What is storm surge? It’s expected to be a major threat during Hurricane Sally
As Hurricane Sally heads for the Gulf Coast, forecasters are warning about the possibility of “life-threatening” storm surge in some areas.
Some areas are under storm surge warnings Monday, meaning “life-threatening inundation, from rising water moving inland from the coastline” is possible over the next 36 hours, according to the National Hurricane Center.
“The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline,” the hurricane center says.
In Mississippi, 7 to 11 feet of inundation is possible from the mouth of the Mississippi River to Ocean Springs, and 5 to 8 feet of inundation is possible from Ocean Springs to the Alabama border. Other areas near the coast could also see high water levels.
What is storm surge?
A storm surge is an “abnormal rise in seawater level” above the predicted tides and happens when a storm’s winds push the water on shore, according to the National Oceanic and Atmospheric Association.
Several factors can impact a surge’s potential harm.
The National Hurricane Center calls storm surge a “very complex phenomenon” as it’s sensitive to small changes in a storm’s intensity, speed, size, pressure and the angle in which it approaches the coast and “coastal features.” The slope and width of a continental shelf also impact storm surge, as shallow slopes can “produce greater storm surge than a steep shelf,” according to the National Hurricane Center
The National Hurricane Center emphasizes that storm surge and storm tide aren’t the same thing.
Storm tide is a combination of storm surge and regular tide, the hurricane center says.
“This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with normal high tide, resulting in storm tides reaching up to 20 feet or more in some cases,” it said.
Why is it dangerous?
Although hurricanes and tropical storms are known for their powerful winds and heavy rains, storm surge is responsible for most of the death and destruction during these storms.
“Storm surge flooding has accounted for nearly half of the deaths associated with land-falling tropical cyclones over the past fifty years,” the National Hurricane Center said.
Surges can bring waves farther inland and, since water weighs about 1,700 pounds per cubic yard, these waves can damage buildings and homes on the coast, according to the hurricane center.
They can also sweep away cars and slam debris into buildings, Weather Underground says.
How to prepare
Storm surge isn’t preventable, so it’s important to pay attention to warnings of an “incoming threat,” NOAA says.
“As a reminder, emergency managers want us to run from the water and hide from the wind,” NOAA said. “Don’t take unnecessary risks during a storm. Conditions can change in the blink of an eye.”
A storm surge warning means there is a “danger of life-threatening inundation from rising water” from a cyclone moving inland within 36 hours, and a watch is issued when there’s a danger of it moving inland within 48 hours, the National Hurricane Center says.
The best way to survive a storm surge is to follow evacuation orders, as being able to maneuver through it or outrun it are unlikely, according to Weather Underground.
“If you receive an evacuation order for a hurricane storm surge, it is a good idea to get out sooner rather than later,” Weather Underground says. “The storm surge can begin to rise a day before the storm hits, cutting off escape routes when low-lying highways are flooded. This is particularly true along the Gulf of Mexico shore.”
This story was originally published September 14, 2020 at 10:52 AM.
