National Hurricane Center (NHC) Atlantic Map

Issued at 2100 UTC THU SEP 26 2024 000 FONT15 KNHC 262051 PWSAT5 TROPICAL STORM ISAAC WIND SPEED PROBABILITIES NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102024 2100 UTC THU SEP 26 2024 AT 2100Z THE CENTER OF TROPICAL STORM ISAAC WAS LOCATED NEAR LATITUDE 37.5 NORTH...LONGITUDE 50.6 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 45 KTS...50 MPH...85 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 SANTA CRUZ AZO 34 X X( X) X( X) 1( 1) 11(12) 3(15) X(15) $$ FORECASTER D. ZELINSKY

Issued at 500 PM AST Thu Sep 26 2024 231 WTNT35 KNHC 262051 TCPAT5 BULLETIN Tropical Storm Isaac Advisory Number 4 NWS National Hurricane Center Miami FL AL102024 500 PM AST Thu Sep 26 2024 ...ISAAC CONTINUING EASTWARD WITH NO CHANGE IN STRENGTH... SUMMARY OF 500 PM AST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...37.5N 50.6W ABOUT 1285 MI...2070 KM W OF THE AZORES ABOUT 880 MI...1415 KM ENE OF BERMUDA MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...E OR 80 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...995 MB...29.39 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 500 PM AST (2100 UTC), the center of Tropical Storm Isaac was located near latitude 37.5 North, longitude 50.6 West. Isaac is moving toward the east near 10 mph (17 km/h), and a turn toward the east-northeast is expected by the weekend. Maximum sustained winds are near 50 mph (85 km/h) with higher gusts. Strengthening is forecast, and Isaac is expected reach or be near hurricane strength by late Friday or early Saturday. Tropical-storm-force winds extend outward up to 60 miles (95 km) from the center. The estimated minimum central pressure is 995 mb (29.39 inches). HAZARDS AFFECTING LAND ---------------------- SURF: Swells generated by Isaac and a large wind fetch from a deep-layer trough are affecting portions of the coast of Bermuda and could spread into the Azores by this weekend. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next complete advisory at 1100 PM AST. $$ Forecaster D. Zelinsky/Bookbinder

...ISAAC CONTINUING EASTWARD WITH NO CHANGE IN STRENGTH... As of 5:00 PM AST Thu Sep 26 the center of Isaac was located near 37.5, -50.6 with movement E at 10 mph. The minimum central pressure was 995 mb with maximum sustained winds of about 50 mph.

Issued at 2100 UTC THU SEP 26 2024 000 WTNT25 KNHC 262050 TCMAT5 TROPICAL STORM ISAAC FORECAST/ADVISORY NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102024 2100 UTC THU SEP 26 2024 TROPICAL STORM CENTER LOCATED NEAR 37.5N 50.6W AT 26/2100Z POSITION ACCURATE WITHIN 30 NM PRESENT MOVEMENT TOWARD THE EAST OR 80 DEGREES AT 9 KT ESTIMATED MINIMUM CENTRAL PRESSURE 995 MB MAX SUSTAINED WINDS 45 KT WITH GUSTS TO 55 KT. 34 KT....... 30NE 40SE 50SW 40NW. 12 FT SEAS.. 60NE 120SE 180SW 210NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 37.5N 50.6W AT 26/2100Z AT 26/1800Z CENTER WAS LOCATED NEAR 37.4N 51.2W FORECAST VALID 27/0600Z 37.6N 48.7W MAX WIND 50 KT...GUSTS 60 KT. 50 KT... 0NE 30SE 0SW 0NW. 34 KT... 40NE 50SE 50SW 40NW. FORECAST VALID 27/1800Z 38.2N 45.5W MAX WIND 60 KT...GUSTS 75 KT. 50 KT... 0NE 40SE 30SW 0NW. 34 KT... 50NE 70SE 60SW 50NW. FORECAST VALID 28/0600Z 39.2N 42.0W MAX WIND 65 KT...GUSTS 80 KT. 64 KT... 0NE 20SE 0SW 0NW. 50 KT... 30NE 40SE 40SW 30NW. 34 KT... 80NE 90SE 80SW 60NW. FORECAST VALID 28/1800Z 40.5N 38.7W MAX WIND 65 KT...GUSTS 80 KT. 64 KT... 0NE 20SE 0SW 0NW. 50 KT... 40NE 50SE 40SW 40NW. 34 KT...110NE 130SE 90SW 100NW. FORECAST VALID 29/0600Z 41.9N 35.9W MAX WIND 60 KT...GUSTS 75 KT. 50 KT... 50NE 50SE 40SW 50NW. 34 KT...150NE 130SE 110SW 130NW. FORECAST VALID 29/1800Z 43.0N 33.8W MAX WIND 60 KT...GUSTS 75 KT. 50 KT... 50NE 60SE 50SW 50NW. 34 KT...160NE 120SE 110SW 140NW. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 125 NM ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 30/1800Z 44.2N 27.8W...POST-TROP/EXTRATROP MAX WIND 50 KT...GUSTS 60 KT. 50 KT... 0NE 50SE 50SW 0NW. 34 KT...130NE 100SE 90SW 120NW. OUTLOOK VALID 01/1800Z 45.5N 22.5W...POST-TROP/EXTRATROP MAX WIND 40 KT...GUSTS 50 KT. 34 KT...110NE 90SE 80SW 120NW. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 37.5N 50.6W NEXT ADVISORY AT 27/0300Z $$ FORECASTER D. ZELINSKY

