000 AXNT20 KNHC 242333 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0005 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 1800 UTC surface analysis and satellite imagery through 2300 UTC. ...SPECIAL FEATURES... Tropical Storm Helene is centered near 19.7N 84.7W at 24/2100 UTC or 130 nm ESE of Cozumel Mexico, moving WNW at 10 kt. Estimated minimum central pressure is 995 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Seas 12 ft or greater are occurring within 120 NM in the NE quadrant and 150 NM in the SE quadrant, with peak seas near 16 ft. Strong convection is occurring within 120 NM to the north, east and southeast of the center, and additional moderate to strong convection is noted across much of the western Caribbean. Additional strengthening is forecast, and Helene is expected to become a hurricane on Wednesday. The storm is forecast to rapidly strengthen over the eastern Gulf of Mexico and become a major hurricane on Thursday. Helene will move to 20.4N 86.0W Wed morning, 21.7N 86.6W Wed afternoon, 23.7N 86.1W Thu morning, 27.0N 84.9W Thu afternoon, move inland and weaken to a tropical storm near 31.5N 84.0W Fri morning, and move inland and weaken to a tropical depression near 35.5N 84.8W Fri afternoon. Helene will move inland over 38.2N 89.0W Sat afternoon. Helene is expected to produce total rain accumulations of 4 to 8 inches over western Cuba and the Cayman Islands with isolated totals around 12 inches. Over the eastern Yucatan Peninsula, 4 to 6 inches of rain are expected with isolated totals over 8 inches. Over the Southeastern U.S., Helene is expected to produce total rain accumulations of 4 to 8 inches with isolated totals around 12 inches. This rainfall will likely result in areas of considerable flash and urban flooding, with areas of significant river flooding likely, including the risk of landslides in areas of steep terrain in the southern Appalachians. The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline, with impacts felt from the Florida Keys to the panhandle of Florida, as well as northeastern Florida through the central South Carolina coast. 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. ...TROPICAL WAVES... A tropical wave in the eastern Atlantic is near 28W from 19N southward, moving toward the west at 10-15 kt. Scattered moderate to locally strong convection is noted from 12N to 16N between 28W and 33W. 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. A tropical wave approaching the Lesser Antilles is near 50W from 17N southward, moving westward at 5-10 knots. Scattered moderate to strong convection is occurring from 11N to 17N between 50W and 61W. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic near 12N17W, then curves southwestward to near 09N38W. The ITCZ extends from 09N38W to 09N50W. Scattered moderate to locally strong convection is noted from 04N to 09N between 21W and 34W. ...GULF OF MEXICO... Please refer to the Special Features section above for details on Tropical Storm Helene. Moderate E winds and seas are increasing in the far SE Gulf of Mexico, including the Florida Straits and Yucatan Channel, in association with Helene. Weak ridging across the rest of the basin supports light to gentle winds and slight seas. Scattered moderate convection is occurring off the coast of Texas and far northern Mexico ahead of an approaching cold front. For the forecast, away from the immediate impacts from Helene, increasing NE winds are expected tonight into Wed over the western Gulf, becoming moderate to locally fresh N winds into Thu, then gradually becoming NW and weakening on Fri. Seas will become moderate to rough over the aforementioned area. Widespread showers and thunderstorms will also occur across much of the basin, with gusty winds and rough seas expected near convection. ...CARIBBEAN SEA... Please refer to the Special Features section above for details on Tropical Storm Helene. Away from Helene, moderate to locally fresh SE winds and moderate seas are occurring across much of the basin. For the forecast, away from the immediate impacts from Helene, fresh to strong S to SE winds will persist after Helene moves northward out of the basin late Wed into Thu, and very rough seas will accompany these winds. Elsewhere, E to SE trades will continue. By Fri into this weekend, a seasonal trade regime with slight to moderate seas will prevail. ...ATLANTIC OCEAN... Please refer to the Tropical Waves section for information on potential tropical development in the eastern Atlantic this week. A 1004 mb low is centered near 39N58W, and surface troughing extends from 31N56W to 22N70W. Scattered moderate convection is occurring along and ahead of this trough. A secondary trough is noted from 31N61W to off the coast of northeast Florida. Elsewhere, a 1024 high dominates eastern portions of the Atlantic. The pressure gradient between this ridge and a 1012 mb low over northwest Algeria supports fresh to locally strong NE winds downwind of the Canary Islands. For the forecast W of 55W, increasing S to SE winds will develop off the coast of Florida ahead of Helene, and showers and thunderstorms will accompany these winds. The tropical wave near the Cabo Verde Islands will encounter environmental conditions that will be 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 will be a medium chance of tropical development in the next 48 hours, and a high chance of development in the next seven days. $$ ADAMS