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PMDCA 



TROPICAL DISCUSSION - INTERNATIONAL DESKS

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

855 AM EDT THU MAY 16 2024



WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI MAY 16/12UTC:



A SFC HIGH PRESSURE OVER THE NORTH CENTRAL ATLANTIC WILL MOVE EAST

OVER THE NEXT FEW DAYS...WHILE A SFC LOW PRESSURE MOVES INTO THE

WESTERN ATLANTIC OFF THE COAST OF EASTERN US AND MOVE NORTHEAST.

BY EARLY NEXT WEEK...ANOTHER SFC LOW PRESSURE EXITS EASTERN US AND

MOVES INTO THE WESTERN ATLANTIC. THIS EXPECTED PATTERN WILL CAUSE

THE LOCAL WINDS TO REMAIN MAINLY FROM THE EAST TO SOUTHEAST FOR

THE NEXT SEVERAL DAYS. HOWEVER...THE SFC LOW EARLY NEXT WEEK MAY

CAUSE AN INCREASE IN MOISTURE FOR THE EARLY AND MIDDLE PART OF

NEXT WEEK...WHICH WILL ALSO COMBINE WITH OTHER MID AND UPPER LEVEL

FEATURES THAT COULD CAUSE SIGNIFICANT INSTABILITY AND STRONG

THUNDERSTORMS...BUT ONE MUST CONSIDER THAT THIS WOULD BE LATE IN

THE FORECAST PERIOD AND CONFIDENCE IS LOW AT THIS TIME. THAT BEING

SAID...THE REST OF THE WORKWEEK COULD OBSERVE LOCALLY INDUCED

SHOWERS AND THUNDERSTORMS ACROSS CENTRAL AND WESTERN PR IN THE

AFTERNOON HOURS THROUGH SATURDAY...WHILE MAINLY FAIR WEATHER WOULD

BE EXPECTED FOR THE USVI WITH ONLY A FEW BRIEF SHOWERS. THE LATEST

MODEL GUIDANCE SUGGESTS THAT THERE IS A POSSIBILITY OF SAHARAN

DUST STARTING TO MOVE OVER THE LOCAL ISLANDS LATE SATURDAY THROUGH

MONDAY...BEFORE THE AFOREMENTIONED INCREASE IN MOISTURE THAT WOULD

BE EXPECTED LATE TUESDAY INTO WEDNESDAY.



A WEAK MID LEVEL TROUGH IS FORECAST TO DEVELOP OVER THE LOCAL

ISLANDS BY VERY LATE FRIDAY INTO SATURDAY...AS THE TROUGH AXIS

MOVES EAST OF THE ISLANDS BY MONDAY. BY TUESDAY...A STRONG MID

LEVEL TROUGH WILL START AMPLIFYING OVER THE CENTRAL

CARIBBEAN...WITH ITS AXIS OVER CENTRAL CUBA AND MOVING VERY SLOWLY

EAST...HAVING ITS AXIS OVER EASTERN CUBA BY WEDNESDAY. THE UPPER

LEVELS PAINT A SIMILAR PICTURE...AN UPPER TROUGH WILL PASS OVER

THE LOCAL ISLANDS ON FRIDAY INTO SATURDAY...BUT THE TROUGH AXIS IS

NOT EXPECTED TO BE TO THE EAST OF THE LOCAL ISLANDS UNTIL MONDAY

MORNING. ON TUESDAY...A STRONG UPPER TROUGH ALSO WITH ITS AXIS

OVER CUBA AND THE CENTRAL CARIBBEAN WILL MOVE SLOWLY TO THE

EAST...AND ITS AXIS WILL ALSO BE OVER EASTERN CUBA BY LATE

WEDNESDAY. HAVING THESE MID AND UPPER LEVEL TROUGHS TO THE WEST OF

PR/USVI WOULD PROVIDE SIGNIFICANT INSTABILITY OVER THE LOCAL

ISLANDS. THIS INSTABILITY WILL ALSO COMBINE WITH THE SIGNIFICANT

INCREASE IN MOISTURE EXPECTED FOR TUESDAY ONWARD. IF THE MODELS

WERE TO VERIFY THE FORECAST...THIS SETUP COULD CAUSE RATHER STRONG

THUNDERSTORMS OVER THE AREA. EVEN THOUGH TUESDAY AND WEDNESDAY ARE

STILL FAR IN THE FORECAST PERIOD...IT IS WORTH MENTIONING THAT THE

LONGER RANGE MODELS ARE ALSO SUGGESTING COLDER THAN NORMAL MID

LEVEL TEMPS...WITH THE LATEST GFS MODEL SUGGESTING -8 TO -10C FROM

TUESDAY AFTERNOON INTO WEDNESDAY MORNING. THESE COLD MID LEVEL

TEMPS CONTRIBUTE TO THE POSSIBILITY OF HAIL...ESPECIALLY DURING

THE DAY WHEN COMBINED WITH DIURNAL HEATING...ADDING TO THE

INSTABILITY.



OVERALL...A TYPICAL RAINFALL PATTERN IS EXPECTED FOR THE REST OF

THE WORKWEEK...WITH AFTERNOON CONVECTION ACROSS CENTRAL TO WESTERN

PR...AND ISOLATED SHOWERS ELSEWHERE INCLUDING THE USVI. SAHARAN

DUST MOVES IN FOR THE LATTER PART OF THE WEEKEND INTO

MONDAY...THEN THE CHANCES OF SHOWERS AND STRONG THUNDERSTORMS

INCREASE ON TUESDAY AND WEDNESDAY.



ALAMO...WPC (USA)





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