412 AXNT20 KNHC 221753 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 153 PM EDT Sat Sep 22 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...Special Features... The area of low pressure south of the Cabo Verde Islands has organized into Tropical Storm Kirk. This storm is centered near 8.3N 23.6W at 22/1500 UTC, or 390 nm (730 km) S of the southernmost Cabo Verde Islands, moving W at 12 kt. A westward to west-northwestward motion at a similar forward speed is expected to continue through tonight. A faster westward motion across the deep tropical Atlantic Ocean is expected Sunday through Tuesday. Minimum central pressure is 1005 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Some strengthening is forecast through Sunday, with little change in intensity forecast on Monday and Tuesday. Scattered moderate convection is observed within 150 nm of the center in the western semicircle, especially the NW quadrant. Scattered moderate convection is also noted within 270 nm of the center in the eastern semicircle. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details. Tropical Depression Eleven is centered near 13.2N 53.8W at 22/1500 UTC, or 420 nm (780 km) E of the Windward Islands, moving W at 3 kt. A westward to west-northwestward motion at a slightly faster forward speed is expected during the next couple of days. Estimated minimum central pressure is 1008 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. Little change in strength is forecast during the next day or two, and the depression is forecast to become a remnant low on Sunday and dissipate east of the Lesser Antilles Sunday night. Scattered moderate convection is noted between 90 nm-240 nm from the center in the E semicircle. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more details. Satellite imagery indicates that a frontal non-tropical low pressure system is located about 870 nm west-southwest of the Azores. Conditions are expected to become conducive for this low to acquire subtropical or tropical characteristics during the next day or so, and a subtropical or tropical cyclone is likely to form by early next week while the low meanders over the central Atlantic Ocean. The system has a medium chance of tropical cyclone formation within the next 48 hours. Please refer to the latest Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information. ...TROPICAL WAVES... A tropical wave has its axis along 40W/41W from 03N-16N and is moving west at 10-15 kt. The wave corresponds nicely with a maximum in TPW imagery. Model analyses depict an associated 700 mb trough along 41W. Scattered showers and isolated thunderstorms are located near and east of the wave axis from 09N-14N between 36W-41W. Scattered moderate convection is also noted from 07N-11N between 42W-46W. A western Caribbean Sea tropical wave has its axis along 84W from 08N-21N, moving west around 10 kt. The 700 mb trough associated with this wave is well depicted in model guidance, and TPW imagery shows abundant moisture in its environment. Scattered moderate and isolated strong convection is noted from 12N-18N between 82W-86W, including eastern Nicaragua and northeast Honduras. Puerto Cabezas, Nicaragua is currently reporting thunderstorms. Moisture associated with this wave will continue to spread inland across Central America through tonight, likely containing scattered showers and tstms. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the African coast near the Mauritania/Senegal border to 15N19W. It continues from 07N24W to 06N30W to 08N38W. The ITCZ begins near 09N43W and continues to 09N52W. Aside from the convection associated with the tropical wave and cyclones across the area, scattered showers are located along and within 90 nm south of the monsoon trough between 26W- 31W. ...DISCUSSION... GULF OF MEXICO... An upper-level cyclonic circulation is centered near 27N86W. A surface trough is analyzed over the SE Gulf along 84W from 23N- 26N. Both features are helping to enhance convection slightly across the eastern Gulf east of 86W from 23N-29N, where scattered showers and isolated thunderstorms are observed. A surface trough extending from the coast of SE Louisiana to 25N91W is producing isolated showers and thunderstorms from 24N-26N between 88W-92W. A cold front currently over east-central Texas is expected to move eastward, reaching the Texas coast tonight. This front is likely to just barely reach the NW Gulf off the Texas coast tonight before stalling and dissipating on Sunday. A surface trough located ahead of the front is currently just inland over south Texas. Scattered moderate convection is noted over the NW Gulf north of 27N and west of 92W. Gentle to moderate E to SE winds and seas 3 ft or less will prevail across most of the Gulf of Mexico through the middle of next week. A surface trough will develop over the Yucatan peninsula each evening, shift W over the SW Gulf each night, then dissipate by morning. Moderate to fresh winds will accompany the trough. CARIBBEAN SEA... A tropical wave is moving across the far western Caribbean, and a portion of this wave is entering Central America. Please see the Tropical Waves section for more details. The eastern Pacific monsoon trough combined with diffluence aloft continues to enhance convection over portions of Panama and the waters of the southwest Caribbean from the coasts of Panama and Costa Rica northward to 12N and eastward to 78W. Plenty of moisture will persist over the extreme southwest Caribbean, Panama and Costa Rica through tonight. Elsewhere, fresh to strong winds prevail over the central Caribbean. These winds will diminish across most of the basin by Sun night. ATLANTIC OCEAN... Currently, there are two tropical cyclones and a tropical wave between the west coast of Africa and the Lesser Antilles. Please see the Special Features and Tropical Waves sections for more details. A broad 1011 mb low is centered 175 nm south of Bermuda. A surface trough runs through the low from 30N61W to the low near 29N65W to 28N70W. Scattered moderate convection is seen extending out to 180 nm from the center of the low in the eastern semicircle. Strong upper-level winds and dry air are expected to limit development for the next day or so, but conditions could become more conducive for some development of this system by early next week while it moves westward and west-northwestward over the southwestern Atlantic Ocean. By the middle of next week, upper-level winds are likely to increase again, which would limit additional development as the system turns northward and moves closer to the southeastern coast of the United States. The low has a low chance of tropical cyclone formation during the next 48 hours. A cold front extends from the low north of the area mentioned in the Special Features section and enters the area near 31N45W and extends to 28N50W to 29N57W. A stationary front then continues from 29N57W to 31N60W. Scattered moderate convection is located along the front and extending to 120 nm ahead of the front between 41W-50W. Recent scatterometer data shows winds are near gale force just ahead of the front in the southwesterly flow from 27N-31N between 42W-47W. For additional information please visit http://www.hurricanes.gov/marine $$ HAGEN/GR