000 AXNT20 KNHC 211749 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1249 PM EST Thu Nov 21 2019 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 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1720 UTC. ...SPECIAL FEATURES... Tropical Storm Sebastien is centered near 23.5N 60.5W at 21/1500 UTC, or about 352 nm NNE of the northern Leeward Islands, moving NNE at 7 kt. Estimated minimum central pressure is 999 mb. Maximum sustained wind speed is 55 kt with gusts to 55 kt. Numerous moderate with scattered strong convection is within 240 nm of the center in the SE quadrant. Scattered moderate with isolated strong convection is elsewhere within 250 nm E semicircle. Sebastien is expected to begin a faster northeastward motion during the next few days. Sebastien is forecast to become a hurricane by tonight but a weakening trend is expected to begin by late Friday. The system is likely to become an extratropical cyclone by Saturday. Public Advisories for Sebastien are available via AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC. Forecast/Advisories for Sebastien are available via AWIPS/WMO headers MIATCMAT5/WTNT25 KNHC. ...TROPICAL WAVES... An Atlantic Ocean tropical wave is along 49W from 13N southward, moving W at 10-15 kt. Scattered showers are seen along the wave axis from 06N-09N between 48W-50W. A Caribbean Sea tropical wave is along 77W from 18N southward, moving W at 10 kt. Isolated showers are near the wave axis from 15N-16N. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Sierra Leone near 09N13W to 08N14W. The ITCZ continues from 08N14W to 03N30W to 07N48W, then continues W of a tropical wave near 07N50W to the coast of Suriname near 05N55W. Scattered moderate convection is seen along the ITCZ from 01S to 06N between 26W-35W. GULF OF MEXICO... Mid to upper-level anticyclonic wind flow spans the Gulf of Mexico, along with surface ridging from a 1027 mb high anchored in the Mid-Atlantic. Little to no precipitation can be seen across the basin. Latest scatterometer data depicts fresh to strong southeasterly return flow is occurring over the western Gulf of Mexico with gentle to moderate easterly winds observed in the eastern Gulf. A surface ridge will prevail across the area through Friday, with fresh SE return flow persisting over the western Gulf. A cold front will move off the Texas coast and into the NW Gulf Friday night, cross the northern and central waters this weekend, then weaken and stall over the southern Gulf Sunday night. CARIBBEAN SEA... A cold front passes through western Haiti near 19N74W and stretches westward to northern Jamaica to the NW Caribbean near 20N84W. Isolated showers are seen along the front with scattered thunderstorms seen along the Mona Passage and in southern Dominican Republic. A surface trough is analyzed over the Gulf of Honduras from 16N88W to the Yucatan near 19N88W. Scattered showers are occurring near this feature. Subsidence is seen across the eastern and western Caribbean and inhibiting any convective activity. Latest scatterometer data depicts fresh northerly winds in the Windward Passage, with gentle to moderate trades elsewhere. The cold front will continue moving over the northern Caribbean through tonight, then stall and weaken on Friday. Fresh NE winds will prevail across much of the western Caribbean through Friday, with the strongest winds expected through the Windward and Mona passages as high pressure builds behind the cold front. Easterly trades will freshen across the south-central Caribbean early next week. ATLANTIC OCEAN... For information on T.S. Sebastien, see Special Features section above. A cold front enters the forecast area in the central Atlantic near 31N59W and stretches to northern Haiti near 20N71W. This boundary combined with the moisture from T.S. Sebastien is giving way to numerous showers along and ahead of the front from 25N-31N between 54W-62W. Meanwhile, there is an upper level low near 19N42W with a surface trough associated with it analyzed from 09N44W to 17N40W. Scattered showers with isolated thunderstorms are seen from 07N-24N between 29W-41W. A cold front is dipping southward toward the Cabo Verde Islands, stretching from a 1004 mb low near 34N15W to 30N29W. Otherwise, surface ridging continues to dominate the rest of the basin from a 1025 mb high near 31N38W. A surface trough is hugging the Florida coast from 25N80W to 30N80W with no significant weather associated with it. Latest scatterometer data depicts fresh to strong N winds behind the cold front, mostly N of 21N and between 61W-74W. Tropical Storm Sebastien will strengthen to a hurricane while accelerating northeastward away from the forecast waters tonight. The cold front will continue moving eastward and steer Sebastien into the central Atlantic. High pressure will build behind the cold front across the northern waters through Saturday, then shift eastward Saturday night. Another cold front will cross the region Sunday through Monday. $$ AKR