107 AXNT20 KNHC 270950 TWDAT Tropical Weather Discussion...UPDATED NWS National Hurricane Center Miami FL 550 AM EDT Thu Sep 27 2018 Updated Special Features section to include latest information on Tropical Storm Kirk 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 0845 UTC. ...Special Features...Updated Tropical Storm Kirk is centered near 13.5N 58.3W at 27/0900 UTC, or about 75 nm E of Barbados or 175 nm ESE of Martinique, moving west-northwestward or 290 degrees at 14 kt. The estimated minimum central pressure has risen to 1002 mb. The maximum sustained wind speed is 45 kt with gusts to 55 kt. Kirk remains under vertical shear as noted by its center being displaced from the deep convection. This convection consists of the scattered moderate to strong type intensity within 210 nm of the center in the NE quadrant and within 120 nm of the center in the SE quadrant. Scattered moderate convection is within 60 nm of 12N55W. The latest NHC advisory keeps Kirk moving in its current motion over the over the next few days. On the present forecast track, the center of Kirk will move across the Lesser Antilles within the tropical storm warning area by this evening. Kirk is expected to produce very heavy rain across the northern Windward and southern Leeward Islands Thu through much of Fri. These rains may produce life- threatening flash floods and mudslides. See latest NHC Forecast/Advisory under AWIPS/WMO Headers MIATCMAT2/WTNT22 KNHC for more details. Post-Tropical Cyclone Leslie, located over the central Atlantic Ocean several hundred miles west-southwest of the Azores remains a powerful non-tropical low with hurricane-force winds. The associated shower activity is gradually becoming more organized, and Leslie is expected to again become a subtropical storm, or possibly a tropical storm, later today or on Fri while it moves west-southwestward at about 8 kt over the north-central Atlantic. Latest satellite imagery shows a large shield rain with embedded scattered to numerous showers to southwest of the low from 32N to 35N between 45W and 50W, and also within 30 nm either side of a line from 37N40W to 35N42W to 34N43W. There is a high 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 27W from 03N to 19N, moving westward at 10 to 15 kt. Total precipitable water (TPW) imagery clearly indicates a maximum in low-level moisture to the east of this wave. 700 mb guidance from the GFS model has a sharp 700 mb inverted trough over the wave. Isolated showers and thunderstorms are seen within 180 nm east of the wave from 06N to 09N, and also from 14N to 19N. A rather ill-defined central Atlantic tropical wave has its axis near 38W from 03N to 19N, moving westward at 15 kt. 700 mb guidance from the GFS model depicts a broad 700 mb trough over the environment of this wave. Recent mid-level satellite winds reveal a broad inverted trough over the wave, with winds shifting from northeast to southeast across the wave axis. Based on the current signature status of this wave in model guidance and in satellite animation, low confidence can be expected in tracking this wave for the next several days. Isolated showers and thunderstorms are in the vicinity of where the wave axis intersects the ITCZ, roughly from 05N to 08N between 37W and 40W. A tropical wave has its axis along 75W south of 19N, moving westward at 15 kt. Scattered showers and isolated thunderstorms are noted within 120 nm west of the wave south of 13N. Isolated showers and thunderstorms are within 120 nm either side of the wave north of 13N. ...MONSOON TROUGH/ITCZ... The monsoon trough axis briefly extends off the coast of Africa over Guinea Bissau to near 11N12W. It resumes at 11N24W to 08N30W, where it transitions to the ITCZ to just west of the tropical wave near 38W, and resumes west of the same wave at 07N39W to 06N47W. Outside of the convection mentioned with the two tropical waves, scattered moderate convection is within 120 nm south of the ITCZ between 43W and 45W and within 60 nm north of of the ITCZ between 39W and 41W. ...DISCUSSION... GULF OF MEXICO... Earlier scattered moderate convection that was over the much of the northwestern Gulf has diminished, except recent radar data shows new scattered new scattered moderate isolated strong convection developing ahead of a cold front that is over eastern Texas. This activity is expected to push further into the northwestern Gulf waters through early this morning. Some of the activity may produce strong gusty winds and frequent lightning. The cold front will become stationary along the Texas coast this morning. Scattered showers and thunderstorms are elsewhere west of 89W, while isolated showers and thunderstorms are east of 89W. High pressure to the northeast of the region will support gentle to moderate east to southeast winds and seas less than 4 ft across most of the region through Sun. The only exception is locally fresh winds each night associated with a trough moving over the eastern Bay of Campeche. CARIBBEAN SEA... Instability generated by the eastern Pacific monsoon trough that protrudes into the far southwestern Caribbean, along with pretty decent upper-level ventilation continues to allow for scattered showers and thunderstorms to continue over much of the southwestern Caribbean south of 14N and west of 77W. Scattered showers and isolated thunderstorms are over much of the northwestern Caribbean, and also south of 16N east of 70W, including the vicinity of Trinidad and Tobago. Expect fresh to strong trade winds to continue over the south- central Caribbean through Thu. ATLANTIC OCEAN... Tropical Storm Kirk and two tropical waves between Africa and the Lesser Antilles are described above in the Special Features and Tropical Waves sections. A strong cold front and an associated area of gale force winds extend southward from Post-Tropical Cyclone Leslie, which is centered well north of the area near 36N39W with a pressure of 978 mb. It is producing hurricane force winds. The cold front enters the forecast area near 31N33W, and extends southwestward to 25N40W to 23N50W to 25N59W, then is weakening northwestward to 27N66W. A pre-frontal trough extends from near 25N36W to 20N43W. Satellite imagery shows scattered moderate convection along and within 75 nm east of the front north of 28N, and within 60 nm to the south of the front between 56W and 66W. Similar convection is along and within 60 nm north of the front between 44W and 52W. Isolated showers are along and near the pre-frontal trough. The cold front is forecast to become stationary from near 29N35W to 23N44W and to near 21N51W by this afternoon and dissipate by early Fri afternoon. Large swell generated by Post-Tropical Cyclone Leslie is expected to spread east of 75W by Fri night, and continue through the weekend. Post-Tropical Cyclone Leslie is forecast to again become a tropical or subtropical storm during the next couple of days. More details are described above under the Special Features section. Elsewhere, mid to upper-level ridging, in combination with a very persistent moist low-level easterly flow, is bringing scattered showers and thunderstorms to the waters between the Bahamas and S Florida. Isolated showers and thunderstorms are over the southeastern Bahamas and elsewhere over the waters south of 28N and west of 66W. High pressure is present elsewhere across the discussion area. The high pressure is weakest over the far western half of the area. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre