Topline

Hurricane Helene strengthened into a Category 4 hurricane Thursday before forecasters expect a devastating landfall in Florida. The National Hurricane Center called for “preparations to protect life and property” to be “quickly completed.”

Important facts

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What is a storm surge?

According to the National Weather Service, a storm surge is the “unusual increase in water produced by a storm” that exceeds the normal high tide. Surges are caused by strong onshore winds from a tropical storm or hurricane, and storm surge from tropical cyclones is the leading cause of hurricane-related deaths, the National Hurricane Center said.

How much storm surge is expected?

A storm surge warning is in effect for almost all of Florida’s Gulf Coast. In its 2 p.m. update, the NHC warned that the flood could cause water to reach 15 to 20 feet from Carrabelle, Florida, to the Suwannee River; 10-15 feet from Apalachicola to Carrabelle and Suwannee River to Chassahowitzka; 8-12 feet from Chassahowitzka to Anclote River; and 6-10 feet from Indian Pass to Apalachicola. Storm surges of 5 to 8 feet and 3 to 5 feet are expected in Tampa Bay and Charlotte Harbor, respectively.

How much rain is Helene expected to bring?

Parts of the southeastern U.S. impacted by the storm are expected to receive 6 to 12 inches of rain, with isolated amounts of up to 20 inches, which is “likely to result in catastrophic and potentially life-threatening flash and urban flooding, as well as significant river flooding.”

Did Helene cause evacuation orders in Florida?

Yes. As of Thursday afternoon, the Florida Division of Emergency Management said mandatory and voluntary evacuation orders had been issued in dozens of counties, including 22 mandatory evacuation orders.

Does Helene influence the airlines?

Tampa International Airport closed to the public at 2 a.m. Thursday in anticipation of Hurricane Helene and will reopen when the storm passes. Airlines including United Airlines, Delta, JetBlue, Southwest and Frontier have issued travel warnings because of the storm and are allowing potentially affected passengers to change their plans without penalty.

Crucial quote

“A catastrophic and deadly storm surge is likely along portions of the Florida Big Bend coast,” the National Hurricane Center noted. “Preparations to protect lives and property should be completed by early Thursday.”

Important background

Helene is the eighth named storm of the Atlantic hurricane season and comes weeks after Francine made landfall in Louisiana as a Category 2 on September 11th. Forecasters predicted this year’s busiest storm season (from June 1 to November 30) the Atmospheric Administration has ever predicted – up to 25 named storms and 13 hurricanes – but the season so far has not been as active as predicted.

Further reading

ForbesHurricane Helene: Airlines issue travel warnings as storm heads toward FloridaFrom Suzanne Rowan KelleherForbesState forecasters are issuing the worst hurricane season forecast in their history – here’s whyFrom Brian BushardForbesHurricane Francine makes landfall in Category 2 LouisianaFrom Mary Whitfill Roeloffs