TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 PM EDT WED SEP 20 2023

FORECAST BULLETIN 20 SEP 2023 AT 1830 UTC: A ROBUST HIGH PRESSURE
SYSTEM ALOFT EXTENDS OVER THE SOUTHERN UNITED STATES INTO MEXICO
AND NORTHERN GUATEMALA...FAVORING DRY CONDITIONS THROUGHOUT THE
AREA ON WEDNESDAY. IN THE LOWER LEVELS...AN EASTERLY WAVE IS
MAKING ITS WAY ALONG THE SOUTHERN PORTION OF MEXICO...AND IT IS
FORECAST TO MOVE OVER THE OPEN OCEAN OF THE PACIFIC BY THURSDAY.
ANOTHER EASTERLY WAVE WILL ENTER THE YUCATAN PENINSULA BY
THURSDAY...BRINGING PRECIPITATION TO THE SOUTHEASTERN STATES. DUE
TO THE UNFAVORABLE CONDITIONS ALOFT...THE EASTERLY WAVE IS NOT
EXPECTED TO FAVOR LARGE AMOUNTS OF PRECIPITATION BY FRIDAY. ON
WEDNESDAY...NORTHWEST MEXICO IS FORECAST MAXIMA OF 15-25MM. THE
EASTERLY WAVE WILL FAVOR MAXIMA OF 10-35MM FROM NAYARIT TO WESTERN
PORTIONS OF MICHOACAN...WHILE ELSEWHERE IN MICHOACAN AND GUERRERO
EXPECT MAXIMA OF 15-25MM. SIMILAR AMOUNTS ARE EXPECTED IN
OAXACA...TABASCO...CHIAPAS...AND SOUTHERN CAMPECHE. DRIER
CONDITIONS ARE EXPECTED ON THURSDAY...WHERE MAXIMA ALONG THE
SIERRA MADRE DEL SUR AND SIERRA MADRE OCCIDENTAL CAN EXPECT MAXIMA
OF 15-25MM. SIMILAR AMOUNTS ARE FORECAST FROM VERACRUZ/OAXACA TO
THE NORTHERN YUCATAN PENINSULA. ON FRIDAY...THE AFOREMENTIONED
AREAS CAN EXPECT GENERALIZED MAXIMA OF 15-25MM.

NORTH OF THE BAHAMAS...A SURFACE STATIONARY FRONT EXTENDS FROM THE
CENTRAL ATLANTIC...JUST NORTH OF THE BAHAMAS...INTO FLORIDA...AND
TO THE NORTHEAST GULF OF MEXICO. A PREFRONTAL TROUGH IS POSITIONED
OVER THE CENTRAL BAHAMAS AND EXTENDS INTO CUBA. ALOFT...A DEEP
TROUGH EXTENDS FROM THE UNITED STATES INTO THE CENTRAL CARIBBEAN
SEA AND JUST EAST OF HONDURAS/NICARAGUA. SHORT WAVE TROUGHS ARE
EXPECTED TO MAKE THEIR WAY OVER CUBA AND THE BAHAMAS...PROVIDING
VENTILATION FOR CONVECTION AND SQUALLY WEATHER. BY THURSDAY
EVENING...A LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP NORTH OF
THE BAHAMAS AND MOVE NORTHWARD ON FRIDAY. SQUALLY WEATHER IS
EXPECTED THROUGHOUT THE FORECAST PERIOD IN THE NORTH AND CENTRAL
BAHAMAS. A TROPICAL WAVE IS PROPAGATING OVER THE LESSER ANTILLES
ON WEDNESDAY AND IT WILL BE FOLLOWED BY ANOTHER WAVE...FORECAST TO
ARRIVE BY FRIDAY. THESE WAVES WILL BRING PRECIPITATION TO THE
REGION...AND REACH THE GREATER ANTILLES BY FRIDAY. LOCALIZED
HIGHER AMOUNTS ARE POSSIBLE DUE TO LOCAL EFFECTS. ON
WEDNESDAY...EXPECT MAXIMA OF 20-45MM IN NORTH-CENTRAL
BAHAMAS...EAST-CENTRAL CUBA...AND THE LESSER ANTILLES. ELSEWHERE
AROUND THE REGION EXPECT MAXIMA OF 15-25MM. ON THURSDAY...THE
NORTHERN BAHAMAS CAN EXPECT MAXIMA OF 20-45MM...WHILE CENTRAL-EAST
CUBA CAN SEE AMOUNTS OF 20-35MM. SIMILAR AMOUNTS ARE EXPECTED IN
CENTRAL PORTIONS OF HISPANIOLA. MAXIMA OF 15-25MM ARE EXPECTED
OVER THE CARIBBEAN BASIN. ON FRIDAY...WESTERN HISPANIOLA...THE
SOUTHERN BAHAMAS...AND TURKS AND CAICOS CAN EXPECT MAXIMA OF
20-35MM. THE REST OF THE REGION CAN EXPECT MAXIMA TO REMAIN BELOW
25MM.

