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Hurricane Helene Forecast Discussion Number 14
2024-09-26 23:04:04| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Thu Sep 26 2024 076 WTNT44 KNHC 262043 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
Category:Transportation and Logistics
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Hurricane Helene Wind Speed Probabilities Number 14
2024-09-26 23:01:44| National Hurricane Center (Atlantic)
Issued at 2100 UTC THU SEP 26 2024 230 FONT14 KNHC 262042 PWSAT4 HURRICANE HELENE WIND SPEED PROBABILITIES NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092024 2100 UTC THU SEP 26 2024 AT 2100Z THE CENTER OF HURRICANE HELENE WAS LOCATED NEAR LATITUDE 27.9 NORTH...LONGITUDE 84.6 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 110 KTS...125 MPH...205 KM/H. Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH) ATLANTIC STANDARD TIME (AST)...SUBTRACT 4 HOURS FROM Z TIME EASTERN DAYLIGHT TIME (EDT)...SUBTRACT 4 HOURS FROM Z TIME CENTRAL DAYLIGHT TIME (CDT)...SUBTRACT 5 HOURS FROM Z TIME WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST ...34 KT (39 MPH... 63 KM/H)... ...50 KT (58 MPH... 93 KM/H)... ...64 KT (74 MPH...119 KM/H)... FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE OP IS THE PROBABILITY OF THE EVENT BEGINNING DURING AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY) (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN 18Z THU AND THE FORECAST HOUR (CUMULATIVE PROBABILITY) PROBABILITIES ARE GIVEN IN PERCENT X INDICATES PROBABILITIES LESS THAN 1 PERCENT PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION WHEN THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT. PROBABILITIES FOR 34...50...64 KT SHOWN WHEN THE 5-DAY 64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT. - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - - FROM FROM FROM FROM FROM FROM FROM TIME 18Z THU 06Z FRI 18Z FRI 06Z SAT 18Z SAT 18Z SUN 18Z MON PERIODS TO TO TO TO TO TO TO 06Z FRI 18Z FRI 06Z SAT 18Z SAT 18Z SUN 18Z MON 18Z TUE FORECAST HOUR (12) (24) (36) (48) (72) (96) (120) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION KT GREENSBORO NC 34 X 3( 3) X( 3) X( 3) X( 3) X( 3) X( 3) CHARLOTTE NC 34 3 6( 9) X( 9) X( 9) X( 9) X( 9) X( 9) FLORENCE SC 34 4 3( 7) X( 7) X( 7) X( 7) X( 7) X( 7) COLUMBIA SC 34 11 22(33) X(33) X(33) X(33) X(33) X(33) LITTLE RIVER 34 4 6(10) X(10) X(10) X(10) X(10) X(10) MYRTLE BEACH 34 8 8(16) X(16) X(16) X(16) X(16) X(16) GEORGETOWN SC 34 5 1( 6) X( 6) X( 6) X( 6) X( 6) X( 6) CHARLESTON SC 34 45 8(53) X(53) X(53) X(53) X(53) X(53) BEAUFORT MCAS 34 76 3(79) X(79) X(79) X(79) X(79) X(79) ATLANTA GA 34 16 81(97) X(97) X(97) X(97) X(97) X(97) ATLANTA GA 50 X 11(11) X(11) X(11) X(11) X(11) X(11) AUGUSTA GA 34 75 18(93) X(93) X(93) X(93) X(93) X(93) SAVANNAH GA 34 90 1(91) X(91) X(91) X(91) X(91) X(91) KINGS BAY GA 34 95 1(96) X(96) X(96) X(96) X(96) X(96) KINGS BAY GA 50 8 X( 8) X( 8) X( 8) X( 8) X( 8) X( 8) WAYCROSS GA 34 99 