149
FXCA20 KWBC 041818
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
217 PM EDT WED OCT 04 2023
FORECAST BULLETIN 04 OCT 2023 AT 1830 UTC: THE NATIONAL HURRICANE
CENTER CONTINUES TO ISSUE ADVISORIES ON TROPICAL STORM
PHILIPPE...WHICH IS CURRENTLY ABOUT 200 MILES NNW OF ST THOMAS
USVI. TROPICAL STORM PHILIPPE IS MOVING TO THE NNW...AND IS
EXPECTED TO GRADUALLY TRACK NORTHWARD STARTING TONIGHT. PHILIPPE
IS EXPECTED TO CAUSE HEAVY RAIN ACROSS THE LEEWARD ISLANDS...USVI
AND PUERTO RICO TODAY...WITH FEEDER BANDS POSSIBLY CAUSING
ADDITIONAL RAIN ON THURSDAY AS WELL. THE FORECAST FOR THE 3-DAY
ACCUMULATED RAIN FOR THOSE AREAS IS AS HIGH AS 100-200MM FOR
PORTIONS OF THE LEEWARD ISLANDS...WHILE PR/USVI COULD OBSERVE AS
MUCH AS 50-100MM. MOST OF THE RAINFALL IS EXPECTED TO BE
TODAY...THOUGH SOUTHERLY WINDS BRINGING MOISTURE WOULD CONTINUE TO
CAUSE SHOWERS ACROSS THE LESSER ANTILLES AND NORTHEAST CARIBBEAN
INTO FRIDAY. THERE IS ALSO A TROPICAL WAVE THAT IS EXPECTED TO
CROSS THE LESSER ANTILLES LATE THURSDAY INTO FRIDAY...WHICH WILL
CAUSE ADDITIONAL RAINFALL FOR THE WINDWARD ISLANDS. ACROSS THE
EASTERN PACIFIC...TROPICAL STORM LIDIA IS MOVING TO THE NNW AND IS
EXPECTED TO REMAIN OVER THE WATERS.
ACROSS THE REST OF THE TROPICAL REGION...SEVERAL FEATURES WILL
HELP THE DEVELOPMENT OF SIGNIFICANT RAINFALL ACROSS PORTIONS OF
THE TROPICS. THE MODEL GUIDANCE CONTINUES TO NOT BE IN AGREEMENT
IN MANY AREAS...BUT PARTICULARLY ACROSS NORTHERN SOUTH AMERICA
INTO CENTRAL AMERICA. THERE WERE SOME GENERAL AGREEMENTS IN A FEW
AREAS...AND THUS THE RAINFALL FORECAST REFLECTS THE AGREEMENT. IN
AREAS WHERE THE MODELS DIFFERED GREATLY FROM EACH OTHER...WE TRIED
TO SPLIT THE DIFFERENCE AND NUDGED THE FORECAST ONE WAY OR ANOTHER
DEPENDING ON THE SYNOPTIC FEATURES. IT IS ALSO WORTH MENTIONING
THAT THE GFS MODEL HAD HIGHER AMOUNTS OF RAIN WITH STRONG
THUNDERSTORMS...WHILE THE ECMWF WAS MORE GENERALIZED. THUS MORE
PRIORITY WAS GIVEN TO THE POTENTIAL IMPACTS OF HEAVIER RAIN EVEN
THOUGH THE COVERAGE MAY BE LIMITED.
