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FXCA20 KWBC 281246
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
846 AM EDT WED JUN 28 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUN
28/12UTC: AN UPPER TROUGH WILL INTERACT WITH A STRONG TROPICAL
WAVE...AND WILL CAUSE A SIGNIFICANT INCREASE IN SHOWER AND
THUNDERSTORM ACTIVITY OVER PR/USVI TODAY AND THURSDAY. THIS
TROPICAL WAVE WILL HAVE DEEP MOISTURE...AND WILL KEEP
PRECIPITABLE WATER BETWEEN 2.1 AND 2.3 INCHES THROUGH THURSDAY.
SATELLITE IMAGERY SHOWS LITTLE CLOUDINESS THIS MORNING OVER
PR/USVI...BUT IT SHOWS THE DEVELOPMENT OF THUNDERSTORMS ASSOCIATED
WITH THE APPROACHING TROPICAL WAVE. THE AVAILABLE MOISTURE WILL
GRADUALLY DECREASE STARTING ON FRIDAY AS SAHARAN DUST STARTS TO
MOVE IN...BUT THE PRECIPITABLE WATER WILL REMAIN ABOVE NORMAL ON
FRIDAY...REACHING NORMAL LEVELS BY SATURDAY. THE SAHARAN DUST
PLUME MAY PERSIST OVER PR/USVI THROUGH THE WEEKEND.
THE DEEP MOISTURE MOVING IN IS ALSO REFLECTED IN THE MID
LEVELS...WITH RELATIVE HUMIDITY REMAINING ABOVE NORMAL THROUGH THE
REST OF THE WORKWEEK...PEAKING AT OR ABOVE 2 STANDARD DEVIATIONS
ABOVE NORMAL ON THURSDAY. THERE IS A GOOD CHANCE OF THUNDERSTORMS
TODAY AND THURSDAY...BUT THE 500MB TEMPERATURES ARE EXPECTED TO BE
NEAR OR ABOVE NORMAL. THE EGDI ALGORITHM IS STILL SHOWING THE
POTENTIAL FOR SCATTERED THUNDERSTORMS WITH HEAVY RAIN...THURSDAY
HAVING A BIT HIGHER POTENTIAL THAN TODAY. THE GR02T ALGORITHM IS
INDICATING ONLY A MARGINAL TO SLIGHT RISK OF SEVERE STORMS. AFTER
THE TROPICAL WAVE PASSES...THE SAHARAN DUST IS EXPECTED TO MOVE
IN...AND A TRADE WIND INVERSION MAY BE PRESENT IN THE AREA...WHICH
WILL ALSO ACT TO LIMIT SIGNIFICANT SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY DURING THE WEEKEND INTO EARLY NEXT WEEK.
TODAY...SHOWERS AND THUNDERSTORMS MAY CAUSE CENTRAL TO WESTERN PR
TO OBSERVE OVER 2 INCHES OF RAIN IN SOME AREAS...WHILE EASTERN PR
COULD OBSERVE GENERAL AMOUNTS NEAR 1.5 INCHES. THE USVI ARE
FORECAST TO HAVE A MAX AMOUNT OF AROUND 1 INCH. ON
THURSDAY...EASTERN PUERTO RICO IS EXPECTED TO HAVE THE HIGHEST
AMOUNTS OF RAIN. THIS IS BECAUSE THERE MAY BE THICK CLOUD COVER
OVER PR BY THURSDAY...WHICH MAY LIMIT DEEP CONVECTION ACROSS
WESTERN AND NORTHWESTERN PR. THEREFORE...GIVEN THE SE WIND FLOW
AND DEEP MOISTURE EXPECTED...THE SOUTHERN AND EASTERN SECTIONS OF
PR ARE FORECAST TO OBSERVE BETWEEN 1 AND 3 INCHES OF RAIN...WITH
SOUTHWEST TO SOUTH CENTRAL PR BEING CLOSER TO 1 INCH...WHILE
SOUTHEAST TO NORTHEAST PR CLOSER TO THE 2-3 INCH RANGE. THE USVI
IS FORECAST TO HAVE AN INCH OR LESS OF RAIN. MOISTURE AND SHOWER
ACTIVITY WILL START TO DECREASE SLOWLY ON FRIDAY...AS SAHARAN DUST
MOVES IN. THE 5-DAY TOTAL RAINFALL FORECAST ACROSS PORTIONS OF THE
NORTHWESTERN QUADRANT OF PR IS AROUND 2.5 INCHES...EASTERN PR IS
FORECAST OVER 5 INCHES...AND THE USVI BETWEEN 1.25 AND 2.00 INCHES.
ALAMO/ACOSTA...WPC (USA)
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