000 AXNT20 KNHC 241156 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 AM EDT WED AUG 24 2016 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 0600 UTC surface analysis and satellite imagery through 1115 UTC. ...SPECIAL FEATURES... Tropical Storm Gaston is centered near 14.9N 38.6W at 24/0900 UTC or about 850 nm west of the Cabo Verde Islands moving west- northwest at 15 kt. Estimated minimum central pressure is 999 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Scattered moderate to isolated strong convection is from 13N-17N between 35W-40W. Clusters of scattered moderate convection are from 15N-20N between 39W-43W. Please see the latest NHC Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT2/WTNT32 KNHC and the full Forecast/Advisory under the AWIPS/WMO headers MIATCPAT2/WTNT22 KNHC for more details. A tropical wave moving across the Lesser Antilles is analyzed from 21N66W along 18N63W through a 1009 mb low near 17N61W to 12N59W. This system could become a tropical depression during the next day or two as it moves west-northwest 13 to 17 kt. Conditions could become more conducive later this week while the system moves near the southeastern and central Bahamas. Scattered moderate to isolated strong convection is from 15N-18N between 60W-64W. Scattered showers and possible isolated thunderstorms are from 17N-21N between 56W-67W. There is a medium chance of tropical formation in the next 48 hours. Interests from the islands of the northeastern Caribbean Sea to the Bahamas should continue to monitor the progress of this system. Gusty winds, heavy rains, and possible flash floods and mud slides could occur over portions of these areas regardless of tropical cyclone formation. ...TROPICAL WAVES... See above. ...ITCZ/MONSOON TROUGH... The monsoon trough extends across Africa into the east Tropical Atlantic near 18N16W and continues along 14N21W to 14N27W. The ITCZ begins near 6N44W and continues along 5N49W to South America near 6N58W. The monsoon trough/ITCZ continues to be disrupted by Tropical Storm Gaston. Clusters of scattered moderate to isolated strong convection are from 5N-10N east of 17W to inland over west Africa. ...DISCUSSION... GULF OF MEXICO... A broad upper ridge is anchored over the central Mississippi covering the Gulf waters north of 26N. An elongated upper trough is centered in the northwest Caribbean and extends an upper trough across the Yucatan peninsula to the coast of Mexico near 23N98W generating scattered showers and isolated thunderstorms in the southwest Gulf south of 21N between 93W-97W. A surface trough is in the east Gulf extending from 29N85W to 25N83W generating scattered showers and isolated thunderstorms within 120/150 nm west of the surface trough. Similar showers and thunderstorms are within 45 nm either side of the Florida Keys. A surface ridge extends from over the southeast CONUS to over the Gulf anchored by a 1026 mb high in the northwest Atlantic. This surface ridge will shift north of the Gulf later today with the pressure gradient tightening across the northeast Gulf waters briefly tonight. CARIBBEAN SEA... The primary concern this morning is the tropical wave/low moving through the Lesser Antilles. Please see the Special Features section above for the activity associated with this system over the east Caribbean. An elongated upper low is centered in the northwest Caribbean near 17N85W and extends an upper trough northwest across the Yucatan peninsula into the Gulf of Mexico and southeast to the Gulf of Uraba. Clusters of scattered showers and isolated thunderstorms are within 90 nm of a line from 17N73W to the Yucatan Channel near 22N86W and in the southwest Caribbean south of 12N between Colombia and Costa Rica. This is leaving the remainder of the basin with fair weather this morning. Fresh trade winds will develop across the east and central Caribbean tonight and continue through Saturday. Strong northeast winds are expected along the northwest coast of Colombia tonight. The Special Features low and tropical wave will track northwest through the Bahama chain before reaching the northwest Bahamas late in the weekend. ...HISPANIOLA... Currently showers and thunderstorms are over the southwest peninsula of Haiti. Showers and thunderstorms associated with the tropical wave and low moving through the Lesser Antilles, see Special Features above, are approaching the eastern portion of the Dominican Republic this morning and spread westward throughout the day. The low is expected to be north of the Mona Passage late tonight then northwest of Haiti by late Thursday night, but could still produce gusty winds, heavy rains, and possible flash floods and mud slides over portions of the island. ATLANTIC OCEAN... The primary concern for the central Atlantic this morning is Tropical Storm Gaston and the possible development of the low and tropical wave in the Special Features section above. The upper ridge over the Gulf of Mexico extends a ridge axis across south Georgia/northeast Florida and into the west Atlantic to 29N75W. The upper trough over the south Gulf of Mexico extends a trough axis from the Straits of Florida across the Bahamas to 26N74W. This is creating a diffluent environment to generate scattered showers and isolated thunderstorms from 23N-30N west of 75W. An upper trough north of 30N is supporting a stationary front that extends through 32N66W to 30N72W with scattered showers and isolated thunderstorms within 60 nm either side of the front and continues to 29N75W. A 1016 mb low, the remnants of Fiona, is centered near 27N66W and coupled with diffluent flow from a second upper ridge is generating scattered showers and isolated thunderstorms within 75 nm of a line from 27N69W to beyond 32N62W. An upper low is over the central Atlantic near 27N50W is supporting a surface trough that extends from 30N47W to 25N49W and is generating scattered showers and possible isolated thunderstorms from 25N-31N between 44W-50W. The remainder of the basin east of 60W is dominated by a surface ridge anchored by a 1026 mb high near the Azores and a 1024 mb high near 34N48W. The Special Features low and tropical wave will track northwest through the Bahama chain before reaching the northwest Bahamas late in the weekend. Tropical Storm Gaston is expected to remain east of 60W as it tracks northwest before turning northward late in the weekend. For additional information please visit http://www.hurricanes.gov/marine $$ PAW