AT THE SURFACE...THERE IS WEAK HIGH PRESSURE ACROSS THE CENTRAL
ATLANTIC....THERE IS ALSO A HIGH PRESSURE MOVING INTO THE WESTERN
ATLANTIC AS IT MOVES OFFSHORE FROM THE NORTHEAST US...AND A
STATIONARY FRONT FROM THE CENTRAL ATLANTIC INTO THE NORTHERN
BAHAMAS. IN THE MID LEVELS...THERE IS A BROAD HIGH PRESSURE ACROSS
THE CENTRAL ATLANTIC...A TROUGH ACROSS THE WESTERN ATLANTIC THAT
WILL DEVELOP INTO A MID LEVEL LOW...AND THE ASSOCIATED TROUGH
REACHES THE WESTERN CARIBBEAN BY LATE THURSDAY. THEN IN THE UPPER
LEVELS THERE IS ALSO A TROUGH EXTENDING FROM THE WESTERN ATLANTIC
INTO THE WESTERN CARIBBEAN...WHICH WILL AMPLIFY INTO
THURSDAY...AND AFFECT THE NORTHWESTERN SECTIONS OF SOUTH AMERICA
AND PORTIONS OF CENTRAL AMERICA...PROVIDING VENTILATION AND
INCREASING INSTABILITY...INCREASING THE POTENTIAL FOR SIGNIFICANT
RAINFALL WITH THUNDERSTORMS. HOWEVER...AN UPPER RIDGE WILL BE
MOVING IN LATER ON FRIDAY INTO SATURDAY.
MOST OF THE TROPICAL REGION HAS NEAR TO ABOVE NORMAL
MOISTURE...EXCEPT FOR SOUTHERN MEXICO INTO GUATEMALA...THAT HAS
NEAR TO SLIGHTLY BELOW NORMAL MOISTURE...AS WELL AS PORTIONS OF
THE ATLANTIC SIDE OF CENTRAL AMERICA. THAT SAID...MOST AREAS IN
THE TROPICS ARE FORECAST AT LEAST SOME RAINFALL.
HOWEVER...EXCLUDING THE IMPACTS OF PHILIPPE OVER THE LEEWARDS AND
THE NORTHEAST CARIBBEAN...PORTIONS OF NORTHWESTERN SOUTH AMERICA
AND SOME AREAS IN CENTRAL AMERICA...PARTICULARLY IN THE BORDER
BETWEEN PANAMA AND COSTA RICA...ARE EXPECTED TO OBSERVE VERY
SIGNIFICANT RAINFALL TODAY. THIS IS DUE TO THE AVAILABLE MOISTURE
COMBINING WITH THE MID AND UPPER LEVEL TROUGHS THAT ARE EXPECTED
TO AFFECT THE AREA. RAINFALL TOTALS WITH MAX VALUES OF 25 - 50MM
ARE FORECAST FOR TODAY ACROSS NORTHWESTERN COLOMBIA AND
NORTHWESTERN VENEZUELA. A FEW SECTORS OF WESTERN PANAMA INTO
EASTERN COSTA RICA COULD ALSO OBSERVE BETWEEN 75 AND 100MM TODAY.
FURTHER NORTH IN CENTRAL AMERICA...THE PACIFIC SECTORS OF
NICARAGUA AS WELL AS EL SALVADOR ARE FORECAST UP TO 40MM
TODAY...WHILE NORTHEASTERN NICARAGUA...HONDURAS...GUATEMALA AND
SOUTHERN MEXICO IS FORECAST TO OBSERVE UP TO 15MM. THE WESTERN
COAST OF MEXICO IS FORECAST UP TO 20-35MM HOWEVER. IN THE
CARIBBEAN THE GREATER ANTILLES...FROM HISPANIOLA TO CUBA ARE
FORECAST GENERALLY 05-10MM WITH MAX VALUES UP TO 15-35MM.
THURSDAY WILL HAVE SIGNIFICANT SHOWERS AND THUNDERSTORMS AS WELL.
