000 AXNT20 KNHC 211058 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Thu Sep 21 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 1045 UTC. ...SPECIAL FEATURES... Hurricane Nigel is centered near 40.6N 47.8W at 21/0900 UTC or 430 nm SE of Cape Race Newfoundland, moving NE at 26 kt. Estimated minimum central pressure is 977 mb. Maximum sustained wind speed is 75 kt with gusts to 90 kt. Peak seas related to Nigel are presently to 42 ft. Satellite imagery depicts the cyclone not in as good as shape as it was several hours ago. Upper-level vertical wind shear has begun to impinge on Nigel. The earlier large eye feature is now obscured. Deep convection of numerous moderate to strong type intensity has become displaced to the north and northeast of Nigel from 20N to 43W between 48W-50W and from 42N to 43W between 45W-48W. The convection is being stretched northeastward by the wind shear. Numerous moderate to strong convection is within 120 nm southwest through of Nigel. Nigel is forecast to maintain its present motion for the next day or two. Weakening is forecast during the next couple of days, and Nigel is forecast to become a post-tropical cyclone by Fri. Swells generated by Nigel currently affecting Bermuda will gradually subside through to tonight. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest Nigel NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Atlantic Gale Warning: The pressure gradient between low pressure that is expected to develop along a stationary front N of the Bahamas and high pressure over the southeastern U.S. will result in frequent north to northeast wind gusts to 35 kt N of 30N and W of 75W beginning by early this evening, then north of 30N and between 76W-78W late tonight into early on Fri. Seas with these winds are forecast to be 8-12 ft, but may reach higher values as the north to northeast winds counter act the Gulf Stream current. Please see the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2 for further details. ...TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis along 23W from 04N to 20N, including the Cabo Verde Islands. It is moving westward at 5 to 10 kt. A large cold overcast with embedded numerous moderate to strong convection is west of the wave from 11N to 16N between 25W-29W. A central Atlantic tropical wave has its axis along 38W from 04N to 19N. It is moving westward around 15 kt. Scattered moderate to isolated strong convection is east of the wave from 05N to 09N. Scattered moderate convection is within 120 nm west of the wave from 07N to 13N. A western Atlantic tropical wave has its axis along 53W south of 16N, moving westward at about 10 kt. No significant convection is occurring with this tropical wave. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends off the coast of Senegal near 16N17W and continues southwestward to 10N30W and westward to 11N45W and to 10N52W. The ITCZ axis extends from 10N52W to 10N60W. Nearby significant convection is discussed in the TROPICAL WAVES section above. ...GULF OF MEXICO... A slowly dissipating stationary front extends from near Sarasota, Florida to 28N86W. Scattered showers and a few thunderstorms are over the eastern Gulf waters from 25N to 28N between 83W-86W. Isolated showers are elsewhere east of 87W. Moderate to fresh east to southeast winds are in the NE Gulf per latest ASCAT data over that part of the Gulf. A weak surface trough is noted in the eastern Bay of Campeche, with moderate to fresh northeast winds near it. Only isolated showers are possible near this trough. Seas of 2-4 ft are across the basin. For the forecast, high pressure will be in control of the weather pattern across the Gulf waters allowing for generally gentle to moderate east to southeast winds and slight seas, except pulsing to moderate to fresh offshore the western Yucatan Peninsula in the evenings. Developing low pressure east of Florida will tighten the pressure gradient over the NE Gulf bringing moderate to locally fresh NE winds across the NE Gulf tonight into Fri. A frontal trough associated with the aforementioned low pressure will move across the southeastern Gulf and the Straits of Florida Thu night into Fri. ...CARIBBEAN SEA... A persistent deep-layer trough that stretches from the western Atlantic to east-central Cuba and 13N83W is helping to sustain an area of scattered showers and thunderstorms south of Cuba from 17N to 21N between 75W-81W and in the southwestern Caribbean south of 15N and west of 77W. A weak pressure gradient is allowing for moderate to fresh easterly trade winds in the central Caribbean. Fresh to strong northeast to east winds are again present just off the N Colombia and NW Venezuelan coasts. Seas in the central Caribbean are in the range of 4-7 ft. Elsewhere, gentle to moderate winds and seas of 3-5 ft continue. For the forecast, long period north to northeast swell moving through the Tropical N Atlantic waters and Caribbean passages will subside Thu. Moderate to fresh trade winds in the central Caribbean will change little through the next few days. Northeast to east trade winds will pulse to fresh to strong speeds offshore northern Colombia and northwest Venezuela during the afternoons and at night into early next week. ...ATLANTIC OCEAN... Please read the SPECIAL FEATURES section for details on Hurricane Nigel and on an Atlantic Gale Warning. In addition, please read the TROPICAL WAVES and MONSOON TROUGH/ITCZ sections for details on convection in the Atlantic Ocean. A stationary front extends from just south of Bermuda to 29N73W and to inland Florida just south of Daytona Beach, Florida. The combination of this front and a very sharp upper-level trough over its vicinity is leading to numerous moderate to strong convection from 24N to 31N between 71.5W and 74W and west of 79W. A surface trough extends from near 29N73W to just east of the central Bahamas. It is helping to contribute additional scattered showers and thunderstorms to the waters north and northeast of the Bahamas. Moderate to fresh northeast to east winds are north of the front per latest ASCAT data passes. Farther east, another trough extends from near 31N55W to 24N58W. Only small isolated showers and thunderstorms are near this trough. Otherwise, weak high pressure ridging is the main feature controlling the weather pattern west of 50W. An area of scattered showers and thunderstorms is noted from m near 19N48W. Moderate to fresh trades are evident from 18N to 23N between 43W-54W. This activity is being sustained by an elongated upper-level low that is centered near 18N52W. The low is moving westward as depicted in water vapor imagery. Moderate to fresh trade winds are evident from 17N-27N between the coast of Africa and 55W between broad high pressure north of that area and three tropical waves to the south along the monsoon trough/ITCZ. Locally strong winds are occurring off the coast of Western Sahara. Seas in the broad zone of trade winds are 7-9 ft. Across the remainder of the basin, gentle to moderate winds and 4-7 ft seas remain, except for higher seas of 6-8 ft in northwest to north swell over the waters north of 29N between 49W-56W. This swell was generated by Hurricane Nigel. For the forecast W of 55W, the aforementioned stationary front will lift northward on Fri as low pressure develops along it to the east of northern Florida, and where frequent gusts to gale force are possible tonight into Fri. This non-tropical low pressure system could acquire some subtropical characteristics on Fri while it moves generally northward. In its wake, high pressure ridging will build from E to W just north of the forecast waters into early next week. $$ Aguirre