Issued at 2100 UTC THU SEP 26 2024 007 WTNT24 KNHC 262040 TCMAT4 HURRICANE HELENE FORECAST/ADVISORY NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092024 2100 UTC THU SEP 26 2024 HURRICANE CENTER LOCATED NEAR 27.9N 84.6W AT 26/2100Z POSITION ACCURATE WITHIN 20 NM PRESENT MOVEMENT TOWARD THE NORTH-NORTHEAST OR 25 DEGREES AT 20 KT ESTIMATED MINIMUM CENTRAL PRESSURE 951 MB MAX SUSTAINED WINDS 110 KT WITH GUSTS TO 135 KT. 64 KT....... 50NE 50SE 30SW 40NW. 50 KT.......100NE 100SE 50SW 50NW. 34 KT.......240NE 270SE 100SW 120NW. 12 FT SEAS..120NE 310SE 390SW 210NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 27.9N 84.6W AT 26/2100Z AT 26/1800Z CENTER WAS LOCATED NEAR 26.7N 84.9W FORECAST VALID 27/0600Z 31.5N 83.7W...INLAND MAX WIND 90 KT...GUSTS 110 KT. 64 KT... 40NE 40SE 30SW 0NW. 50 KT...100NE 100SE 50SW 40NW. 34 KT...240NE 270SE 120SW 90NW. FORECAST VALID 27/1800Z 35.8N 85.0W...POST-TROP/EXTRATROP MAX WIND 40 KT...GUSTS 60 KT. 34 KT...120NE 330SE 0SW 0NW. FORECAST VALID 28/0600Z 37.0N 86.5W...POST-TROP/EXTRATROP MAX WIND 30 KT...GUSTS 40 KT. FORECAST VALID 28/1800Z 37.1N 87.0W...POST-TROP/EXTRATROP MAX WIND 25 KT...GUSTS 35 KT. FORECAST VALID 29/0600Z 37.1N 87.3W...POST-TROP/EXTRATROP MAX WIND 20 KT...GUSTS 30 KT. FORECAST VALID 29/1800Z...DISSIPATED REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 27.9N 84.6W INTERMEDIATE PUBLIC ADVISORY...WTNT34 KNHC/MIATCPAT4...AT 27/0000Z NEXT ADVISORY AT 27/0300Z $$ FORECASTER CANGIALOSI