X(99) X(99) X(99) X(99) X(99) X(99) WAYCROSS GA 50 41 X(41) X(41) X(41) X(41) X(41) X(41) WAYCROSS GA 64 2 1( 3) X( 3) X( 3) X( 3) X( 3) X( 3) MAYPORT NS FL 34 93 X(93) X(93) X(93) X(93) X(93) X(93) MAYPORT NS FL 50 5 X( 5) X( 5) X( 5) X( 5) X( 5) X( 5) JACKSONVILLE 34 99 X(99) X(99) X(99) X(99) X(99) X(99) JACKSONVILLE 50 4 X( 4) X( 4) X( 4) X( 4) X( 4) X( 4) GAINESVILLE FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) GAINESVILLE FL 50 11 X(11) X(11) X(11) X(11) X(11) X(11) DAYTONA BEACH 34 92 X(92) X(92) X(92) X(92) X(92) X(92) THE VILLAGES 34 99 X(99) X(99) X(99) X(99) X(99) X(99) ORLANDO FL 34 98 X(98) X(98) X(98) X(98) X(98) X(98) COCOA BEACH FL 34 70 X(70) X(70) X(70) X(70) X(70) X(70) PATRICK AFB 34 72 X(72) X(72) X(72) X(72) X(72) X(72) FT PIERCE FL 34 29 X(29) X(29) X(29) X(29) X(29) X(29) W PALM BEACH 34 7 X( 7) X( 7) X( 7) X( 7) X( 7) X( 7) FT LAUDERDALE 34 4 X( 4) X( 4) X( 4) X( 4) X( 4) X( 4) KEY WEST FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) NAPLES FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) FT MYERS FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) VENICE FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) TAMPA FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) TAMPA FL 50 3 X( 3) X( 3) X( 3) X( 3) X( 3) X( 3) CEDAR KEY FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) CEDAR KEY FL 50 85 X(85) X(85) X(85) X(85) X(85) X(85) CEDAR KEY FL 64 4 X( 4) X( 4) X( 4) X( 4) X( 4) X( 4) TALLAHASSEE FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) TALLAHASSEE FL 50 91 X(91) X(91) X(91) X(91) X(91) X(91) TALLAHASSEE FL 64 31 X(31) X(31) X(31) X(31) X(31) X(31) ST MARKS FL 34 99 X(99) X(99) X(99) X(99) X(99) X(99) ST MARKS FL 50 97 X(97) X(97) X(97) X(97) X(97) X(97) ST MARKS FL 64 50 X(50) X(50) X(50) X(50) X(50) X(50) APALACHICOLA 34 99 X(99) X(99) X(99) X(99) X(99) X(99) APALACHICOLA 50 55 X(55) X(55) X(55) X(55) X(55) X(55) APALACHICOLA 64 16 X(16) X(16) X(16) X(16) X(16) X(16) GFMX 290N 850W 34 99 X(99) X(99) X(99) X(99) X(99) X(99) GFMX 290N 850W 50 82 X(82) X(82) X(82) X(82) X(82) X(82) GFMX 290N 850W 64 34 X(34) X(34) X(34) X(34) X(34) X(34) PANAMA CITY FL 34 85 X(85) X(85) X(85) X(85) X(85) X(85) PANAMA CITY FL 50 3 X( 3) X( 3) X( 3) X( 3) X( 3) X( 3) DESTIN EXEC AP 34 4 X( 4) X( 4) X( 4) X( 4) X( 4) X( 4) ALBANY GA 34 99 1(99) X(99) X(99) X(99) X(99) X(99) ALBANY GA 50 75 5(80) X(80) X(80) X(80) X(80) X(80) ALBANY GA 64 9 1(10) X(10) X(10) X(10) X(10) X(10) COLUMBUS GA 34 51 30(81) X(81) X(81) X(81) X(81) X(81) COLUMBUS GA 50 1 11(12) X(12) X(12) X(12) X(12) X(12) MACON GA 34 95 5(99) X(99) X(99) X(99) X(99) X(99) MACON GA 50 5 79(84) X(84) X(84) X(84) X(84) X(84) DOTHAN AL 34 64 X(64) X(64) X(64) X(64) X(64) X(64) BIRMINGHAM AL 34 2 1( 3) X( 3) X( 3) X( 3) X( 3) X( 3) MONTGOMERY AL 34 4 1( 5) X( 5) X( 5) X( 5) X( 5) X( 5) GFMX 290N 870W 34 4 X( 4) X( 4) X( 4) X( 4) X( 4) X( 4) $$ FORECASTER CANGIALOSI
Category: Transportation and Logistics
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