Tropical Weather Discussion
Issued by NWS
Issued by NWS
770 AXNT20 KNHC 261006 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 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 0600 UTC surface analysis and satellite imagery through 0930 UTC. ...SPECIAL FEATURES... Hurricane Helene is centered near 24.2N 86.2W at 26/0900 UTC or 300 nm SW of Tampa Florida, moving NNE at 10 kt. Estimated minimum central pressure is 966 mb. Maximum sustained wind speed is 80 kt with gusts to 100 kt. Seas 12 ft or greater are occurring within 240 NM in the NE quadrant, 270 NM in the SE quadrant, and 150 NM in the SW quadrant, and 180 NM in the NW quadrant with peak seas near 36 ft. Numerous moderate to scattered strong convection is ongoing within about 180 NM of the center. Strengthening is forecast, and Helene is expected to become a major hurricane later today, and make landfall as a Category 3 hurricane this evening in the Florida Big Bend. 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 24 hours. Helene will move to 26.8N 85.2W this afternoon, then inland to 31.6N 84.0W Fri morning. 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 today. 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 life-threatening flash and urban flooding, along with significant river flooding. Numerous landslides are expected 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: Showers and thunderstorms have increased this morning, with numerous moderate to isolated strong convection now present from 13N to 18N between 32W and 41W, in association with broad low pressure centered near 15N36W with 1009 mb. A broad area of fresh to strong E winds and seas of 8 to 10 ft are noted N of the center. This low is along a tropical wave several hundred miles W of the Cabo Verde Islands. Earlier satellite wind data suggests the system still lacks a well-defined circulation, but environment conditions appear favorable for gradual development, and a tropical depression is likely to form during the next day or two while it moves W to WNW at 10 to 15 kt across the eastern and central Tropical Atlantic. 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... See Special Features section above for details on a tropical wave W of the Cabo Verde Islands, from which a low pressure center has developed. An eastern Atlantic tropical wave is noted midway between the coast of mainland Africa and the Cabo Verde Islands, from 08N to 22N, moving W at around 10 kt. Scattered moderate to isolated strong convection is noted between the Cabo Verde Islands and Africa, from 12N to 17N. A tropical wave is near the Lesser Antilles along 59W, from 19N southward, moving W at around 15 kt. Scattered moderate convection is moving through the Windward and Leeward Islands in association with this wave. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic near 18N16W and continues westward to the 1009 mb low pressure (AL98) near 15N36W and then southwestward to 09N43W. Convection near the monsoon trough is primarily associated with the tropical waves depicted in the sections above. The ITCZ is analyzed from 08N43W to 05N53W. No significant convection is occurring near the ITCZ at this time. 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 S of 11N, offshore Panama and Colombia. ...GULF OF MEXICO... Please refer to the Special Features section above for details on Hurricane Helene. Aside from Helene, which dominates the entire eastern half of the basin, no significant convection is occurring, and a weak cold front extends in the NW Gulf from southeast Louisiana to Deep South Texas. Moderate or weaker winds and slight to moderate seas are found in the western Gulf. For the forecast, little change is expected in the western Gulf into the weekend, with marine conditions in the eastern Gulf gradually improving Fri into Fri night, after Hurricane Helene moves inland into the southeastern U.S. ...CARIBBEAN SEA... Please refer to the Special Features section above for details on Hurricane Helene. A deep layer trough ahead of a tropical wave that is nearing the Lesser Antilles extends S from Puerto Rico to Venezuela. It is inducing scattered moderate convection. Elsewhere, away from Helene, moderate to fresh E trade winds and seas of 3 to 5 ft are occurring in the central and eastern Caribbean. Moderate or weaker winds and seas of 1 to 3 ft are found in the SW Caribbean. For the forecast, little change is expected in the basin into the weekend, with marine conditions improving into tonight in the NW Caribbean as Hurricane Helene moves farther N of the area toward the Florida Gulf coast. ...ATLANTIC OCEAN... Please refer to the Special Features section above for details on Hurricane Helene and Invest 98L in the eastern Atlantic. Showers have dissipated in association with a weak surface trough N of 27N along 50W. Otherwise, a broad ridge anchored by a 1022 m high pressure centered SW of the Azores is dominating much of the basin. The pressure gradient between it and lower pressure in the tropics is supporting fresh NE winds E of 35W, with seas of 4 to 7 ft. Elsewhere, moderate or weaker E winds and moderate seas prevail. For the forecast W of 55W, Tropical Storm force winds and very rough seas will impact waters offshore Florida through tonight as Hurricane Helene passes W of the area. 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 28N and E of 65W, producing seas of 6 to 8 ft. $$ Konarik