090
FXCA20 KWBC 061236
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
836 AM EDT THU JUL 06 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
06/12UTC: SAHARAN DUST WILL BE PRESENT ACROSS THE LOCAL ISLANDS
TODAY...KEEPING DRY AIR OVER PR/USVI AND LIMITING SHOWER ACTIVITY.
SURFACE HIGH PRESSURE ACROSS THE CENTRAL TO EAST CENTRAL ATLANTIC
WILL KEEP AN EAST TO EAST SOUTHEAST WIND FLOW FOR THE NEXT SEVERAL
DAYS. A MID-LEVEL HIGH PRESSURE WILL MEANDER OVER THE SOUTHWESTERN
ATLANTIC...FROM NORTH OF PR INTO THE BAHAMAS THROUGH MONDAY. BY
LATE TUESDAY THIS MID LEVEL HIGH PRESSURE WILL MOVE WEST INTO THE
NORTHERN BAHAMAS...BUT A MID LEVEL RIDGE WILL MOVE IN FROM THE
EAST AND OVER THE NORTHEASTERN CARIBBEAN. THE LATEST MODEL
GUIDANCE CONTINUES TO INDICATE THAT THERE WILL BE A TRADE WIND
INVERSION AT AROUND THE 850 HPA LEVEL TODAY...WHICH WILL ALSO WORK
TO INHIBIT STRONG STORMS. AN UPPER-LEVEL LOW TO THE NORTH OF
PUERTO RICO...AT AROUND 25N AND 62W IS EXPECTED TO CONTINUE MOVING
EAST OVER THE NEXT FEW DAYS. HOWEVER...AFTER THAT...THE GFS MODEL
SUGGESTS THAT THE UPPER LOW WILL MOVE TO THE SOUTHWEST INTO THE
NORTHEASTERN CARIBBEAN BY EARLY NEXT WEEK...WHILE THE ECMWF AND
OTHER GLOBAL MODELS KEEP THE UPPER LOW AND ASSOCIATED TROUGH
MEANDERING IN THE ATLANTIC AT AROUND 25N 55W. THAT SAID...THE GFS
MODEL SEEMS TO BE CORRECTING EASTWARD AND IS FURTHER TO THE EAST
AND CLOSER TO THE OTHER MODELS COMPARED TO YESTERDAY. A TROPICAL
WAVE IS FORECAST TO APPROACH PR/USVI ON LATE SATURDAY INTO
SUNDAY...WHICH IS A BIT FASTER THAN THE MODELS WERE SUGGESTING
BEFORE...AND THE GFS BEING A BIT FASTER THAN THE ECMWF. THIS WAVE
WILL CAUSE AN INCREASE IN MOISTURE AND SHOWER
ACTIVITY...ESPECIALLY ON SUNDAY. BY LATE SUNDAY INTO
MONDAY...SAHARAN DUST COULD MOVE IN...LINGERING INTO MIDWEEK.
WITH THE EXPECTED SAHARAN DUST...THE OVERALL AVAILABLE MOISTURE
WILL BE SLIGHTLY BELOW NORMAL TODAY...WITH PRECIPITABLE WATER
VALUES BETWEEN 1.4 AND 1.6 INCHES. MOISTURE WILL INCREASE
GRADUALLY ON FRIDAY...CAUSING PRECIPITABLE WATER TO INCREASE TO
NEAR 1.8 INCHES...BUT WILL DECREASE AGAIN BY MIDDAY SATURDAY TO
1.4 INCHES. THE ARRIVAL OF THE TROPICAL WAVE LATE SATURDAY INTO
SUNDAY WILL CAUSE THE MOISTURE TO INCREASE TO ABOVE NORMAL...WITH
PRECIPITABLE WATER MAXING OUT NEAR 2.2 INCHES...THEN GRADUALLY
DECREASING ON MONDAY.
FOR TODAY...THE OVERALL WEATHER IS EXPECTED TO BE RELATIVELY DRY
AND HAZY. ISOLATED SHOWER ACTIVITY MAY BE OBSERVED IN THE MORNING
ACROSS EASTERN PR...WHILE A SMALL AREA OF WESTERN PR MAY HAVE
SHOWER ACTIVITY DUE TO LOCALLY INDUCED CONVECTION. THE INCREASE IN
MOISTURE AND DECREASE OF SAHARAN DUST ON FRIDAY INTO SATURDAY
WOULD ALLOW SCATTERED SHOWERS ACROSS THE USVI AND EASTERN PR IN
THE NIGHT AND EARLY MORNING HOURS...WHILE LOCALLY INDUCED SHOWERS
ARE FORECAST ACROSS WESTERN PR. THE EXPECTED TROPICAL WAVE LATE
SATURDAY INTO EARLY SUNDAY IS EXPECTED TO CAUSE AN INCREASE IN
SHOWER ACTIVITY...BUT THE ARRIVAL OF SAHARAN DUST LATE SUNDAY INTO
MONDAY WOULD DECREASE THE CHANCES OF SIGNIFICANT RAIN ONCE AGAIN.
THE 5-DAY RAINFALL TOTALS ARE FORECAST TO BE NEAR 2 INCHES ACROSS
EASTERN AND WESTERN PR...AND NEAR 0.50 TO 0.75 INCHES FOR THE
USVI. LATE SATURDAY INTO SUNDAY IS EXPECTED TO BE THE RAINIEST
PERIOD IN THE NEXT 5 DAYS DUE TO THE ARRIVAL OF THE TROPICAL WAVE.
ALAMO...WPC (USA)
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