356
FXCA20 KWBC 121729
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 PM EDT THU OCT 12 2023
FORECAST BULLETIN 12 OCT 2023 AT 1700 UTC: THE MODEL GUIDANCE ONCE
AGAIN SEEMS TO BE SUGGESTING MORE PRECIPITATION ACROSS THE AREA BY
THE THIRD DAY OF THE FORECAST...AND ADJUSTING DOWNWARD FOR THE
FIRST TWO DAYS. THEREFORE THE FORECAST FOR TODAY AND TOMORROW HAS
BEEN ADJUSTED ACCORDINGLY. IN ADDITION...THE GFS MODEL SEEMS TO BE
MORE AGGRESSIVE...THOUGH MORE ISOLATED WITH THE HIGH PRECIP
AREAS...COMPARED TO THE ECMWF MODEL WHICH SUGGESTS LOWER MAX
RAINFALL BUT ALSO HAS A MORE GENERALIZED COVERAGE OF RAINFALL.
THEREFORE...CONSIDERING THAT THE MODELS HAVE BEEN TRENDING
DOWNWARD IN THE NEAR TERM...WE DECIDED TO CAP THE VERY HIGH
ISOLATED RAINFALL AMOUNTS...BUT SHOW A GENERAL TREND OVER AREAS
THAT WOULD BE RECEIVING SIGNIFICANT RAINFALL. PLEASE BE AWARE THAT
AMOUNTS COULD BE HIGHER THAN THE RANGE IN THE FORECAST OVER VERY
ISOLATED AREAS.
A TROPICAL WAVE MOVING WEST ACROSS THE EASTERN PACIFIC IS
CURRENTLY SOUTH OF OAXACA IN MEXICO. THE MODEL GUIDANCE IS A BIT
BETTER TODAY AT DEFINING THE LOCATION OF THE WAVE FOR
SATURDAY...BUT THEN IT SEEMS TO START TO LOSE DEFINITION IN THE
GUIDANCE FOR SUNDAY. IN THE LOWER LEVELS...THERE IS A LOW PRESSURE
NEAR 31N/72W THAT IS MOVING EAST AND WILL BE OVER THE CENTRAL
ATLANTIC BY SUNDAY. THERE IS ALSO A SFC HIGH PRESSURE EXTENDING
FROM THE EAST TROPICAL ATLANTIC INTO THE CENTRAL TROPICAL
ATLANTIC...AND BY SUNDAY THERE WILL BE A WEAK HIGH PRESSURE OVER
THE WEST CENTRAL TROPICAL ATLANTIC. ANOTHER SFC LOW PRESSURE
ACROSS THE NORTHEAST GULF OF MEXICO WILL MOVE SLOWLY TO THE
NORTHEAST...CENTERING ACROSS SOUTHEAST GEORGIA BY SATURDAY AND
THEN FURTHER NORTHEAST ACROSS THE MID-ATLANTIC STATES OF EASTERN
US BY SUNDAY. IN THE MID LEVELS THERE IS A BROAD HIGH PRESSURE
CENTERED OVER THE SOUTHWEST ATLANTIC...CAUSING SOME STABILITY OVER
THE GENERAL AREA FOR THE NEXT SEVERAL DAYS...AS THE HIGH PRESSURE
DRIFTS SLOWLY TO THE WEST. ANOTHER BROAD AREA OF HIGH PRESSURE IS
PRESENT IN THE UPPER LEVELS AND IS CENTERED OVER CUBA...THIS WILL
ALSO HELP PROMOTE SOME STABILITY AND IT IS ALSO DRIFTING SLOWLY TO
THE WEST...POSSIBLY BEING CENTERED OVER THE WESTERN CARIBBEAN AND
SOUTHERN GULF OF MEXICO BY SUNDAY.
