000 AXNT20 KNHC 262358 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 UTC Thu Sep 26 2024 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 31N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1800 UTC surface analysis and satellite imagery through 2350 UTC. ...SPECIAL FEATURES... Hurricane Helene is centered near 27.9N 84.6W at 26/2100 UTC or 110 nm W of Tampa Florida, moving NNE at 20 kt. Estimated minimum central pressure is 951 mb. Maximum sustained wind speed is 110 kt with gusts to 135 kt. Peak seas to 35 ft are affecting the NE Gulf of Mexico. Numerous strong convection and scattered tstms are ongoing N of 24N and E of 87W. A continued fast motion to the north-northeast is expected through landfall in the Florida Big Bend this evening. After landfall, Helene is expected to turn northwestward and slow down over the Tennessee Valley on Friday and Saturday. Helene is a category 3 hurricane on the Saffir- Simpson Hurricane Wind Scale. Additional strengthening is expected, and Helene will likely be an extremely dangerous category 4 hurricane at landfall. Weakening is expected after Helene moves inland, but the fast forward speed will allow strong, damaging winds, especially in gusts, to penetrate well inland across the southeastern United States, including over the higher terrain of the southern Appalachians. Over portions of the Southeastern U.S. into the Southern Appalachians, Helene is expected to produce total rain accumulations of 6 to 12 inches, with isolated totals around 20 inches. This rainfall will likely result in catastrophic and potentially life-threatening flash and urban flooding, along with significant river flooding. Numerous significant landslides are expected in steep terrain across the southern Appalachians. Swells generated by Helene will affect much of Florida and the coasts of Georgia and the Carolinas during the next couple of days. Swells will also continue across portions of Cuba and the Yucatan Peninsula through tonight. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest Helene NHC Forecast Advisory and Public Advisory at www.hurricanes.gov for more details. Invest 98L in the Central Atlantic: A 1008 mb low pressure is near 16N39W and a tropical wave is analyzed along the low pres, which is moving westward at 10-15 kt. Scattered moderate convection is observed within 210 nm NW semicircle of the low. Strong to near gale force winds are mainly in the NE quadrant within 150 nm from the low. Environmental conditions are expected to be conducive for further development and a tropical depression is expected to form tonight or on Friday while the disturbance moves generally westward to west-northwestward at 10 to 15 mph. The system is then forecast to slow down and turn north-northwestward late Friday and Saturday. There is a high chance of tropical cyclone formation in the next 48 hours. Please read the latest Tropical Weather Outlook issued by the National Hurricane Center at hurricanes.gov ...TROPICAL WAVES... A tropical wave is in the E Atlantic extending from 07N to 21N with axis near 22W, which is moving westward at 10-15 kt. Scattered moderate convection is observed from 05N to 17N between 16W and 34W. Fresh winds and moderate seas are in the northern semicircle of the low. A tropical wave is in the E Caribbean south of 20N with axis near 62W, moving westward at 15 kt. Scattered moderate convection is present from 12N to 20N between 56W and 66W. ...MONSOON TROUGH/ITCZ... The monsoon trough reaches the Atlantic through the coast of Senegal near 15N17W and continues westward to the 1008 mb low pressure (AL98) and then to 13N45W. Convection near the monsoon trough is primarily associated with the tropical waves depicted in the sections above. A segment of the East Pacific monsoon trough is analyzed over the far southwest Caribbean, and is aiding in the development of scattered moderate convection south of 13N, offshore Panama and Colombia. ...GULF OF MEXICO... Please refer to the Special Features section above for details on Major Hurricane Helene in the eastern Gulf. Aside from Helene, which dominates the entire eastern half of the basin, a stationary front extends from Pensacola, Florida to NE Mexico. The cyclonic circulation of the hurricane is transporting a dry continental airmass over much of the western Gulf, especially west of 88W, allowing for generally tranquil conditions. N of 22N and W of 90W, winds are moderate to fresh from the NNW, except for strong winds over the offshore and adjacent waters of Louisiana. Seas over this region are mainly rough to 15 ft. Over the SW Gulf, winds are gentle to moderate from the NW and some showers associated with Hurricane John over the SW Mexican offshore waters are impacting the Bay of Campeche. For the forecast, Helene will move inland to 31.5N 83.7W Fri morning, weaken as an extratropical cyclone near 35.8N 85.0W Fri afternoon, weaken as an extratropical cyclone near 37.0N 86.5W Sat morning, 37.1N 87.0W Sat afternoon, 37.1N 87.3W Sun morning, and dissipate Sun afternoon. Winds and seas related to Helene will prevail across the eastern Gulf waters through late Fri. Light to gentle winds and slight seas will prevail across the basin beginning on Sat through early next week. ...CARIBBEAN SEA... Please refer to the Special Features section above for details on Major Hurricane Helene in the eastern Gulf of Mexico. Scattered showers associated with the outer rainbands of Major Helene continue to affect the NW Caribbean. In the eastern Caribbean, a robust tropical wave is producing scattered showers and a few thunderstorms. Moderate to fresh trades are ongoing over the central and eastern basin along with moderate seas to 4 ft. Over the NW Caribbean and south of Cuba, moderate to fresh southerly winds and rough seas to 8 ft are ongoing. Light to gentle winds and slight to moderate seas are prevalent elsewhere in the basin. For the forecast, Major Hurricane Helene over the NE Gulf of Mexico will continue to move NE away from the basin, making landfall over the Florida Big Bend tonight. Fresh to strong winds and rough seas will continue over the far NW Caribbean through tonight. After that, gentle to moderate winds and slight seas will prevail across the area beginning on Fri through early next week. ...ATLANTIC OCEAN... Please refer to the Special Features section above for details on Hurricane Helene located in the eastern Gulf of Mexico and Invest 98L in the central Atlantic. A pair of surface troughs are analyzed over the central subtropical Atlantic, which are supporting scattered showers between 45W and 55W. The remainder of the Atlantic is under the influence of a broad subtropical ridge, maintaining fairly tranquil weather conditions. Moderate or weaker winds and slight to moderate prevail over a good portion of the basin. For the forecast W of 55W, Hurricane Helene is near 27.9N 84.6W at 5 PM EDT, and is moving north-northeast at 20 kt. Maximum sustained winds are 110 kt with gusts to 135 kt, and the minimum central pressure is 951 mb. Helene will move inland to 31.5N 83.7W Fri morning, weaken as an extratropical cyclone near 35.8N 85.0W Fri afternoon, weaken as an extratropical cyclone near 37.0N 86.5W Sat morning, 37.1N 87.0W Sat afternoon, 37.1N 87.3W Sun morning, and dissipate Sun afternoon. Elsewhere, Tropical Storm Issac, well N of the region to the NE of Bermuda, will continue moving away from the area, but generate N swell that will propagate into waters N of 29N and E of 65W, producing seas of 6 to 8 ft. $$ Ramos