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Hurricane Helene Forecast Discussion Number 13
2024-09-26 16:54:54| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Thu Sep 26 2024 020 WTNT44 KNHC 261454 TCDAT4 Hurricane Helene Discussion Number 13 NWS National Hurricane Center Miami FL AL092024 1000 AM CDT Thu Sep 26 2024 Helene is gaining strength as it approaches the Florida Big Bend. A large eye has become apparent in satellite images, and that feature has been gradually clearing out over the past few hours. Convective banding is wrapping around the eye, and recent microwave images and reports from the NOAA and Air Force Hurricane Hunter aircraft indicate than an eyewall is almost completely closed. The minimum pressure has been dropping steadily to near 960 mb, and based on the aircraft flight-level wind data, the initial intensity is estimated to have increased to 90 kt. There have been several reports of tropical-storm-force winds occurring in portions of South Florida and the Florida Keys during the past few hours. The large hurricane is picking up speed and has turned slightly to the north-northeast. The latest initial motion is 025/12 kt. A notably faster north-northeastward motion is expected through landfall, which is expected to occur in the Florida Big Bend region this evening. After Helene moves inland, it is forecast to track over Georgia and then slow down or stall over the Tennessee Valley when it merges with a mid- to upper-level low pressure system. Only minor changes were made to the previous NHC track forecast. Significant intensification is expected until Helene reaches the coast since the overall atmospheric and oceanic conditions will remain conducive. The amount of strengthening will likely depend on how much the inner core can contract and consolidate. The HWRF and HMON models show significant strengthening to category 4 status, while most of the other models are a little lower. The main message is that Helene will likely make landfall as a large major hurricane in the Florida Big Bend this evening, and all preparations in the hurricane warning area should be rushed to completion. It should also be re-emphasized that Helene is a very large hurricane. In fact, comparing the system with previous hurricanes in the Gulf of Mexico over the past couple of decades, Helene is at the upper bound in terms of size. As a result, storm surge, wind, and rainfall impacts will extend far away from the center and well outside the forecast cone, particularly on the east side. In addition, 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 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 is likely along portions of the Florida Big Bend coast, where inundation could reach as high as 20 feet above ground level, along with destructive waves. There is also a danger of life-threatening storm surge along the remainder of the west coast of the Florida Peninsula. Residents in those areas should follow advice given by local officials and evacuate if told to do so. 2. Potentially catastrophic hurricane-force winds are expected within the eyewall of Helene when it makes landfall in the Florida Big Bend region this evening. Preparations to protect life and property should be rushed to completion. Damaging and life-threatening hurricane-force winds, especially in gusts, will penetrate well inland over portions of northern Florida and southern Georgia later today and tonight where Hurricane Warnings are in effect. Strong wind gusts are also likely farther north across portions of northern Georgia and the Carolinas, particularly over the higher terrain of the southern Appalachians. 3. 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 26/1500Z 25.5N 85.5W 90 KT 105 MPH 12H 27/0000Z 28.8N 84.3W 105 KT 120 MPH 24H 27/1200Z 33.9N 84.5W 55 KT 65 MPH...INLAND 36H 28/0000Z 36.4N 86.6W 30 KT 35 MPH...POST-TROP/EXTRATROP 48H 28/1200Z 36.5N 87.5W 25 KT 30 MPH...POST-TROP/EXTRATROP 60H 29/0000Z 36.3N 87.6W 20 KT 25 MPH...POST-TROP/EXTRATROP 72H 29/1200Z 36.2N 87.2W 20 KT 25 MPH...POST-TROP/EXTRATROP 96H 30/1200Z...DISSIPATED $$ Forecaster Cangialosi
Category:Transportation and Logistics
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Summary for Hurricane Helene (AT4/AL092024)
2024-09-26 16:54:28| National Hurricane Center (Atlantic)
...HELENE STRENGTHENING AND EXPECTED TO MAKE LANDFALL IN THE FLORIDA BIG BEND THIS EVENING AS A MAJOR HURRICANE... ...PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION... As of 10:00 AM CDT Thu Sep 26 the center of Helene was located near 25.5, -85.5 with movement NNE at 14 mph. The minimum central pressure was 960 mb with maximum sustained winds of about 105 mph.
