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Hurricane watchers to emphasize storm surge danger

As Hurricane Ike loomed off Texas in September, thousands along the coast decided to stay put. It was only a Category 2 storm, probably not enough to blow off roofs or break windows, they assumed.

But Ike created a storm surge of up to 18 feet, enough to take down large granite buildings and concrete fuel tanks, and wash away 3,800 homes.

The water rose gradually, but the streets flooded before those hunkering down could flee. Texas emergency officials risked their lives to rescue more than 600 people trapped in the rushing water. They couldn't save a woman who tied herself to a bridge that failed, along with about 20 others killed by Ike.

"Make no mistake," said John Simsen, Galveston County's emergency management coordinator, "the power of a wall of water is devastating. You just can't imagine it until you live it."

The experience has prompted the National Hurricane Center to put more emphasis on storm surge this hurricane season, which starts today and ends Nov. 30. Too many people in Texas didn't realize how deadly and destructive storm surge could be.

The same scenario could easily happen in the Tampa Bay area, Simsen warned. In fact, it could be worse.

Storm surge is the single greatest hurricane threat facing Tampa Bay, emergency officials say.

"Seems like I remember you guys have a hospital right near the water, right?" Simsen said, referring to Tampa General Hospital. "Yeah … that's not good."

• • •

Emergency officials have long used the battle cry "run from the water, hide from the wind" to drive home dire warnings of storm surge.

Too many people still don't get it.

Many have become conditioned, and at times comforted, by the Saffir-Simpson Hurricane Scale, which predicts potential damage based on wind levels. Emergency officials have devised charts showing shingles blowing off roofs and palm trees bending as winds increase.

But that's not enough, hurricane experts now say. People need to worry about storm surge first, storm category second — especially in the Tampa Bay area, which hasn't had a direct hit by a hurricane since 1921.

So this year, the National Hurricane Center is removing all storm surge and flooding values from its Saffir-Simpson scale. Researchers are working to create a separate storm surge warning that's easy for the public to digest.

Forecasters will start using words like "inundation" and "probabilistic storm surge" in their advisories.

All you really need to know, said Hillsborough County emergency management director Larry Gispert, is that if a hurricane comes here, "we're all going to be in the same bathtub."

• • •

Like Galveston, much of the Tampa Bay area is surrounded by a low continental shelf. That's why you can go to the beach and walk out into the water for quite a ways before your head is underwater.

That kind of shallow graduation makes it a lot easier for gulf waters to slosh right up onto land — and over homes, cars, buildings, highways, animals and people. Experts predict that a worst-case scenario — a Category 5 storm with a large radius, slowly moving south to north and hitting landfall somewhere between north Pinellas and Pasco counties — could create up to 30 feet of storm surge.

In that scenario, throw out everything you've always thought about flood zones and elevation levels. It's not just the beach and coastal areas that would disappear.

Miles of homes and businesses would be washed away, said Pinellas County emergency management's Tom Iovino. Areas such as Oldsmar, Snell Isle, downtown St. Petersburg, Ybor City and all of South Tampa would be underwater.

Even those areas not generally prone to flooding could get "inundation," National Hurricane Center spokesman Dennis Feltgen said. That word will be used a lot in hurricane advisories and will help people understand exactly how much water they'll get in their neighborhood if and when a storm makes landfall.

For example, if a 20-foot storm surge is predicted and your home's elevation is 11 feet above sea level, you will get 9 feet of water inundation.

Hurricane Center officials are also working on a special storm surge warning that will complement the Saffir-Simpson scale. It's being developed and tested, and could be implemented in the next few years, Feltgen said.

Gispert and other local emergency officials hope the added emphasis on storm surge, rather than storm category, will change attitudes. Hurricanes like Ike and Katrina have already helped publicize the dangers of water vs. wind.

Those who have lived through it, like Galveston's Simsen, are happy to share their stories and advice.

"Pay no attention to storm category," he said. "Leave, and leave early."

But he knows something scary about the Tampa Bay area, or anywhere else that faces a hurricane threat this season.

Some people still won't leave.

Emily Nipps can be reached at nipps@sptimes.com or (727) 893-8452.

The "new" Saffir-Simpson wind scale

This season, the National Hurricane Center is removing all mention of storm surge from the old Saffir-Simpson Hurricane Scale models. The new scale will focus exclusively on wind damage and forecasters will estimate storm surge separately, rather than attach storm surge values to the storm's predicted intensity. Here are the five categories of hurricanes:

Category 1: Sustained winds of 74 to 95 mph. Some damage could occur to buildings, poorly constructed signs, trees.

Category 2: Sustained winds of 96 to 110 mph. Some roofing material, door and window damage of buildings will occur. Considerable damage to mobile homes (mainly pre-1994 construction) and power lines.

Category 3: Sustained winds of 111 to 130 mph. Some damage to houses and buildings will occur with a minor amount of wall failures. Near total power loss with outages that could last from several days to weeks.

Category 4: Sustained winds of 131 to 155 mph. Damage to windows, doors and roofs. Windborne debris will cause extensive damage, and people struck by debris could be injured or killed. Most trees will be snapped or uprooted.

Category 5: Sustained winds greater than 155 mph. Complete roof failure on many homes and industrial buildings will occur. Small buildings could be blown over or away. Power outages will last for weeks to possibly months.

Hurricane watchers to emphasize storm surge danger 05/29/09 [Last modified: Sunday, May 31, 2009 8:07pm]

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