395 AXNT20 KNHC 251802 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 202 PM EDT Tue Sep 25 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... Leslie has become a post-tropical cyclone as of 1500 UTC, and the final advisory has been issued. Leslie is centered near 31.6N 44.4W, or about 940 nm WSW of the Azores, moving E at 10 kt. A faster northeastward motion is expected on Wednesday, followed by a northward turn Wednesday night. Estimated minimum central pressure is 1007 mb. Maximum sustained winds are 30 kt with gusts to 40 kt. Scattered moderate convection is limited to the eastern semicircle and extends outward up to 330 nm from the center. Strengthening is expected, and Leslie is forecast to become a large and powerful post-tropical cyclone by Wednesday with winds increasing to hurricane force on Thursday. By Thursday or Friday, Leslie is expected to reacquire subtropical or tropical characteristics while the cyclone moves slowly eastward to east- northeastward over the north-central Atlantic. See the final NHC forecast/advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. A broad 1014 mb low is centered about 175 nm south of Cape Hatteras, North Carolina. A surface trough extends SW from the low to 29N77W. Scattered moderate convection is in the northeastern semicircle of the low from 30N-35N and west of 70W. Satellite and surface data indicate that the circulation of the low remains elongated and not well defined. However, this system could still become a tropical depression this afternoon or tonight while it moves slowly northwestward to northward. By Wednesday, additional development appears unlikely due to strong upper-level winds while the system moves northward and north-northeastward near the eastern United States coast. Regardless of development, this system is likely to bring scattered showers and thunderstorms across portions of northeastern South Carolina and eastern North Carolina this afternoon and tonight. In addition, dangerous surf conditions and rip currents are expected along portions of the North Carolina coast today. For more information, please see products from your local National Weather Service office. There is a medium chance of tropical cyclone formation within 48 hours. The remnant of Kirk is analyzed as a 1007 mb low near 10.5N47W or about 825 nm east of the Windward Islands. A tropical wave runs through the low along 47W from 04N-16N. Movement is W near 20 kt. This system continues to produce a large area of showers and thunderstorms, along with winds to near gale force on its north side. Scattered moderate convection is seen from 08N-14N between 44W-51W. Although satellite data indicate that the system still lacks a closed circulation, this disturbance could still redevelop into a tropical cyclone during the next day or two before it moves into an area of highly unfavorable upper-level winds as it approaches the Caribbean Sea. Interests in the Windward and Leeward Islands should monitor the progress of this disturbance as gusty winds and locally heavy rains are likely by Thursday even if the system does not redevelop into a tropical cyclone. There is a medium chance of redevelopment within the next 48 hours. For more information on this system, see High Seas Forecasts issued by the National Weather Service. ...TROPICAL WAVES... An eastern Atlantic tropical wave is along 21W/22W from 03N-17N, moving west at 10-15 kt. A 700 mb trough associated with this wave is well depicted in model guidance. Saharan air is not as prevalent near the wave as it was yesterday. The SAL has moved out ahead of the wave and is not as dense, as suggested by GOES-16 geocolor imagery and split-window imagery. Isolated showers and storms extend up to 60 nm west of the wave axis from 08N-13N. Scattered moderate convection is between the wave axis and the coast of Africa from 11N-14N. A tropical wave is along 58W from 03N-17N, moving west at 15 kt. The wave corresponds with a moisture maximum in TPW imagery. Scattered moderate convection is located from 06N-15N between 53W-59W. This tropical wave could enhance showers and thunderstorms over the Windward Islands this afternoon through tonight. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the African coast near the Senegal/Guinea-Bissau border to 07N21W to 07N25W. The ITCZ begins at 06N27W and continues to 07N36W to 10N44W, then resumes west of the remnants of Kirk near 08N48W to near the coast of Suriname near 06N57W. Outside of the convection mentioned with the two tropical waves and the remnants of Kirk, scattered showers and thunderstorms are located from 02N-09N between 26W-37W. ...DISCUSSION... GULF OF MEXICO... Upper-level diffluence over the north-central Gulf Coast is enhancing scattered showers and thunderstorms north of 27N between 84W-90W. A thermal trough over the east-central Bay of Campeche is weakening and is no longer producing any significant shower activity. 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... A surface trough moving slowly westward over the eastern Caribbean extends from 20N64W to 15N65W. Scattered showers and isolated thunderstorms are in the vicinity of the Virgin Islands, Puerto Rico and the adjacent waters from 18N-22N between 61W-66W. The eastern Pacific monsoon trough combined with diffluence aloft continues to enhance scattered moderate and isolated strong convection in the SW Caribbean from 11N-15N, between 78W and the coasts of Nicaragua and eastern Honduras. Puerto Cabezas is currently reporting thunderstorms, and satellite imagery shows deep convection over extreme eastern Honduras and northeastern Nicaragua. Expect fresh to strong winds over the central Caribbean through midweek, with moderate to fresh winds thereafter through Friday. ATLANTIC OCEAN... Currently, there are three tropical waves in the tropical Atlantic between Africa and the Lesser Antilles. There is also a low with development potential off the southeast coast of the U.S. For information on those features as well as post tropical cyclone Leslie, please read the Special Features and Tropical Waves sections above. A cold front is located on the northern border of the forecast area from 32N53W to 31N57W, where it becomes a dissipating stationary front. The dissipating stationary front extends westward to 32N64W and continues WNW out of the forecast area. Little to no shower activity is observed with the front at this time. Elsewhere, ridging over the northeast Atlantic is helping to create fair weather north of 20N and east of 35W. For additional information please visit http://www.hurricanes.gov/marine $$ Hagen