5-Day Uncertainty Track last updated Thu, 26 Sep 2024 20:47:23 GMT


Wind Speed Probabilities last updated Thu, 26 Sep 2024 20:47:23 GMT

Storm Surge Watch/Warning Map last updated Thu, 26 Sep 2024 20:44:30 GMT

Issued at 400 PM EDT Thu Sep 26 2024 000 WTNT64 KNHC 261955 TCUAT4 Hurricane Helene Tropical Cyclone Update NWS National Hurricane Center Miami FL AL092024 400 PM EDT Thu Sep 26 2024 ...HELENE ACCELERATING TOWARD THE FLORIDA BIG BEND... ...TROPICAL STORM CONDITIONS OCCURING ACROSS MOST OF THE WEST COAST OF FLORIDA... Data from an Air Force Hurricane Hunter aircraft indicate that the minimum pressure of Helene has decreased to 951 mb (28.08 inches). A Weatherflow station at Egmont Channel at the entrance to Tampa Bay recently measured a sustained wind of 54 mph (87 km/h) and a gust to 68 mph (109 km/h). The Sarasota-Bradenton International Airport recently measured a sustained wind of 43 mph (69 km/h) and a gust to 63 mph (101 km/h). SUMMARY OF 400 PM EDT...2000 UTC...INFORMATION ---------------------------------------------- LOCATION...27.3N 84.7W ABOUT 145 MI...235 KM WSW OF TAMPA FLORIDA ABOUT 165 MI...265 KM S OF APALACHICOLA FLORIDA MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 21 MPH...33 KM/H MINIMUM CENTRAL PRESSURE...951 MB...28.08 INCHES $$ Forecaster D. Zelinsky

...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... As of 5:00 PM EDT Thu Sep 26 the center of Helene was located near 27.9, -84.6 with movement NNE at 23 mph. The minimum central pressure was 951 mb with maximum sustained winds of about 125 mph.

Issued at 300 PM EDT Thu Sep 26 2024 000 WTNT64 KNHC 261856 TCUAT4 Hurricane Helene Tropical Cyclone Update NWS National Hurricane Center Miami FL AL092024 300 PM EDT Thu Sep 26 2024 ...STORM SURGE AND WINDS INCREASING ALONG THE FLORIDA WEST COAST... ...300 PM EDT POSITION UPDATE... A Weatherflow station at Egmont Channel at the entrance to Tampa Bay recently measured a sustained wind of 50 mph (80 km/h) and a gust to 62 mph (100 km/h). SUMMARY OF 300 PM EDT...1900 UTC...INFORMATION ---------------------------------------------- LOCATION...26.9N 84.8W ABOUT 160 MI...255 KM WSW OF TAMPA FLORIDA ABOUT 195 MI...315 KM S OF APALACHICOLA FLORIDA MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 20 MPH...31 KM/H MINIMUM CENTRAL PRESSURE...959 MB...28.32 INCHES $$ Forecaster Berg

...STORM SURGE AND WINDS INCREASING ALONG THE FLORIDA WEST COAST... ...300 PM EDT POSITION UPDATE... As of 3:00 PM EDT Thu Sep 26 the center of Helene was located near 26.9, -84.8 with movement NNE at 20 mph. The minimum central pressure was 959 mb with maximum sustained winds of about 120 mph.

Issued at 225 PM EDT Thu Sep 26 2024 000 WTNT64 KNHC 261825 TCUAT4 Hurricane Helene Tropical Cyclone Update NWS National Hurricane Center Miami FL AL092024 225 PM EDT Thu Sep 26 2024 ...AIR FORCE HURRICANE HUNTERS FIND HELENE A MAJOR HURRICANE... The Air Force Hurricane Hunters found that the maximum sustained winds have increased to near 120 mph (195 km/h). This makes Helene a dangerous category 3 major hurricane. Additional strengthening is expected before Helene makes landfall in the Florida Big Bend this evening. SUMMARY OF 225 PM EDT...1825 UTC...INFORMATION ---------------------------------------------- LOCATION...26.7N 84.9W ABOUT 170 MI...280 KM WSW OF TAMPA FLORIDA ABOUT 205 MI...335 KM S OF APALACHICOLA FLORIDA MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 16 MPH...26 KM/H MINIMUM CENTRAL PRESSURE...959 MB...28.32 INCHES $$ Forecaster Cangialosi/Berg/Brown

...AIR FORCE HURRICANE HUNTERS FIND HELENE A MAJOR HURRICANE... As of 2:25 PM EDT Thu Sep 26 the center of Helene was located near 26.7, -84.9 with movement NNE at 16 mph. The minimum central pressure was 959 mb with maximum sustained winds of about 120 mph.

