Everyone heard it: An unsurvivable 15- to 20-foot storm surge forecast for Louisiana. Category 4 Hurricane Laura’s 150-mph winds would shove a mountain of deadly water onto the Cajun coast. Here’s the most I could find:
Those higher amounts were truly the exception with 5-feet above ground level really the more common readings. No one is complaining, but let’s dive into this surge a bit (no pun intended).
You can relate to a car accident and it’s easy to understand what matters is the speed and size of the vehicle coming at you along with the angle it hits you (t-bone vs. side-swipe). That’s simple physics. Bigger and faster equals “badder.”
Likewise, surge increases with the size of the storm, the speed of the winds, the distance traveled over water, the angle the storm approaches the coast (head-on strikes equal higher surge). The bathymetry, or depth of the ocean, matters also, but a shallow coast is pretty even in the Gulf vs. the Eastern Seaboard.
So let’s look at our famous hurricanes this century for comparison: Katrina, Rita, Ike and Laura. By satellite, they all seem pretty similar in size and scope:
Looks are deceiving, of course. Katrina wins for surge -- at 28 feet in southern Mississippi -- with Ike coming in with 17 feet (21 feet at Eagle’s Point where Bacliff is). Rita produced 15 feet and Laura, generally, produced 5 to 10 feet, with a few exceptions. All of them were plenty strong -- Ike at 110 mph, Laura at 150 mph, Katrina at 175 mph and Rita at 180 mph. Also, all of them pretty well t-boned the coast with similar angles of approach: