TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
407 PM EDT MON SEP 30 2024

FORECAST BULLETIN 30 SEP 2024 AT 2000 UTC:

THE NATIONAL HURRICANE CENTER IS MONITORING SEVERAL TROPICAL
CYCLONES ACROSS THE ATLANTIC BASIN...AS WELL AS A FEW AREAS OF
POSSIBLE DEVELOPMENT IN BOTH THE ATLANTIC AND EASTERN PACIFIC
BASINS. OUT OF THE AREAS WITH POSSIBLE DEVELOPMENT...THERE IS AN
AREA IN THE WESTERN CARIBBEAN IN TOT HE GULF OF MEXICO THAT HAS A
LOW CHANCE OF TROPICAL CYCLONE FORMATION AT 48 HOURS...BUT A
MEDIUM CHANCE OF TROPICAL CYCLONE FORMATION TO 7 DAYS. THERE IS
ALSO AN AREA ACROSS THE EASTERN PACIFIC...JUST SOUTH OF SOUTHERN
MEXICO...THAT HAS A LOW CHANCE OF TROPICAL CYCLONE FORMATION
THROUGH 48 HOURS...BUT A HIGH CHANCE OF FORMATION THROUGH 7 DAYS.
BOTH OF THESE SYSTEMS COULD BRING SIGNIFICANT RAINFALL TO THE
SURROUNDING AREAS REGARDLESS OF DEVELOPMENT. PLEASE SEE THE LATEST
OUTLOOKS AND ADVISORIES ISSUED BY THE NATIONAL HURRICANE CENTER.

AT THE SURFACE...THERE IS A HIGH PRESSURE ACROSS THE WESTERN
TROPICAL ATLANTIC...A DEVELOPING LOW PRESSURE ACROSS THE SOUTHERN
CARIBBEAN...AND A LOW PRESSURE ACROSS THE EASTERN PACIFIC TO THE
SOUTH OF MEXICO. THE LOW PRESSURE SYSTEMS ACROSS THE SOUTHERN TO
WESTERN CARIBBEAN AS WELL AS THE EASTERN PACIFIC...WHICH ARE ALSO
IN THE VICINITY OF THE ITCZ/MONSOON TROUGH...WILL KEEP CENTRAL
AMERICA AND SOUTHERN MEXICO...AS WELL AS NORTHWESTERN SOUTH
AMERICA WITH ABOVE NORMAL MOISTURE FOR THE NEXT FEW DAYS. IN
ADDITION...THERE IS A TROPICAL WAVE...CURRENTLY JUST EAST OF THE
YUCATAN PENINSULA...THAT IS MOVING WEST...AND EXPECTED TO BE OVER
SOUTHERN MEXICO BY WEDNESDAY NIGHT INTO THURSDAY.

IN THE MID LEVELS...THERE IS A BROAD HIGH PRESSURE CURRENTLY
CENTERED OVER THE WESTERN TROPICAL ATLANTIC...BUT IT EXTENDS OVER
THE LESSER AND GREATER ANTILLES. A MID LEVEL LOW IS PRESENT OVER
THE SOUTHERN CARIBBEAN...WHICH ALSO HAS DECENT VORTICITY
ASSOCIATED WITH IT...NEAR COSTA RICA. ANOTHER MID LEVEL LOW IS
OBSERVED OVER THE EAST PACIFIC...JUST SOUTH OF SOUTHERN MEXICO.
THESE TWO MID LEVEL LOWS ARE VERTICALLY STACKED WITH THE LOWS AT
THE SURFACE. AT THE UPPER LEVELS...A BROAD HIGH PRESSURE IS ALSO
PRESENT OVER THE WESTERN ATLANTIC...CENTERED OVER THE NORTHERN
BAHAMAS...WHILE AN UPPER LOW IS OBSERVED OVER THE CENTRAL
CARIBBEAN. THERE IS ALSO ANOTHER UPPER HIGH OVER NORTHEASTERN
MEXICO. OVER THE NEXT FEW DAYS...THESE SYSTEMS WILL MOVE AND
INTERACT WITH THE LOCAL TERRAIN OVER CENTRAL AMERICA AND SOUTHERN
MEXICO TO CAUSE DAYS OF SIGNIFICANT RAINFALL IN SOME
AREAS...PARTICULARLY OVER PORTIONS OF THE PACIFIC COAST WHERE DEEP
MOISTURE IS BEING PUSHED INLAND. THERE IS ALSO SOME UNCERTAINTY IN
THE AMOUNTS OF RAIN AS THE DIFFERENT MODEL GUIDANCE DIFFERS
SIGNIFICANTLY FROM DAY TO DAY. THE ECMWF MODEL SEEMS TO BE HAVING
A BETTER HANDLE ON THE SITUATION WITH THE LATEST GUIDANCE BEING
MOST LIKE THE LATEST OBSERVATIONS...AS WELL AS THE RECENT MODEL
PERFORMANCE HAS BEEN BETTER FOR THE ECMWF VS THE OTHER
MODELS...FOR THAT REASON WE DECIDED TO LEAN A BIT CLOSER TO THE
ECMWF WITH THE LOCATION OF MOST SIGNIFICANT RAIN. THAT BEING
SAID...BY THE WEDNESDAY TO THURSDAY TIME PERIOD...THE DIFFERENCE
IN THE MODEL SOLUTIONS SEEM TO BE VERY SIGNIFICANT AND THERE IS
LOWER THAN USUAL CONFIDENCE IN THE RAINFALL FORECAST FOR CENTRAL
AMERICA INTO SOUTHERN MEXICO FOR MIDWEEK.

