TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
926 AM EDT THU JUL 18 2024

WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI JUl 18/12UTC: A
DENSE CONCENTRATION OF SAHARAN DUST IS EXPECTED TO AFFECT PR/USVI
THROUGH THE END OF THE WEEK...CAUSING VERY HAZY SKIES. THE LATEST
GUIDANCE SHOWS THAT THE CLEANER AIR WILL START TO ARRIVE DURING
THE DAY ON SUNDAY. THE CLEANER AIR MAY PREVAIL THROUGH THE FIRST
HALF OF THE UPCOMING WORKWEEK...BUT ADDITIONAL SAHARAN DUST COULD
START MOVING IN ONCE AGAIN LATE WEDNESDAY INTO THE LATTER PART OF
NEXT WEEK. OVER THE NEXT WEEK...A COUPLE OF TROPICAL WAVES ARE
FORECAST TO MOVE INTO THE CARIBBEAN. THE FIRST WAVE WILL MOVE IN
ON FRIDAY INTO SATURDAY...CAUSING THE PRECIPITABLE WATER TO
INCREASE TO AROUND 2.3 INCHES...WHICH IS 2 STANDARD DEVIATIONS
ABOVE NORMAL. MOISTURE WILL DECREASE TO NORMAL OR SLIGHTLY BELOW
NORMAL LEVELS THIS WEEKEND INTO NEXT WEEK...THOUGH MOISTURE WILL
INCREASE TO THE UPPER END OF NORMAL AFTER MONDAY. THE NEXT
TROPICAL WAVE IS EXPECTED TO MOVE IN ON WEDNESDAY OF NEXT WEEK.
THE MOISTURE INCREASE ASSOCIATED WITH THIS TROPICAL WAVE IS
FORECAST TO BE BRIEF...HOWEVER. BEHIND THIS WAVE IS WHEN THE
SAHARAN DUST IS EXPECTED TO RETURN...AND WITH IT...THERE COULD BE
A WIND SURGE. THE MODEL GUIDANCE IS CURRENTLY SUGGESTING THAT THE
WIND SURGE ON THE LATTER PART OF NEXT WEEK COULD HAVE WIND SPEEDS
OF AROUND 20KTS AT THE SFC AND AS MUCH AS 30-35KTS WHEN WE LOOK AT
THE 925-700MB AVG WINDS.

AS FAR AS RAINFALL PATTERN GOES...THE PATTERN ITSELF IS EXPECTED
TO BE TYPICAL...WITH SOME PASSING SHOWERS AFFECTING THE USVI AND
EASTERN PR...THEN AFTERNOON CONVECTION DEVELOPING ACROSS SECTIONS
OF WESTERN PR...ESPECIALLY IN AREAS OF LOW LEVEL CONVERGENCE.
ALTHOUGH THERE IS SOME TROUGHINESS OVER THE NORTHEAST CARIBBEAN IN
THE UPPER LEVELS EXPECTED INTO SATURDAY...THE WINDS ARE WEAK AND
THE DYNAMICS AND ENHANCED FORCING WOULD BE VERY LIMITED.
THEREFORE...THE MID AND UPPER LEVELS ARE NOT PARTICULARLY
CONDUCIVE TO PROMOTE PROLONGED AND ENHANCED CONVECTION. THE TUTT
THAT AFFECTED THE AREA RECENTLY IS MOVING TO THE NORTH
NORTHWEST...AND IT IS EXPECTED TO REMAIN OVER THE WESTERN TROPICAL
ATLANTIC FOR THE NEXT SEVERAL DAYS...WHILE A WEAK UPPER RIDGE
WOULD DEVELOP OVER THE LOCAL ISLANDS THIS WEEKEND. BECAUSE THE
AVAILABLE MOISTURE IS EXPECTED TO INCREASE SIGNIFICANTLY ON
FRIDAY...CAUSING THE POTENTIAL FOR SCATTERED THUNDERSTORMS AND
INCREASE THE OVERALL COVERAGE AND AMOUNTS OF RAIN. BECAUSE OF
THIS...FRIDAY MAY BE THE RAINIEST DAY OUT OF THE NEXT WEEK.
ALTHOUGH THE MODEL BLENDS SHOW AROUND AN INCH TO AN INCH AND A
HALF OF RAIN ON FRIDAY INTO SATURDAY ACROSS EASTERN PR...THE GFS
MODEL IS VERY BULLISH IN THE AMOUNTS OF ITS SOLUTION...SUGGESTING
OVER 2.5 INCHES ACROSS THAT EASTERN THIRD OF MAINLAND PR FOR THE
24-HR PERIOD BETWEEN FRIDAY MORNING INTO SATURDAY MORNING. FROM
SATURDAY ONWARD...THE MODEL GUIDANCE OVERALL DOES NOT SUGGEST
LARGE AREAS WITH DAILY RAINFALL TOTALS OF OVER ONE INCH...AND IN
GENERAL WITH THE TYPICAL PATTERN OF RAIN OVER PR/USVI.


ALAMO...WPC (USA)