000 AXNT20 KNHC 181120 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 AM EDT SUN SEP 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 0600 UTC surface analysis and satellite imagery through 1045 UTC. ...SPECIAL FEATURES... Tropical Depression Julia is centered near 31.3N 76.7W at 18/0900 UTC or about 190 nm east-southeast of Charleston, South Carolina and about 245 nm south-southwest of Cape Hatteras, North Carolina moving north-northwest at 4 kt. Estimated minimum central pressure is 1010 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. Scattered moderate to isolated strong convection is from 30N-32N between 75W-78W. Scattered showers and isolated thunderstorms are from 28N-32N between 72W-75W. Isolated showers and thunderstorms are from 27N-30N between 68W- 72W. Please see the latest NHC Forecast/Advisory under the AWIPS/WMO headers MIATCMAT1/WTNT21KNHC for more details. Tropical Storm Karl is centered near 17.7N 42.3W at 18/0900 UTC or about 1115 nm east of the Leeward Islands moving west at 11 kt. Estimated minimum central pressure is 1006 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Clusters of scattered moderate to isolated strong convection are from 17N- 21N between 38W-43W. Please see the latest Forecast/Advisory under the AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details. A tropical wave located between Africa and the Capo Verde Islands extends along 22W from 9N-18N with a 1007 mb low along the wave near 13N22W. Wave and low are moving west-northwest at 5 to 10 kt over the past 24 hours. Wave coincides with a global model 700 mb trough and remains embedded within a surge of moisture as shown on the Total Precipitable Water imagery. Clusters of scattered moderate to isolated strong convection are from 15N-19N between 17W-23W. Environmental conditions are expected to be conducive for development, and a tropical depression is likely to form by mid-week. Regardless of development, this system could bring rain and gusty winds to the Cabo Verde Islands during the next couple of days. This system has a medium chance of tropical formation within the next 48 hours. Please see the Tropical Weather Outlook under AWIPS/WMO Headers MIATWOAT/ABNT20 KNHC for more details. ...TROPICAL WAVES... Tropical wave approaching the Lesser Antilles extends along 61W from 11N-20N moving west 10 to 15 kt over the past 24 hours. Wave coincides with a global model 700 mb trough but remains within an area of dry air. No associated showers or deep convection. ...ITCZ/MONSOON TROUGH... Monsoon trough extends across Africa into the Tropical Atlantic near 16N16W then through the 1007 mb low in the Special Features section above, continuing along 9N29W to 12N37W. The ITCZ is being disrupted by the Tropical Storm Karl. Clusters of scattered moderate to isolated strong convection are from 6N-10N between 14N-18N, from 9N-15N between 22W-27W, and from 7N-10N between 28W-33W. ...DISCUSSION... ...GULF OF MEXICO... An upper ridge dominates the Gulf again this morning anchored near 26N91W and extending a upper ridge axis southwest over Mexico near Tampico and northeast across Georgia and the Carolinas then into the northwest Atlantic. At the surface, a weak surface ridge covers the east Gulf of Mexico anchored by a 1019 mb high over western North Carolina. A mid level trough extends from southeast Louisiana along 90W to 28N covering the north/central Gulf and generating scattered showers and possible isolated thunderstorms north of 27N to over the north Gulf coast between 89W-91W. The diurnal surface trough has dissipated but lingering moisture continues to generate scattered showers and isolated thunderstorms over the Bay of Campeche south of 20.5N between 93W-96W. The mid level trough will continue to bring possible showers and thunderstorms to the north Gulf through tonight before it weakens on Monday. The surface ridge will shift slowly west across the north Gulf through Monday night. The diurnal surface trough will develop over the Yucatan peninsula during the late afternoons, then move into the southwest Gulf waters late each night into the early morning hours before dissipating. ...CARIBBEAN SEA... A cutoff upper low is over the far northwest Caribbean centered along the coast of the Yucatan near 19N88W extending an upper trough north to the west tip of Cuba. This is generating scattered showers and isolated thunderstorms south of 18N to the coast of Honduras west of 84W and north of 19N to the coast of Cuba between 78W-82W. The monsoon trough extends south of the Caribbean waters but is still generating scattered showers and isolated thunderstorms in the southwest Caribbean within 45 nm along the coast of Panama and Costa Rica. An upper ridge dominates the central Caribbean anchored near 13N79W and extending an upper ridge axis across east Cuba and through the Windward Passage. A second cutoff upper low is over the east Caribbean near 14N66W supporting a surface trough that extends from 20N64W through the Virgin Islands to 14N65W generating scattered showers and isolated thunderstorms from 15N-19N between 63W-66W, including the Virgin Islands and eastern Puerto Rico. The remainder of the Caribbean is under clear skies again this morning. Fresh to strong trade winds will develop along the coast of Colombia today through Monday night before diminishing. The surface trough will continue to move west in tandem with the upper trough. A tropical wave will enter the east Caribbean this morning and interact with the upper low and surface trough as it moves across the east Caribbean. The tropical wave will reach the central Caribbean on Wednesday. ...HISPANIOLA... Skies remain clear across the island this morning. The upper low and associated surface trough over the east Caribbean will move west to over the Dominican Republic early Monday, then over the remainder of the island by Monday night. This will bring moisture and accompanying showers and thunderstorms to the island starting late tonight, spreading west, and continue through Wednesday. ...ATLANTIC OCEAN... Primary features of concern are Tropical Storms Karl in the central Atlantic and Tropical Depression Julia off the southeast CONUS. See Special Features above. An upper trough over the west Atlantic covers the area north of 22N west of 70W while the upper ridge over the central Caribbean extends across east Cuba and through the Windward Passage to 30N62W. To the east of the upper ridge is a surface trough that extends from 31N58W through a weak 1015 mb low near 27N65W to 22N71W. Scattered showers and isolated thunderstorms are north of 25N east of the surface trough to 57W. An upper low is centered near 22N55W generating scattered showers and possible isolated thunderstorms from 21N- 23N between 53W-57W. The east Atlantic, north of Tropical Storm Karl is dominated by a surface ridge anchored by a 1029 mb high near the Azores. Tropical Depression Julia is expected to move slowly north-northwest through Monday night before turning northward and becoming a remnant low through Tuesday night. Tropical Storm Karl is expected to move west through tonight then turn west-northwest through Tuesday night. For additional information please visit http://www.hurricanes.gov/marine $$ PAW