What is a storm surge? Why is it so dangerous?

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It’s no secret that tropical storms and hurricanes produce damaging winds and unleash heavy rains that can lead to deadly flooding. But what is perhaps less obvious is that the storm surges they produce can be just as destructive and often pose the greatest threat to life and property along coastlines.

A storm surge is an abnormal rise in water generated by a storm, beyond the predicted astronomical tides, according to the National Hurricane Center. It is caused when the force of the winds moving cyclonically around the storm pushes water towards the shore.

The height of a storm surge depends on the size of the storm, its forward motion and angle of approach, as well as the depth of the coastline, said Dennis Feltgen, meteorologist and spokesman for the National Hurricane Center. A change in a storm’s track, even just 20 miles, can make a difference, he said, and every mile of coastline along the eastern United States and the Gulf of Mexico is sensitive. storm surges from tropical cyclones.

“Storm surges have historically been the leading cause of death from tropical cyclones,” accounting for about 50% of all direct deaths, Feltgen said.

In 2017, the National Weather Service and National Hurricane Center began issuing storm surge watches and warnings along the East Coast and Gulf Coast, and in 2019 in Puerto Rico and the US Virgin Islands. Since 2017, 21 tropical cyclones — including 14 hurricanes, including five major ones — have made landfall and prompted storm surge watches or warnings, he said.

In 2021, Hurricane Ida swept through Louisiana as a Category 4 storm, producing dangerously high storm surges and testing the city’s system to withstand catastrophic flooding. Some areas along the coast experienced storm surge reaching 14 feet, according to a report from the center. Ida’s winds and storm surges are estimated to have caused approximately $55 billion in damage in Louisiana.

In 2008, Ike, a Category 2 hurricane that made landfall near Galveston Island in Texas, produced surges up to 20 feet above normal tide levels. Property damage was estimated at $24.9 billion. And, before that, Hurricane Katrina in 2005 produced a storm surge 25 to 28 feet above normal tide levels and caused an estimated $75 billion in damage to the New Orleans area and the along the Mississippi coast.

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