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FXCA20 KWBC 281236
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
736 AM EST TUE NOV 28 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI NOV 28/12UTC:
MOSTLY FAIR WEATHER WITH BRIEF SHOWERS ACROSS EASTERN PR AND THE
USVI ARE EXPECTED THROUGH THE WEEK. THE RAINFALL AMOUNTS ARE
EXPECTED TO BE VERY MODEST EACH DAY AS THE AVAILABLE MOISTURE
COULD BE BELOW NORMAL FOR MOST OF THE 5-DAY FORECAST PERIOD. THE
ONLY EXCEPTION BEING FRIDAY INTO SATURDAY WHERE THE MOISTURE
REACHES NORMAL LEVELS FOR A BRIEF PERIOD ACCORDING TO THE LATEST
GUIDANCE.
A WEAK SURFACE RIDGE OVER THE ATLANTIC WILL KEEP EASTERLY WINDS
ACROSS THE NORTHEAST CARIBBEAN TODAY. HOWEVER...A STRONGER HIGH
PRESSURE WILL START TO MAKE ITS WAY INTO THE WESTERN ATLANTIC BY
LATE WEDNESDAY INTO THURSDAY AS IT MOVES EAST. THE SURFACE HIGH
PRESSURE IS EXPECTED TO BE CENTERED OVER BERMUDA BY VERY LATE
THURSDAY INTO FRIDAY. THIS WILL KEEP THE EASTERLY WINDS OVER THE
LOCAL ISLANDS ON THURSDAY...BUT COULD BE SLIGHTLY NORTHEASTERLY BY
FRIDAY INTO SATURDAY. IN THE MID LEVELS...A HIGH PRESSURE
CENTERED OVER THE NORTH CENTRAL CARIBBEAN WILL MOVE SLOWLY TO THE
WEST...EXPECTED TO BE CENTERED OVER CUBA BY SATURDAY...WHICH WILL
DOMINATE AND PROMOTE STABILITY OVER THE CARIBBEAN REGION THROUGH
THE WEEK. IN THE UPPER LEVELS...A HIGH PRESSURE RIDGE WILL PERSIST
OVER THE NORTHEASTERN CARIBBEAN THROUGH MIDWEEK...BUT A SHORTWAVE
TROUGH COULD DEVELOP OVER THE CENTRAL CARIBBEAN ON
WEDNESDAY...WHICH WILL MOVE EAST AS IT WEAKENS. THAT SAID...AN
UPPER TROUGH WILL AMPLIFY ACROSS THE SOUTHEAST CARIBBEAN ON
THURSDAY...BUT NO IMPACT IS EXPECTED ACROSS PR/USVI AS THE AXIS
WOULD BE TO THE EAST OF THE LOCAL ISLANDS AND THERE IS A STRONG
MID LEVEL HIGH PRESSURE. ACCORDING TO THE LATEST GUIDANCE...THE
UPPER LEVEL WINDS WILL BE LIGHT AND NORTHERLY TODAY INTO EARLY
WEDNESDAY...THEN THE WINDS WILL BECOME WESTERLY LATE WEDNESDAY
INTO THURSDAY...THEN NORTHERLY AGAIN ON FRIDAY INTO THE WEEKEND AS
A STRONG HIGH PRESSURE MOVES INTO THE SOUTHWESTERN CARIBBEAN.
THE EGDI FORECAST ALGORITHM IS SUGGESTING THAT SHALLOW CONVECTION
IS POSSIBLE BUT THERE IS NO INDICATION THAT THUNDERSTORMS ARE TO
BE EXPECTED THIS WEEK. THIS IS CONSISTENT WITH WHAT ONE WOULD
EXPECT WITH A STRONG MID LEVEL HIGH PRESSURE DOMINATING THE AREA.
THE TWIN ALGORITHM IS SUGGESTING THAT A TRADE WIND INVERSION WILL
BE PRESENT AT AROUND THE 900-850 HPA LEVEL THROUGH MOST OF THIS
WEEK...ALSO FAVORING MOST OF THE SHOWER ACTIVITY BEING ADVECTIVE
AND SHALLOW. THE AVAILABLE MOISTURE IS EXPECTED TO BE BELOW NORMAL
THROUGH THE REST OF THE WORKWEEK WITH PRECIPITABLE WATER GENERALLY
BETWEEN 1.1 AND 1.4 INCHES. A BRIEF INCREASE IN MOISTURE COULD
OCCUR LATE FRIDAY INTO EARLY SATURDAY WITH PRECIPITABLE WATER
INCREASING TO ABOUT 1.7 INCHES OVERNIGHT FRIDAY...BUT THEN
HOVERING AROUND 1.5 INCHES BY SATURDAY MIDDAY. THEREFORE..AN
INCREASE IN SHOWER ACTIVITY COULD BE EXPECTED OVERNIGHT FRIDAY
INTO SATURDAY...BUT IT WOULD STILL BE GENERALLY ADVECTIVE SHOWERS
AFFECTING EASTERN PUERTO RICO AND THE USVI.
THE 5-DAY TOTAL RAINFALL FORECAST SUGGESTS THAT EASTERN AND
NORTHEASTERN PUERTO RICO WOULD HAVE AROUND OR JUST UNDER AN INCH
OF RAIN. THE USVI...VIEQUES AND CULEBRA WILL HAVE BETWEEN 0.25 AND
0.50 INCHES. CENTRAL AND WESTERN PUERTO RICO ARE ALSO FORECAST TO
HAVE BETWEEN 0.25 TO 0.5 INCHES OF RAIN.
ALAMO...WPC (USA)
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