Category: Transportation and Logistics
Hurricane Helene Public Advisory Number 13
2024-09-26 16:54:28| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Thu Sep 26 2024 000 WTNT34 KNHC 261454 TCPAT4 BULLETIN Hurricane Helene Advisory Number 13 NWS National Hurricane Center Miami FL AL092024 1000 AM CDT Thu Sep 26 2024 ...HELENE STRENGTHENING AND EXPECTED TO MAKE LANDFALL IN THE FLORIDA BIG BEND THIS EVENING AS A MAJOR HURRICANE... ...PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION... SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...25.5N 85.5W ABOUT 255 MI...405 KM SW OF TAMPA FLORIDA ABOUT 290 MI...470 KM S OF APALACHICOLA FLORIDA MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...960 MB...28.35 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * Mexico Beach eastward and southward to Flamingo * Tampa Bay * Charlotte Harbor A Hurricane Warning is in effect for... * Anclote River to Mexico Beach A Hurricane Watch is in effect for... * Englewood to Anclote River, including Tampa Bay A Tropical Storm Warning is in effect for... * Florida Keys, including the Dry Tortugas * Flamingo to Anclote River, including Tampa Bay * West of Mexico Beach to the Okaloosa/Walton County Line * Flamingo northward to Little River Inlet * Lake Okeechobee * Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials. A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. Preparations to protect life and property should be rushed to completion. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area. A Hurricane Watch means that hurricane conditions are possible within the watch area. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 1000 AM CDT (1500 UTC), the center of Hurricane Helene was located near latitude 25.5 North, longitude 85.5 West. Helene is moving toward the north-northeast near 14 mph (22 km/h). A significant increase in forward speed is expected during the next 24 hours. On the forecast track, Helene will make landfall in the Florida Big Bend region this evening. After landfall, Helene is expected to turn northwestward and slow down over the Tennessee Valley on Friday and Saturday. Maximum sustained winds have increased to near 105 mph (165 km/h) with higher gusts. Additional strengthening is forecast, and Helene is expected to be a major hurricane when it reaches the Florida Big Bend coast this 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. Helene is a very large hurricane. Hurricane-force winds extend outward up to 60 miles (95 km) from the center and tropical-storm-force winds extend outward up to 345 miles (555 km). The minimum central pressure based on data from the Air Force Hurricane Hunters is 960 mb (28.35 inches). HAZARDS AFFECTING LAND ---------------------- Key Messages for Helene can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC and on the web at hurricanes.gov/text/MIATCDAT4.shtml STORM SURGE: 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. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide... Carrabelle, FL to Suwannee River, FL...15-20 ft Apalachicola, FL to Carrabelle, FL...10-15 ft Suwannee River, FL to Chassahowitzka, FL...10-15 ft Chassahowitzka, FL to Anclote River, FL...8-12 ft Indian Pass, FL to Apalachicola, FL...6-10 ft Anclote River, FL to Middle of Longboat Key, FL...5-8 ft Tampa Bay...5-8 ft Middle of Longboat Key, FL to Englewood, FL...4-7 ft East of Mexico Beach, FL to Indian Pass, FL...3-5 ft Englewood, FL to Flamingo, FL...3-5 ft Charlotte Harbor...3-5 ft The deepest water will occur along the immediate coast near and to the east of the landfall location, where the surge will be accompanied by large and dangerous waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office. For a complete depiction of areas at risk of storm surge inundation, please see the National Weather Service Peak Storm Surge Graphic, available at hurricanes.gov/graphics_at4.shtml?peakSurge. WIND: Hurricane conditions are expected within the U.S. hurricane warning area late today. Tropical storm conditions have already begun in the Florida Keys and portions of south Florida, and these conditions are expected to spread northward across the tropical storm warning areas in the southeastern U.S. through early Friday. Strong, damaging winds, especially in gusts, will likely penetrate as far inland as the higher terrain of the southern Appalachians. Tropical storm conditions are expected over portions of the warning area in western Cuba during the next couple of hours. RAINFALL: Hurricane Helene is expected to produce total rain accumulations of 4 to 8 inches over western Cuba. 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 20 inches. This rainfall will likely result in catastrophic and potentially life-threatening flash and urban flooding, along with significant river flooding. Numerous significant landslides are expected in steep terrain across the southern Appalachians. For a complete depiction of forecast rainfall associated with Hurricane Helene, please see the National Weather Service Storm Total Rainfall Graphic, available at hurricanes.gov/graphics_at4.shtml?rainqpf and the Flash Flood Risk graphic at hurricanes.gov/graphics_at4.shtml?ero. For a list of rainfall observations (and wind reports) associated this storm, see the companion storm summary at WBCSCCNS4 with the WMO header ACUS44 KWBC or at the following link: www.wpc.ncep.noaa.gov/discussions/nfdscc4.html. TORNADOES: The risk for several tornadoes will gradually increase today through tonight. The greatest threat is expected from parts of northern Florida into southeast Georgia, the Midlands and Low Country of South Carolina, and southern North Carolina. SURF: Swells generated by Helene will affect much of Florida and the coasts of Georgia and the Carolinas during the next couple of days. Swells will also continue across portions of Cuba and the Yucatan Peninsula through tonight. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 100 PM CDT. Next complete advisory at 400 PM CDT. $$ Forecaster Cangialosi
Category: Transportation and Logistics