TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT THU SEP 21 2023

FORECAST BULLETIN 21 SEP 2023 AT 1700 UTC: A ROBUST HIGH PRESSURE
SYSTEM IN THE MID TO UPPER LEVELS EXTENDS OVER THE SOUTHERN UNITED
STATES INTO MEXICO...AND NORTHERN CENTRAL AMERICA. THIS IS
FAVORING DRIER CONDITIONS OVER THE NEXT SEVERAL DAYS.
PRECIPITATION IS EXPECTED ALONG THE WEST AND SOUTHERN PORTION OF
MEXICO WITH THE PROPAGATION OF AN EASTERLY WAVE. ON
THURSDAY...MAXIMA OF 20-35MM IS EXPECTED IN THE YUCATAN PENINSULA
AND INTO TABASCO AND CHIAPAS. SOUTHERN VERACRUZ AND OAXACA CAN
EXPECT MAXIMA OF 15-25MM. WESTERN MEXICO...ALONG THE SIERRA MADRE
OCCIDENTAL...AND FROM JALISCO TO GUERRERO CAN EXPECT AMOUNTS OF
15-20MM. ON FRIDAY AND SATURDAY...DRY CONDITIONS ARE EXPECTED TO
PERSIST...AND ISOLATED MAXIMA GENERALLY BETWEEN 15-25MM ARE
EXPECTED ALONG THE SIERRA MADRE OCCIDENTAL...SOUTHERN MEXICO...AND
INTO THE YUCATAN PENINSULA FOR BOTH DAYS.

IN THE CARIBBEAN...A SURFACE FRONTAL BOUNDARY THAT HAS BEEN QUASI
STATIONARY IS EXPECTED TO CONTINUE AFFECTING THE NORTHERN PART OF
THE CARIBBEAN ON THURSDAY. BY FRIDAY...A PREFRONTAL SHEAR LINE IS
FORECAST TO DEVELOP OVER THE BAHAMAS AND INTO CUBA AND FAVOR LARGE
AMOUNTS OF PRECIPITATION BY SATURDAY. TO THE SOUTH...TROPICAL
WAVES ARE FORECAST IN THE SOUTHERN PART OF THE
CARIBBEAN...BRINGING MOISTURE AND RAINFALL TO THE ANTILLES AND
PARTS OF HISPANIOLA AND PUERTO RICO OVER THE NEXT SEVERAL DAYS.
ALTHOUGH AN UPPER TROUGH IS EXPECTED TO DEEPEN AND ASSIST WITH
VENTILATION...THE CURRENT CONVERGENT PHASE OF THE MJO AND DRY AIR
IN THE EASTERLY TRADES ARE NOT FAVORING HIGHER AMOUNTS OF
PRECIPITATION OVER MOST OF THE CARIBBEAN BASIN. SHORT WAVE TROUGHS
ARE EXPECTED OVER THE BAHAMAS AND CUBA...WHERE THE MODERATE
AMOUNTS OF PRECIPITATION ARE EXPECTED ON SATURDAY. ON
THURSDAY...THE NORTHERN BAHAMAS CAN EXPECT MAXIMA OF 20-45MM WITH
A RISK OF SQUALLY WEATHER. CENTRAL CUBA AND WESTERN HISPANIOLA CAN
EXPECT MAXIMA OF 20-35MM...ISOLATED MAXIMA OF 15-25MM ARE EXPECTED
ELSEWHERE IN THE CARIBBEAN BASIN. ON FRIDAY...THE SOUTHERN
BAHAMAS...TURKS AND CAICOS...EAST CUBA...AND WEST HISPANIOLA CAN
EXPECT MAXIMA OF 20-35MM. THE NORTHERN BAHAMAS...EAST CUBA...EAST
HISPANIOLA AND PUERTO RICO CAN EXPECT MAXIMA OF 15-25MM. THE
LESSER ANTILLES CAN EXPECT SIMILAR AMOUNTS. ON SATURDAY...THE
NORTHERN BAHAMAS...AND PORTIONS OF NORTHWEST CUBA CAN EXPECT
MAXIMA OF 30-60MM...WHILE THE SOUTHERN BAHAMAS...TURKS AND
CAICOS...AND WESTERN HISPANIOLA ARE FORECAST MAXIMA OF 20-45MM.
THE LESSER ANTILLES CAN EXPECT MAXIMA OF 20-35MM. ELSEWHERE IN THE
CARIBBEAN BASIN...EXPECT MAXIMA OF 15-25MM.

