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FXCA20 KWBC 061835
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
235 PM EDT TUE AUG 06 2024
FORECAST BULLETIN 06 AUG 2024 AT 1830 UTC:
THE NATIONAL HURRICANE CENTER (NHC) IS ISSUING ADVISORIES ON
TROPICAL STORM DEBBY...WHICH IS AFFECTING THE SOUTHEAST USA...AND
ITS CENTER IS FORECAST TO MOVE OFFSHORE INTO THE WESTERN ATLANTIC
THIS AFTERNOON...BUT THEN MAKE LANDFALL ONCE AGAIN OVER THE
SOUTHEAST USA ON THURSDAY AFTERNOON. IN ADDITION...NHC IS ALSO
MONITORING A TROPICAL WAVE IN THE CARIBBEAN...WHICH HAS A 10%
CHANCE OF DEVELOPING INTO A TROPICAL CYCLONE THROUGH 48
HOURS...AND 30% CHANCE OF FORMATION THROUGH 7 DAYS. THE EASTERN
PACIFIC IS VERY ACTIVE. ALTHOUGH CARLOTTA HAS BECOME POST
TROPICAL...AND DANIEL HAS DISSIPATED...THERE ARE STILL TWO ACTIVE
TROPICAL CYCLONES IN THE EAST PACIFIC...TOPICAL STORMS EMILIA AND
FABIO...BUT THEY ARE EXPECTED TO REMAIN OVER OPEN WATERS AND NOT
AFFECT LAND AREAS DIRECTLY.
OVER THE NEXT FEW DAYS...LINGERING SAHARAN DUST WILL BE MOVING
THOUGH THE CARIBBEAN TODAY AS THE CONCENTRATION DIMINISHES...AND
ANOTHER SIGNIFICANT PLUME OF SAHARAN DUST WILL BE APPROACHING THE
LEEWARD ISLANDS BY THURSDAY MORNING. THE AVAILABLE MOISTURE IS
NEAR NORMAL FOR MOST OF THE ATLANTIC BASIN...WITH THE EXCEPTION OF
AREAS NEAR TROPICAL STORM DEBBY INTO THE BAHAMAS AND THE GREATER
ANTILLES...THE SOUTHERN CARIBBEAN...AND SOME SECTIONS OF SOUTHERN
MEXICO. BY THURSDAY...DEBBY WILL PULL SOME MOISTURE FROM THE
SOUTH AND INTO THE BAHAMAS...AND A TROPICAL WAVE MOVING THROUGH
THE CARIBBEAN WILL INTERACT WITH THE PANAMANIAN LOW AND WILL MOVE
DEEP MOISTURE INTO THE WESTERN CARIBBEAN AND OVER NICARAGUA AND
HONDURAS. THE MID AND UPPER LEVELS ARE NOT PROVIDING ANY
PARTICULARLY STRONG DYNAMICS OVER LAND AREAS GENERALLY SPEAKING.
HOWEVER...THERE IS A MID LEVEL VORTICITY MAXIMA THAT COULD AFFECT
NICARAGUA ON THURSDAY AS THE PANAMANIAN LOW INTERACTS WITH A
TROPICAL WAVE AND MOVES INTO NICARAGUA. THERE IS ALSO AN UPPER
LEVEL LOW OVER NORTHWESTERN MEXICO...BUT THIS LOW WILL WEAKEN INTO
AN OPEN TROUGH.
PORTIONS OF CENTRAL AMERICA WILL RECEIVE SIGNIFICANT RAIN OVER THE
NEXT 3 DAYS. THE LATEST MODEL GUIDANCE IS SUGGESTING A 3-DAY
RAINFALL TOTAL OF AS MUCH AS 100MM FROM PANAMA TO NORTHEASTERN
HONDURAS...THOUGH ISOLATED HIGHER AMOUNTS...NEAR 150MM IS BEING
FORECAST BY THE GFS MODEL. THIS IS BECAUSE OVER THEN EXT 3
DAYS...THE PANAMANIAN LOW WILL STRENGTHEN AND MOVE WEST AND
INTERACT WITH THE MONSOON TROUGH. THERE IS ALSO A TROPICAL WAVE
THAT WILL MOVE THROUGH THE AREA...WHICH WILL CAUSE AN INCREASE IN
MOISTURE AND CONVECTION. AS THE PANAMANIAN LOW MOVES WEST AND INTO
NICARAGUA BY THURSDAY...THE MOISTURE CONVERGENCE OVER PANAMA AND
COSTA RICA WILL PRODUCE SIGNIFICANT RAINFALL OVER THE AREA. THE
LATEST FORECAST MODELS INDICATE THAT TODAY COULD ACTUALLY BE THE
DRIEST DAY OVER SOUTHERN CENTRAL AMERICA...WITH MAX RAINFALL
TOTALS OVER WESTERN PANAMA INTO COSTA RICA NEAR 25-45MM...WHILE
THURSDAY COULD BE A WETTER DAY FOR PANAMA...WITH AS MUCH AS
50-75MM OF RAIN WITH ISOLATED HIGHER AMOUNTS.
