000 AXNT20 KNHC 132355 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 PM EDT TUE SEP 13 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...SPECIAL FEATURES... Tropical Storm Ian is centered near 27.0N 52.7W at 13/2100 UTC or about 705 nm east-southeast of Bermuda moving north-northwest at 14 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Please see the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT5/WTNT25 KNHC for more details. Numerous strong convection is within 45 nm of 28N from 51W-54W. Scattered moderate to strong convection covers the remainder of the area from 27N-32N between 50W-55W. A 1011 mb low is inland over the Florida peninsula near Daytona Beach with a surface trough extending from off the Georgia coast near 31N81W through the low to 28N82W. This system is producing showers and thunderstorms inland Florida. Scattered to numerous showers and isolated thunderstorms are from 28N-31N west of 79W with isolated showers and thunderstorms covering the area north of 25N west of 75W. This system is generating strong winds with frequent gusts to gale force along the coast of Florida from Melbourne to Jacksonville. Gale conditions will continue through 14/0600 UTC tonight. Please see the High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. This system has been maintaining its organization through the afternoon and early evening, and advisories will likely be initiated later this evening. There is a high chance of tropical development over the next 48 hours as the system moves north- northwestward at 8 to 13 kt. Please see the Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. ...TROPICAL WAVES... Tropical wave in the east Tropical Atlantic extends from 20N23W through a 1009 mb low near 15N21W to 12N19W moving northwest 5 to 10 kt over the past 12 hours. Wave is to the east of a 700 mb low based on the global models and is embedded within a broad surge of moisture as seen on the Total Precipitable Water Imagery. Although this system has a low chance of tropical development, locally heavy rains and gusty winds are likely over portions of the Cabo Verde Islands through Wednesday. Clusters of scattered moderate to isolated strong convection from 11N17N between 20W-26W. Tropical wave in the central Tropical Atlantic extends along 37W from 10N-19N moving west near 25 kt over the past 24 hours. Although this wave coincides with 600 to 800 satellite winds, the 700 mb global model does not support a wave in this location. No associated deep convection. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across Africa into the east Tropical Atlantic near 17N16W and continues through the 1009 mb low near 15N21W to 9N31W where the ITCZ begins and continues along 7N45W 8N51W to South America near 7N59W. Clusters of scattered moderate to isolated strong convection are within 120 nm either side of the monsoon trough between 32W-37W and within 90 nm either side of the ITCZ between 49W-53W. ...DISCUSSION... ...GULF OF MEXICO... A cutoff upper trough covers central Gulf of Mexico centered near 27N87W and supporting surface trough that extends from 28N93W through a 1012 mb low near 26N90W to 24N86W. Scattered to numerous showers and isolated thunderstorms are within 75 nm of 87W from 26N-30N with scattered showers and isolated thunderstorms within 60/75 nm north of the surface trough. An upper ridge extends across the northwest Caribbean then into the west Atlantic creating a diffluent environment over the southeast Gulf to generate scattered showers and isolated thunderstorms south of 28N between 81W-86W. The 1011 mb low in the central Gulf will drift westward while dissipating by late Wednesday. ...CARIBBEAN SEA... An upper ridge extends from west to east across south Mexico into the northwest Caribbean near Belize then continues northeast across central Cuba into the west Atlantic. A cutoff upper low is centered south of Haiti near 16N72W covering the central Caribbean. A second upper ridge anchored in the east/central Atlantic extends across the west Tropical Atlantic and the remainder of the east Caribbean. Afternoon scattered showers and isolated thunderstorms that developed inland over Cuba, Jamaica, and Hispaniola are now moving south into the Caribbean waters within 60 nm along the coastlines. The monsoon trough extends from over Colombia near 11N75W then across Nicaragua into the east Pacific region near 11N84W generating scattered showers and isolated thunderstorms within 45 nm along the immediate coast of Colombia and Nicaragua. Weak high pressure over the west Atlantic will maintain light to moderate trade winds across the basin through the end of the week. ...HISPANIOLA... Afternoon scattered showers and isolated thunderstorms have developed over the central portion of the island again this evening. The upper trough will persist across the island through Wednesday then shift west Thursday through the end of the week. Afternoon and evening showers and thunderstorms will continue through the end of the week when a clearing trend beginning Saturday. ...ATLANTIC OCEAN... The activity over the far west Atlantic is due to a 1011 mb low that is inland over northeast Florida and is in the Special Features. Please see above. An upper ridge axis extends from the northwest Caribbean across Cuba along 23N80W to beyond 32N75W enhancing the activity described above. The west Atlantic is dominated by a weak surface ridge anchored by a 1021 mb high near 33N71W. A broad upper ridge is in the east/central Atlantic near 21N49W extending a ridge axis southwest to over the east Caribbean. Beneath this upper ridge is a weak surface trough that extends from 21N52W to 15N57W with scattered showers and possible isolated thunderstorms within 45 nm either side of the trough axis. Scattered showers and isolated thunderstorms are further north within 30/45 nm of line from 26N49W to 21N50W and south of the surface trough from 10N-13N between 57W-63W including the Windward Islands. The east Atlantic is dominated by a second surface ridge anchored by a 1027 mb high near the Azores and and a 1023 mb high near 32N40W. West Atlantic surface ridge will persist through the end of the week. For additional information please visit http://www.hurricanes.gov/marine $$ PAW