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FXCA20 KWBC 121240
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
839 AM EDT WED JUL 12 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
12/12UTC: A TROPICAL WAVE WILL CAUSE SIGNIFICANT SHOWER ACTIVITY
TODAY AND TONIGHT...THOUGH LINGERING MOISTURE COULD CAUSE LOCALLY
NUMEROUS SHOWERS INTO EARLY THURSDAY. THE TJUA DOPPLER RADAR IS
ALREADY SHOWING MODERATE SHOWERS MOVING THROUGH PORTIONS OF
PR/USVI AND THE LOCAL WATERS. THE TROPICAL WAVE WILL BRING DEEP
MOISTURE TODAY AND TONIGHT...CAUSING PRECIPITABLE WATER TO PEAK
NEAR TWO STANDARD DEVIATIONS ABOVE NORMAL BY THIS EVENING. SAHARAN
DUST WILL RETURN EARLY ON THURSDAY FOR THE USVI...PERHAPS BY MID
MORNING FOR PR...CAUSING ANOTHER DRYING TREND FOR THE LATTER PART
OF THE WORKWEEK. THERE WILL BE A TRADE WIND INVERSION FROM
THURSDAY AFTERNOON INTO THE WEEKEND...WHICH WILL HELP LIMIT
CONVECTION OVER PR. DURING THE 5-DAY PERIOD...TODAY INTO VERY
EARLY THURSDAY IS EXPECTED TO BE THE RAINIEST PERIOD...FRIDAY IS
EXPECTED TO BE THE DRIEST DAY.
A SFC HIGH PRESSURE ACROSS THE WESTERN ATLANTIC WILL KEEP E-ESE
WINDS DURING THE NEXT 5 DAYS...WITH THE EXCEPTION OF THE INFLUENCE
FROM THE TROPICAL WAVE TODAY. A WEAK MID LEVEL HIGH PRESSURE IS
STILL FORECAST TO MEANDER ACROSS THE TROPICAL ATLANTIC FOR THE
NEXT SEVERAL DAYS. IN THE UPPER LEVELS...A LOW PRESSURE ACROSS
HISPANIOLA WILL SLOWLY MOVE SSW...THEN MOVE WEST ACROSS THE
CARIBBEAN OVER THE NEXT FEW DAYS. SOUTHERLY WINDS IN THE UPPER
LEVELS ARE EXPECTED ACROSS THE LOCAL ISLANDS FOR THE REST OF THE
WEEK.
FOR TODAY...THE AFOREMENTIONED TROPICAL WAVE WILL CAUSE RAINY
CONDITIONS FOR THE LOCAL ISLANDS...EASTERN PR IS EXPECTED TO HAVE
THE MOST PERSISTENT AND SIGNIFICANT SHOWERS...WHILE THE USVI WILL
HAVE SCATTERED SHOWERS BUT WITH LESS ACCUMULATIONS OVERALL. MODEL
GUIDANCE SOLUTIONS ARE SUGGESTING THAT THE MOST SIGNIFICANT
RAINFALL WILL BE THIS AFTERNOON AND EVENING. THAT SAID...SATELLITE
IMAGERY SHOWS A NARROW BAND OF CONVECTION DEVELOPING TO THE EAST
OF THE WAVE AXIS...CURRENTLY OVER THE LEEWARD ISLANDS...WHICH
COULD MOVE INTO PR/USVI ON THURSDAY MORNING. THE ECMWF IS MORE
AGGRESSIVE THAN THE GFS ON THE RAINFALL AMOUNTS FOR THURSDAY
MORNING. FOR THAT REASON...WE INCREASED THE RAINFALL AMOUNTS FOR
THURSDAY...BUT KNOW THAT THIS RAINFALL IS EXPECTED VERY EARLY IN
THE FORECAST PERIOD ON THURSDAY...AS THERE IS SAHARAN DUST AND DRY
AIR QUICKLY MOVING IN ON THURSDAY MORNING. THEREFORE...CONSIDERING
THE MODEL GUIDANCE AND RECENT HISTORY WITH TROPICAL WAVES...OUR
FORECAST FOR TODAY FAVORS NEAR 2 INCHES OF RAIN ACROSS A GOOD
PORTION OF EASTERN PR...WITH ONE INCH OR SO ACROSS CENTRAL TO W-SW
PR. THE USVI ARE FORECAST TO HAVE BETWEEN 0.50 AND 0.75 INCHES OF
RAIN TODAY. THE FORECAST LINGERING RAINFALL ON THURSDAY MORNING
COULD CAUSE UP TO AN INCH OF RAIN ACROSS EASTERN PR...WHILE A
QUARTER OF AN INCH OR SO IS FORECAST FOR THE USVI.
THE 5-DAY RAINFALL TOTALS ARE FORECAST TO BE 3 TO 3.5 INCHES
ACROSS EASTERN PR...AND AROUND 2 INCHES ACROSS CENTRAL TO WESTERN
PR. FOR THE USVI...BETWEEN 0.75 AND 1.25 INCHES ARE FORECAST.
ALAMO/GALVEZ...WPC (USA)
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