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 https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml. The latest NHC Forecast/Advisory and Public Advisory can be read at www.hurricanes.gov 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 morning.


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.

$$ Hagen