Issued at 100 PM CDT Thu Sep 26 2024 000 WTNT34 KNHC 261747 TCPAT4 BULLETIN Hurricane Helene Intermediate Advisory Number 13A NWS National Hurricane Center Miami FL AL092024 100 PM CDT Thu Sep 26 2024 ...HELENE ALMOST A MAJOR HURRICANE WITH ADDITIONAL STRENGTHENING FORECAST BEFORE LANDFALL IN THE FLORIDA BIG BEND... ...PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION... SUMMARY OF 100 PM CDT...1800 UTC...INFORMATION ---------------------------------------------- LOCATION...26.4N 85.0W ABOUT 195 MI...315 KM SW OF TAMPA FLORIDA ABOUT 230 MI...365 KM S OF APALACHICOLA FLORIDA MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H PRESENT MOVEMENT...NNE OR 25 DEGREES AT 16 MPH...26 KM/H MINIMUM CENTRAL PRESSURE...959 MB...28.32 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Cuba has discontinued the tropical storm warning for the island. 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 100 PM CDT (1800 UTC), the center of Hurricane Helene was located near latitude 26.4 North, longitude 85.0 West. Helene is moving toward the north-northeast near 16 mph (26 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 110 mph (175 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). A weather station in Tarpon Point recently reported a sustained wind of 41 mph (67 km/h) with a gust to 54 mph (87 km/h). The minimum central pressure based on data from the Air Force Hurricane Hunters is 959 mb (28.32 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 occurring in the Florida Keys and portions of southern and southwestern 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: 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 complete advisory at 400 PM CDT. Hourly position and intensity information will be provided in Tropical Cyclone Updates beginning at 300 PM EDT/200 PM CDT. $$ Forecaster Cangialosi

...HELENE ALMOST A MAJOR HURRICANE WITH ADDITIONAL STRENGTHENING FORECAST BEFORE LANDFALL IN THE FLORIDA BIG BEND... ...PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION... As of 1:00 PM CDT Thu Sep 26 the center of Helene was located near 26.4, -85.0 with movement NNE at 16 mph. The minimum central pressure was 959 mb with maximum sustained winds of about 110 mph.

000
ABNT20 KNHC 261739
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Thu Sep 26 2024

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Active Systems:
The National Hurricane Center is issuing advisories on Hurricane
Helene, located over the eastern Gulf of Mexico and on Tropical
Storm Isaac, located over the central Subtropical Atlantic Ocean.

Eastern and Central Tropical Atlantic (AL98):
Showers and thunderstorms associated with an area of low pressure
located several hundred miles west of the Cabo Verde Islands
continue to show signs of organization. Recent satellite imagery
suggests the system does not yet have a well-defined surface
circulation. However, environmental conditions are expected to be
conducive for further development. A tropical depression is
expected to form later today or tomorrow while the disturbance
moves generally westward to west-northwestward at 10 to 15 mph. The
system is then forecast to slow down and turn northward late Friday
and Saturday.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 7 days...high...90 percent.

Western Caribbean:
An area of low pressure could form over the western Caribbean by the
middle of next week. Environmental conditions are expected to be
conducive for slow development thereafter, while the system moves
generally northwestward.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.

&&
Public Advisories on Tropical Storm Isaac are issued under WMO
header WTNT35 KNHC and under AWIPS header MIATCPAT5.
Forecast/Advisories on Tropical Storm Isaac are issued under WMO
header WTNT25 KNHC and under AWIPS header MIATCMAT5.

$$
Forecaster D. Zelinsky/Bookbinder

Potential Storm Surge Flooding Map last updated Thu, 26 Sep 2024 15:54:26 GMT

Probabilistic Storm Surge Graphics last updated Thu, 26 Sep 2024 15:40:02 GMT

5-Day Uncertainty Track last updated Thu, 26 Sep 2024 14:56:01 GMT


Wind Speed Probabilities last updated Thu, 26 Sep 2024 15:23:16 GMT

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