Meteorologists and experts often refer to storm surges when measuring the impact of a hurricane, but what does the phrase actually mean?
A storm surge is a “rise in sea level” that occurs during tropical cyclones, such as typhoons or hurricanes, according to National Geographic. At the center of every cyclone is an “eye,” which is surrounded by an “eye wall,” defined by a ring of clouds where the winds are strongest. Outside of the eye wall are clouds that spiral outward, which are called “spiraling rain bands.”
Because of the Coriolis effect and the rotation of Earth, water is pushed in the direction the wind is blowing. Since these storms produce such strong winds, water is pushed toward the coastal regions at an alarming rate. Combined with the heightened atmospheric pressure on the edges of a hurricane or cyclone, the storm collects the water it’s been pushing and causes it to swell near the eye and the eye wall.
Once the storm reaches land, the water being held in the eye wall essentially bursts over typically dry ground, causing a storm surge. If the surge occurs at the same time as high tide, water can reach as high as 33 feet.
Maria LaRosa, a meteorologist for The Weather Channel tells PEOPLE there are a lot of factors that can determine the strength of a storm surge.
“The amount of water rise can depend on storm strength, speed of forward motion, what angle the storm is coming in at relative to the coast, how shallow the body of water is close to the coast, and tides,” LaRosa says.
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Combined with the torrential rain, storm surges are especially dangerous in coastal areas because they cause so much flooding, which is the number one cause of death and economic damage associated with hurricanes, National Geographic reports.
“A storm surge is one of the greatest threats to life and property during a storm,” LaRose tells PEOPLE. “These water rises can be 25 feet (like Katrina), but even a three-foot storm surge can flood homes and float cars. A six-foot storm surge may not sound like a lot, but that is a level over most people’s heads.”
“This rise can happen quickly, too,” she adds. “Imagine dry ground and then six hours later, the water is up to the second level of your home. Wave action on top of this water rise makes it even more destructive and dangerous.”
LaRosa points out that although storm surges can be threatening to all coastal communities, during Hurricane Florence, N.C. was “especially concerning” because of the barrier islands in the Outer Banks.
“[The Outer Banks have] low elevation and very few routes to safety,” LaRosa says. “Those choosing to ride out a storm producing 7-11 feet of water rise risk not only the flooding aspect, for example, but being cut off completely from escape or help, perhaps for days even weeks. The surge of water being pushed into rivers also complicates and worsens the river flood threat. It’s already there because of the incredible rainfall, but a river can’t drain if water is trying to push it back, increasing river levels faster and farther out of their banks.”