IN CENTRAL AMERICA ON THURSDAY...AN EASTERLY WAVE IS MAKING ITS
WAY THROUGH THE NORTHERN PORTION OF THE REGION AND MODERATE
AMOUNTS ARE EXPECTED ALONG THE SOUTHERN PORTIONS OF
GUATEMALA...AND INTO EL SALVADOR...WHERE EXPECT MAXIMA OF 25-50MM.
GUATEMALA...SOUTHERN BELIZE...AND SOUTHWESTERN HONDURAS CAN EXPECT
MAXIMA OF 20-35MM. WHILE ELSEWHERE OVER THE REGION...MAXIMA OF
15-25MM ARE EXPECTED. ON FRIDAY...AVAILABLE MOISTURE IN SOUTHERN
GUATEMALA...AND MOISTURE CONVERGENCE ALONG EASTERN NICARAGUA WILL
FAVOR MAXIMA OF 20-35MM. ELSEWHERE...EXPECT ISOLATED MAXIMA OF
15-25MM. ON SATURDAY...EL SALVADOR AND SOUTHERN GUATEMALA...AND
WESTERN COSTA RICA ARE FORECAST MAXIMA OF 20-35MM. DRY AIR IS
EXPECTED OVER THE AREA AND ISOLATED MAXIMA OF 15-25MM ARE EXPECTED
OVER THE REGION.

IN NORTHERN SOUTH AMERICA...TROPICAL WAVES ARE LOCATED OVER
PORTIONS OF VENEZUELA AND THE GUIANAS...AND WITH THEM AN INCREASE
IN MOISTURE OVER THE REGION. ALOFT...UPPER DIVERGENCE WILL PROVIDE
VENTILATION FOR CONVECTION OVER THE AREA...WHERE MODERATE AMOUNTS
OF PRECIPITATION ARE EXPECTED ON THURSDAY. EAST-CENTRAL
VENEZUELA...NORTHERN GUYANA...AND SURINAME CAN EXPECT MAXIMA OF
30-60MM. NORTHERN VENEZUELA CAN EXPECT MAXIMA OF 20-45MM...WHILE
ELSEWHERE IN VENEZUELA...RORAIMA AND PARA IN BRASIL...AND SOUTH
GUYANA...CAN EXPECT MAXIMA OF 20-35MM. ISOLATED MAXIMA OF 15-25MM
ARE EXPECTED ELSEWHERE IN THE REGION. ON FRIDAY...FROM EASTERN
VENEZUELA TO WESTERN SURINAME CAN EXPECT MAXIMA OF 20-45MM...WHILE
WESTERN VENEZUELA TO CENTRAL AND SOUTH COLOMBIA CAN EXPECT MAXIMA
OF 20-35MM. WESTERN COLOMBIA CAN SEE SOME ONSHORE FLOW FAVORING
MAXIMA OF 20-45MM. RESIDUAL MOISTURE FROM THE TROPICAL WAVES WILL
FAVOR MAXIMA OF 15-25MM IN EASTERN SURINAME AND FRENCH
GUIANA...AND PORTIONS OF NORTHERN BRASIL. SIMILAR AMOUNTS ARE
EXPECTED IN NORTH COLOMBIA AND ECUADOR. AS THE TROPICAL WAVES
REACH COLOMBIA AND WESTERN VENEZUELA...UPPER DIVERGENCE OVER
COLOMBIA WILL ASSIST IN MODERATE AMOUNTS OF PRECIPITATION ON
SATURDAY. NORTH AND WEST COLOMBIA CAN EXPECT MAXIMA OF 30-60MM.
FROM SOUTHEAST COLOMBIA TO NORTHEAST VENEZUELA EXPECT GENERALIZED
MAXIMA OF 20-45MM. ELSEWHERE IN THE REGION...EXPECT ISOLATED
MAXIMA TO REMAIN BELOW 25MM.

