBBEAN LATE FRIDAY NIGHT
INTO SATURDAY. A SURFACE HIGH PRESSURE ACROSS THE WESTERN ATLANTIC
WILL MAINTAIN AN EASTERLY TO SOUTHEASTERLY WIND FLOW THROUGH
FRIDAY AFTERNOON. A SURFACE LOW WILL DEVELOP JUST EAST OF THE
SOUTHERN BAHAMAS LATE FRIDAY INTO SATURDAY...RELAXING THE LOCAL
PRESSURE GRADIENT AND CAUSING LIGHT WINDS OVER PR/USVI STARTING
LATE FRIDAY INTO EARLY NEXT WEEK.
LOCALLY INDUCED AND TRADE WIND SHOWERS ARE EXPECTED THROUGH THE
REST OF THE WORKWEEK...WITH CENTRAL TO WESTERN PR OBSERVING
AFTERNOON SHOWERS. GIVEN THE BELOW NORMAL MOISTURE EXPECTED
TODAY...THE RAINFALL AMOUNTS ARE EXPECTED TO BE MODEST...WITH A
MAX OF JUST OVER A HALF AN INCH OF RAIN ACROSS THE NORTHWESTERN
QUADRANT OF PR THIS AFTERNOON...AND UNDER A QUARTER OF AN INCH
ACROSS EASTERN PR AND PERHAPS A FEW HUNDREDTHS OF AN INCH ACROSS
THE USVI. THERE IS SOME DISCREPANCY IN THE HI-RES MODEL GUIDANCE
THOUGH. THE NBM SHOWS SOME AREAS OF OVER 1 INCH OF RAIN ACROSS
NW-PR...WHILE THE ECMWF SUGGESTS VERY LITTLE RAIN...AND ONLY
AROUND A QUARTER OF AN INCH OF RAIN ACROSS THE MUNICIPALITY OF
RINCON...IN THE EXTREME NORTHWEST OF THE ISLAND. FOR FRIDAY...AS
THE WINDS START TO DECREASE GRADUALLY...THE AFTERNOON CONVECTION
OVER PR MIGHT BE A BIT FURTHER EAST...WITH THE MODEL GUIDANCE
SUGGESTING THE HIGHEST AMOUNTS OF RAIN SOMEWHERE BETWEEN THE
MUNICIPALITIES OF CIALES TO SAN SEBASTIAN...IN THE NORTH CENTRAL
TO NORTHWESTERN PR. BECAUSE FRIDAY MAY HAVE SLIGHTLY HIGHER
MOISTURE...AND THE MID AND UPPER LEVEL TROUGHS ARE APPROACHING
FROM THE WEST...THE AMOUNTS OF RAIN IN THE FORECAST FOR FRIDAY
AFTERNOON ARE A BIT HIGHER...WITH MAX VALUES OVER AN INCH WITH A
POSSIBILITY OF ISOLATED THUNDERSTORMS. AS THE UPPER TROUGH
CONTINUES TO APPROACH PR/USVI...ON SATURDAY AND SUNDAY...CENTRAL
TO EASTERN PR IS EXPECTED TO HAVE THE HIGHEST AMOUNTS OF RAIN WITH
THE BEST CHANCE FOR THUNDERSTORMS. BEST AREA FOR
CONVECTION...MEANING THAT CENTRAL TO EASTERN PR WOULD HAVE THE
HIGHEST RAINFALL ACCUMULATION ON SATURDAY AND SUNDAY. AT THIS
TIME...SATURDAY APPEARS TO BE THE DAY WITH THE HEAVIEST RAIN.
ALAMO/ACOSTA...WPC (USA)
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