000 AXNT20 KNHC 181748 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 AM EDT TUE OCT 18 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...SPECIAL FEATURES... A non-tropical 1004 mb surface low is centered northeast of the Turks and Caicos near 23N70W with a surface trough extending from 26N65W through the low then across the Turks and Caicos to northeast Cuba near 20N75W. Clusters of scattered moderate to isolated strong convection are from 25N to the Greater Antilles between 60W-72W. The low is expected to slowly intensify as upper level winds become more conducive, and a subtropical or tropical cyclone could form during the next couple of days. There is a medium chance of tropical formation in the next 48 hours as the low moves northeast today, then toward the north and northwest later in the week. Please see the Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. ...TROPICAL WAVES... Tropical wave in the east Atlantic extends along 28W/29W from 7N- 15N moving west 5 to 10 kt over the next 24 hours. Wave coincides with a weak 700 mb trough and is embedded within a surge of moisture. Scattered moderate to isolated strong convection is from 9N-12N between 25W-30W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across Africa into the east Tropical Atlantic near 11N16W then along 8N20W 8N27W to 5N39W. The ITCZ has been disrupted across the Atlantic basin. Scattered moderate convection is from 4N to the equator between 18W-22W. ...DISCUSSION... ...GULF OF MEXICO... An upper ridge is anchored over central Alabama moving into central Georgia and extends a ridge axis south into the northeast Gulf to 27N88W. A second upper ridge extends from the northwest Yucatan to the central Texas coast. Strong subsidence and dry, stable air aloft dominates much of the Gulf this afternoon. A surface ridge extends over the Gulf from northeast to southwest anchored by a series of 1020 mb highs. One high is in the west Atlantic near 35N68W, with a second over South Carolina and a third over central Georgia. The southerly surface flow around the surface ridge is bringing isolated showers within 45/60 nm of 90W north of 25N to inland over southeast Louisiana. The remainder of the Gulf is under fair weather this afternoon. The surface ridge will persist through Wednesday then shift east ahead of a cold front that will move into the northwest Gulf Thursday. The front will race east reaching from central Florida to the Yucatan peninsula by Friday night. ...CARIBBEAN SEA... A broad upper ridge anchored over Honduras extends an upper ridge axis east to over the Leeward Islands covering the Caribbean with near zonal westerly flow aloft. A mid to lower level trough extends from the west Atlantic to over the west Caribbean supporting a surface trough that extends at 18/1500 UTC from 19N81W through a newly developed 1010 mb near 16N81W then along 13N80W to 11N80W. Scattered showers and isolated thunderstorms are within 120 nm east of the surface trough. The mid level trough is generating scattered to numerous showers and scattered thunderstorms are within 120 nm of line from 13N79W to across Hispaniola and Puerto Rico near 18N67W. The surface trough and low will persist through the end of the week. A cold front will move into the northwest Caribbean this weekend from the Gulf of Mexico. ...HISPANIOLA... The mid to lower level trough over the west Atlantic extends into the north Caribbean between 70W-85W covering the island with diffluent flow to generate isolated to scattered showers over the island of Hispaniola with possible isolated thunderstorms developing later this afternoon. This could give the island showers and possible thunderstorms through the end of the week. ...ATLANTIC OCEAN... A deep layered trough extends over the west Atlantic from 65W- 80W supporting the low and surface trough in the special features above. The upper ridge over the Caribbean extends into the central Atlantic from the Leeward Islands near 18N63W along 24N54W to beyond 32N52W. This is providing difflunce aloft to enhance the activity associated with the special features low/trough. A deep layered trough over the east/central Atlantic is supporting a remnant stationary front that extends through 32N36W 25N43W to 21N49W. Isolated showers are possible within 60 nm either side of the front north of 26N. A surface ridge dominates most of the east Atlantic with a weakness in the vicinity of a 1018 mb low near 29N24W. The west Atlantic, special features low will move northeast today, then toward the north and northwest later in the week. Fresh to near gale force winds will occur mainly on the northwest side of the low. A cold front will move into the west Atlantic this weekend. For additional information please visit http://www.hurricanes.gov/marine $$ PAW