108
FXCA20 KWBC 191732
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EDT THU SEP 19 2024

FORECAST BULLETIN 19 SEP 2024 AT 17 UTC:

THE MAIN SYSTEM OF INTEREST IN THE FORECAST CYCLE IS THE EXPECTED
DEVELOPMENT OF A BAROCLINIC CENTRAL AMERICAN GYRE OVER CENTRAL
AMERICA BETWEEN FRIDAY AND SATURDAY. NOTE THAT THIS SYSTEM COULD
BECOME A SIGNIFICANT EVENT GIVEN THAT IT IS FORECAST TO LAST
NEARLY A WEEK AS IT MEANDERS NORTHWESTWARD TOWARDS SOUTHEAST
MEXICO THROUGH LATE NEXT WEEK. CONSIDERING THAT CONFIDENCE ON FLOW
EVOLUTION AND ESPECIALLY PRECIPITATION WITH CAG EVENTS DECAYS
RAPIDLY WITH TIME...THE DISTRIBUTION OF THE AREAS AT HIGHEST RISK
FOR EXCESSIVE RAINFALL IS STILL LOW PAST SUNDAY.

ON THURSDAY...A QUASI-STATIONARY AMPLIFIED MID-UPPER FLOW PATTERN
CONTINUES ESTABLISHED OVER AREAS NORTH OF 15N. OF SPECIAL INTEREST
IS A POTENT UPPER RIDGE LOCATED OVER CENTRAL MEXICO...WHICH IS
FAVORING THE AMPLIFICATION OF A ROBUST UPPER TROUGH TO ITS EAST.
THIS TROUGH IS ALREADY EXTENDING ITS BASE INTO GUATEMALA AND EL
SALVADOR. SUCH UNSEASONABLY STRONG UPPER TROUGH IS EXPECTED TO
CONTINUE INTERACTING WITH THE MOIST POOL BUILDING ACROSS THE
NORTHWEST CARIBBEAN...TO TRIGGER THE FORMATION OF THE CAG.
CONFIDENCE IN THIS EVOLUTION IS INCREASING GIVEN THE EXPECTED
ARRIVAL OF A KELVIN WAVE THIS WEEKEND. IN THE MEAN TIME...AN
EASTERLY WAVE IS ENHANCING CONVECTION IN CENTRAL AMERICA IN
COMBINATION WITH LONG FETCH LOW-LEVEL WESTERLIES PRESENT IN THE
PACIFIC BASINS OF COSTA RICA AND PANAMA (SEE BELOW FOR WAVE
POSITIONS AND RAINFALL AMOUNTS). BUT AS THE CAG FORMS...EXPECT THE
WAVE TO DISSIPATE ON SATURDAY WHILE POTENTIAL RAINFALL
ACCUMULATIONS CONTINUE TO INCREASE. BY FRIDAY...EXPECT THE
HEAVIEST PRECIPITATION IN WEST PANAMA AND WEST COSTA RICA ...WHERE
ENHANCED ONSHORE FLOW WILL FAVOR MAXIMA OF 40-80MM. AS THE CAG
STARTS GAINING STRUCTURE...EXPECT SCATTERED HEAVY THUNDERSTORMS TO
DOT MOST OF NORTHERN CENTRAL AMERICA WHERE EXPECT AMOUNTS IN THE
15-20MM/DAY AND MAXIMA OF 30-60MM RANGE. IN CENTRAL PANAMA EXPECT
MAXIMA OF 20-45MM. ON SATURDAY...EXPECT AMOUNTS OF 20-40MM/DAY AND
MAXIMA OF 50-100MM DEVELOPING IN MOST OF COSTA RICA AND SOUTHWEST
NICARAGUA...AS SOUTHWESTERLY LOW-LEVEL WINDS START DEVELOPING WEST
OF CENTRAL AMERICA. IN EL SALVADOR/HONDURAS/SOUTHERN GUATEMALA
EXPECT MAXIMA OF 30-60MM. IN NORTHEAST NICARAGUA AND EAST HONDURAS
EXPECT MAXIMA OF 20-45MM...WHILE ISOLATED SIMILAR AMOUNTS ARE
EXPECTED IN SOUTHERN PANAMA.

A SECONDARY REGION OF INTEREST ENCOMPASSES THE NORTHWEST BAHAMAS
AND WEST CUBA...GIVEN DIRECT INFLUENCES OF THE AFOREMENTIONED
UPPER TROUGH. GIVEN THAT THE TROUGH IS FORECAST TO PERSIST THROUGH
SEVERAL DAYS IN THE REGION...IT WILL PROVIDE RECURRENT PERIODS OF
VENTILATION TO SUSTAIN INTERMITTENT SCATTERED SHOWERS AND
THUNDERSTORMS THROUGH THE ENTIRE FORECAST CYCLE. ON THURSDAY
EXPECT MAXIMA OF 20-35MM AND A MARGINAL RISK FOR SEVERITY IN THE
NORTHWEST BAHAMAS...WHILE IN WEST AND CENTRAL CUBA EXPECT MAXIMA
OF 15-25MM. ON FRIDAY...EXPECT MAXIMA GENERALLY IN THE 15-25MM/DAY
RANGE ACROSS BOTH THE NORTHWEST BAHAMAS AND WEST AND CENTRAL CUBA.
EXPECT SIMILAR AMOUNTS ON SATURDAY...BUT A DECREASE IN THE
SEVERITY RISK FOR CUBA.

EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC
TYPE INIT SOF 20/00 20/12 21/00 21/12 22/00 22/12 23/00 23/12
EW    82W 18N   83W   85W   87W   89W   CAG ----- ----- -----
TW    93W 22N   95W   98W  102W  105W  108W  111W  114W EXITS

AN EASTERLY WAVE IS INITIALIZE AT 82W AND IS SLOWING DOWN AS IT
ENTERS CENTRAL AMERICA ON THURSDAY...TO FAVOR MAXIMA OF 20-45MM IN
EAST HONDURAS/EAST NICARAGUA AND NORTHERN COSTA RICA. IN SOUTHERN
COSTA RICA AND WEST PANAMA EXPECT MAXIMA OF 35-70MM. SIMILAR
AMOUNTS ARE EXPECTED IN THE GULF OF FONSECA REGION WITH A RISK FOR
MCS FORMATION. ON FRIDAY...THE WAVE WILL ENHANCE CONVECTION IN
HONDURAS AND EL SALVADOR PRIMARILY...TO FAVOR MAXIMA OF 30-60MM
AND A GENERALIZED RISK FOR HEAVY THUNDERSTORMS. NOTE THAT IT IS
FORECAST TO THEN BECOME ILL-DEFINED AS THE CAG ESTABLISHES OVER
CENTRAL AMERICA.

A TROPICAL WAVE IS INITIALIZED AT 92W AND TO THE SOUTH OF 22N.
THIS WAVE IS ILL-DEFINED BUT WILL PROPAGATE ACROSS SOUTHERN
MEXICO...STIMULATING CONVECTION LOCALLY OVER FROM JALISCO TO
OAXACA TO FAVOR MAXIMA OF 20-35MM ON THURSDAY...FOLLOWED BY A
DECREASE IN MAXIMA TO 15-20MM ON FRIDAY...AS IT PROPAGATES ACROSS
SOUTHWEST MEXICO. THE WAVE IS FORECAST TO RAPIDLY EXIT THE COASTS
OF JALISCO ON SATURDAY WITH LIMITED IMPACTS IN CONTINENTAL
CONVECTION.

JACKMAN...(BMS-BARBADOS)
LEDESMA...(WPC)
TINOCO...(WPC)
GALVEZ...(WPC)

























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