Florida is on storm surge watch as Helene grows stronger: Here's what that means

(This story was updated to add new information. )

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.

Hurricane and storm surge watches cover much of the Gulf Coast of Florida as Tropical Storm Helene is projected to is projected to strengthen into a major hurricane and move northward from the Caribbean into the Gulf of Mexico.

The sudden rise of water topped by already high and powerful waves could deliver 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 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.

More: How Gulf Coast storm could become Cat 3 Hurricane Helene – and hit Florida hard

Storm surge is only one factor that affects water levels. 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.

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(This story was updated to add new information. )

This article originally appeared on USA TODAY: Florida is on storm surge watch as Helene grows stronger: Here's what that means