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Hurricane Helene Public Advisory Number 14
2024-09-26 22:59:09| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Thu Sep 26 2024 618 WTNT34 KNHC 262042 TCPAT4 BULLETIN Hurricane Helene Advisory Number 14 NWS National Hurricane Center Miami FL AL092024 500 PM EDT Thu Sep 26 2024 ...HELENE IS A VERY DANGEROUS AND LARGE MAJOR HURRICANE... ...DAMAGING HURRICANE WINDS AND CATASTROPHIC STORM SURGE EXPECTED TO BEGIN IN THE FLORIDA BIG BEND THIS EVENING... SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...27.9N 84.6W ABOUT 130 MI...205 KM W OF TAMPA FLORIDA ABOUT 175 MI...280 KM S OF TALLAHASSEE FLORIDA MAXIMUM SUSTAINED WINDS...125 MPH...205 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 23 MPH...37 KM/H MINIMUM CENTRAL PRESSURE...951 MB...28.09 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 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 500 PM EDT (2100 UTC), the eye of Hurricane Helene was located near latitude 27.9 North, longitude 84.6 West. Helene is moving toward the north-northeast near 23 mph (37 km/h). A continued fast motion to the north-northeast is expected through landfall in the Florida Big Bend 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 125 mph (205 km/h) with higher gusts. Helene is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Additional strengthening is expected, and Helene will likely be an extremely dangerous category 4 hurricane at landfall. Weakening is expected after Helene moves inland, but the 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. Hurricane-force winds extend outward up to 60 miles (95 km) from the center and tropical-storm-force winds extend outward up to 310 miles (500 km). A weather station at Venice Municipal Airport recently reported a sustained wind of 46 mph (74 km/h) with a gust of 69 mph (111 km/h). Another observation near Venice Beach reported a sustained wind of 51 mph (82 km/h) with a gust to 66 mph (106 km/h). The estimated minimum central pressure based on data from the Air Force Hurricane Hunters is 951 mb (28.09 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 hurricane warning area this evening. Tropical storm conditions are occurring in the southern and central 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. RAINFALL: 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 continues through tonight over much of Florida, southeast Georgia, central and southern South Carolina, and southern North Carolina. The tornado risk will continue Friday across the Carolinas and southern Virginia. SURF: Swells generated by Helene will affect much of Florida and the coasts of Georgia and the Carolinas during the next couple of days. 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 800 PM EDT. Next complete advisory at 1100 PM EDT. $$ Forecaster Cangialosi
Category:Transportation and Logistics
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Tropical Storm Isaac Graphics
2024-09-26 22:54:33| National Hurricane Center (Atlantic)
5-Day Uncertainty Track last updated Thu, 26 Sep 2024 20:54:33 GMT Wind Speed Probabilities last updated Thu, 26 Sep 2024 20:54:33 GMT
Category: Transportation and Logistics
Tropical Storm Isaac Forecast Discussion Number 4
2024-09-26 22:52:34| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Sep 26 2024 000 WTNT45 KNHC 262052 TCDAT5 Tropical Storm Isaac Discussion Number 4 NWS National Hurricane Center Miami FL AL102024 500 PM AST Thu Sep 26 2024 Little change with the structure of Isaac has been noted this afternoon. Episodic bursts of deep convection have been observed over the western semi-circle throughout the day, but cloud tops have largely failed to break -60C. There remains a relative void of thunderstorms over the eastern half of Isaac's circulation as it traverses across 26C water. ASCAT passes, combined with a blend of subjective Dvorak estimates from TAFB and SAB, plus objective estimates from UW-CIMSS collectively support maintaining an initial intensity of 45 kt for this advisory. For the next couple of days, the track guidance is tightly clustered as Isaac continues on a general east to east-northeast heading, remaining embedded within a well established mid-latitude trough. Beyond Saturday, there has been a large change in the dynamic model suite. A vast majority of the the guidance, including the deterministic ECMWF and several of its ensemble members, have shown a rather dramatic poleward shift, similar to previous runs of the GFS. This is ultimately induced by a slight decrease in forward speed, which in turn allows Isaac to be steered by a strong closed mid-latitude trough digging out of eastern Canada into the north Atlantic. This would force Isaac to the northeast and eventually northward. Isaac's medium range track confidence is quite low, owing to lack of model consistency during the past several runs. To avoid making too large of a change, the forecast track after Day 3 has shifted to the left for this advisory. However, it falls well to the east of the guidance envelope and further large changes may be needed. Despite the longer range track uncertainty, Isaac appears to be in an environment that should be generally conducive for some strengthening, especially during the next day or two. After that, unusually cold upper-tropospheric temperatures should help sustain the tropical cyclone for a while, even as it moves over colder SSTs in the 24-25 deg C range. By the end of the forecast period, much colder SSTs and a dramatic increase in shear should cause Isaac to become post-tropical. This transition could occur more quickly than forecast if the system takes a more northerly turn early next week. No changes of note were made to the official intensity forecast, which still shows Isaac reaching hurricane strength during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 37.5N 50.6W 45 KT 50 MPH 12H 27/0600Z 37.6N 48.7W 50 KT 60 MPH 24H 27/1800Z 38.2N 45.5W 60 KT 70 MPH 36H 28/0600Z 39.2N 42.0W 65 KT 75 MPH 48H 28/1800Z 40.5N 38.7W 65 KT 75 MPH 60H 29/0600Z 41.9N 35.9W 60 KT 70 MPH 72H 29/1800Z 43.0N 33.8W 60 KT 70 MPH 96H 30/1800Z 44.2N 27.8W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 01/1800Z 45.5N 22.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster D. Zelinsky/Bookbinder
Category: Transportation and Logistics