Thursday, July 03, 2014

Hurricane Arthur & Storm Surge

What a difference two years makes. For those of you keeping score at home, two of the biggest weather forecast misfires of 2012 involved the storm surge of Hurricanes Isaac and Sandy. They were both Category 1 storms, but their Category 3 size storm surges did most of their damage. It seems even when weather predictions go out of their way to warn of surge, when it is associated with the words "category" and "one," folks are more likely to think they can ride out the storm ("hunker down" being the term of art in Louisiana).

But as we learned, Cat 3 size water packs one hell of a punch. If you're going to hunker, you better make sure you're behind some big levees or on higher ground. If not, you'd better make a plan to get there.

So nowadays, NHC has experimental storm surge inundation maps. They've also got rainfall totals estimations, because flash flooding is like the tornado of flooding, and shows up often without much advance warning. And in places that have functioning drainage systems and less rain than New Orleans (we deal with flash flooding on a sometimes hourly basis), the people may not be used to any flooding, so that's also a big upgrade.

To demonstrate the power of storm surge, the attached screenshot is the NHC's potential storm surge inundation map of St. Simons Island and Glynn County. For reference, this location is now a few hundred miles behind Hurricane Arthur. But the power of that Category 1 storm was enough to forecast high water up into the Marshes of Glynn, and from North Florida all the way to the Chesapeake. You can see why they ordered the evacuation of Hatteras Island in North Carolina if you click on the NHC surge forecast and scroll over to the Outer Banks. Coastal living is glorious, but it comes at a price.

If you're looking for other resources to follow during #hurricaneseason in the Atlantic and Gulf, here are some good clicks (if you aren't already). Feel free to leave any good ones I've missed in the comments:

National Weather Service Storm Prediction Center

Eric Holthaus who is also live-blogging Hurricane Arthur at Slate

Weather Underground

The Weather Channel Breaking

And of course, your local NWS spots, government accounts, and Emergency Management offices. Mine include:

Glynn County (GA) Government