490
FXCA20 KWBC 301244
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
844 AM EDT TUE MAY 30 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM MAY
30/12UTC: OVER THE NEXT SEVERAL DAYS...EASTERN PR WILL HAVE A
CHANCE OF SHOWERS UNDER AN ESE WIND FLOW AND NEAR NORMAL MOISTURE.
THAT SAID...THE AVAILABLE MOISTURE WILL INCREASE TO ABOVE NORMAL
LEVELS FROM THURSDAY EVENING ONWARD...WITH PRECIPITABLE WATER
POSSIBLY SURPASSING 2 INCHES. AFTERNOON CONVECTION ACROSS NW-PR IS
POSSIBLE EACH AFTERNOON BUT THE AMOUNTS OF RAIN MAY BE MODEST
ESPECIALLY ON WEDNESDAY AND THURSDAY DUE TO THE LACK OF DYNAMICS
THROUGH THURSDAY. HOWEVER...THERE WILL BE A SLIGHT INCREASE IN
MOISTURE TODAY AND THE RELATIVE HUMIDITY IN THE MID LEVELS WILL
INCREASE TODAY AS WELL...SO THERE IS A BETTER CHANCE OF
SIGNIFICANT RAIN TODAY COMPARED TO WEDNESDAY AND THURSDAY. AN
INCREASE IN INSTABILITY MAY OCCUR ON FRIDAY INTO SATURDAY. THE
USVI WILL OBSERVE SCATTERED SHOWERS EACH DAY...LEAVING A FEW
HUNDREDTHS OF AN INCH OF RAIN FOR THE MOST PART. HOWEVER...THE
INCREASE IN MOISTURE IN THE LATTER PART OF THE FORECAST PERIOD MAY
CAUSE A FEW TENTHS OF AN INCH OF RAIN ACROSS THE USVI ON SATURDAY.
A SURFACE HIGH PRESSURE ACROSS THE EAST CENTRAL ATLANTIC AND A
WEAK SFC LOW ACROSS THE WESTERN ATLANTIC IS CAUSING ESE WINDS OVER
THE LOCAL ISLANDS. THE WIND DIRECTION WILL BECOME ALMOST SOUTHERLY
BY FRIDAY INTO SATURDAY AS A SURFACE LOW DEVELOPS NORTH OF THE
LOCAL ISLANDS AND MOVES EAST. THIS LOW WILL BRING MOISTURE FROM
THE SOUTH AND WILL CAUSE THE PRECIPITABLE WATER TO INCREASE TO
ABOVE NORMAL LEVELS. THERE ARE RIDGES IN THE MID AND UPPER LEVELS
OVER THE LOCAL ISLANDS...WHICH ARE EXPECTED TO REMAIN THROUGH
THURSDAY. MID AND UPPER LEVEL TROUGHS WILL APPROACH THE LOCAL
ISLANDS ON FRIDAY INTO SATURDAY. THIS WILL CAUSE AN INCREASE IN
INSTABILITY AND CAUSE AN ENHANCED CHANCE OF THUNDERSTORMS. THIS IS
ALSO REFLECTED IN THE EGDI ALGORITHM WHICH IS SUGGESTING ISOLATED
TO SCATTERED THUNDERSTORMS FOR WESTERN PR AND THE LOCAL WATERS ON
FRIDAY AND SATURDAY.
THE AMOUNTS OF RAIN ARE FORECAST TO BE GENERALLY UNDER A HALF AN
INCH FOR EASTERN PR THROUGH THURSDAY...THEN INCREASING ON FRIDAY
AS MOISTURE AND INSTABILITY INCREASES. NORTHWESTERN PR IS EXPECTED
TO HAVE CONVECTION EACH AFTERNOON...BUT THE HI-RES GUIDANCE FAVORS
TODAY AS HAVING THE HIGHEST AMOUNTS...NEAR ONE INCH OF RAIN
GENERALLY SPEAKING. EVEN THOUGH INSTABILITY INCREASES LATER IN THE
WEEK...THE MODEL GUIDANCE WAS NOT AS AGGRESSIVE IN THE RAINFALL
FORECAST FOR NORTHWESTERN PR...THOUGH IT COULD BE DUE TO
CLOUDINESS. THEREFORE...WE WERE CONSERVATIVE IN THE AMOUNTS OF
RAIN LATER IN THE WEEK THOUGH THERE IS CONSIDERABLE UNCERTAINTY AT
THE MOMENT...ESPECIALLY SINCE THE EGDI ALGORITHM SUGGESTS THE
POSSIBILITY OF SCATTERED THUNDERSTORMS. THE 5-DAY TOTAL RAINFALL
FORECAST IS CURRENTLY SUGGESTING JUST OVER 2 INCHES OF RAIN ACROSS
EAST-SOUTHEAST PR AND ALSO ACROSS NW-PR...WITH THE USVI OBSERVING
UNDER A HALF AN INCH OF RAIN.
ALAMO...WPC (USA)
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