AS PREVIOUSLY MENTIONED...THE MODEL GUIDANCE HAS TONED DOWN THE
AMOUNT OF RAIN ACROSS THE TROPICAL REGION FOR TODAY. CONSIDERING
THE BROAD MID AND UPPER LEVEL HIGH PRESSURES OVER THE
CARIBBEAN...THIS IS NOT VERY SURPRISING. MOST OF THE EXPECTED
RAINFALL TODAY WOULD BE DUE TO WIND FLOW AND OROGRAPHIC LIFTING IN
SOME AREAS. MOST AREAS IN THE BASIN THAT EXPECT SOME RAIN TODAY
WOULD BE IN THE ORDER OF 01-10MM WITH MAX VALUES BETWEEN 15-25MM.
HOWEVER...PORTIONS OF COSTA RICA AND WESTERN PANAMA COULD OBSERVE
UP TO 40MM IN ISOLATED AREAS...WHILE WESTERN COLOMBIA COULD
OBSERVE UP TO 35MM ACROSS ISOLATED AREAS AS WELL. THE CARIBBEAN IS
EXPECTED TO SEE LITTLE TO NO RAIN INTO THE WEEKEND...THAT
IS...WITH THE EXCEPTION OF VERY ISOLATED AMOUNTS OF 25MM OR
HIGHER...MOST AREAS IN THE CARIBBEAN WOULD OBSERVE 15MM OR LESS
THROUGH THE WEEKEND.
FOR FRIDAY...THE FORECAST FOR SIGNIFICANT RAINFALL ALSO DECREASED.
MAX RAINFALL AMOUNTS ARE FORECAST TO BE GENERALLY BETWEEN 15-25MM
ACROSS MOST AREAS OF CENTRAL AMERICA...AS WELL AS SOUTHERN AND
EASTERN MEXICO...AND PORTIONS OF NORTH CENTRAL SOUTH AMERICA. THAT
SAID...ISOLATED AREAS OF COSTA RICA...WESTERN COLOMBIA AND
NORTHWESTERN ECUADOR...COULD OBSERVE SIGNIFICANT
THUNDERSTORMS...AND THE FORECAST IS FOR MAX VALUES BETWEEN 40-80MM
WITH THE STRONGEST STORMS. THE AMOUNTS OF RAIN INCREASE FOR
SATURDAY INTO EARLY SUNDAY...BUT GIVEN THE RECENT HISTORY OF THE
MODEL GUIDANCE...OUR FORECAST CAPS THE VERY HIGH RAINFALL AMOUNTS
AS MODELS SEEM TO BE CORRECTING EACH DAY. SO FOR SATURDAY INTO
SUNDAY...ACROSS THE SOUTHERN HALF OF MEXICO...WESTERN
COLOMBIA...AND PORTIONS OF NORTHWESTERN ECUADOR...SHOWERS AND
THUNDERSTORMS ARE FORECAST...WITH MAX VALUES UP TO 40-80MM WITH
THE STRONGEST STORMS. NORTHWESTERN PERU COULD HAVE SOME STORMS AS
WELL...THOUGH AMOUNTS UP TO 50MM OR SO WOULD BE EXPECTED.
ELSEWHERE IN THE TROPICAL REGION...RAINFALL AMOUNTS UP TO 15-25MM
COULD BE EXPECTED...THOUGH ONCE AGAIN THE CARIBBEAN SEEMS TO BE
FAIRLY DRY WITH LITTLE IN THE WAY OF SIGNIFICANT RAINFALL
COVERAGE.
POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 13/00 13/12 14/00 14/12 15/00 15/12 16/00
TW 15N 96W 98W 100W 102W 104W DISS
A TROPICAL WAVE IS INITIALIZED AT 96W AND TO THE SOUTH OF 15N. THE
TROPICAL WAVE IS MOVING WEST ALONG THE COAST OF MEXICO...BUT THE
IMPACT ON THE RAINFALL POTENTIAL OVER MEXICO SEEMS TO BE MINIMAL.
THE TROPICAL WAVE STARTS TO LOSE DEFINITION IN THE MODEL GUIDANCE
AFTER SATURDAY.
ALAMO...WPC (USA)
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