Hurricane Helene rapidly intensified to a 140 mph Category 4 hurricane on Thursday over the northeastern Gulf of Mexico, striking Florida’s Big Bend shortly before midnight as its strongest hurricane on record.
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In the 24 hours leading up to landfall, Helene’s winds increased 55 mph and its central pressure dropped 34 mb, down to an exceptionally low 938 mb.
By way of central pressure, Helene was the ninth most intense hurricane to hit Florida since 1900 and the most intense to hit the country’s most hurricane-prone state since Category 5 Hurricane Michael in 2018.
Helene was also the third hurricane to hit Florida’s Big Bend over the past 13 months; Category 3 Hurricane Idalia struck in August 2023 and Category 1 Hurricane Debby hit only 53 days ago, both less than 25 miles from where Helene came ashore late Thursday.
Record-shattering storm surge
The low pressure in Helene created an extra-wide wind field, with tropical storm winds extending over 450 miles across at the time of landfall, making it one of the largest landfalling U.S. hurricanes in modern records.
The breadth of strong winds swept a catastrophic storm surge onto the shallow continental shelf flanking Florida’s Gulf Coast, leading to devastating and extreme widespread flooding by late Thursday.
Storm surge records were shattered at long-term tide stations from the Tampa area northward to Cedar Key and Steinhatchee. Below are the peak storm tide levels at available gauges during Helene, which give storm surge flooding above normally dry land, along with previous recordholders:
Cedar Key: 9.29 feet (previous record 6.89 feet during Hurricane Idalia; records back to 1914)
Clearwater Beach: 6.67 feet (previous record 4.02 feet during March 1993 Storm of the Century; records back to 1973)
East Bay (Tampa): 7.2 feet (previous record 4.56 feet during Hurricane Idalia; records back to 2019)
Old Port Tampa: 6.83 feet (previous record 4.18 feet during Hurricane Idalia; records back to 1996)
St. Petersburg: 6.31 feet (previous record 3.97 feet during Hurricane Elena; records back to 1947)
A gauge along the Steinhatchee River off Riverside Drive in Steinhatchee hit 9.63 feet (above ground or MHHW), a record for the gauge, before transmission failed around 11:30 PM ET as waters were still rising.
Tidal gauges are few and far between in this stretch of Florida so we’ll not know the full scale and true peak of Helene’s storm surge until survey teams are able to reach the area in the coming days.
Based on the data available and early photos of widespread storm surge destruction in places like Cedar Key, it’s almost certain areas of the Big Bend – especially east of St. Marks in places like Fish Creek, Steinhatchee, Horseshoe Beach, Suwannee, and Cedar Key – saw the full extent of the 15 to 20 feet of storm surge forecast by the National Hurricane Center.
Helene’s core slides east of Tallahassee
Helene spared Florida’s capital its most destructive eastern side, with its center passing about 50 miles east of Tallahassee.
Winds gusted as high as 67 mph in the Capital City shortly after midnight but hurricane conditions remained farther east.
The highest reported gusts so far from Helene were from Perry, Florida, about 10 miles inland from where Helene came ashore.
Winds gusted to 99 mph at Perry-Foley Airport only minutes after Helene made official landfall and to 104 mph atop the 11-foot mast of a Doppler on Wheels or DOW mobile weather instrument at Perry Airport.
As Helene raced inland, it brought wind gusts to 96 mph to parts of south Georgia near Valdosta. Shortly before daybreak Friday, winds were gusting as high as 82 mph at Bush Field in Augusta, Georgia, over 250 miles north of where Helene made landfall 6 hours earlier.
Hurricane-hunting drones capture the worst of Helene
Much of Helene’s bluster over land was reduced by friction and by the extensive tree canopy blanketing north Florida and south Georgia.
Over water, crewed hurricane hunters flying the hurricane were rocked by Helene’s full force, but managed to jettison an uncrewed drone into the eye of Helene at its height Thursday evening.
The drone spiraled quickly downward and skimmed the top of the ocean, where it measured wind gusts as high as 158 mph before crashing into the Gulf as planned.
Though data from these new expendable drones are preliminary and subject to adjustment, they allow forecasters to measure winds at the dangerous interface where the spray from towering ocean waves kisses the air inside major hurricanes, an ultra-low altitude far too dangerous for conventional crewed hurricane hunting planes to fly.
Flash flood emergencies stretching into the southern Appalachians
By early Friday, flash flood warnings were covering north Georgia and the southern Appalachians, with over half a dozen flash flood emergencies, including a flash flood emergency for ongoing flooding across the city of Atlanta.
According to radar, upward of 20 inches of rain has fallen, with some of the highest totals so far across the Piedmont and Sandhills of South Carolina and the western mountains of North Carolina east of Asheville.
The flash flood threat will persist through today over north Georgia and into the mountains of the western Carolinas, with the potential for catastrophic flooding and significant landslides in areas of steep terrain.
Isaac becomes a hurricane, Joyce forms, and watching the Gulf (again) for next week
While Helene was moving inland overnight, Isaac in the open North Atlantic strengthened into the 6th hurricane of the 2024 season. Isaac may strengthen further but will move into the North Atlantic graveyard next week and poses no threat to land.
Meanwhile, Tropical Storm Joyce formed over the central Atlantic late Friday morning but will turn north and isn’t a threat to land.
We’ll be returning to the Gulf next week for what models indicate is yet another system lifting north from the western Caribbean.
It’s still early yet, but computer models suggest some development possible over the far southern Gulf or western Caribbean by middle to late next week. We’ll have more details as we get a clearer picture next week.
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