000 AXNT20 KNHC 251803 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Wed Sep 25 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 1200 UTC surface analysis and satellite imagery through 1755 UTC. ...SPECIAL FEATURES... Recently-upgraded Hurricane Helene is centered near 22.0N 86.4W at 25/1800 UTC or 100 nm NNE of Cozumel Mexico, moving NNW at 9 kt. Estimated minimum central pressure is 980 mb. Maximum sustained wind speed is 70 kt with gusts to 85 kt. Peak seas are currently near 29 ft. Seas of 12 ft or greater are occurring within 180 nm in the E semicircle and 90 nm in the W semicircle. Numerous strong convection is observed within 100 nm of the center, while scattered moderate to isolated strong is occurring within 400 nm to the north and east and 200 nm to the west and south 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 turn toward the north and north- northeast with an increase in forward speed is expected later today through Thursday, bringing the center of Helene across the eastern Gulf of Mexico and to the Florida Big Bend coast by Thursday evening. After landfall, Helene is expected to slow down and turn toward the northwest over the southeastern United States Friday and Saturday. 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. A 24-hour rainfall total of 8.60 inches (218.4 mm) was recently reported in Embalse Herradura, Pinar del Rio, Cuba, by the Meteorological Service of Cuba. Over the Southeastern U.S. into the Southern Appalachians, Helene is expected to produce total rain accumulations of 5 to 10 inches with isolated totals around 15 inches. This rainfall will likely result in areas of considerable flash and urban flooding, with areas of significant river flooding. Landslides are possible in areas of steep terrain in the southern Appalachians. 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. 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: A broad 1009 mb low pressure is near 13N32W and a tropical wave is analyzed along the low pres and south of 20N, moving westward at 10-15 kt. Scattered showers and isolated thunderstorms are evident from 12N to 19N and between 29W and 39W. A recent scatterometer satellite data show fresh to locally strong easterly winds north of the low pressure. 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 central Atlantic tropical wave is along 56W, south of 20N, moving westward at 10 kt. Scattered moderate convection is observed from 12N to 20N and between 52W and 65W. ...MONSOON TROUGH/ITCZ... The monsoon trough reaches the Atlantic through the coast of Senegal near 15N17W and continues westward to a 1009 mb low pres (AL98) near 13N32W and then to 11N45W. Scattered showers are noted from 07N to 15N and east of 23W. ...GULF OF MEXICO... Please refer to the Special Features section above for details on Tropical Storm Helene located in the Yucatan Channel. Aside from Helene, a generally dry airmass dominates the western half of the Gulf of Mexico, except for a couple of showers west of 95W and south of 25N. Moderate or weaker winds and slight to moderate seas are found in these waters. For the forecast, Hurricane Helene is near 21.6N 86.3W at 11 AM EDT, and is moving north-northwest at 9 kt. Maximum sustained winds are 70 kt with gusts to 85 kt, and the minimum central pressure is 979 mb. Helene will move to 23.0N 86.4W this evening, 25.7N 85.7W Thu morning, 29.7N 84.6W Thu evening, move inland and weaken to a tropical storm near 34.3N 85.0W Fri morning, and weaken to a tropical depression near 36.6N 86.9W Fri evening. Marine conditions will gradually improve across the Gulf waters beginning on Fri or Fri night. ...CARIBBEAN SEA... Please refer to the Special Features section above for details on Tropical Storm Helene located in the Yucatan Channel. 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, Hurricane Helene is near 21.6N 86.3W at 11 AM EDT, and is moving north-northwest at 9 kt. Maximum sustained winds are 70 kt with gusts to 85 kt, and the minimum central pressure is 979 mb. Helene will move N of area into the Gulf of Mexico near 23.0N 86.4W this evening. Marine conditions will gradually improve across the NW Caribbean by late Thu or Thu night. ...ATLANTIC OCEAN... Please refer to the Special Features section above for details on Tropical Storm Helene located in the Yucatan Channel and Invest 98L in the central Atlantic. A couple of surface troughs in the north-central Atlantic result in scattered showers north of 24N and between 47W and 59W. 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 28N 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, Hurricane Helene is near 21.6N 86.3W at 11 AM EDT, and is moving north-northwest at 9 kt. Maximum sustained winds are 70 kt with gusts to 85 kt, and the minimum central pressure is 979 mb. Helene will move to 23.0N 86.4W this evening, 25.7N 85.7W Thu morning, 29.7N 84.6W Thu evening, move inland and weaken to a tropical storm near 34.3N 85.0W Fri morning, and weaken to a tropical depression near 36.6N 86.9W Fri evening. As Helene move across the eastern Gulf of Mexico, expect increasing winds and building across the waters just E of the Florida Peninsula. $$ Delgado