642
FXCA20 KWBC 181854
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 PM EDT WED SEP 18 2024

FORECAST BULLETIN 18 SEP 2024 AT 18 UTC:

NOTE...A TROPOSPHERIC KELVIN WAVE IS FORECAST TO ENTER CENTRAL
AMERICA AND MEXICO THIS WEEKEND. AS THIS COMBINES WITH THE
CYCLOGENETIC IMPACTS OF AN UPPER TROUGH DEEPENING ACROSS THE GULF
OF MEXICO/NORTHERN CENTRAL AMERICA...EXPECT THE POTENTIAL FOR THE
FORMATION OF A BAROCLINIC CENTRAL AMERICAN GYRE. ALTHOUGH THIS
EVOLUTION IS EXPECTED PAST THE CURRENT FORECAST CYCLE...IT IS
IMPORTANT TO CONSIDER MONITORING THIS SITUATION.

IN THE MID-UPPER LEVELS...A QUASI-STATIONARY AND AMPLIFIED
RIDGE/TROUGH PATTERN HAS ESTABLISHED. THIS CONSISTS OF A MASSIVE
RIDGE CENTERING OVER CENTRAL MEXICO AND A TROUGH EXTENDING FROM
THE EASTERN USA INTO THE YUCATAN PENINSULA REGION. INTENSE
NORTHERLY FLOW IN THE EASTERN PERIPHERY OF THE RIDGE WILL LIKELY
AMPLIFY THE UPPER TROUGH...TO DEVELOP AN AXIS INTO GUATEMALA/EL
SALVADOR AND REGIONS OFFSHORE BY FRIDAY. IN THE LOWER
LEVELS...HIGH VALUES OF AVAILABLE MOISTURE ARE PRESENT IN THE
CENTRAL AND WESTERN CARIBBEAN. WAVES IN THE TRADES ARE PROPAGATING
ACROSS THE REGION BUT THEY ARE ILL-DEFINED AT THIS TIME (SEE BELOW
FOR POSITIONS AND IMPACTS). REGARDLESS OF WAVE STRUCTURE...THE
SLOW DOWN OF PERTURBATIONS PROPAGATING IN THE TRADES IS EXPECTED
TO FAVOR A GRADUAL INCREASE IN MOISTURE AND ASSOCIATED
PRECIPITATING CONVECTION IN CENTRAL AMERICA. ALSO OF
RELEVANCE...WESTERLIES ARE FORECAST TO GRADUALLY INTENSIFY ALONG
THE SOUTHERN FRINGES OF THE ITCZ/MONSOON TROUGH IN THE EASTERN
PACIFIC...WHICH WILL RESULT IN INTERMITTENT PERIODS OF HEAVY
RAIN-PRODUCING CONVECTION IN WESTERN PANAMA AND THE PACIFIC BASIN
OF COSTA RICA. THROUGH EARLY FRIDAY MOST ACTIVITY WILL ORGANIZE
WITH AN EASTERLY WAVE (SEE BELOW FOR POSITIONS AND RAINFALL
ACCUMULATION). HOWEVER...AS THE CAG STARTS TO ORGANIZE AND LONG
FETCH WESTERLIES IMPACT SOUTHERN CENTRAL AMERICA STARTING ON
FRIDAY...EXPECT HEAVY RAINFALL TO START DEVELOPING ON FRIDAY
THROUGH EARLY SATURDAY IN COSTA RICA AND WEST PANAMA. ON FRIDAY
INTO EARLY SATURDAY EXPECT MAXIMA OF 50-100MM/DAY IN SOUTHERN
COSTA RICA AND WEST PANAMA...WHILE IN CENTRAL/EAST PANAMA AND
WESTERN COLOMBIA EXPECT MAXIMA OF 25-50MM.

ALSO IN ASSOCIATION WITH THE PERSISTENT UPPER TROUGH ACROSS THE
SOUTHEAST USA...A MOIST PLUME IS FORECAST TO CONTINUE ACROSS THE
NORTHWEST BAHAMAS AND WEST CUBA. THIS WILL CONTINUE TO FAVOR
SCATTERED CONVECTION ON A DAILY BASIS AND MODERATE RAINFALL
ACCUMULATION. THROUGH EARLY THURSDAY EXPECT MAXIMA GENERALLY IN
THE 15-35MM/DAY RANGE. GIVEN ENHANCED VENTILATION AND
INSTABILITY...EXPECT A SLIGHT RISK FOR SEVERITY IN THE NORTHWEST
BAHAMAS ON THURSDAY AND FRIDAY...WHILE IN CUBA EXPECT A MARGINAL
RISK DEVELOPING ON FRIDAY.

QUIET CONDITIONS FOR THIS TIME OF THE YEAR ARE EXPECTED IN MOST OF
THE EASTERN CARIBBEAN. ALTHOUGH A SURFACE TROUGH IS PRESENT ACROSS
THE WINDWARD ISLANDS ON WEDNESDAY AND IS FORECAST ON
THURSDAY...LIMITED AMOUNTS OF AVAILABLE MOISTURE WILL RESULT IN
VERY CONSERVATIVE ACCUMULATION FOR MID-SEPTEMBER.

EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC
TYPE INIT SOF 19/00 19/12 20/00 20/12 21/00 21/12 22/00 22/12
EW    77W 16N   79W   82W   84W   85W   87W   CAG ----- -----
TW    89W 17N   92W   94W   97W  DISS ----- ----- ----- -----

AN EASTERLY WAVE IS PROPAGATING ACROSS PANAMA ON WEDNESDAY TO
FAVOR MAXIMA OF 20-35MM. ON THURSDAY...IT WILL FAVOR MAXIMA OF
35-70MM IN WEST PANAMA AND SOUTHERN COSTA RICA...AND MAXIMA OF
30-60MM IN EAST NICARAGUA AND EASTERN HONDURAS. IN WEST
NICARAGUA/GULF OF FONSECA REGION IT WILL FAVOR MAXIMA OF 20-45MM.
ON FRIDAY...THE WAVE WILL FAVOR MAXIMA OF 40-80MM IN NORTHERN
NICARAGUA...HONDURAS AND EL SALVADOR...WHILE IN SOUTHERN NICARAGUA
AND NORTHERN COSTA RICA IT WILL FAVOR MAXIMA OF 25-50MM.

AN ILL-DEFINED TROPICAL WAVE IS PROPAGATING ACROSS
GUATEMALA/SOUTHEAST MEXICO ON WEDNESDAY TO FAVOR GENERALLY MAXIMA
OF 20-35MM. ON THURSDAY...THIS WILL FAVOR MAXIMA OF 15-25MM FROM
OAXACA/SOUTHERN VERACRUZ INTO GUERRERO/MORELOS WHILE DISSIPATING.

LEDESMA...(WPC)
TINOCO...(WPC)
GALVEZ...(WPC)

























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