662
FXCA20 KWBC 271248
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
848 AM EDT THU JUN 27 2024
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI JUN 27/12UTC:
SATELLITE IMAGERY SHOWS THE PRESENCE OF AN EXTENSIVE PLUME OF
SAHARAN DUST EXTENDING ACROSS THE CENTRAL/SOUTHERN LESSER
ANTILLES...ACROSS PUERTO RICO AND THE VI INTO THE CENTRAL
BAHAMAS...SOUTHEAST CUBA AND JAMAICA. LESSER AMOUNTS OF DUST SEEM
TO BE PRESENT IN THE LEEWARD ISLANDS DUE TO VENTILATION IN THE
BASE OF A TUTT. THE TUTT EXTENDS FROM THE CENTRAL NORTHJ ATLANTIC
NEAR 36N 46W INTO THE CENTRAL LESSER ANTILLES/NORTHERN WINDWARD
ISLANDS. PRECIPITABLE WATER IN PUERTO RICO AND THE VI APPEARS TO
BE IN THE 48-52MM RANGE...WHICH REPRESENT VALUES CLOSE TO SLIGHTLY
HIGHER THAN NORMAL FOR THIS TIME OF THE YEAR. HOWEVER...A WEAK
TRADE WIND CAP AND DRY AIR IN THE 600-800 HPA LAYER ARE LIMITING
CONVECTIVE DEVELOPMENT AND PRECIPITATION PRIMARILY DUE TO DRY AIR
ENTRAINMENT PROCESSES. OF INTEREST ARE TWO TROPICAL WAVES LOCATED
IN THE FAR EASTERN TROPICAL ATLANTIC. THE NHC IS CLOSELY
MONITORING THE WAVE LOCATED NEAR 33W THIS MORNING...AND THEY SEE A
70% CHANCE FOR DEVELOPMENT IN THE NEXT SEVEN DAYS.
REGARDING THE EVOLUTION OF THE UPPER LEVEL FLOW...THE TUTT IS
FORECAST TO MOVE LITTLE THROUGH SATURDAY WHILE REMAINING TO THE
EAST OF THE ISLANDS. AFTER THIS PERIOD...AN UPPER RIDGE CURRENTLY
LOCATED TO ITS SOUTHEAST IS FORECAST TO EXPAND INTO THE EASTERN
CARIBBEAN. IN THE MID-LEVELS...THE CURRENT STABILIZING INFLUENCE
OF THE MID-LEVEL RIDGE LOCATED OVER THE SOUTHEAST BAHAMAS IS
FORECAST TO DECREASE...ALLOWING AN INCREASE IN PERIODS WITH
LOCALIZED VERTICAL DEVELOPMENT OF CONVECTIVE CELLS. YET...UPPER
CONVERGENT MJO CONDITIONS WILL LIKELY ENHANCE PERIODS WITH
SUBSIDENCE...LIMITING POTENTIAL RAINFALL AMOUNTS THROUGH EARLY
NEXT WEEK. PRECIPITATION WILL BE SENSITIVE TO MOIST PLUMES
ASSOCIATED WITH PERTURBATIONS IN THE TRADES. THE NEXT MOIST PLUME
IS FORECAST TO CROSS THE ISLANDS FROM SATURDAY MORNING THROUGH
SUNDAY MORNING...ELEVATING TOTAL PRECIPITABLE WATER TO
50-52MM...WHIC IS STILL WITHIN THE NORMAL RANGE FOR THE SEASON.
UNDER THE INFLUENCE OF EASTERLY TRADE WIND DIRECTIONS AND 15-20KT
SPEEDS...EXPECT THE ASSOCIATED INCREASE IN ACCUMULATION PRIMARILY
CLUSTERING IN EASTERN PUERTO RICO AND THE VI. AFTERNOON CONVECTION
IN WESTERN PORTIONS OF THE ISLAND SHOULD INCREASE IN INTENSITY BUT
TO A LESSER EXTENT...DUE TO DRY AIR ENTRAINMENT PROCESSES AND
ENHANCED WIND SHEAR.
THE PERIOD OF SPECIAL INTEREST STARTS EARLY ON TUESDAY
MORNING...WHEN THE SYSTEM MONITORED BY THE NHC ENTERS THE EASTERN
CARIBBEAN. THE CURRENT GUIDANCE AND NHC OUTLOOKS SUGGEST THIS
SYSTEM PASSING WELL TO THE SOUTH OF PUERTO RICO/VI...WHICH IS
CONSISTENT WITH THE BLOCKING INFLUENCE OF A MID-UPPER RIDGE
EXTENDING ALONG THE NORTHERN CARIBBEAN. NEVERTHELESS...MODEL
GUIDANCE IS ALREADY AGREEING FAIRLY WELL ON A FEEDER BAND
STRUCTURE/MOIST PLUME CROSSING PUERTO RICO/VI FROM TUESDAY MORNING
THROUGH EARLY WEDNESDAY MORNING ACCOMPANIED BY PRECIPITABLE WATER
VALUES OF 55-60MM...WELL ABOVE NORMAL. UNDER THE INFLUENCE OF FAST
SOUTHEASTERLY TRADES AND POTENTIALLY A TRADE WIND CAP DEPENDING ON
THE ORGANIZATION OF THE CYCLONE TO THE SOUTH...THE HEAVIEST
PRECIPITATION IS LIKELY TO CLUSTER IN EASTERN AND SOUTHEASTERN
PORTIONS OF THE ISLAND. IT IS VERY EARLY TO SPEAK ABOUT
ACCUMULATION BUT MAXIMA WILL VERY LIKELY EXCEED THE 1-3 INCH/DAY
RANGE IN AREAS BETWEEN SANTA ISABEL/GUAYAMA AND FAJARDO ENDING BY
12 UTC ON WEDNESDAY JULY 3. NOTE THAT THE AFOREMENTIONED UPPER
CONVERGENT MJO CONDITIONS MIGHT FAVOR DRIER SOLUTIONS...BUT
CONSIDERING THAT THIS IS AN SCENARIO OF TROPICAL CYCLONE-RELATED
PRECIPITATION ON A DAY 7...THE CURRENT FORECAST WILL LIKELY CHANGE
SIGNIFICANTLY.
GALVEZ...WPC (USA)
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