000 AXNT20 KNHC 181738 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Thu Nov 18 2021 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... Gulf of Mexico Gale Warning: Gale-force NW-N winds will develop offshore of Veracruz Fri afternoon behind a cold front that will move through the basin today. Seas will build to around 15 ft with the gale-force winds. Conditions should diminish below gale- force Fri evening. Please see the latest NWS High Seas Forecast issued by the National Hurricane Center at website://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more information. ...MONSOON TROUGH/ITCZ... The monsoon trough remains mostly confined to the African continent, reaching the Atlantic through the coast of Sierra Leone near 08N13W and extending to 07N14W. The ITCZ extends from 07N14W to 05N21W to 06N39W. A surface trough is west of the ITCZ, extending from 09N37W to 03N42W. Scattered moderate convection is noted from the equator to 08N and between 36W to 43W. Similar convection is within 210 nm on either side of the ITCZ between 25W to 35W. GULF OF MEXICO... Please see the Special Features section above for details on a Gale Warning in effect near Veracruz, Mexico. As of 1500 UTC, a cold front has entered the northwestern Gulf of Mexico extending from near Galveston, Texas to near The Padre Island National Seashore, Texas. Fresh to strong NW winds are west of the front. A surface trough preceding the front is associated with a line of strong convection extending from Grand Isle, Louisiana to the central Gulf near 25N93W. Convection is within 30 nm east of the trough. Deep moisture and divergence aloft over the southeast Gulf is leading to scattered convection mainly east of 85W, including the Florida Straits. Fresh E winds prevail over the Florida Straits and far SE Gulf, otherwise gentle to moderate winds dominate ahead of the front. Seas are 4 to 6 ft in the SE Gulf, and 2 to 4 ft elsewhere. For the forecast, the cold front moving offshore Texas will bring strong winds and rough seas over the western and portions of the northern Gulf, reaching gale force off Veracruz Fri. The front will stall from near Naples, Florida, to the Bay of Campeche this weekend, before dissipating. Looking ahead, another front will move into the northwest Gulf early Mon, and reach from southwest Florida to the southwest Gulf by late Mon night. CARIBBEAN SEA... A surface trough extends along the coast of The Yucatan Peninsula southward into the Gulf of Honduras. Most of the scattered moderate convection associated with this trough has moved north of the basin into the Gulf, however lingering showers and thunderstorms are north of 20N offshore western Cuba. Elsewhere across the Caribbean, dry conditions prevail. The pressure gradient between the strong subtropical ridge near Bermuda and lower pressures across N South America result in fresh to strong NE to E winds across the central Caribbean. The latest ASCAT pass shows the strongest winds are occurring south of Hispaniola. Elsewhere, winds are mainly moderate to fresh. Seas of 6 to 9 ft are occurring in the area of strong winds, with 5 to 7 ft seas in the eastern Gulf and 4 to 6 ft elsewhere. For the forecast, the fresh to locally strong NE winds persist in a broad swath from the northeast Caribbean into the southwest Caribbean. Winds and seas will diminish through Fri as high pressure north of the area shifts east, ahead of a cold front moving into the Gulf of Mexico and western Atlantic. Winds and seas further diminish early next week, ahead of a second cold front moving through the Gulf Mon and reaching the Yucatan Channel by late Mon night. ATLANTIC OCEAN... A cold front enters the tropical Atlantic near 31N44W and extends to 23N60W, then continues westward as a dissipating cold front to 24N69W, and finally transitions to a shear line that continues to the central Bahamas. No convection is associated with this boundary. Fresh to strong winds are occurring north of the cold front and shear line, extending to 30N with seas of 8 to 10 ft. Fresh NE to E winds with seas up to 7 ft are south of the front and west of 50W. Farther east, scatterometer satellite imagery revealed weak surface troughing from 23N31W to 18N43W surrounded by gentle winds left in the wake of a lingering low pressure center. No significant precipitation is associated with this feature. North of the surface trough, an area of moderate to fresh E winds is north of 28N between 25W and 40W. Seas of 6 to 8 ft prevail in the central and E tropical Atlantic. Moderate or weaker winds and fairly tranquil weather conditions are present elsewhere. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Marine and aviation interests should monitor this ongoing situation by reading the Volcanic Ash Advisory issued by Meteo-France, at http://vaac.meteo.fr/volcanoes/la-palma/. For the forecast, The shear line will dissipate today in advance of a cold front that will move off the NE Florida coast Fri. The front will stall from along roughly 28N this weekend, before lifting north ahead of a strong front that will move off the northeast Florida coast late Mon. The second front will reach from Bermuda to eastern Cuba by late Tue. $$ Mora