THE CARIBBEAN...ESPECIALLY THE LESSER ANTILLES WILL OBSERVE VERY
MODEST AMOUNTS OF RAIN...IN THE ORDER OF 01-10MM PER DAY. ACROSS
THE GREATER ANTILLES...PUERTO RICO/USVI WILL ALSO OBSERVE MODEST
AMOUNTS OF RAINFALL...WHILE HISPANIOLA COULD HAVE LOCALIZED
SIGNIFICANT RAINFALL OVER THE HIGHER ELEVATIONS...WITH MAX VALUES
OF 50-75MM OVER THE 3-DAY PERIOD...WHILE CUBA ALSO IS FORECAST TO
OBSERVE 50-75MM OVER THE 3-DAY PERIOD. THIS IS BECAUSE AS THE
TROPICAL WAVE PASSES THROUGH THE CARIBBEAN...TROPICAL STORM DEBBIE
WOULD PULL MOISTURE FROM THE SOUTH AND OVER CUBA. BASED ON THE
IMPACT OF THE FEEDER BAND FROM DEBBIE OVER CUBA...THE RAINIEST DAY
COLD BE ON WEDNESDAY INTO THURSDAY...BUT CUBA COULD EXPECT DAILY
RAINFALL OF AROUND 15-25MM EACH DAY. THE BAHAMAS WOULD HAVE A
SIMILAR PATTERN. FEEDER BANDS FROM DEBBIE WILL PULL MOISTURE FROM
THE CARIBBEAN UP INTO THE BAHAMAS...ESPECIALLY TODAY AND
WEDNESDAY. THE DAILY RAINFALL FORECAST FOR THE BAHAMAS ARE ALSO IN
THE ORDER OF 15-25MM TODAY...THEN AROUND 20-35MM ON WEDNESDAY INTO
THURSDAY. THEN FOR THURSDAY INTO FRIDAY...WE CAN EXPECT NEAR
15-25MM FOR THE BAHAMAS. IT IS WORTH POINTING OUT THAT THE GLOBAL
MODELS SEEM TO BE UNDERESTIMATING THE PRECIP OVER THE
AREA...THEREFORE WE BUMPED UP THE RAINFALL FORECAST A BIT OVER
WHAT THE GLOBAL MODELS WERE SUGGESTING.
THE RAINFALL PATTERN OVER MEXICO WILL BE SIMILAR TO WHAT HAS BEEN
OBSERVED OVER THE LAST SEVERAL DAYS. THE SIERRA MADRE OCCIDENTAL
AND ALONG THE WEST COAST. THIS IS BECAUSE OF DIURNAL ONSHORE FLOW
FROM THE EAST PACIFIC. HOWEVER...THERE IS AN UPPER LOW ACROSS
NORTHWESTERN MEXICO WHICH WILL WEAKEN INTO A TROUGH BY MIDWEEK.
THIS FEATURE WILL ENHANCE SHOWER AND THUNDERSTORM POTENTIAL OVER
NORTHWESTERN MEXICO TODAY AND WEDNESDAY...AND THUS ARE EXPECTED TO
BE DE WETTEST DAYS OVER THAT REGION. THE FORECAST RAINFALL ACROSS
THE SIERRA MADRE OCCIDENTAL AND THE WEST COAST OF MEXICO IS
GENERALLY IN THE ORDER OF 05-10MM/DAY WITH MAX VALUES NEAR
15-30MM...THOUGH NORTHWESTERN MEXICO COULD HAVE UP TO 45MM OR SO
TODAY AND WEDNESDAY. THURSDAY INTO FRIDAY COULD BE THE DRIEST DAY
FOR MEXICO.
NORTHERN SOUTH AMERICA WILL HAVE SOME RAINFALL EACH DAY...BUT THE
MOST SIGNIFICANT RAIN WILL OCCUR OVER WESTERN
COLOMBIA...NORTHWESTERN TO CENTRAL VENEZUELA AND NORTHERN GUYANA.
THE 3-DAY RAINFALL FORECAST FOR THE AFOREMENTIONED AREAS ARE FOR
MAX VALUES NEAR 75-125MM OVER WESTERN COLOMBIA AND NORTHWESTERN
VENEZUELA. CENTRAL VENEZUELA INTO NORTHERN GUYANA ARE FORECAST
NEAR 50-75MM OF TOTAL RAIN IN THE 3-DAY PERIOD. THIS IS DUE TO A
COMBINATION OF FACTORS...AS THE PANAMANIAN LOW MOVES INTO THE
SOUTHERN CARIBBEAN...THERE WILL BE SOME ONSHORE FLOW OF DEEP
MOISTURE INTO WESTERN COLOMBIA...ESPECIALLY TODAY AND WEDNESDAY.
ON THURSDAY INTO FRIDAY...DEEPER MOISTURE WILL MOVE INTO GUYANA
AND VENEZUELA...WHICH WILL INTERACT WITH THE LOCAL TERRAIN AND
PRODUCE SHOWERS AND THUNDERSTORMS OVER THE AREA. THEREFORE
THURSDAY INTO FRIDAY IS EXPECTED TO BE THE WETTEST DAY FOR
VENEZUELA AND GUYANA.
ALAMO...(WPC)
FERNANDER...(BDM)
JACKMAN...(BMS)
MATHIAS...(CIAARA/MB)
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