POSITIONS OF TROPICAL/EASTERLY WAVES INITIALIZED AT 12 UTC
TYPE SOF INIT 22/00 22/12 23/00 23/12 24/00 24/12 25/00 25/12
TW   21N  54W   58W   61W   63W   65W   67W   71W   75W   78W
TW   20N  65W   67W   69W   71W   73W   76W   78W   80W   82W
EW   20N  89W   92W   96W   98W  101W  103W  106W  110W  114W
EW   21N 109W  111W  114W  117W  EXITS

A TROPICAL WAVE IS INITIALIZED AT 54W AND TO THE SOUTH OF 21N. ON
THURSDAY...IT WILL FAVOR MAXIMA OF 30-60MM IN GUYANA...AND WEST
SURINAME...AS WELL AS...MAXIMA OF 20-35MM IN NORTHERN PARA AND
RORAIMA IN BRASIL. ON FRIDAY...THE WAVE WILL FAVOR MAXIMA OF
20-45MM IN WESTERN VENEZUELA...GUYANA..WEST SURINAME...AND
RORAIMA-BRASIL. MAXIMA OF 15-25MM ARE EXPECTED IN THE LESSER
ANTILLES AND INTO PORTIONS OF NORTHEAST VENEZUELA. ON
SATURDAY...THE WAVE WILL FAVOR MAXIMA OF 20-45MM IN SOUTHWEST
VENEZUELA AND SOUTH EAST COLOMBIA. MAXIMA OF 20-35MM ARE EXPECTED
IN NORTHEAST VENEZUELA...WHILE MAXIMA OF 15-25MM IS EXPECTED IN
NORTHERN VENEZUELA. LOCALIZED HIGHER AMOUNTS ARE POSSIBLE
THROUGHOUT THE REGION.

A TROPICAL WAVE IS INITIALIZED AT 65W AND TO THE SOUTH OF 20N. ON
THURSDAY...THE WAVE WILL FAVOR MAXIMA OF 30-60MM IN EAST
VENEZUELA...20-45MM IN NORTHERN VENEZUELA...AND 20-35M IN
SOUTHWEST VENEZUELA. MAXIMA OF 15-25MM ARE EXPECTED IN PUERTO RICO
AND THE VIRGIN ISLANDS. ON FRIDAY...THE WAVE WILL FAVOR MAXIMA OF
20-35MM IN WESTERN VENEZUELA AND EAST AND CENTRAL COLOMBIA...AND
MAXIMA OF 15-25MM IN NORTHEAST VENEZUELA AND NORTH COLOMBIA.
HISPANIOLA COULD SEE SIMILAR AMOUNTS. ON SATURDAY...THE WAVE WILL
FAVOR MAXIMA OF 30-60MM IN NORTHWEST COLOMBIA...AND MAXIMA OF
15-25MM IN CENTRAL PORTIONS OF COLOMBIA.

AN EASTERLY WAVE IS INITIALIZED AT 89W AND TO THE SOUTH OF 20N. ON
THURSDAY...THE WAVE WILL FAVOR MAXIMA OF 25-50MM IN EXTREME
SOUTHEAST GUATEMALA AND EL SALVADOR...20-35MM IN SOUTHERN
BELIZE...GUATEMALA..WEST HONDURAS...AND FROM CAMPECHE TO CHIAPAS
IN MEXICO. ON FRIDAY...THE WAVE WILL FAVOR MAXIMA OF 15-25MM FROM
OAXACA TO PORTIONS OF EASTERN MICHOACAN. BY SATURDAY...SIMILAR
AMOUNTS ARE EXPECTED IN SOUTHERN JALISCO...COLIMA...AND WEST
MICHOACAN.

AN EASTERLY WAVE IS INITIALIZED AT 109W AND TO THE SOUTH OF 21N.
ON THURSDAY...THE WAVE WILL HAVE MINIMAL EFFECTS TO LAND AS IT
PROPAGATES WEST OVER THE OPEN OCEAN WATERS OF THE EAST PACIFIC
OCEAN. IT WILL EXIT THE FORECAST AREA BY FRIDAY.

ACOSTA...WPC (USA)