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Hurricane Ian is pulling water away from ocean shores. Here’s what’s happening.

Why experts say it’s dangerous to walk along shores where ocean water has receded

Onlookers take in the sights of the water in Hillsborough Bay that receded before the impact of Hurricane Ian on Wednesday. (Octavio Jones/For The Washington Post)

Just hours before Hurricane Ian thrashed Florida, water from beaches up and down the coast was sucked away. Crashing waves and shallow shoreline were replaced by the ocean’s sandy barren bottom. Shards of white seashells and drying seaweed poked out from the muck.

Tampa-area residents shared videos of moving water that had been funneled from the coast to the new shoreline on the horizon. Beaches spanning the coast were temporarily sucked dry, with reports from coastlines near Tampa Bay, Punta Gorda and Osprey.

“Charlotte Harbor is going in reverse,” tweeted Brett Adair in a video that showed water moving away from the coast.

The phenomenon is called a negative storm surge — also known as a blowout tide — and it’s what happens when offshore hurricane winds push water from the coast, leaving beaches desolate. Blowout tides are the opposite of storm surge, which fiercely pushes water over the shore.

Blowout tides pose their own threat, depending on the location relative to the eye of the storm.

As Ian approached southwestern Florida from the Gulf of Mexico side, areas north of the center saw water sucked away from the shore; areas south of the storm encountered the same thing, except the water would subsequently return with a vengeance.

Video from Sept. 28 on Bayshore Boulevard in Tampa shows bare sand after Hurricane Ian gathered water offshore as the storm grew. (Video: @dougie_doowop via Twitter)

“People can let their guard down when they see the water receding. and think that their risk is lower … it can be a false sense of security and the water can rush back in very quickly when the winds change direction,” said Hal Needham, an extreme weather and disaster scientist with GeoTrek.

When Needham, who is in Punta Gorda, walked along the beach Tuesday, he saw waves that went all the way up the sea wall. When he strolled the bay an hour ago, the area that was once harbor had turned dry.

Hurricane Irma drained the water from Florida’s largest bays — but it wasn’t gone for long

“You can just tell that the forces of nature are at work,” Needham said. “It makes you realize this is not normal weather and a lot of strange things are going on.”

While many residents may be tempted to stroll across the sand bed that used to be ocean, experts warn that this could be dangerous.

“STOP: Do not walk out into receding water in Tampa Bay or Charlotte Harbor — the water WILL return through storm surge and poses a life-threatening risk” the Florida Division of Emergency Management said in a tweet.

As with the similar telltale signs of a tsunami, experts warn that if you see ocean water drain away suddenly, get as far away from the water as possible.

Between Port Charlotte and Naples, forecasters at the National Hurricane Center warned of a life-threatening surge of up to 18 feet.

“We’ll get a strong onshore wind and the storm surge will rapidly push it. And it can move in so quickly that it really takes people off guard and that’s why it’s such a destructive hazard,” Needham said.

North of the storm center, in Tampa, where winds were primarily blowing from the land toward the ocean, the negative surge was expected to reach 12 feet before winds reversed and brought in a positive surge of a few feet Wednesday night.

In September 2017, when Category 4 Hurricane Irma hit Florida, residents similarly flocked to Tampa Bay in droves to see the bare, waterless beaches. Irma’s exceptional ocean pull gobbled shore waters into its center before spewing it back in a damaging storm surge when the winds shifted as the eye of the storm passed. Five years ago, tidal gauges in Naples reported a 6-foot dip between sunrise and 2 p.m. before the water climbed 5.5 feet in an hour, an inch per minute.

The Atlantic hurricane season

The latest: The 2022 season started out slow, but has rapidly intensified this fall with conditions prime for storms. Fiona brought severe flooding to Puerto Rico before making landfall in Canada, and now we’re tracking Hurricane Ian as it heads for Florida. For the seventh year in a row, hurricane officials expect an above-average season of hurricane activity.

Tips for preparing: We rounded up seven safety tips to help you get ready for hurricanes. Here’s some other guidance about keeping your phone charged and useful in dangerous weather, and what to know about flood insurance.

Understanding climate change: It’s not just you — hurricanes and tropical storms have hit the U.S. more frequently in recent years. And last summer alone, nearly 1 in 3 Americans experienced a weather disaster. Read more about how climate change is fueling severe weather events.