IN CENTRAL AMERICA...AN EASTERLY WAVE IS EXPECTED TO PROPAGATE
OVER THE AREA ON WEDNESDAY. IN ADDITION...THE EASTERLY TRADE WINDS
ARE FAVORING MOISTURE CONVERGENCE ALONG THE EASTERN COASTS. THESE
WILL BE THE MAIN PRODUCERS OF RAINFALL FOR THE REGION OVER THE
NEXT FEW DAYS. ON WEDNESDAY...EL SALVADOR...AND PORTIONS OF THE
SURROUNDING COUNTRIES CAN SEE MAXIMA OF 35-70MM. FROM EASTERN
GUATEMALA...INTO HONDURAS...AND NICARAGUA...EXPECT MAXIMA OF
20-35MM. SOUTHEASTERN NICARAGUA...COSTA RICA...AND WEST PANAMA CAN
EXPECT MAXIMA OF 20-45MM. WHILE ELSEWHERE IN CENTRAL
AMERICA...EXPECT MAXIMA TO NOT EXCEED 25MM. AMOUNTS ARE EXPECTED
TO DECREASE ON THURSDAY...WHERE GUATEMALA...BELIZE...WEST
HONDURAS...AND EL SALVADOR CAN EXPECT MAXIMA OF 20-35MM. THE FROM
NICARAGUA TO PANAMA...CAN EXPECT MAXIMA OF 15-25MM. ON
FRIDAY...EAST HONDURAS...TO NORTHERN COSTA RICA...CAN EXPECT
MAXIMA OF 20-35MM....AND THE REST OF THE REGION CAN EXPECT
ISOLATED MAXIMA OF 15-25MM.

IN NORTHERN SOUTH AMERICA...A KELVIN WAVE IS PROPAGATING OVER THE
REGION AND IT IS FORECAST TO EXIT BY FRIDAY. IN THE MEANTIME...THE
EFFECTS OF THE KELVIN WAVE WILL BE MARGINAL...YET THE RAINIEST DAY
IS FORECAST FOR THURSDAY. IN THE LOWER LEVELS...TROPICAL WAVES ARE
EXPECTED OVER THE REGION AND WILL HAVE VENTILATION FOR CONVECTION
FROM THE KELVIN WAVE. LOCALIZED HIGHER AMOUNTS ARE POSSIBLE DUE TO
LOCAL EFFECTS. ON WEDNESDAY...VENEZUELA...WEST GUYANA...SOUTHERN
COLOMBIA...AND REGIONS OF NORTHERN BRASIL ARE FORECAST MAXIMA OF
20-35MM. NORTHWEST COLOMBIA IS EXPECTED SIMILAR AMOUNTS. ELSEWHERE
IN THE REGION...EXPECT ISOLATED MAXIMA OF 15-25MM. ON
THURSDAY...THE ARRIVAL OF THE SECOND TROPICAL WAVE WILL FAVOR
MAXIMA OF 20-45M FROM EAST-CENTRAL VENEZUELA...TO NORTHERN
SURINAME. FRENCH GUIANA...AND NORTHERN BRASIL CAN EXPECT MAXIMA OF
20-35MM. SIMILAR AMOUNTS ARE EXPECTED IN THE LAKE MARACAIBO
REGION. COLOMBIA AND WESTERN VENEZUELA...INTO NORTHERN PERU...AND
ECUADOR CAN EXPECT MAXIMA OF 15-25MM. ON FRIDAY...EXPECT ISOLATED
MAXIMA OF 20-35MM IN SOUTHEAST
COLOMBIA...VENEZUELA...GUYANA...SURINAME...AND NORTHERN BRASIL.
WEST COLOMBIA CAN EXPECT FAVORABLE ONSHORE FLOW FROM THE WEST FOR
MAXIMA OF 20-45MM. NORTHERN COLOMBIA AND FRENCH GUIANA CAN EXPECT
MAXIMA OF 15-25MM.

POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 21/00 21/12 22/00 22/12 23/00 23/12 24/00 24/12
TW   21N  46W   49W   52W   55W   58W   61W   64W   67W   70W
TW   20N  60W   62W   64W   66W   68W   71W   73W   76W   78W
EW   18N  84W   86W   89W   91W   94W   97W  100W  103W  106W
EW   19N 102W  105W  107W  109W  112W  115W  EXITS

A TROPICAL WAVE IS INITIALIZED AT 46W AND TO THE SOUTH OF 21N. IT
IS EXPECTED TO REMAIN OVER THE OPEN WATERS OF THE ATLANTIC
OCEAN...MAKING IT TO LAND BY THURSDAY OVER FRENCH GUIANA AND
SURINAME...WHERE EXPECT GENERALIZED MAXIMA OF 20-45MM. ON
FRIDAY...EXPECT MAXIMA OF 20-35MM FROM SURINAME TO EASTERN
VENEZUELA. THE LESSER ANTILLES COULD SEE MAXIMA OF 15-20MM.

A TROPICAL WAVE IS INITIALIZED AT 60W AND TO THE SOUTH OF 20N. ON
WEDNESDAY...THE WAVE WILL FAVOR MAXIMA OF 20-45MM IN THE LESSER
ANTILLES...AND GENERALIZED MAXIMA OF 15-35MM IN EAST VENEZUELA AND
GUYANA. ON THURSDAY...THE WAVE WILL FAVOR MAXIMA OF 20-45MM IN
CENTRAL-EAST VENEZUELA. WEST VENEZUELA AND PUERTO RICO AND THE
VIRGIN ISLANDS ARE FORECAST MAXIMA OF 15-25MM. ON FRIDAY...THE
WAVE WILL FAVOR MAXIMA OF 20-35MM IN WESTERN VENEZUELA AND EAST
COLOMBIA...AND MAXIMA OF 15-25MM IN NORTHWEST VENEZUELA AND
NORTHEAST COLOMBIA. HISPANIOLA COULD SEE SIMILAR AMOUNTS.
LOCALIZED HIGHER AMOUNTS ARE POSSIBLE THROUGHOUT THE REGION.

AN EASTERLY WAVE IS INITIALIZED AT 84W AND TO THE SOUTH OF 18N. ON
WEDNESDAY...THE WAVE WILL FAVOR MAXIMA OF 35-70MM IN EL SALVADOR
AND PORTIONS OF HONDURAS...GUATEMALA...AND NICARAGUA. MAXIMA OF
20-45MM IN COSTA RICA...AND MAXIMA OF 20-35MM IN HONDURAS...AND
NICARAGUA. ON THURSDAY...THE WAVE PROPAGATES WEST...WHERE IT WILL
FAVOR MAXIMA OF 20-35MM IN SOUTHERN BELIZE...GUATEMALA..WEST
HONDURAS...AND EL SALVADOR. MAXIMA OF 15-25MM IS EXPECTED IN THE
YUCATAN PENINSULA INTO CHIAPAS AND TABASCO. ON FRIDAY...THE WAVE
WILL FAVOR MAXIMA OF 15-25MM IN OAXACA AND GUERRERO.

AN EASTERLY WAVE IS INITIALIZED AT 102W AND TO THE SOUTH OF 19N.
ON WEDNESDAY...THE WAVE WILL FAVOR MAXIMA OF 20-35MM FROM NAYARIT
TO SOUTHERN MICHOACAN. AND MAXIMA OF 15-25 IN GUERRERO. ON
THURSDAY...THE WAVE WILL HAVE MINIMAL EFFECTS TO LAND AS IT
PROPAGATES WEST OVER THE OPEN OCEAN WATERS OF THE EAST PACIFIC
OCEAN.

ACOSTA...WPC (USA)