000 AXNT20 KNHC 181805 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 PM 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...SPECIAL FEATURES... Tropical Depression Julia is centered near 31.8N 77.1W at 18/1500 UTC or about 161 nm east-southeast of Charleston, South Carolina moving west at 2 kt. Estimated minimum central pressure is 1010 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. Scattered showers and isolated tstms are within 240 nm SE semicircle. Please see the latest NHC Forecast/Advisory under the AWIPS/WMO headers MIATCMAT1/WTNT21KNHC for more details. Tropical Storm Karl is centered near 18.0N 43.4W at 18/1500 UTC or about 1051 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. Scattered showers are within 180 nm N semicircle. Please see the latest Forecast/Advisory under the AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details. A vigorous tropical wave is in the E Atlantic near the Cabo Verde Islands extending from 08N to 18N with axis near 23W moving W at 5 to 10 kt over the past 24 hours. The wave is associated with a 1007 mb low located near 12N23W expected to move near 15N26W within the next 24 hours. Scattered heavy showers and isolated tstms are from 07N to 17N E of 28W. Environmental conditions are expected to be conducive for development, and a tropical depression is likely to form by mid-week while the low moves west-northwestward to northwestward across the eastern tropical Atlantic. Regardless of development, locally heavy rains and gusty winds are possible in 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... A tropical wave is entering the E Caribbean waters. The wave extends from 10N to 20N with axis near 62W moving west at 15 kt over the past 24 hours. The wave is in a region of favorable deep layer wind shear, however CIRA LPW imagery from the surface to 850 mb show patches of dry air within its environment that likely limit the convective activity to isolated showers across the Lesser Antilles. ...ITCZ/MONSOON TROUGH... Monsoon trough extends across Africa into the Tropical Atlantic near 17N16W then through the 1007 mb low associated with the wave in the Special Features section above, continuing along 7N28W to 08N36W. The ITCZ is being disrupted by the Tropical Storm Karl. For convection information, please refer the tropical wave in special features. ...DISCUSSION... ...GULF OF MEXICO... Weak surface ridging prevails across the Gulf of Mexico anchored by a 1017 mb high in the NE basin near 28N87W. The exception is a surface trough in the far NW Gulf extending from 30N91W to 28N94W to 26N97W that support isolated showers over SE Louisiana coastal waters. The surface ridge provides variable gentle winds in the NE portion of the basin and return flow of the same magnitude elsewhere. Abundant moisture across the Gulf being advected from the Caribbean and favorable deep layer wind shear support isolated showers NW of a line from 28N82W to 20N95W. Ridging will be the main feature across the basin the next two days. ...CARIBBEAN SEA... The main features in the basin are a surface trough moving across Puerto Rico and a tropical wave that is moving across the Lesser Antilles. The surface trough extends from 21N65W to 15N65W and the wave axis is near 62W. These two features along with a broad upper level low over the E Caribbean support scattered showers and tstms over Puerto Rico and adjacent waters and the basin E of 70W. For more details on the tropical wave, see section above. An area of diffluence in the NW Caribbean support a surface trough from 21N86W to 16N87W and associated scattered to isolated showers S of 20N W of 83W. Otherwise, the E Pacific monsoon trough support scattered showers and tstms within 60 nm of northern Panama. Similar activity is observed within 90 nm off the coast of Nicaragua. Otherwise, moderate trades dominate the basin, except within 120 nm off the coast of Colombia where fresh to locally strong winds are present mainly due to orographic effects. By Tuesday near sunrise, the tropical wave will merge with the surface trough W of Haiti. ...HISPANIOLA... Skies remain clear across the island mainly due to strong subsidence from aloft as noted in water vapor imagery. An upper low and associated surface trough currently over Puerto Rico will move west to over the Dominican Republic early Monday, then over the remainder of the island by Monday night. A tropical wave will merge with this trough near sunrise Tuesday when the system is expected to be W of Haiti or moving across the Windward Passage. These features 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 in the forecast waters are Tropical Storms Karl in the central Atlantic and a vigorous tropical wave currently near the Cape Verde Islands. Please refer to the Special Features and tropical waves sections above. In the SW basin, scattered showers and tstms associated with Tropical Depression Julia N of the area are N of 28N between 71W and 78W. Farther east, a surface trough extends from 31N60W to 24N66W with scattered showers and isolated thunderstorms north of 24N between 57W and 65W. The east Atlantic, north of Tropical Storm Karl is dominated by a surface ridge anchored by a 1030 mb high near the Azores. For additional information please visit http://www.hurricanes.gov/marine $$ RAMOS