000 AXNT20 KNHC 181805 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Mon Sep 18 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 1200 UTC surface analysis and satellite imagery through 1700 UTC. ...SPECIAL FEATURES... Hurricane Nigel is centered near 27.2N 51.4W at 18/1500 UTC or about 760 nm ESE of Bermuda, and moving NW at 10 kt. Estimated minimum central pressure is 984 mb. Maximum sustained winds are 70 kt with gusts to 85 kt. Seas are peaking near 29 ft near and just north of the center. Numerous moderate to isolated strong convection is found near and up to 130 nm in a W semicircle. Scattered moderate convection is present up to 80 nm in a E semicircle from the center, and near an outer rainband farther north from 28N to 31N between 45W and 55W. Nigel will continue on its current motion for the next couple of days, before turning northward by Tuesday and accelerate toward the northeast afterward. Intensification is expected and Nigel could become a major hurricane on Tuesday, then gradually weaken by midweek. 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. ...TROPICAL WAVES... A newly analyzed tropical wave is off the Africa coast near 19W from 18N southward, and moving west around 5 kt. Scattered moderate convection is found from 4N to 18N between the Mauritania-Liberia coast and 22W. A central Atlantic tropical wave is near 42W from 12N southward, and moving west at 10 to 15 kt. Widely scattered moderate convection is noted from 05N to 12N between 38W and 44W. ...MONSOON TROUGH/ITCZ... A monsoon trough enters the Atlantic near the Gambia-Guinea Bissau border then extends west-southwestward across 08N30W to 06N44W. An ITCZ continues from 06N44W to 07N52W. Scattered moderate convection is evident up to 200 nm south of the trough between 22W and 38W, and up to 300 nm north of the trough between 27W and 38W. Widely scattered moderate convection is seen up to 100 nm along either side of the ITCZ. The eastern end of the East Pacific monsoon trough is producing numerous showers and scattered thunderstorms across the Caribbean waters north of Costa Rica, Panama and northwestern Colombia. ...GULF OF MEXICO... A modest cold front reaches west-southwestward from just north of Tampa, Florida to the central Gulf, then turns northwestward as a stationary front to near Corpus Christi, Texas. Widely scattered showers and isolated thunderstorms are occurring along and up to 80 nm south of this boundary. A surface trough at the western Bay of Campeche is causing similar conditions at the southwestern Gulf, including the Bay of Campeche. A pre-frontal trough is triggering isolated thunderstorms over southern Florida, including the Florida Keys. Gentle to moderate NNE to NE winds and seas of 2 to 3 ft exist near and north of the frontal boundary. Light to gentle winds and 1 to 2 ft seas prevail south of the frontal boundary, including the Florida Straits. For the forecast, the entire frontal boundary will become stationary and weaken tonight. Winds will be moderate or weaker with slight seas through Thu, pulsing to between moderate and fresh offshore western Yucatan in the evenings. At the northeastern Gulf, both winds and seas will increase by the end of the week due to building high pressure north of the area. ...CARIBBEAN SEA... An upper-level trough runs east-northeastward from a low near the Island of Youth across Jamaica and Hispaniola. These features are inducing isolated thunderstorms across the northwestern and north-central basin. Refer to the Monsoon Trough/ITCZ section for additional weather in the Caribbean Basin. A modest trade-wind pattern continues for much of the basin. Fresh ENE to ESE winds and 4 to 6 ft seas are present at the south- central basin. Light to gentle winds and seas of 1 to 3 ft are noted at the northwestern basin. Gentle monsoonal winds with seas at 2 to 4 ft exist offshore from Costa Rica and Panama. Gentle to moderate NE to SE winds and 3 to 5 ft seas prevail for the rest of the basin. For the forecast, long-period N to NE swell may impact the Caribbean passages and Tropical North Atlantic through the early part of this week. Moderate to fresh trades will prevail in the central Caribbean, locally strong at times offshore northern Colombia, with moderate or weaker winds elsewhere through the week. ...ATLANTIC OCEAN... Please read the Special Features section for details about Hurricane Nigel. A modest cold front runs southwestward from off the Carolina coast across 31N78W to near Daytona Beach, Florida. A pre-frontal trough extends northeastward from southern Florida to just south of Daytona Beach. Widely scattered showers and isolated thunderstorms are found from the central Bahamas northward between 72W and the Florida coast. Gentle to moderate SW to NW winds and 4 to 6 ft are present in this area. Convergent southerly winds feeding toward Hurricane Nigel are triggering scattered moderate convection from 17N to 28N between 44W and 48W. A surface trough along with remnants of a shear line are causing scattered moderate convection from 19N to 24N between 20W and 35W. Refer to the Monsoon Trough/ITCZ and Tropical Waves sections at the beginning for additional convection in the Atlantic Basin. Outside the direct impact of Hurricane Nigel, fresh to strong SE to SW winds and seas of 8 to 12 ft are evident north of 22N between 42W and 48W. Otherwise, moderate to locally fresh NNE to E winds with 6 to 8 ft seas in large northerly swell exist north of 19N between the Africa coast and 48W. West of Nigel to 70W and north of 20N, gentle with locally moderate NE to SE winds and seas of 4 to 6 ft in moderate mixed swells prevail. For the tropical Atlantic from 06N to 20N between 42W and the Lesser Antilles, light to gentle winds and 4 to 6 ft in moderate mixed swells are present. Farther east, gentle to moderate NNE to NE winds and 3 to 5 ft seas are noted from 09N to 19N between the central Africa coast and 42W, including Cabo Verde Islands. Gentle to moderate monsoonal and southerly winds and seas of 4 to 6 ft in moderate southerly swell prevail elsewhere in the Atlantic Basin. For the forecast W of 55W, Nigel will strengthen to a major hurricane near 30N54W early Tue, move to near 35N 54.5W early Wed, then begin to slowly weaken as it moves to near 40N48W early Thu. The cold front will reach from near 31N72W to near Jupiter, Florida Tue morning, then stall over the northern forecast waters through the end of the week. Winds and seas may increase west of the stalled boundary by the end of the week as a tight pressure gradient develops due to building high pressure inland and a developing coastal trough off the Carolinas. $$ Forecaster Chan