Tropics 101: What is storm surge? How does it impact coastal communities?

Storm surge flooding is the greatest threat to life and property during a tropical system, and storm surge directly accounts to approximately half of the deaths associated with tropical storms and hurricanes in the U.S.

As a tropical system inches closer to shore, the familiar tropical storm and hurricane watches or warnings go into effect for those living near the coast.

However, you may also hear of storm surge watches and warnings also being issued. These alerts were first put into operation by the National Weather Service during the 2017 Atlantic Hurricane Season.

What is storm surge?

The National Hurricane Center defines storm surge as “an abnormal rise of water generated by a storm, over and above the predicted astronomical tides.” This is different from storm tide, which is “the water level rise due to the combination of storm surge and the astronomical tide.”

Storm surge occurs when winds within the tropical system push ocean water onshore. As the water approaches land, it accumulates or “piles up”, creating the surge of water known as storm surge.

Why is storm surge so dangerous? How does storm surge impact coastal communities?

The height, or strength of storm surge depends on a number of factors:

  • the storm’s wind speeds
  • the overall forward speed of the storm
  • the size of the storm
  • shape of the coastline, bays and estuaries
  • slope of the ocean bottom

Storm surge waters can swell as high as 34 feet! Along coastal Alabama, the highest recorded storm surge occurred in Gulf Shores during the September 1906 hurricane, when waters reached 11.8 feet. In Mobile during 2005, Hurricane Katrina caused storm surge waters to rise 11.45 feet.

That much ocean water is going to go somewhere, and that somewhere is inland. This is why storm surge watches or warnings will be in effect miles away from the actual coastline.

It is important to note that storm surge flooding is the greatest threat to life and property during a tropical system, and storm surge directly accounts to approximately half of the deaths associated with tropical storms and hurricanes in the U.S. 

NOAA coastal flooding forecasts are given as feet above ground level in order to account for variations within land elevation and other geographical features.

For the latest tropical forecast information, including storm surge watches and warnings, be sure to check the National Hurricane Center.

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