210 AXNT20 KNHC 261205 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 AM EDT Wed Sep 26 2018 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 1115 UTC. ...Special Features... The earlier remnants of Kirk have regenerated back into a tropical storm as of 0900 UTC this morning. At 0900 UTC Tropical Storm Kirk is centered near 11.8N 52.7W, which is about 405 nm east of Barbados or 515 nm ESE of Martinique, moving westward at 16 kt. The estimated minimum central pressure is 1004 mb. The maximum sustained wind speed is 40 kt with gusts to 50 kt. Latest satellite imagery shows that deep convection of the numerous moderate to strong type intensity has increased near the center of the tropical cyclone, while at the same time it has gradually become symmetrical during the past few hours. This convection is observed within 120 nm of the center in the SE semicircle and within 90 nm of the center in the NW semicircle. Scattered moderate isolated strong convection is to the northeast of Kirk from 14N to 16N between 49W and 52W, and from 10N to 13N between 53W and 56W. The latest NHC advisory has Kirk moving in a westward to west-northwestward motion through Fri night. On this forecast track, Kirk is expected to approach Barbados and the northern Windward Islands Thu afternoon and move into the eastern Caribbean Sea by Fri morning. Little change in strength is forecast until Kirk moves through the central Lesser Antilles Thu afternoon and evening. Rapid weakening is expected on Fri after Kirk emerges over the Caribbean Sea. See latest NHC Forecast/Advisory under AWIPS/WMO Headers MIATCMAT2/WTNT22 KNHC for more details. A strong cold front has been added to the analysis over the central Atlantic extending from an area of low pressure associated with Post-Tropical Cyclone Leslie north of the area. The cold front extends from 31N39W to 28N45W to 28N55W to 29N60W. The latest ASCAT data show gales are currently occurring north of 29N between 40W-42W. Winds in this area are forecast to diminish below gale force late this afternoon. However, winds will remain around 30 kt in the area during the next couple of days. Scattered moderate convection is along and within 120 nm ahead of the front for the portion of the front that's east of 41W. Meanwhile, Post- Tropical Cyclone Leslie, centered about 740 nm west-southwest of the Azores, is producing gale force winds. Scattered moderate convection is from 34N-38N between 37W-42W. Leslie is expected to reacquire subtropical or tropical characteristics on Thu or Fri while the cyclone meanders over the north-central Atlantic. There is a medium chance of this system becoming a tropical or subtropical cyclone during the next 48 hours. For more information on this system, see High Seas Forecasts issued by the National Weather Service. ...TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis along 23W from 03N to 17N, moving westward at 10 to 15 kt. Model guidance depicts a broad 700 mb trough over or slightly ahead of this wave. The satellite-derived low to mid-level winds nicely display a NE to SE wind shift across the wave. Satellite imagery shows isolated showers and thunderstorms are within 150 nm west and 120 nm east of the wave axis from 11N to 15N. A tropical wave has its axis along 70W south of 19N, moving westward at 15 kt. This wave appears to be weakening and losing definition. However, the Total Precipitable Water (TPW) satellite animation shows a broad pool of moisture between 65W-70W. Scattered showers and isolated thunderstorms are near and east of the wave axis between Trinidad and the south coast of the Dominican Republic. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends off the coast of Africa over Senegal at 13N17W and continues to 10N23W to 07N31W, where the ITCZ begins and continues to 07N41W. Outside of the convection mentioned with the tropical wave, scattered moderate convection is within 210 nm north and 180 nm south of the ITCZ and monsoon trough between 29W-41W. ...DISCUSSION... GULF OF MEXICO... A very moist and unstable air mass along with upper-level diffluence over the north-central Gulf Coast is currently resulting in scattered showers and thunderstorms north of 27.5N between 89W-93W. This activity pulsated up and down last night but has generally been moving slowly westward. Isolated showers are near a trough over the NE Gulf within 100 nm offshore of the Big Bend area of FL. A thermal trough over the east-central Bay of Campeche is helping to enhance scattered showers and isolated thunderstorms, currently seen from 20N-24N between 91W-94W. A surface trough will develop over the Yucatan peninsula each evening, shift W over the SW Gulf each night, then dissipate each morning. Elsewhere across the Gulf, gentle to moderate winds will increase to between moderate and fresh during the second half of this week as high pressure builds N of the region. CARIBBEAN SEA... Convection associated with the tropical wave in the eastern Caribbean is described above in the Tropical Waves Section. Most of the central Caribbean from 71W-80W is free of any significant convection at this time. Instability generated by the eastern Pacific monsoon trough that protrudes into the far southwestern Caribbean, along with low-level speed convergence and to some extent a weak upper low near 12N80W, which is at the base of an upper trough, has resulted in numerous moderate and isolated strong convection between 81W and the coasts of northern Costa Rica, Nicaragua and eastern Honduras. This activity is likely producing heavy rainfall over eastern Nicaragua and NE Costa Rica. Expect fresh to strong winds over the central Caribbean through midweek, with moderate to fresh winds thereafter through Friday. ATLANTIC OCEAN... The eastern Atlantic tropical wave, Tropical Storm Kirk, Post Tropical Cyclone Leslie and the cold front bringing gale force winds to the area have all been described above in the Special Features and Tropical Waves sections. A pre-frontal surface trough is analyzed just ahead of the cold front mentioned above over the central Atlantic. The trough then extends SW to 25N45W to 20N59W. All convection associated with this is north of 25N and east of 50W. Another surface trough extends from 29N30W to 23N31W. Only isolated showers are within 60 nm of the trough. Otherwise, ridging over the northeast Atlantic is helping to maintain generally stable and create fair weather north of 20N and east of 30W. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre/Hagen