000 AXNT20 KNHC 252338 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 2330 UTC. ...SPECIAL FEATURES... Hurricane Helene is centered near 22.5N 86.6W at 25/2100 UTC or 400 nm SW of Tampa Florida, moving N at 10 kt. Estimated minimum central pressure is 978 mb. Maximum sustained wind speed is 75 kt with gusts to 90 kt. Seas 12 ft or greater are occurring within 180 NM in the NE quadrant, 210 NM in the SE quadrant, 90 NM in the SW quadrant and 120 NM in the NW quadrant with peak seas near 32 ft. Strong convection is occurring within 120 NM to the south of the center, with scattered moderate to locally strong convection occurring within 150 NM to the north of the center. Strengthening is forecast, and Helene is expected to be a major hurricane when it reaches the Florida Big Bend coast Thursday evening. Weakening is expected after landfall, but Helene's 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. A northward or north-northeastward motion at a faster forward speed is expected during the next 36 hours. Helene will move to 24.1N 86.2W Thu morning, 27.4N 85.2W Thu afternoon, inland to 32.1N 84.6W Fri morning, and continue to move inland toward the north and northwest away from the Gulf of Mexico this weekend. Swells generated by Helene will affect the southern coast of Cuba and the Yucatan Peninsula of Mexico during the next couple of days. Swells will spread northward toward the west coast of Florida and the northeastern Gulf Coast later today and Thursday. These swells are likely to cause life-threatening surf and rip current conditions. The combination of a life-threatening storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. Hurricane Helene is expected to produce total rain accumulations of 4 to 8 inches over western Cuba, the Cayman Islands and the northeast Yucatan Peninsula, with isolated totals around 12 inches. This rainfall brings a risk of considerable flooding. 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 18 inches. This rainfall will likely result in catastrophic and potentially life-threatening flash and urban flooding, along with significant river flooding. Landslides are possible in steep terrain across the southern Appalachians. 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: A broad, 1009 mb low pressure system is located near 15N34W. This low is associated with a tropical wave, and continues to produce disorganized shower and thunderstorm activity. Seas in these waters are 5-8 ft. Environmental conditions appear favorable for gradual development of this system, and a tropical depression is likely to form in a few days while it moves westward to west-northwestward across the eastern and central tropical Atlantic. There is a medium chance of tropical formation in the next 48 hours and a high chance of formation in the next seven days. Please read the latest Tropical Weather Outlook issued by the National Hurricane Center at hurricanes.gov ...TROPICAL WAVES... A tropical wave approaching the Lesser Antilles has been repositioned from the previous discussion, and is located along 55W, south of 20N. Scattered moderate convection is observed from 13N to 17N and between 54W and 60W. ...MONSOON TROUGH/ITCZ... The monsoon trough reaches the Atlantic near 17N16W and continues westward to the 1009 mb low pres (AL98) near 15N34W and then to 13N46W. Scattered showers are noted from 06N to 16N and east of 22W. ...GULF OF MEXICO... Please refer to the Special Features section above for details on Hurricane Helene. Aside from Helene, a generally dry airmass dominates the western third of the Gulf of Mexico, except for a couple of showers west of 95W and south of 20N. Moderate or weaker winds and slight to moderate seas are found in these waters. For the forecast away from the immediate impacts from Hurricane Helene, N to NE winds will freshen tonight in the western Gulf into Thu before slowly diminishing on Fri. Moderate to rough seas will expand north and west across the western Gulf tonight, with seas by Fri night. For the weekend into early next week, gentle to moderate breezes and slight seas will prevail across the basin. ...CARIBBEAN SEA... Please refer to the Special Features section above for details on Hurricane Helene. Outside of the influence of Helene, moderate to fresh SE trade winds and moderate seas are occurring in the central Caribbean. Moderate or weaker winds and slight to moderate seas are found in the eastern and SW Caribbean. For the forecast away from the immediate impacts from Hurricane Helene, fresh to locally strong winds in the NW Caribbean will diminish through the day on Thu. Rough to very rough seas will slowly subside Thu night into Fri. Elsewhere, a moderate trade regime will prevail through this weekend and into early next week with slight seas. ...ATLANTIC OCEAN... Please refer to the Special Features section above for details on Hurricane Helene and Invest 98L in the central Atlantic. A surface trough in the north-central Atlantic results in scattered showers north of 27N and between 46W and 53W. The remainder of the Atlantic is under the influence of a broad 1022 mb high pressure system centered south of the Azores. The pressure gradient between this ridge and lower pressures in the deep tropics support fresh to locally strong NE winds from 19N to 26N and east of 27W. Seas in these waters are 4-7 ft. Moderate to locally fresh southerly winds are present south of 10N and east of 40W, along with seas of 4-7 ft. Elsewhere, moderate or weaker winds and moderate seas are prevalent. For the forecast W of 55W, as Hurricane Helene moves through the Gulf of Mexico and inland across the southeastern United States, expect increasing winds and building seas tonight through Thu across the waters just E of the Florida Peninsula. Winds and seas will diminish this weekend. Elsewhere, a moderate trade regime will prevail across much of the basin away from the potential tropical development in the central Atlantic. $$ ADAMS