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FXCA20 KWBC 071851
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 PM EDT WED AUG 07 2024
FORECAST BULLETIN 07 AUG 2024 AT 1830 UTC:
THE NATIONAL HURRICANE CENTER (NHC) IS ISSUING ADVISORIES ON
TROPICAL STORM DEBBY...WHICH IS AFFECTING THE SOUTHEAST USA...ITS
CENTER IS FORECAST TO MAKE LANDFALL OVER SOUTH CAROLINA ON
THURSDAY MORNING. IN ADDITION...NHC IS ALSO MONITORING A TROPICAL
WAVE IN THE CARIBBEAN...WHICH HAS A 0% CHANCE OF DEVELOPING INTO A
TROPICAL CYCLONE THROUGH 48 HOURS...AND A LOW 10% CHANCE OF
FORMATION THROUGH 7 DAYS. THERE ARE TWO ACTIVE TROPICAL CYCLONES
IN THE EAST PACIFIC...TROPICAL STORMS EMILIA AND FABIO...THEY ARE
EXPECTED TO REMAIN OVER OPEN WATERS...EMILIA IS FORECAST TO ABSORB
TROPICAL STORM FABIO BY THURSDAY.
OVER THE NEXT FEW DAYS...MINOR CONCENTRATION OF SAHARAN DUST
CONTINUES TO MOVE THOUGH THE CARIBBEAN TODAY...AND ANOTHER
SIGNIFICANT PLUME OF SAHARAN DUST WILL APPROACH 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...AND SOME SECTIONS OF SOUTHERN MEXICO. BY
THURSDAY...DEBBY WILL PULL SOME MOISTURE FROM THE SOUTH AND ALONG
WITH A TUTT LOW EAST OF THE ISLANDS, THE BAHAMAS CAN EXPERIENCE
SOME SEVERE WEATHER INTO FRIDAY...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 125MM FROM PANAMA TO NORTHEASTERN
HONDURAS...THOUGH ISOLATED HIGHER AMOUNTS...NEAR 150MM IS BEING
FORECAST BY THE GFS MODEL. THIS IS BECAUSE OVER THE NEXT 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 THURSDAY COULD BE A WETTER
DAY FOR PANAMA, SOUTHERN COSTA RICA AND THE EAST COAST OF
NICARAGUA WITH MAX RAINFALL TOTALS OVER THESE AREAS NEAR 50-100MM
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...WITH A MAXIMA OF ABOUT 15-25MM ON
SATURDAY...WHILE HISPANIOLA COULD HAVE LOCALIZED SIGNIFICANT
RAINFALL OVER THE HIGHER ELEVATIONS...WITH MAX VALUES OF 40-60MM
OVER THE 3-DAY PERIOD...WHILE CUBA ALSO IS FORECAST TO OBSERVE
20-45MM 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
TODAY 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 THROUGH FRIDAY. THE DAILY
RAINFALL FORECAST FOR THE BAHAMAS ARE ALSO IN THE ORDER OF 20-35MM
TODAY...THEN AROUND 15-25MM ON FRIDAY INTO SATURDAY. . IT IS WORTH
POINTING OUT THAT THE GLOBAL MODELS SEEM TO BE UNDERESTIMATING THE
PRECIPITATION 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 IS EXPECTED TO RECEIVE THE MOST
SIGNIFICANT RAIN OVER THE NEXT 3 DAYS. THIS IS BECAUSE OF DIURNAL
ONSHORE FLOW FROM THE EAST PACIFIC INTERACTING WITH THE LOCAL
TERRAIN EFFECTS AND SOME UPPER LEVEL SUPPORT. THERE IS AN UPPER
LOW ACROSS NORTHWESTERN MEXICO WHICH WILL WEAKEN INTO A TROUGH
TODAY. HOWEVER AN UPPER LEVEL TROUGH WILL STRENGTHEN OVER NORTH
CENTRAL TO NORTHEASTERN MEXICO BY FRIDAY...WHILE AN UPPER RIDGE
STRENGTHENS OVER THE BAJA PENINSULA...THIS WILL CAUSE A LOCALIZED
UPPER JET OVER WESTERN TO NORTHWESTERN MEXICO ON FRIDAY AND
ENHANCE SHOWER AND THUNDERSTORM POTENTIAL. THEREFORE...FRIDAY IS
EXPECTED TO BE THE WETTEST DAY OVER THE REGION. THE FORECAST
RAINFALL ACROSS THE SIERRA MADRE OCCIDENTAL AND THE WEST COAST OF
MEXICO OVER THE NEXT 3 DAYS IS GENERALLY IN THE ORDER OF
10-15MM/DAY WITH MAX VALUES NEAR 20-45MM...THOUGH NORTHWESTERN
MEXICO COULD HAVE UP TO 50MM OR SO ON FRIDAY.
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 40-80MM OVER WESTERN COLOMBIA...OVER NORTHWESTERN
AND CENTRAL VENEZUELA...INTO NORTHERN GUYANA ARE FORECAST A TOTAL
OF NEAR 30-60MM OF 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 FRIDAY. 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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