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Atlantic Tropical Weather Discussion

AXNT20 KNHC 261048

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Tue Sep 26 2023

Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through 
1030 UTC.


Tropical Storm Philippe is centered near 17.7N 49.0W at 26/0900 
UTC, about 805 nm E of the Northern Leeward Islands, and moving 
WNW at 11 kt. Maximum sustained winds are 45 kt with gusts to 55 
kt. Estimated minimum central pressure is 1001 mb. Peak seas are 
18 to 22 ft near and just northeast of the center. Westerly 
upper-level wind shear continues to displace the associated deep 
convection to the east of the center this morning. Scattered 
moderate to isolated strong convection is seen within 420 nm of
the center in the NE semicircle. Philippe will continue on the 
current motion and gradually weaken for the next few days. Please 
read the latest HIGH SEAS FORECAST issued by the National 
Hurricane Center, at the website The latest NHC 
Forecast/Advisory and Public Advisory can be read at for more details.

Invest Area (AL91): An eastern Atlantic tropical wave is near 
35/36W from 17N southward through a 1009 mb low at 10.5N35.5W, and
moving west around 15 kt. Numerous moderate to scattered strong 
convection is noted from 05N to 15N between 31W and 43W. Fresh to 
strong E winds and 8 to 9 ft seas exist mainly on the north side 
of the low pressure. Environmental conditions are forecast to be 
conducive for development, and a tropical depression is expected 
to form in 2 to 3 days as the system moves west-northwestward 
across the central tropical Atlantic. There is a medium chance of 
formation through 48 hours.


A western Caribbean tropical wave is near 81W from 20N southward.
Upper-level diffluence is enhancing scattered strong convection
from 14N to 22N between 78W and 85W. These strong clusters of
thunderstorms are producing outflow boundaries containing very 
strong wind gusts which have increased seas to 7 to 9 ft across 
much of the western Caribbean.


A monsoon trough enters the Atlantic along the west coast of
Africa near 12N16W then reaches southwestward to near 08N19W and
continues to the aforementioned AL91, and to 10N43W. No
significant additional convection is noted other than that
mentioned in the sections above.

The eastern end of the East Pacific monsoon trough is causing
scattered moderate isolated strong convection over the Caribbean 
waters near Panama, to the south of 11N.


A broad surface trough extends southward from the western Florida
Panhandle to the western Yucatan peninsula. Scattered
thunderstorms are occurring along and to the east of the trough
axis, over the eastern Gulf. Only isolated thunderstorms are noted
to the west of the trough axis. Gentle to moderate SE to S winds 
and seas of 2 to 3 ft are noted across the eastern Gulf, east of
the trough axis. Gentle E winds with 2 to 3 ft seas prevail for 
the rest of the Gulf.

For the forecast, the surface trough over the east-central Gulf 
will drift slowly into the western Gulf through mid week and 
dissipate. Scattered showers and thunderstorms are expected along 
and to the east of the trough, over the eastern half of the Gulf, 
through Wed night. Meanwhile, weak high pressure will persist over
the north-central and northeast Gulf. This pattern will support 
gentle to moderate NE to E winds and slight seas across the basin 
through the middle of the week. Winds may increase over the 
northern Gulf the end of the week into the weekend as high 
pressure ridging strengthens over the southeastern United States.


Strong thunderstorms over the NW Gulf have been inducing areas of
strong winds and seas of 8 to 9 ft over portions of the western
Caribbean during the past 12 hours. Otherwise, fresh trades
prevail over the central Caribbean, locally strong near the coasts
of Colombia and Venezuela. Seas are 5-8 ft across the central
basin and 3-5 ft in the eastern Caribbean.

For the forecast, strong thunderstorms over portions of the 
western Caribbean overnight have generated locally strong winds 
and seas of 8 to 9 ft, that are forecast to gradually subside 
later today. High pressure north of the area will support moderate
to fresh trade winds across most of the eastern and central 
Caribbean into mid week, with fresh to strong pulses off northwest
Venezuela and northeast Colombia during mainly the overnight and 
early morning hours through Wed morning. Seas will build in mixed 
NE and E swell across the waters east of the Leeward Islands 
starting late today, ahead of Tropical Storm Philippe. Tropical 
Storm Philippe will move to near 20N54W Wed afternoon, 22N57W Thu
afternoon, weakening to a tropical depression near 22N61W early 
Sat morning, and weakening to a remnant low near 22N64W early Sun 


Refer to the SPECIAL FEATURES section at the beginning for 
details on Tropical Storm Philippe and Invest AL91.

A 1020 mb high pressure is centered near 31N73W. Ridging in this
area is producing winds gentle or weaker over the western
Atlantic, except for moderate to locally fresh E-SE winds from
South Florida through the Bahamas to north of Hispaniola. West of
65W, seas are 5 ft or less. Scattered showers and t-storms are
seen over portions of the central and NW Bahamas. A surface 
trough extends from 31N63W to 25N65W with isolated showers along 
it. A high pressure ridge extends from 1022 mb high pressure near 
33N25W to 1023 mb high pressure near 32N37W to 29N58W. Winds are 
moderate or weaker north of 25N across the E Atlantic with seas 6 
to 7 ft in mixed swell. Over the tropical eastern and central 
Atlantic, Tropical Storm Philippe and Invest AL91 are causing 
strong winds and rough seas from 11N to 23N between 32W and 53W.

For the forecast west of 50W, Tropical Storm Philippe will move 
to near 20N54W Wed afternoon, 22N57W Thu afternoon, weakening to a
tropical depression near 22N61W early Sat morning, and weakening 
to a remnant low near 22N64W early Sun morning. Rough seas ahead 
of the storm can be expected east of 60W starting late today. 
Elsewhere, seas may build by Thu north of the Bahamas and east of 
Florida in NE swell.