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FXCA20 KWBC 181237
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
836 AM EDT TUE JUL 18 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
18/12UTC: THE TROPICAL WAVE THAT AFFECTED THE ISLANDS YESTERDAY IS
MOVING AWAY...AND DRIER AIR WITH SAHARAN DUST WILL BE MAKING ITS
WAY IN TODAY. THE PLUME OF SAHARAN DUST LOOKS SIGNIFICANT AND WILL
STAY OVER PR/USVI THROUGH AT LEAST THE REST OF THE WORKWEEK...BUT
THE LATEST GUIDANCE SAYS IT WILL LINGER INTO SATURDAY. THE
AVAILABLE MOISTURE WILL DECREASE TODAY...CAUSING PRECIPITABLE
WATER VALUES TO GO DOWN TO AROUND 1.6 INCHES BY THIS
AFTERNOON...WHICH IS STILL ON THE LOWER END OF NORMAL.
HOWEVER...THE PRECIPITABLE WATER VALUES WILL SLOWLY DECREASE AND
WILL BE LOW NORMAL THEREAFTER...VALUES DECREASING TO 1.2 INCHES BY
FRIDAY AFTERNOON AND EVENING...THEN GRADUALLY INCREASING ON
SATURDAY BUT REMAINING NEAR TO BELOW NORMAL. DURING THE 5-DAY
PERIOD...MOSTLY FAIR WEATHER AND HAZY CONDITIONS ARE EXPECTED.
THAT SAID...THERE IS A CHANCE OF BRIEF SHOWERS THAT COULD AFFECT
EASTERN PR/USVI IN THE MORNINGS AND OVERNIGHT...WITH WESTERN PR
HAVING LIMITED AFTERNOON CONVECTION.
A SFC HIGH PRESSURE OVER THE WEST CENTRAL ATLANTIC WILL KEEP E-ESE
WINDS DURING THE NEXT FEW DAYS...THEN A STRONG SURFACE HIGH
PRESSURE ACROSS THE CENTRAL ATLANTIC WILL MAINTAIN THE EASTERLY
WINDS FROM THIS WEEKEND ONWARD. A MID LEVEL HIGH PRESSURE IS
FORECAST TO MOVE FROM THE CENTRAL ATLANTIC TO WESTERN ATLANTIC BY
FRIDAY INTO SATURDAY...THEN A WEAK MID LEVEL TROUGH WILL MOVE INTO
THE SOUTHWESTER ATLANTIC THIS WEEKEND. UPPER LEVEL WINDS WILL BE
FROM THE WEST THROUGH THURSDAY NIGHT...THEN AN UPPER LOW MOVES TO
THE NORTHEAST OF THE LOCAL ISLANDS...CAUSING NORTHERLY UPPER LEVEL
WINDS LOCALLY. UPPER LEVEL WINDS WILL BE WEAK THIS WEEKEND AS
ANOTHER UPPER LOW GRADUALLY DEVELOPS OVER THE CARIBBEAN SEA. THERE
WILL BE A TRADE WIND INVERSION AT AROUND 850HPA FOR THE REST OF
THE WEEK.
OVERALL...SOME LINGERING MOISTURE COULD CAUSE SHOWER ACTIVITY
EARLY THIS MORNING...BEFORE MUCH DRIER AIR AND SAHARAN DUST MOVES
IN. THE COMBINATION OF THIS DRIER AIR MOVING IN WITH THE TRADE
WIND INVERSION WILL MAKE IT DIFFICULT FOR SIGNIFICANT RAINFALL TO
DEVELOP OVER THE LOCAL ISLANDS...AND MAINLY FAIR WEATHER AND HAZY
SKIES ARE EXPECTED TO PREVAIL. THAT SAID...BRIEF SHOWERS WOULD
STILL BE POSSIBLE.
ALAMO/ACOSTA...WPC (USA)
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