With the latest forecast for Nate showing Mobile Bay in the center of the likely track, residents in low-lying areas should prepare for a significant storm surge.
All the predictions in this article are based on the 10 AM Friday forecast from the National Hurricane Center. The surge predictions below can change as the official forecast changes. We provide this new tool to help people prepare and plan. Always keep up with the latest forecasts from the Hurricane Center.
Based on a new experimental surge model, it looks like the west end of Dauphin Island will be overwashed, meaning totally covered by a surge of about 4 feet, while Bayou La Batre will see a surge of six feet or more above normal high tide. Downtown Mobile, and the communities around Dog River could also see 6 feet of surge, more than enough to flood many homes. The Eastern Shore of Mobile Bay will also see a surge, with the highest water levels in Daphne, approaching six feet.
Fairhope, is predicted to have about a 5-foot surge, while Pt. Clear and the Y-Weeks community will experience about a 4-foot surge.
Bon Secour, Fort Morgan, Gulf Shores and Orange Beach will likely experience between 3 and 4 foot surge.
You can access this experimental surge model called CERA here.
Storm surge is caused when powerful winds push extra water toward shore, piling it up and causing what is in effect a really high tide.
The effect is greatest in the upper reaches of Mobile Bay, due to the funnel-like shape of the bay itself, which narrows as you go north.
In downtown Mobile and the head of the bay, "We always see about a six-foot increase from whatever the surge is on Dauphin Island," said Scott Douglass, a coastal engineer who has studied the Alabama Coast for decades. "It is the stress of the wind, blowing the water north. You get a tilt in the surface of the bay, with more water in the north end. "That’s why the bridge fell down in Ivan in Pensacola. The wind pushed the water up in that end of the bay, where U.S. 90 was, and I-10. Same thing happened in Katrina on Lake Ponchatrain. Wind pushes these waterbodies and tilts the surface."
Douglass believes federal and local governments are falling behind when it comes to accurately predicting storm surge because they rely on an old and outdated computer model, called the SLOSH model. He advocates the adoption of a new model called the Coastal Emergency Risks Assessment or CERA.
"This model has been deadly accurate in the last few storms," Douglass said. "All the uncertainty is in the track of the storm, not the surge predictions. As the forecast is resolved, we get better data on the surge, and it is just dead on.
"That’s really important information. If I can see 5.6 feet predicted in my area, I say, ‘OK, I’m evacuating.’ We need to use this sort of data. They say this is still experimental, but after several years, we know it works. It’s like an experimental drug. We see it is working, so let’s start using it. We can warn people very effectively."
The CERA maps have been created by coastal engineers at various universities and government institutions working in concert, and treating the model as an open source computing project. Louisiana State University, the University of North Carolina, Notre Dame, SeaGrant Louisiana, the Department of Homeland Security, and the National Oceanic and Atmospheric Administration have all participated in the creation of the CERA model.
At present, the surge maps issued by the National Hurricane Center do not offer much detail about surge in a particular location. Rather, they paint broad strips of coastline pink or red depending on how close they are to the storm’s predicted path. With the CERA maps, you can look at individual neighborhoods or facilities with much higher resolution.
This should help people follow the most important maxim in surviving a hurricane. Run from water, hide from wind. If you are in an area that is going to be affected by surge, get out before the storm comes.
A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.
For a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
"Those guys work on it together, constantly improving its accuracy," Douglass said. "With open source, they just fix it, and hand out the better version to everyone else. It has really made for a powerful tool, and one we should be using to give people the best information possible."
"That color stairstepping you are seeing on this graphic is real. Those water heights are going to be quite accurate. And it reflects what we see in the bay during the past storms."
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