The days before the August 27 arrival of hurricane Laura at the Louisiana Coast brought a new term to the news. “An unsurvivable storm surge” was how the National Hurricane Center (NHC) characterized the coming disaster. Even though the word “unsurvivable” wasn’t in the Merriam-Webster Dictionary yet, it sent a clear message to coastal residents to get out of the area.
Drinking with a straw is a good way to visualize a storm surge. Negative pressure draws liquid up from the cup into the straw. Because a hurricane is an extreme low-pressure area, it works like a gigantic straw, drawing ocean water upward and raising the sea level. In the case of Laura, the “straw” was 350 miles wide. The resulting rise of water was 20 feet. Add to this the waves created by 125 mph wind.
A storm surge is more than just the onslaught of wind and waves. It’s the event where the ocean intrudes upon the land and takes over. Imagine the situation near the beach. A one-story beachfront home may be 15 feet tall, much less if it’s the mobile-home type. It sits maybe 4 feet above the high-tide water line. A hurricane attacks it with a 20-foot surge. So the hurricane already has a 1-foot advantage. Six-foot wind-driven waves top the surge level. Residents who made it to the rooftop when the building flooded are now standing in 12 inches of water, trying to hold on against waves that top out 7 feet above roof level. There’s no way that humans can brave that massive force, and this is where the word “unsurvivable” comes in.
Having been through 3 hurricanes much less powerful than Laura, I can attest that things don’t play out this systematically. The rise of water is very fast, amid gusts of wind that hit suddenly like explosions. Rain is driven horizontally at speeds of 100 miles per hour, not falling from the sky as it normally does. Tree branches, metal roofing, topsoil and other debris are hitting anything that’s in their way. Being in the path of the storm surge, one finds that there’s nothing but angry water instead of yesterday’s solid ground.
The new “unsurvivable” term, which is sure to find its way into dictionaries, illustrates the NHC’s message well. When a hurricane is coming, get away from the coast.
Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.