THAT BEING SAID...THE CARIBBEAN REGION IS FORECAST TO OBSERVE
RELATIVELY MODEST AMOUNTS OF RAIN...WITH THE GENERAL PATTERN BEING
THAT OF SCATTERED SHOWERS AND THEN LOCALIZED AFTERNOON SHOWERS AND
THUNDERSTORMS...PARTICULARLY OVER THE GREATER ANTILLES. THE
EXCEPTION IS CUBA...WHERE MOISTURE ADVECTION IS EXPECTED ACROSS
WESTERN CUBA ON TUESDAY AND WEDNESDAY...ENHANCING THE SHOWER AND
THUNDERSTORM ACTIVITY OVER THE AREA. MUCH OF NORTHERN SOUTH
AMERICA COULD OBSERVE THE SAME DAILY PATTERN...WITH LITTLE SHOWER
ACTIVITY IN THE MORNING HOURS...BUT AFTERNOON CONVECTION
DEVELOPING OVER MUCH OF BRAZIL. CONTINUING IN NORTHERN SOUTH
AMERICA...THE WESTERN PORTIONS OF COLOMBIA WILL HAVE SOME DIRECT
LOW LEVEL FLOW FROM THE PACIFIC...BRINGING PLENTY OF MOISTURE TO
THE AREA. THIS WILL CAUSE DAILY MAX RAINFALL OVER THE AREA THAT
COULD BE INT HE ORDER OF 20-50MM WITH TUESDAY BEING THE RAINIEST
DAY.

JUST ABOUT ALL AREAS OF CENTRAL AMERICA INTO SOUTHERN MEXICO ARE
EXPECTED TO RECEIVE SOME RAINFALL FROM TODAY THROUGH THURSDAY
MORNING. THE LATEST GUIDANCE FAVORS SOUTHERN NICARAGUA AND
HONDURAS TO HAVE DAILY MAX VALUES BETWEEN 25-50MM...WHILE SOUTHERN
GUATEMALA IS FORECAST MAX VALUES OF 40-80MM ON WEDNESDAY INTO
THURSDAY. AGAIN... THIS RAINFALL FORECAST REFLECTS SOME
UNCERTAINTY AS THE GLOBAL MODELS DIFFER...PARTICULARLY FOR THE
RAINFALL SOLUTION ON WEDNESDAY INTO THURSDAY. OVERALL THE GFS
MODEL WAS BULLISH WITH ITS RAINFALL SOLUTION COMPARED TO THE
ECMWF. WE WILL CONTINUE TO MONITOR THE MODEL GUIDANCE AND
PERFORMANCE. 

EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 01/00 01/12 02/00 02/12 03/00 03/12 04/00
TW   23N  86W  88W   90W   91W   92W   94W   95W   DISS

ALAMO...(WPC)
TINOCO-MORALES...(WPC)