000 AXNT20 KNHC 211756 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 156 PM EDT Fri Apr 21 2017 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 1645 UTC. ...SPECIAL FEATURES... The center of Post-Tropical Cyclone Arlene at 1500 UTC was near 39.3N 49.9W and is moving southwest at 20 knots. The estimated minimum central pressure is 995 mb. The maximum sustained wind speed is 45 knots with gusts to 55 knots. Isolated moderate convection is within 120 nm of the center. Please refer to the public advisory under the WMO header WTNT31 KNHC and under the AWIPS header MIATCPAT1 for more details. A tight pressure gradient generated between a broad low pressure system centered south of Post-Tropical Cyclone Arlene and an area of high pressure to the west is supporting gale-force winds north of 30N between 47.5W and 52W. Seas in this area will range between 12 to 17 ft through the gale event. These conditions will continue through tonight. Please see the latest High Seas Forecast product under the WMO header FZNT02 KNHC and under the AWIPS header MIAHSFAT2 for further details. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across the western Africa coast from 09N13W to 03N18W. The Intertropical Convergence Zone continues from 03N18W to 00N24W to the coast of Brazil near 02S44W. Scattered moderate convection prevails south of 04N between 16W and 39W and south of 07N east of 16W. ...DISCUSSION... GULF OF MEXICO... High pressure extends across the northern Gulf coast supporting moderate southeast winds over the northern Gulf, and moderate easterly winds over the southern Gulf. The combination of an upper trough and a surface trough extending from 25N84W southward across the Yucatan Channel supports numerous showers and scattered thunderstorms south of 26N and east of 89W. A thermal trough over the southwestern Gulf has dissipated. Over the next 24 hours a broad area of low pressure may develop over the southeastern Gulf as moisture spreads north and east across southern Florida. CARIBBEAN SEA... A surface trough extends from the southeastern Gulf to the Yucatan Channel near 21N86W to 17N86W. The combination of this surface trough and an upper level trough over the area supports scattered showers and thunderstorms north of a line from 21N87W to 14N75W. Generally light to gentle winds are within 180 nm of the surface trough axis. High pressure north of the eastern Caribbean supports mainly moderate trade winds over the remainder of the Caribbean, except light winds over the southwestern Caribbean. Over the next 24 hours the showers and thunderstorms over the northwestern Caribbean will gradually shift north and east as a broad area of low pressure develops over the Gulf of Mexico, and the upper trough lifts northeast. Little change is expected elsewhere. ...HISPANIOLA... Increasing moisture from an upper trough to the west of the area is supporting showers and isolated thunderstorms across western Haiti. Expect the moisture to spread across the remainder of Hispaniola through Saturday with showers and thunderstorms likely across the island Saturday and Sunday. ATLANTIC OCEAN... Post-Tropical Cyclone Arlene is over central Atlantic waters north of the area. Gale- force winds are south of a 990 mb surface low located south of Arlene. See the Special Features section above for further details. A surface ridge extends across the western Atlantic anchored by a 1021 mb high centered near 30N69W. Showers are beginning to spread across the waters southeast of the Bahamas to the east of an upper trough. An old frontal trough extends from 22N64W to 25N74W. No convection is associated with this boundaries at this time. To the east, a cold front enters the area from 31N39W to 23N50W. Isolated moderate convection is within 300 nm east of the front north of 26N. High pressure of 1019 mb centered near 28N22W dominates the remainder of the eastern Atlantic. Over the next 24 hours showers and thunderstorms will increase across the Bahamas. The gale force winds will end Saturday morning. For additional information please visit http://www.hurricanes.gov/marine $$ Latto