000 AXNT20 KNHC 200546 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 146 AM EDT TUE SEP 20 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 0000 UTC surface analysis and satellite imagery through 0430 UTC. ...SPECIAL FEATURES... Tropical Storm Karl is centered near 19.7N 50.5W at 20/0300 UTC or about 660 nm ENE of the Leeward Islands moving WNW at 12 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Scattered moderate and isolated strong convection is from 18N-23N between 47W-51W. See latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMAT2/ WTNT22 KNHC for more details. Tropical Depression Thirteen is centered near 14.2N 29.0W at 20/0300 UTC or about 310 nm WSW of the Cape Verde Islands moving WNW at 8 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Scattered moderate convection is from 15N-18N between 25W-31W. See latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. ...TROPICAL WAVES... Tropical wave extends from 11N69W to 20N68W moving W at 15 kt. The wave remains within broad 700 mb troughing over the central Caribbean Sea and is embedded within an area of maximum low-level moisture as noted in Total Precipitable Water imagery. The wave is expected to remain beneath an upper level low noted on water vapor imagery centered near 15N69W. Isolated moderate convection is from 15N-20N between 64W-69W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends from the African coast near 16N17W to 11N23W. Aside from convection associated with Tropical Depression Thirteen...scattered moderate convection is from 10N-14N between 15W-19W. Isolated moderate convection is from 04N-08N between 29W-40W. ...DISCUSSION... GULF OF MEXICO... An upper level trough axis extends from over the Carolinas SW to a base over the NW Gulf with water vapor imagery indicating very dry air and strong subsidence over much of the northwestern portion of the basin this evening. The troughing aloft supports a surface trough analyzed from the Florida panhandle near 30N86W to 25N91W providing focus for isolated showers and tstms occurring within 120 nm E and 90 nm W of the boundary. Addition isolated showers and tstms are occurring from 21N-24N between 91W-97W. This convection is likely enhanced due to upper level diffluence associated with an upper level ridge anchored in the vicinity of 25N88W. While fairly tranquil weather prevails across the basin this evening...light to gentle E-NE winds are expected through Tuesday. By Wednesday...surface ridging is forecast to build in across the SE CONUS and northern Gulf with gentle to occasional moderate E-SE winds expected through the remainder of the week. CARIBBEAN SEA... A broad and elongated upper level low is centered over the eastern Caribbean near 15N69W and stretches NW to another upper level low centered over eastern Cuba. Given the broadness of the feature... much of the western portion of the basin including Central America is under the influence of NW flow aloft. The upper level low is advecting moisture and cloudiness across much of the eastern and north-central Caribbean and along with a tropical wave along 68W is providing focus for isolated showers and possible tstms N of 12N between 60W-69W...and N of 16N between 69W-75W. Otherwise... other active convection is occurring in the adjacent offshore waters of Cuba as scattered showers and tstms are occurring within 90 nm of the coast. Finally...moderate to occasional fresh trades persist with the strongest of these trades generally remaining across south-central portions of the basin. ...HISPANIOLA... Isolated showers are noted across portions of the island and adjacent coastal waters as an upper level low is centered across the Caribbean Sea near 15N69W. A tropical wave noted beneath the upper level low along 68W will continue to provide increased cloudiness and higher probability of precipitation through Wednesday. ATLANTIC OCEAN... The remnant low of Julia in the SW North Atlc is analyzed as a 1011 mb low centered off the North Carolina coast near 34N76W. A cold front extends from the low SW to the South Carolina coast near 32N81W with scattered showers and tstms occurring N of 28N W of 78W. To the SW...a surface trough extends from the NW Bahamas near 27N78W to 30N73W providing focus for scattered showers and isolated tstms occurring within 90 nm either side of the boundary. Farther east...a weakness in the central Atlc ridging is another surface trough analyzed from 23N67W to 29N63W. Isolated showers and tstms are occurring within 120 nm either side of the boundary and N of 29N between 59W-66W. Otherwise...aside from Tropical Storm Karl and Tropical Depression Thirteen...the remainder of the central and eastern Atlc is under the influence of a surface ridge anchored by a 1029 mb high centered SW of the Azores near 35N40W. For additional information please visit http://www.hurricanes.gov/marine $$ HUFFMAN