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FXCA20 KWBC 161236
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
835 AM EDT TUE MAY 16 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY
16/12UTC: NEAR NORMAL MOISTURE IS EXPECTED THIS MORNING...BUT WILL
GRADUALLY INCREASE ACROSS PR/USVI THROUGH THE DAY. THE AVAILABLE
MOISTURE WILL REACH ABOVE NORMAL LEVELS BY THIS EVENING...AND WILL
CONTINUE ABOVE NORMAL THROUGH LATE THURSDAY. HIGH LAPSE RATES ARE
EXPECTED TODAY IN THE MID LEVELS...AND THE LOW LEVEL AND MID LEVEL
RELATIVE HUMIDITY WILL INCREASE AS THE DAY PROGRESSES AS
WELL...STAYING ABOVE NORMAL THROUGH MIDWEEK. THUNDERSTORMS ARE
EXPECTED EACH AFTERNOON FOR THE NEXT SEVERAL DAYS...THOUGH MOSTLY
ACROSS THE NORTHWESTERN QUADRANT OF PR...SOME THUNDERSTORM
ACTIVITY IS POSSIBLE ACROSS THE NORTHERN HALF OF PR AND NEAR THE
USVI TODAY AND ON WEDNESDAY. SATURDAY ALSO LOOKS LIKE A THERE
COULD BE DECENT THUNDERSTORM ACTIVITY...AS THE EGDI ALGORITHM IS
INDICATING THE POSSIBILITY OF SCATTERED THUNDERSTORMS ACROSS PR.
THE PRECIPITABLE WATER THROUGH THE MORNING WILL BE NEAR 1.6
INCHES...BUT WILL INCREASE TO ALMOST 2.0 BY THIS EVENING...THEN
REMAINING NEAR 2.0 AND 2.2 THROUGH THURSDAY...THEN DECREASE
SLIGHTLY TO 1.8 OR SO FOR FRIDAY AND SATURDAY. IN THE UPPER
LEVELS...THERE IS A WEAK TROUGH APPROACHING FROM THE WEST...WHICH
WILL ENHANCE INSTABILITY WHEN COMBINED WITH THE MOISTURE ADVECTION
AND DIURNAL HEATING. THE UPPER TROUGH WILL MOVE EAST AND ANOTHER
RIDGE WILL TAKE ITS PLACE FROM WEDNESDAY ONWARD. A SURFACE HIGH
PRESSURE ACROSS THE EASTERN ATLANTIC..AND A SURFACE TROUGH ACROSS
THE WESTERN ATLANTIC WILL CAUSE A SOUTHEASTERLY WIND FLOW ACROSS
THE LOCAL ISLANDS THIS WEEK. HOWEVER...A WEAK HIGH PRESSURE WILL
MOVE NORTH OF THE NORTHEASTERN CARIBBEAN TODAY...CAUSING LIGHT ESE
WINDS...BUT WILL RETURN TO SE WINDS ON WEDNESDAY ONWARD. IN TERMS
OF RAINFALL...THE MODEL GUIDANCE IS BEING AGGRESSIVE...WITH THE
ECMWF ENSEMBLES SUGGESTING OVER AN INCH OF RAIN THIS AFTERNOON
ACROSS NORTHWESTERN PR...AND OVER 2.5 INCHES ON WEDNESDAY. GIVEN
THAT THERE IS A RIDGE IN THE UPPER LEVELS EXPECTED ON
WEDNESDAY...WE WERE CONSERVATIVE IN THE AMOUNTS OF RAIN FOR
WEDNESDAY. HOWEVER...IF THE MODELS CONTINUE TO SUGGEST HIGH
AMOUNTS OF RAIN...WE WILL MAKE ADJUSTMENTS TO THE FORECAST.
THIS WEEK...EXPECT AFTERNOON CONVECTION TO CAUSE RAINFALL TOTALS
OF NEAR TO OVER AN INCH EACH DAY. ISOLATED AREAS COULD RECEIVE
OVER AN INCH OF RAIN...EVEN OVER 2 INCHES WOULD BE POSSIBLE. DUE
TO THE ESE-SE AND RELATIVELY LIGHT WIND FLOW EXPECTED...MOST OF
THE HEAVIER SHOWER ACTIVITY IS EXPECTED TO OCCUR ACROSS THE
INTERIOR TO NORTHWEST QUADRANT OF PR. ISOLATED TO SCATTERED
SHOWERS CAN BE EXPECTED ACROSS THE USVI EACH DAY...WITH THE MID TO
LATTER PART OF THE WEEK POSSIBLY HAVING ISOLATED THUNDERSTORMS.
ALAMO/ACOSTA...WPC (USA)
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