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With catastrophic storm surge expected along Florida's coast when Hurricane Helene slams ashore Thursday, northern Gulf Coast residents Gene and Margaret Taylor understand better than anyone about the tragedy that water can bring.

As Hurricane Katrina approached in August 2005, the Taylor family fled their Gulf front home in Bay St. Louis, Mississippi, fleeing miles inland to his brother's home. The now legendary hurricane pulverized their home and community with a record-breaking 28-foot-storm surge.

Gene Taylor first thought his bare street looked like it did "when the French first arrived" in Mississippi during the late 1600s. "We could never have imagined the house would be gone," he recalled.

Helene is forecast to produce another historic surge, this one along the region where Florida’s coast wraps around the northeast corner of the Gulf of Mexico, often referred to as the “Big Bend.” Throughout the Gulf Coast, but especially here, residents are no stranger to the troubles that flow in with floodwaters.

The "catastrophic and deadly storm surge" could reach 15 to 20 feet above ground somewhere along the coast, the National Hurricane Center warned Wednesday.

Warnings ranging as high as 12 feet are in effect elsewhere along almost the entire west coast of Florida, said Jamie Rhome, the center's deputy director.

“The large size of this storm is going to push so much water," Rhome said. “When it comes to storm surge the size of the hurricane is more important than the intensity of the storm, which is hard for some people to digest."

Helene is enormous. Hurricane-force winds extend outward up to 25 miles from the center and tropical storm-force winds extend outward up to 345 miles from the center.

What is storm surge?

When the ocean level rises suddenly as a storm is making landfall. Accompanied by large and battering waves, it can cause extreme flooding, not only along the coast but miles inland along streams and rivers.

Strong winds around the eye of a hurricane cause ocean water to circulate. As a storm arrives in shallower waters along the coast, the ocean bottom disrupts that circulation and forces water upward and inland. Other influencing factors are the timing of high tide, shape of the sea floor and coast and the angle of the storm's approach.

Florida's northern Gulf Coast is particularly vulnerable. Its wide continental shelf allows water to stack up. When Hurricane Dennis neared the coast some 150 miles to the west in 2005, a 6- to 9-foot wall of water surged into the village of St. Marks, shocking residents and meteorologists alike.

How destructive is storm surge?

A cubic yard of water weighs 1,700 pounds. Imagine the force when a storm surge several yards high and miles long, topped by rough waves, batters oceanside structures for hours.

As Gene Taylor and his neighbors can attest in Mississippi, it obliterates buildings, sweeps foundations clean, and rushes over narrow barrier islands, cutting new inlets. A high tide line marked by piles of debris was found six miles inland after Katrina.

Taylor will never forget boating down the swollen and flooded Jourdan River on the morning after Katrina. He and his son first tried to reach their home by Jeep but were blocked by water in every direction. Retrieving an old Boston Whaler they had taken with them, they used a highway as a boat ramp to launch, then navigated using the electrical poles they could see under the water.

At one point, Taylor told his son to stop the boat, pointing to a pool table they were about to run over. “The table was floating on the surface with the balls and rack, exactly where it would be if a game was going to start,” he said.

As they neared Bay St. Louis, they noticed in shock that the four-lane bridge over U.S. 90 was gone.

Taylor, a U.S. Congressman at the time and former city councilman, knew most of his neighbors. As they motored south, he counted off the names of people who lived in homes that had vanished. When they got to the spot where their home had overlooked the Gulf for more than 100 years, there was nothing left.

“There wasn’t a leaf on a tree,” he said. “The only things in the trees were curtains, rugs, clothing and bed sheets.”

It was like nature had toilet-papered their yard, he joked with USA TODAY this week. As they headed back to his brother’s home, they were surprised to see 3 or 4 people on a widow’s walk – on what would have been the third floor of the home – cooking dinner on a grill.

Life-threatening storm surge

Emergency management officials and meteorologists warn over and over again that those who live near the ocean and along inland waterways that connect to the sea should evacuate away from the coast when asked.

Florida has planned and drilled for an event of this magnitude for years, U.S. Congressman Jared Moskowitz, D-Coral Gables, told USA TODAY Wednesday. Moskowitz is a former director of Florida’s state emergency management division.

“It’s going to be a historic storm surge,” Moskowitz said. He urged Floridians to heed the warnings of emergency management officials. “If they tell you to evacuate, you need to leave."

More:Florida is on storm surge watch as Idalia grows stronger: Here's what that means

Often during landfalling hurricanes, dire calls for help come in over police scanners from people who waited to late to leave as the ocean surges suddenly higher, even far inland where people never expected the ocean to reach.

Hurricane Ian’s storm surge in Southwest Florida in 2022 – estimated at a peak of 15 feet in Fort Myers Beach – prompted emergency water rescues as the sun set, but still claimed 41 lives.

No storm in recent history caused more deaths in the mainland U. S. than Katrina, with many of the more than 500 direct deaths attributed to storm surge. It delivered one of the higher surges in modern records, estimated at 24-28 feet along about 20 miles of the Mississippi coast, penetrating up to 12 miles along rivers like the Jourdan, according to the hurricane center's final report. Water surged 8 to 12 feet in Mobile Bay, and as high as 19 feet in eastern New Orleans and in St. Bernard and Plaquemines parishes.

As a result of improved forecasting and messaging, fewer people are dying in storm surge in recent years, while flooding from extreme rainfall claims a greater percentage of lives.

Last year, the peak storm surge forecast for Hurricane Idalia was very close to the level actually produced by the storm on the Florida coast south of Tallahassee, said Cody Fritz, team lead for the hurricane's storm surge unit. The goal is "to present an accurate forecast as early as possible," Fritz told USA TODAY earlier this year.

The hurricane center credits that forecast and the evacuation response from the residents of coastal communities in Levy and Taylor counties with preventing any storm surge deaths from Idalia.

Every storm is different

Simply because your area hasn't seen a huge storm surge does not mean you won't ever see one, Fritz said. Each storm and its accompanying surge can have different characteristics that contribute to the height of the water and how far inland it extends.

For the Taylors, Katrina served as a deadly reminder that no two storms are the same.

“So many people died because they thought they would be safe in a building that went through Hurricane Camille in 1969,” Taylor said. “We know of several people who swam out and said if Katrina had been at night and they couldn’t see the debris coming at them, it would have killed them.”

How high will the storm surge be:

Between the storm surge and tides, the hurricane center said the water could reach the following heights above ground in certain locations along the Florida coast:

Big Bend:

• Carrabelle to Suwannee River 15-20 feet

Panhandle:

• Apalachicola to Carrabelle 10-15 feet
• Indian Pass to Apalachicola 6-10 feet
• Mexico Beach to Indian Pass 3-5 feet

South along Gulf Coast:

• Suwannee River to Chassahowitzka 10-15 feet
• Chassahowitzka to the Anclote River 8-12 feet
• Anclote River to Middle of Longboat Key5-8 feet
• Tampa Bay 5-8 feet
• Middle of Longboat Key to Englewood 4-7 feet
• Englewood to Flamingo 3-5 ft
• Charlotte Harbor 3-5 feet
• Florida Keys 1-3 feet

Atlantic Coast:

• Flagler/Volusia County Line to South Santee River, South Carolina 1-3 feet

(This story was updated to to correct a misspelling/typo)

Dinah Voyles Pulver covers climate change and the environment for USA TODAY. She's been writing about hurricanes, tornadoes and violent weather for more than 30 years. Reach her at [email protected] or @dinahvp.