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FXCA20 KWBC 191257
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
857 AM EDT THU OCT 19 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI OCT 19/12UTC:
TROPICAL STORM TAMMY IS FORECAST BY THE NATIONAL HURRICANE CENTER
TO APPROACH THE NORTHERN LEEWARD ISLANDS THIS WEEKEND. THE
PROXIMITY OF TAMMY TO THE LEEWARD ISLANDS WILL ADD UNCERTAINTY TO
THE WEEKEND FORECAST OVER PR/USVI. THE GLOBAL MODEL GUIDANCE SEEMS
TO BE COMING INTO SOME AGREEMENT...BUT THE FORECAST BY THE
NATIONAL HURRICANE CENTER IS A BIT WEST OF THE GUIDANCE CONSENSUS.
GIVEN THE CURRENT FORECAST...EASTERN PR...AS WELL AS CENTRAL TO
WESTERN PR COULD OBSERVE 2-4 INCHES OF RAIN THROUGH THE WEEKEND.
THE USVI IS FORECAST TO OBSERVE MAINLY 1-2 INCHES OF RAIN THROUGH
THE WEEKEND.
FOR TODAY...SHOWERS AND THUNDERSTORMS ARE FORECAST...ESPECIALLY
ACROSS THE NORTHWESTERN QUADRANT AND CENTRAL PR. THERE IS
CURRENTLY A BROAD SFC HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC
AND A STATIONARY FRONT TO THE NORTHWEST OF PR/USVI...CAUSING THE
WINDS TO BE FROM THE EAST. WINDS MAY INCREASE SLIGHTLY AND BECOME
SOUTHEASTERLY EARLY ON FRIDAY...THEN WINDS COULD DECREASE
GRADUALLY ON SATURDAY AS IT BECOMES NORTHERLY LATE SATURDAY...BUT
THE WIND DIRECTION WILL DEPEND ON THE EVENTUAL TRACK TRACK AND
INTENSITY OF TAMMY.
THERE IS A MID LEVEL HIGH PRESSURE OVER THE CENTRAL ATLANTIC THAT
IS DOMINATING THE AREA...BUT THE LATEST GUIDANCE STILL SUGGESTS A
WEAK MID LEVEL LOW OVER THE NORTHEAST CARIBBEAN TODAY...SLIGHTLY
INCREASING INSTABILITY. IN THE UPPER LEVELS THERE IS A LOW
PRESSURE CENTERED JUST SOUTH OF THE USVI...WHICH IS EXPECTED TO
SLOWLY MOVE WEST AND MEANDER CLOSE TO HISPANIOLA AND PR INTO THE
WEEKEND AS IT GRADUALLY WEAKENS...OPENING INTO A TROUGH AS THE
AXIS OF THE TROUGH MOVES OVER PR ON SUNDAY. HOWEVER...THE
AVAILABLE MOISTURE MAY BE MUCH BELOW NORMAL BY SUNDAY...SO THE
ACTUAL RAINFALL EXPECTED ON SUNDAY INTO MONDAY MAY BE LIMITED. THE
EGDI ALGORITHM IS SUGGESTING ISOLATED TO SCATTERED THUNDERSTORMS
TODAY THROUGH FRIDAY...WITH A DECENT SIGNATURE THIS AFTERNOON
ACROSS WESTERN PR...BUT THE STRONGEST SIGNATURE IS ACTUALLY FOR
VERY LATE TONIGHT INTO EARLY FRIDAY ACROSS EASTERN PR AND THE
SURROUNDING WATERS. THE GLOBAL MODELS ARE IN AGREEMENT THAT SUNDAY
AND MONDAY WOULD BE DRIER FOR PR/USVI WITH LIMITED SHOWER
ACTIVITY...WITH MAX TOTALS UNDER A HALF AN INCH OVER ANY ONE AREA.
IN GENERAL...THE 5-DAY RAINFALL TOTAL IS FORECAST TO BE BETWEEN
2-4 INCHES FOR CENTRAL TO WESTERN PR AS WELL AS EASTERN PR...WITH
EASTERN PR ON THE HIGHER END OF THE RANGE. WHILE 1-2 INCHES IS
FORECAST ACROSS VIEQUES..CULEBRA...AND THE USVI. THIS IS BECAUSE
MOST OF THE RAINFALL OVER THE NEXT FEW DAYS COULD BE DUE TO THE
PROXIMITY OF TAMMY OVER THE AREA.
ALAMO...WPC (USA)
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