000 AXNT20 KNHC 201044 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 644 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 0600 UTC surface analysis and satellite imagery through 1030 UTC. ...SPECIAL FEATURES... Tropical Storm Karl is centered near 20.2N 52.8W at 20/0900 UTC or about 540 nm ENE of the Leeward Islands moving WNW at 15 kt. Estimated minimum central pressure is 1006 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Scattered moderate convection is from 17N-24N between 48W-54W. See latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details. Tropical Depression Thirteen is centered near 14.4N 29.6W at 20/0900 UTC or about 340 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 and isolated strong convection is from 13N- 19N between 25W-30W. See latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. ...TROPICAL WAVES... Tropical wave extends from 10N72W to 18N71W 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 the influence of an upper level low noted on water vapor imagery centered near 15N69W. No significant deep convection is noted with the wave at this time. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends from the African coast near 15N17W to 14N20W. Aside from convection associated with Tropical Depression Thirteen...scattered moderate and isolated strong convection is from 13N-16N between 15W-19W. Isolated moderate convection is from 04N-08N between 32W-42W. ...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 morning. The troughing aloft supports a surface trough analyzed from the Florida panhandle near 31N84W to 25N90W providing focus for isolated showers and tstms occurring N of 23N between 85W-89W and S of 24N W of 90W. This convection is likely enhanced due to upper level diffluence associated with an upper level ridge anchored in the vicinity of 24N88W. While fairly tranquil weather prevails across the basin this morning...light to gentle E-NE winds are expected through Tuesday night. 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 on the western periphery of the troughing. 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 72W is providing focus for isolated showers and possible tstms E of 66W and N of 17N between 70W-82W. 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 72W 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 33N80W with scattered showers and tstms occurring N of 28N between 76W-80W. Farther east...a weakness in the central Atlc ridging along with maximum middle to upper level diffluence is generating an area of scattered showers and tstms from 29N-32N between 61W-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 1026 mb high centered near 36N47W and a 1027 mb high centered across the Azores near 39N30W. For additional information please visit http://www.hurricanes.gov/marine $$ HUFFMAN