henri wind forecast sunday morning
Henri nearly a hurricane, warnings posted for New England.
03:31 - Source: CNN

Editor’s Note: This story has previously been published related to other hurricanes’ threat of storm surge. It has been updated to reflect conditions with Henri.

CNN  — 

When Ida makes landfall – likely Sunday– a dangerous storm surge of 10 to 15 feet is expected from Morgan City, Louisiana, to the mouth of the Mississippi River, according to the National Hurricane Center.

Much of the threat is due to storm surge, which CNN meteorologists have estimated could force 4 feet of water into coastal neighborhoods, damaging homes and flooding streets with frigid ocean water.

While many people focus on the wind speed of storms, the danger often comes from the water flowing in from the ocean.

Privately, you may be wondering (and you wouldn’t be alone): “What is a storm surge?”

“A storm surge is a rise in water level caused by a strong storm’s wind pushing water on-shore,” said CNN meteorologist Brandon Miller. “The wind literally piles up the ocean water and pushes it on the land.”

All that water has nowhere to go

That water doesn’t just leave. Depending on how much water was pushed ashore and the area’s watershed, it may hang around, causing further damage to communities.

Due to climate change, storm surge has become an even greater threat in recent years.

“Sea levels have risen in most places by about 1 foot over the past century. The higher baseline ocean level allows storm surges to reach even higher, increasing their destructive capabilities,” Miller said.

The National Weather Service in a 2014 report said that most surge deaths occurred in Hurricane Katrina and several other big, powerful storms. In a majority of storms, excessive rainfall that leads to drownings is the leading cause of death. Florence is expected to also be a rainmaker, with totals of 35 inches possible in some areas.

CNN’s Brandon Miller, Gene Norman, Judson Jones and Emily Smith contributed to this report.