NHC to Issue New Hurricane Storm Surge Maps to Improve Life-Saving Evacuations

By Mark Leberfinger, AccuWeather.com Staff Writer
May 12, 2014; 4:01 AM ET
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The National Hurricane Center (NHC) will issue a new experimental map this hurricane season in hopes of improving decision-making for possible coastal evacuations from a storm.

The storm surge forecast map will provide emergency management officials and the public with a better idea of where and how they could be affected by the surge brought by a hurricane.

Storm surge, or the rise in water levels with a landfalling hurricane, is the greatest threat from a hurricane, AccuWeather.com Tropical Weather Expert Dan Kottlowski said.

The remains of a house destroyed by a storm surge due to Hurricane Sandy rests submerged in a flooded depression, Friday, Nov. 2, 2012, in the Staten Island borough of New York. (AP Photo/ John Minchillo)

"Storm surge is just part of the rise in water," Kottlowski said. "Total inundation or the total rise in water from a hurricane making landfall is a combination of storm surge, tides, the shape and orientation of the coast and depth of the continental shelf."

Storm surge is associated with more than half of all hurricane deaths, Storm Surge Specialist Jamie Rhome of the NHC said.

The map will help better communicate two things: How deep the water could be from a storm surge and how far inland it could go, Rhome said.

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It's hard for people to visualize water from the ocean being pushed over land, he said.

"Most people don't experience it," he said. "People understand the wind from a hurricane because they experience wind every day."

Storm surge is very strongly tied to the exact forecast of a hurricane.

"So, if the hurricane moves a little to the left or a little to the right, then the storm surge changes dramatically," Rhome said.

A sample map from the National Hurricane Center shows storm surge potential for the New York City area from a hypothetical hurricane. (Photo/National Hurricane Center).

The map was in development well before Hurricane Sandy raked New Jersey and New York in 2012, but the hurricane helped speed up its development, Rhome said.

"Sandy highlighted the desperate need for this information," he said.

Such a map would have helped in a Sandy scenario, but couldn't have predicted the catastrophe associated with Hurricane Katrina, Kottlowski said.

"The storm surge from Katrina triggered a rise in water which caused the levees to fail," he said. "The failure of the levees was more from the levees not being built properly and local officials failing to recognize needed repairs and upgrades. Storm surge maps would have helped people affected by Sandy to understand the danger of the rise in water and would have convinced more people to evacuate. These maps would not have helped people save their property."

The map will be issued every six hours once a hurricane or tropical storm watch is issued, Rhome said.

"We hope it will greatly improve evacuation decision-making because evacuation orders are based on storm surge threat," he said.

Depending on the situation, the map forecast will be based on several hundred to several thousand scenarios. It won't be based on a worst-case scenario but on the upper band of possibilities, Rhome said.

The hurricane center is also looking for feedback on the maps for its usefulness, accuracy and how the information was used. The feedback will be used to determine whether the maps will become a part of the regular products the center issues, Rhome said.

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