TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 PM EDT MON SEP 16 2024

FORECAST BULLETIN 16 SEP 2024 AT 1915 UTC:

A SYSTEM OF INTEREST IS A DEEPENING UPPER TROUGH ACROSS THE EAST
COAST OF THE USA. THIS SYSTEM IS INTERACTING WITH A MOIST AIRMASS
LOCATED ACROSS THE BAHAMAS. AS THE TROUGH DEEPENS...PERIODS WITH
ENHANCED VENTILATION AND SUFFICIENT COLD AIR IN THE MID-LEVELS TO
FAVOR STRONG CONVECTION AND ISOLATED SEVERE WEATHER. ON
MONDAY...EXPECT MAXIMA OF 20-35MM IN THE NORTHWEST BAHAMAS WITH A
SLIGHT RISK FOR SEVERITY. ALSO ON MONDAY...A MOIST PLUME MOVING IN
FROM HISPANIOLA INTO EAST CUBA WILL FAVOR MAXIMA OF 20-35MM IN
HAITI AND EAST CUBA. ON TUESDAY...EXPECT A PEAK IN PRECIPITATION
AND THE POTENTIAL FOR SEVERITY IN THE NORTHWEST BAHAMAS. THIS
INCLUDES ENHANCEMENT BY THE DIVERGENT ENTRANCE OF AN UPPER JET.
EXPECT ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 30-60MM WITH A
MODERATE RISK FOR SEVERITY. IN CENTRAL AND WEST CUBA EXPECT MAXIMA
OF 30-60MM. ON WEDNESDAY...THE MOIST PLUME SET UP ACROSS THE
NORTHWEST BAHAMAS WILL CONTINUE TO INTERACT WITH THE UPPER TROUGH
TO ITS NORTHWEST. ALTHOUGH THE RISK FOR SEVERITY
DECREASES...EXPECT POTENTIALLY SIMILAR AMOUNTS. IN WEST AND
CENTRAL CUBA EXPECT A DECREASE IN ACCUMULATION TO MAXIMA OF
20-40MM.

IN MEXICO...AN UPPER RIDGE HAS ESTABLISHED OVER SOUTHERN PORTIONS
OF THE GULF OF CALIFORNIA AND EXTENDS NORTH INTO THE US ROCKY
MOUNTAINS. THIS SYSTEM IS VENTILATING CONVECTION...PARTICULARLY IN
CENTRAL MEXICO AND THE SIERRA MADRE ORIENTAL AND ADJANCENT COASTAL
PLAINS. IN THE MEAN TIME...MUCH DRIER CONDITIONS HAVE ESTABLISHED
NORTHWEST OF A LINE FROM JALISCO...ZACATECAS...COAHUILA...WHERE
EXPECT ISOLATED CONVECTION THROUGH THE CYCLE. ON MONDAY...EXPECT
ENHANCED MOISTURE CONVERGENCE TO FAVOR MAXIMA OF 20-45MM ALONG THE
SIERRA MADRE ORIENTAL...WHILE IN AREAS TO THE SOUTH OF 20N EXPECT
MAXIMA OF 15-30MM. A SURFACE TROUGH ACROSS CHIAPAS/WEST GUATEMALA
WILL FAVOR MAXIMA OF 25-50MM. ON TUESDAY...EXPECT THE LARGEST
AMOUNTS TO CLUSTER IN OAXACA/SOUTHERN VERACRUZ AND CHIAPAS...AND
EXTEND INTO THE WESTERN YUCATAN PENINSULA...WHERE EXPECT MAXIMA OF
20-45MM. ON WEDNESDAY...EXPECT THE HEAVIEST PRECIPITATION TO
CLUSTER IN CHIAPAS...WHERE AN APPROACHING TROPICAL WAVE WILL FAVOR
MAXIMA OF 30-60MM. IN THE MEAN TIME...DIURNAL CONVECTION IN THE
YUCATAN PENINSULA AND SOUTH/SOUTHWEST MEXICO WILL FAVOR MAXIMA OF
20-35MM.

A DRY AIR MASS CONTINUES TO ENTER THE NORTHEAST CARIBBEAN...WHICH
IS YIELDING TO CONSERVATIVE RAINFALL AMOUNTS. SOUTH OF THIS AIR
MASS...AN ILL-DEFINED ITCZ/FEEDER BAND-LIKE STRUCTURE IN
ASSOCIATION WITH TROPICAL DEPRESSION GORDON...IS FORECAST TO
CONTINUE ENHANCING SHOWERS AND ISOLATED THUNDERSTORMS IN THE
CENTRAL LESSER ANTILLES. THROUGH TUESDAY MORNING EXPECT
05-10MM/DAY AND MAXIMA OF 15-20MM FRMO BARBADOS INTO DOMINICA. ON
TUESDAY EXPECT MAXIMA OF 15MM IN THE NORTHERN WINDWARD ISLANDS.
THIS DECREASES THEREAFTER.

MUCH WETTER CONDITIONS ARE UNRAVELING IN CENTRAL AMERICA...IN
ASSOCIATION WITH THE PILE UP OF ILL-DEFINED WAVES IN THE TRADES.
NOTE THAT MODELS SEEM TO BE UNDERFORECASTING RAINFALL TOTALS...SO
CONSIDERING POTENTIALLY WETTER GUIDANCE SOLUTIONS SHOULD BE
EVALUATED. ON MONDAY...EXPECT MAXIMA OF 20-45MM FROM NORTHWEST
COLOMBIA INTO COSTA RICA. SIMILAR AMOUNTS ARE EXPECTED IN EAST
NICARAGUA/EAST HONDURAS AS TRADE WIND SHOWERS AND THUNDERSTORMS
INTERACT WITH AN UPPER TROUGH TO THE NORTHWEST. ON TUESDAY...A
TROPICAL WAVE IS FORECAST TO ENTER COSTA RICA/NICARAGUA. THIS WILL
FAVOR MAXIMA OF 25-50MM EXTENDING WEST INTO THE GULF OF FONSECA.
ON WEDNESDAY...EXPECT THE LARGEST AMOUNTS TO CLUSTER WITH THE
TROPICAL WAVE IN WEST HONDURAS/EL SALVADOR INTO GUATEMALA WHERE
EXPECT MAXIMA OF 30-60MM. ENHANCED ITCZ MOISTURE CONVERGENCE WILL
FAVOR MAXIMA OF 30-60MM IN WEST PANAMA...MOST OF COSTA RICA INTO
SOUTHWEST NICARAGUA...WHILE ELSEWHERE IN PANAMA EXPECT MAXIMA OF
20-45MM. ALSO ON WEDNESDAY...ENHANCED ONSHORE LOW-LEVEL FLOW WILL
FAVOR MAXIMA OF 30-60MM IN WESTERN COLOMBIA.

EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC
TYPE INIT SOF 17/00 17/12 18/00 18/12 19/00 19/12 20/00 20/12
TW    79W 18N   80W   82W   84W   86W   89W   91W   93W   95W

AN ILL-DEFINED TROPICAL WAVE IS PROPAGATING ACROSS THE SOUTHWEST
CARIBBEAN WHILE ENHANCING CONVECTION IN PANAMA. THIS SYSTEM IS
FORECAST TO PROPAGATE SLOWLY WESTWARD WHILE CONTRIBUTING TO A
GRADUAL INCREASE IN CONVECTION AND ASSOCIATED RAINFALL AMOUNTS IN
CENTRAL AMERICA THROUGH THE NEXT THREE DAYS.


JACKMAN...(BMS - BARBADOS)
FERNANDER...(BDM - THE BAHAMAS)
GALVEZ...(WPC)