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Storm surge concerns for Florida ahead of Helene. Here’s what storm surge is and why it’s dangerous

Hurricane Helene set to make landfall in Florida on Thursday

St. Pete Beach is No. 1 beach in the U.S. for 2021, according to TripAdvisor travelers. (Image: Visit St. Pete/Clearwater) (WKMG 2021)

Helene is expected to ram into Florida on Thursday as a major hurricane, bringing heavy wind and rain into the Sunshine State.

So far, Helene has been approaching Florida’s Gulf Coast while it continues to strengthen, prompting coastal communities to brace for impact.

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As a result, a storm surge warning has been put into effect for most of the state’s Gulf Coast, according to the NOAA.

Storm surge warnings along Florida's Gulf Coast as of 2 a.m. on Sept. 26 (National Oceanic and Atmospheric Administration)

WHAT IS STORM SURGE?

The NOAA defines storm surge as “the abnormal rise in seawater level during a storm, measured as the height of the water above the normal predicted astronomical tide.”

This surge is typically sparked by storm winds pushing water onshore, though how high the surge reaches depends on factors like the storm’s path, intensity, size, and speed.

Meanwhile, storm tide is the combination of a given storm surge and the regular astronomical tide.

This example illustrates water level differences for storm surge, storm tide, and a normal (predicted) high tide as compared to sea level. Storm surge is the rise in seawater level caused solely by a storm. Storm tide is the total observed seawater level during a storm, which is the combination of storm surge and normal high tide. (National Oceanic and Atmospheric Administration)

HOW MUCH STORM SURGE IS PREDICTED?

As of the NHC’s most recent predictions on Wednesday night, the Big Bend area of Florida’s Gulf Coast — where Helene is expected to touch down in the state — could see as much as 20 feet of storm surge.

Closer to Central Florida, Tampa Bay is expected to receive around 5-8 feet of storm surge as Helene passes by.

Even down in the Florida Keys or up along Georgia’s Atlantic Coast, storm surge could still reach between 1-3 feet thanks to Helene’s rampage.

Peak Storm Surge Forecast (Sept. 25 at 11 p.m.) - Water levels along the immediate coast could reach the following heights above ground level within the indicated areas. Elevated water levels will likely be accompanied by large and destructive waves. (National Oceanic and Atmospheric Administration)

Many areas along the Gulf Coast have already been designated as vulnerable “evacuation zones” by the Florida Division of Emergency Management.

To see whether your location is in an evacuation zone, click here.