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| #1200367 (Received by flhurricane at: 4:48 PM 26.Sep.2024) TCDAT4 Hurricane Helene Discussion Number 14 NWS National Hurricane Center Miami FL AL092024 500 PM EDT Thu Sep 26 2024 Helene has rapidly intensified today while nearing landfall in the Florida Big Bend. Doppler radar and aircraft data indicate that the eyewall is now completely closed and the eye has become more circular and is clearing out. The aircraft data also indicated that the inner core has contracted significantly today while the tropical-storm-force winds have expanded. Based on all of the data, the initial intensity is set at 110 kt. The latest minimum pressure based on the aircraft data is around 951 mb. Tropical-storm-force winds are occurring across portions of west-central and southwestern Florida, and conditions are expected to deteriorate rapidly in the hurricane warning area during the next several hours. It should be emphasized that Helene is at the upper bound of hurricanes in terms of storm size and impacts are and will occur well away from the center. The large hurricane is now accelerating north-northeastward, with the latest initial motion estimated to be 025/20 kt. This general motion is expected to continue, taking the core of the major hurricane to the Florida Big Bend later this evening. After landfall, a turn to the north over Georgia is expected late tonight and early Friday, followed by a slowdown or a complete stall over the Tennessee Valley late Friday and Saturday when Helene merges with a mid- to upper-level low. The hurricane has intensified by 30 kt since sunrise and given the conducive environmental conditions and contracting inner core, it seems likely that Helene will be at or very near category 4 strength when it makes landfall in the Florida Big Bend this evening. The fast forward speed when Helene moves inland will result in a far inland penetration of strong winds over parts of the southeastern United States, including strong gusts over the higher terrain of the southern Appalachians. Accordingly, a higher-than-normal gust factor is indicated in the official forecast while Helene is inland. KEY MESSAGES: 1. A catastrophic and deadly storm surge will occur along portions of the Florida Big Bend coast, where inundation could reach as high as 20 feet above ground level, along with destructive waves. If you live in this area and were told to evacuate by local officials, your opportunity to do so is almost over. There is also a danger of life-threatening storm surge along the remainder of the west coast of the Florida Peninsula. 2. Potentially catastrophic hurricane-force winds are expected within the eyewall of Helene and will spread inland over portions of northern Florida and southern Georgia when Helene makes landfall in the Florida Big Bend region this evening. Persons in these areas should be prepared to take shelter in the interior portion of a well-built structure and remain sheltered until after hazardous conditions pass. You may need to remain sheltered after the storm due to downed trees and power lines, as well as flooding, in the area. 3. Damaging wind gusts will penetrate well inland over portions of Georgia and the Carolinas tonight, particularly over the higher terrain of the southern Appalachians. Residents in these areas should be prepared for the possibility of long-duration power outages. If you use a generator after the storm, be sure it is placed outside at least 20 feet away from doors, windows, and garages to avoid deadly carbon monoxide poisoning. 4. Catastrophic and life-threatening flash and urban flooding, including numerous significant landslides, is expected across portions of the southern Appalachians through Friday. Considerable to locally catastrophic flash and urban flooding is likely for northwestern and northern Florida and the Southeast through Friday. Widespread significant river flooding and isolated major river flooding are likely. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 27.9N 84.6W 110 KT 125 MPH 12H 27/0600Z 31.5N 83.7W 90 KT 105 MPH...INLAND 24H 27/1800Z 35.8N 85.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 36H 28/0600Z 37.0N 86.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 48H 28/1800Z 37.1N 87.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 60H 29/0600Z 37.1N 87.3W 20 KT 25 MPH...POST-TROP/EXTRATROP 72H 29/1800Z...DISSIPATED $$ Forecaster Cangialosi |
