Higher-Than-Predicted Storm Surge Warning for Louisiana and Mississippi Ahead of Sally

Soon-to-be Hurricane Sally will not be a terribly strong storm when it makes landfall on the northern Gulf Coast. However, the approach of the storm is of great concern. Sally is moving on a path that could create a "geomorphic" worst-case scenario. The embayment formed by the LA delta and the Mississippi coast will trap water pushed in front of the storm. The storm's approach will have wind, waves, water directed to the north and west, straight onshore and into Mississippi Sound and Chandeleur Sound. From there, waters will enter Lake Pontchartrain. Sally is moving slowly, so surge-related flooding could last for more than a day. All of these areas feature broad, shallow continental shelves which tend to accentuate storm surge.

The storms path will determine whether Pontchartrain flooding is driven north or south, although both are possible as winds switch and the water sloshes back across the lake. All interests in southeastern Louisiana, coastal Mississippi (especially along Bay St Louis) all the way into Alabama and Mobile Bay should prepare for higher than expected storm surge. Don't be fooled by the size of the storm. Surges could easily exceed current predictions of 10-11 feet, and the water will remain high for a long time allowing significant inland penetration of wave energy. No, this will not be Katrina, but it is still a storm of great concern for all low-elevation areas.