USA TODAY National
While wind speeds grab our attention as a hurricane approaches, one of the more deadly and destructive aspects of these storms is the surge of water that moves over the shore and up into rivers and bays at landfall.
The sudden rise of water topped by already high and powerful waves delivers a battering blow that can sweep homes off their foundations and flood low-lying areas miles inland.
How storm surge happens
In the open ocean, hurricane winds push water toward the center of the storm. Instead of piling up, the water spirals downward and flows outward.
As the water is pushed downward, some is pushed out to sea and some is pushed toward the coast.
As the storm approaches land and shallow water, the ocean floor blocks the outflowing water, causing the ocean to surge onto land.
The Gulf of Mexico is more vulnerable to storm surge
The ocean floor and shape of the coast can influence the height of storm surge – the difference between water levels when a storm approaches. Along the Gulf of Mexico, wide, gently sloping continental shelves make the coastline more vulnerable to water piling up. On the Atlantic coast, narrower shelves with steep slopes produce lower a lower surge.
Size and speed also are important. When approaching an open coast, a faster-moving hurricane produces a higher surge. But when a storm moves toward an enclosed bay, such as Tampa Bay on Florida’s Gulf Coast, a slower storm produces a bigger surge.
Storm surge is only one factor that affects water level. If a storm arrives during a lunar high tide, the water level will be even higher. The surge and tide combined are referred to as storm tide.
This article originally appeared on USA TODAY: Florida is on storm surge watch as Idalia grows stronger: Here's what that means
Reporting by Javier Zarracina, Ramon Padilla, Stephen J. Beard and Dinah Voyles Pulver, USA TODAY / USA TODAY
USA TODAY Network via Reuters Connect
Slate Magazine