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FXCA20 KWBC 071419
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
919 AM EST THU NOV 07 2024
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI NOV 07/12UTC:
THE LARGE SCALE ANALYSIS SHOWS THAT THE CARIBBEAN CONTINUES TO BE
UNDER UPPER DIVERGENT MJO CONDITIONS. NO SIGNIFICANT KELVIN WAVE
IS PRESENT AT THIS TIME...BUT ENHANCED VENTILATION CONTINUES TO
AID AREAS OF DEEP CONVECTION ACROSS THE BASIN. THE MJO IS EXPECTED
TO CONTINUE UPPER DIVERGENT THROUGH NEXT WEAK...ALTHOUGH EXPECT A
TREND TOWARDS MORE NEUTRAL CONDITIONS AS WE MOVE INTO MID NOVEMBER.
THE SYNOPTIC ANALYSIS SHOWS A POTENT RETROGRADING TUTT CENTERING
JUST TO THE SOUTHWEST OF PUERTO RICO. THIS TUTT ASSOCIATES WITH
TWO INDUCED TROUGHS. ONE IS LOCATED NEAR THE MONA PASSAGE AT
67-68W...WHILE ANOTHER IS LOCATED JUST TO THE EAST OF THE VIRGIN
ISLANDS OR NEAR 63W. SCATTERED DEEP CONVECTION IS OCCURRING WITH
THESE SYSTEMS...BUT THE STRONGEST CELLS ARE REMAINING OFFSHORE AT
THIS TIME. ALSO OF INTEREST...A TROPICAL WAVE IS PROPAGATING
WESTWARD NEAR 57W AND IS FORECAST TO APPROACH THE ISLANDS ON
SATURDAY.
IN TERMS OF THE FORECAST...THE TUTT IS EXPECTED TO CONTINUE
RETROGRADING RAPIDLY WESTWARD WHILE A MID-UPPER RIDGE PATTERN
ESTABLISHES OVER THE ISLANDS STARTING ON FRIDAY EVENING INTO
SATURDAY MORNING. ALTHOUGH A MID-LEVEL RIDGE IS EXPECTED TO EXTEND
OVER THE NORTHEAST CARIBBEAN FROM THE WEEKEND INTO THE REST OF THE
FORECAST CYCLE...IT IS NOT EXPECTED TO BE SUFFICIENTLY STRONG TO
FULLY LIMIT THE VERTICAL DEVELOPMENT OF CONVECTION. INITIALLY/ON
THURSDAY...EXPECT SCATTERED CONVECTIVE STRUCTURES IN ASSOCIATION
WITH THE TUTT AND THE INDUCED WAVES. THIS WILL INTERFERE WITH
DIURNAL HEATING PROCESSES...ENHANCING THE WEIGHT OF MESOSCALE
STRUCTURES DEVELOPING OFFSHORE. OF INTEREST IS A MOIST PLUME
BREWING TO THE SOUTH OF THE ISLANDS...WHICH WILL LIKELY ENTER
SOUTHWEST PUERTO RICO OVERNIGHT...AND HAS THE POTENTIAL OF
DEVELOPING MODERATE ACCUMULATIONS INTO FRIDAY MORNING. THE NEXT
SYSTEM OF INTEREST IS THE TROPICAL WAVE...WHICH IS FORECAST TO
ARRIVE DURING SATURDAY EVENING. ALTHOUGH THE STABILIZING INFLUENCE
OF THE BUILDING MID LEVEL RIDGE SHOULD BE INCREASING...THE WAVE IS
FORECAST TO ARRIVE WITH PRECIPITABLE WATER VALUES NEARING OR
EXCEEDING 60MM. THE GDI IS ALSO HIGH WITH THIS SYSTEM...SUGGESTING
THE POTENTIAL FOR MODERATE AND LOCALLY HEAVY PRECIPITATION IN
SATURDAY EVENING INTO SUNDAY MORNING. BASED ON THE DIURNAL CYCLE
OF CONVECTION AND TIMING OF THE WAVE...EXPECT THE LARGEST
ACCUMULATIONS IN THE VI AND SOUTHEAST PUERTO RICO THROUGH SUNDAY
MORNING.
ON SUNDAY...EXPECT THE AMPLIFICATION OF A LARGE UPPER TROUGH IN
THE NORTH ATLANTIC. THIS WILL ENHANCE SURFACE PRESSURES AND FAVOR
A BACKING OF THE TRADES TO EAST NORTHEASTERLIES OVER THE ISLANDS.
ALTHOUGH THE MID-UPPER FLOW IS EXPECTED TO CONTINUE BECOMING MORE
HOSTILE FOR DEEP CONVECTION...MODELS ARE HINTING THE DEVELOPMENT
OF A SHORT-LIVED SHEAR LINE ACROSS THE VI/EASTERN PUERTO RICO LATE
ON SUNDAY INTO MONDAY MORNING. THIS COULD HIGHLIGHT PRECIPITATION
LOCALLY TO FAVOR MAXIMA GENERALLY UNDER 1 INCH/DAY.
THE LAST EVOLUTION OF INTEREST IS THE DEEPENING OF A ROBUST UPPER
TROUGH BETWEEN THE BAHAMAS AND BERMUDA ON WEDNESDAY. MODELS ARE
CONFIDENT ABOUT THIS EVOLUTION...WHICH WILL LIKELY FAVOR A RAPID
LOWERING OF SURFACE PRESSURES TO THE NORTH OF THE ISLANDS. THIS
WILL YIELD TO A SHIFT OF THE TRADES FROM EASTERLIES TO
SOUTH-SOUTHEASTERLIES BY WEDNESDAY...RELOCATING THE REGIONS OF
DIURNAL CONVECTION FROM MORNING SHOWERS IN EASTERN PUERTO RICO AND
ISOLATED AFTERNOON CONVECTION IN THE WEST CORDILLERA TO MORNING
SHOWERS ALONG THE SOUTHERN TIER OF PUERTO RICO. HOWEVER...IN TERMS
OF PRECIPITATION AMOUNTS...EXPECT CONSERVATIVE ACCUMULATION GIVEN
THE WEAK YET PERSISTENT INFLUENCE OF THE MID-LEVEL RIDGE PATTERN
OVER THE REGION.
GALVEZ...WPC (USA)
JACKMAN... BMS (BARBADOS)
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