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)