(Bloomberg) -- Helene grew to a Category 4 hurricane as it rapidly gained speed heading toward Florida’s west coast, where the massive storm threatens to push a wall of water onshore and rake a large swath of the southeastern US with tree-snapping power.
Helene is expected to make landfall late Thursday or early Friday in Florida’s rural Big Bend area. Its top winds reached 130 miles per hour west of Tampa, the US National Hurricane Center said at 6:20 p.m. local time.
NHC senior hurricane specialist John Cangialosi warned of intense storm surge as Helene pushes ashore.
“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,” Cangialosi wrote. “If you live in this area and were told to evacuate by local officials, your opportunity to do so is almost over.”
Helene’s tropical-storm-force winds extend 310 miles, which means as the hurricane’s eye crosses Florida’s shore its outer winds will have pushed beyond Atlanta. More than 275,000 customers already are without power across the southeast US, according to PowerOutage.us, with the majority in Florida.
Based on the radius of tropical-storm-strength winds, Helene will be the largest Gulf of Mexico hurricane to make landfall since Irma in 2017 and probably one of the three largest since 1988, said Phil Klotzbach, a hurricane researcher with Colorado State University.
In addition to the damage Helene inflicts on the Florida coast, forecasters are expecting severe rains and flash flooding deep into the Appalachian Mountains and the Ohio Valley. Widespread power outages also are expected.
“Because of its size and fast forward speed, Helene will be resilient to falling apart,” said Peter Mullinax, a meteorologist at the US Weather Prediction Center. “This is why tropical storm warnings extend so far north, even into parts of the Carolinas. It’s just going to take longer for the storm to dramatically weaken.”
Across the Appalachians, record or historic flooding is expected as Helene moves north, the National Weather Service in Greenville-Spartanburg said in a statement. “This will be one of the most significant weather events to happen in the western portions of the area in the modern era,” it said.
Helene is expected to bring intense thunderstorms, which will likely generate “spin-up tornadoes” far inland, said Jennifer Collins, a geosciences professor at the University of South Florida in Tampa. Those tornadoes, which tend to arrive with little warning, occur when downdrafts of rain-cooled air create fierce winds at a storm’s leading edge.
“They’re often a very small size and don’t come from the classic severe supercell storm you could easily see on radar,” Collins said.
Chuck Watson, a disaster modeler with Enki Research, wrote in a blog post Thursday that total damage and losses could exceed $20 billion.
Helene’s path is imperiling Tampa-based fertilizer producer Mosaic Co., RBC Capital Markets analyst Andrew Wong said in a note Thursday. A possible five-day outage of Mosaic’s phosphate operations in Florida could dent the company’s profit by up to $25 million by some measures.
The storm’s remnants also have the potential to damage 10% of US cotton production, mainly in eastern Alabama and Georgia, according to Commodity Weather Group. Cotton futures have risen this month on weather risks and on Tuesday reached the highest price since late June.
Mandatory and voluntary evacuations are underway in 23 counties, according to the Florida Division of Emergency Management. In addition, Florida declared an emergency in all but six of 67 counties. Georgia, North Carolina, South Carolina and Virginia have also all declared emergencies.
--With assistance from Ilena Peng, Mary Hui and Kim Chipman.
(Updates first and second paragraphs.)
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