NORTHWESTERN COLOMBIA AND VENEZUELA...AS WELL AS EASTERN INTO
CENTRAL AND SOUTHERN VENEZUELA ARE FORECAST THUNDERSTORMS THAT
COULD PRODUCE MAX VALUES OF 25-50MM OR EVEN HIGHER ACROSS ISOLATED
AREAS. MUCH LOWER AMOUNTS OF RAIN ARE FORECAST ELSEWHERE IN SOUTH
AMERICA...UP TO 25MM OR SO. THE PACIFIC SIDE OF CENTRAL AMERICA IS
FORECAST AS MUCH AS 35MM FROM NICARAGUA TO SOUTHERN MEXICO...AND
THE NORTHERN HALF OF NICARAGUA TO SOUTHERN MEXICO IS FORECAST MAX
VALUES OF 15MM. THE WESTERN COAST OF MEXICO INTO THE NORTH CENTRAL
SECTORS ARE FORECAST MAX VALUES OF 15-35MM. HOWEVER...A SMALL
PORTION OF NORTHEASTERN MEXICO...CLOSE TO THE BORDER WITH
TEXAS...COULD HAVE SIGNIFICANT THUNDERSTORMS FROM THURSDAY INTO
FRIDAY...WITH MAX VALUES THAT COULD REACH 75-125MM. THE CARIBBEAN
AND THE BAHAMAS WILL HAVE VARYING AMOUNTS OF RAIN...THOUGH MOST OF
THE RAIN WILL BE BETWEEN 05-15MM WITH MAX VALUES BETWEEN
20-45MM...BUT THE HIGH RAINFALL AMOUNTS WILL BE VERY LOCALIZED AND
DEPENDENT ON THE INDIVIDUAL LOCAL EFFECTS...AS PHILIPPE TRACKS
NORTH AND AWAY FROM THE LEEWARD ISLANDS. FRIDAY INTO SATURDAY
LOOKS TO BE A BIT DRIER FOR THE CARIBBEAN IN GENERAL...THOUGH A
TROPICAL WAVE IS EXPECTED TO MOVE INTO THE CARIBBEAN...THE AMOUNTS
OF RAIN ACROSS THE LESSER ANTILLES AND PUERTO RICO ARE EXPECTED TO
HAVE MAX VALUES UP TO 15-20MM...THOUGH HIGHER AMOUNTS ARE POSSIBLE
IN VERY ISOLATED AREAS OF NORTHWESTERN PR. HISPANIOLA COULD HAVE
THUNDERSTORMS PRODUCING UP TO 35MM ON FRIDAY...WHILE THE BAHAMAS
AND THE WESTERN CARIBBEAN ARE EXPECTED MAX TOTALS OF UP TO 15MM.
PORTIONS OF COLOMBIA AND VENEZUELA COULD OBSERVE ISOLATED
THUNDERSTORMS. THESE THUNDERSTORMS COULD PRODUCE UP TO 50MM BUT
THE MODEL GUIDANCE SUGGESTED ISOLATED ACTIVITY. ANOTHER
SIGNIFICANT AREA OF THUNDERSTORMS ON FRIDAY IS COSTA RICA AND
AGAIN NORTHEAST MEXICO...WHERE UP TO 50MM OF RAIN COULD BE
OBSERVED. ELSEWHERE IN CENTRAL AMERICA AND MEXICO...ISOLATED
THUNDERSTORM ACTIVITY COULD PRODUCE MAX VALUES BETWEEN 15 AND
35MM...WITH THE ATLANTIC SIDE OF THE REGION BEING DRIER.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 05/00 05/12 06/00 06/12 07/00 07/12 08/00
TW 15N 55W 57W 60W 62W 65W 67W 70W 73W
A TROPICAL WAVE IS INITIALIZED AT 55W AND TO THE SOUTH OF 15N. THE
TROPICAL WAVE IS NOT EXPECTED TO HAVE AN IMPACT IN THE LOCAL
ISLANDS UNTIL THURSDAY INTO FRIDAY...WHEN IT IS EXPECTED TO REACH
THE WINDWARD ISLANDS...CAUSING SOME RAINFALL ACROSS THE AREA. THE
TROPICAL WAVE WILL MOVE THROUGH THE EASTERN CARIBBEAN THROUGH THE
LATTER PART OF THE WORKWEEK.
ALAMO...WPC (USA)
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