Intuiting Hurricane Michael Storm Surge
By: Bj Campbell
Tags: Random, Weather, Hurricane

I just got done watching the most incredible piece of live TV I have ever seen in my life, bar none. But it wasn’t on TV. It was this guy:

Brett Adair, of whom I know little to none, just got done piling into a (hopefully paid off) Tahoe and driving through Hurricane Michael, livestreaming the entire thing to his storm chaser feed, which is here:

https://livestormchasing.com/stream/brett.adair

The link is dead. Don’t go there. Hurricane Michael killed it.

A video capture of some of the stream, but not all of it, has been housed at KABB Fox 29’s Facebook page, but the stream itself had a big label on it that said “not for broadcast,” so I’m unclear whether KABB is guilty of copyright violation in posting it. That is to say, go here, watch this, but the link might break after I publish the article:

It was insane. When I picked up the feed, he was just off of Marina Drive, in Port Saint Joe Florida, a place I used to tie my boat off of when I was a Gulf sailor to walk to the Piggly Wiggly. Hurricane Michael was twenty miles offshore, south-southwest. I was glued. This was pure South Alabama You Only Live Once stuff. They were hilarious. Like Blue Collar Comedy meets Reed Timmer. “Well, we got a good backwind, maybe we can just Dukes of Hazzard this thing.” Glorious.

Eventually they bailed, drove through Port Saint Joe for a bit, dodged some downed power lines which was probably safer than it sounds because the grid was down, and parked at the Dollar General because they figured it was the strongest building in town. Then the YOLO kicked in. They crossed the bridge and headed to Mexico Beach, hoping to get there before the eyewall went over it.

They got as far as here:

image captured from Google Streetview, all rights to them and/or the owners of this cottage / etc

Then the storm surge came in. It was wild. I’d never realized how quickly it surges — it looked for all the world like one of those Indonesian tsunami videos. They were trapped and they knew it.

They backed their (hopefully paid off) Tahoe up against that CMU wall, next to a trailered pontoon boat, freaked out a bit with each other, and decided the only reasonable survival strategy was to bail on the truck and climb up the stairs to that house. I’m sure this decision saved their lives. I don’t know if they broke in, or just huddled on the porch, or what, but I know for sure given the over 100 mile per hour winds I’d have put something through a window and jumped in, if debris hadn’t already done the job for me.

But the live feed kept running. For what seemed like five or ten minutes, the surge came in, waves crested the hood of the Tahoe, and eventually it began to literally float away, all the while feeding Brett’s satellite uplink, while the people on the feed couldn’t turn away. The feed went dead for me after the Tahoe had been somewhat relocated, possibly to another house.

Author’s disclaimer: Don’t try this at home kids. This entire thing was fantastically unwise.

I have read on Twitter than Brett checked in via Facebook and said he was okay, but I haven’t confirmed it because Facebook is evil and I cancelled my account. If you’re in the media, and reading this, maybe go check on him. He’s got a hell of a story. Also, cancel your Facebook account, because it’s evil.

So the mariner / civil engineer in me wants to know, exactly how big was that storm surge, anyway?

A Not-Too-Bad October 10th Storm Surge Estimate

This is an image captured from the Bay County GIS platform, showing aerial photography on a nice, sunny, not-completely-devastated-by-a-category-four-hurricane kind of day, with the roads and one foot interval topography overlaid on it:

This is from county maintained GIS data, which is usually based on LIDAR from aircraft. It’s not often accurate. What they do, is shoot laser dots onto the ground and measure them with range finders from an airplane, and then tie the resultant three dimensional computer grid into known surveyed benchmarks. The grids can be loose, and the computer connects the dots as best as possible. That’s why, for instance, we don’t see that CMU wall in the topography in the image. It also often has around a foot of error in either direction, on a Mean Sea Level basis, sometimes more if it’s in an area with a lot of vegetative canopy cover that can interfere with the laser rangefinding.

But it’s probably pretty good for the roads. You can see Highway 98 is about an elevation of 13.5 MSL, and Wentletrap Avenue is around a 23, for about a ten foot difference. This makes some sense, and jives with our Google Streetview snapshot, which shows the wall being approximately one story tall. So chances are good that the Tahoe was parked about an elevation of 14 feet mean sea level, as the grade for the drive was pretty flat.

That means there was probably over ten feet of surge in Mexico Beach when they pulled in, it just wasn’t over the road yet.

I don’t know what depth of water it takes to float a Tahoe, but I’d imagine around three feet would do it, and there were waves crashing over the grill of this vehicle, sometimes over the hood, and a few over the roof, before my feed cut out. So call that 17 feet MSL, water level.

Is that the surge though? Not technically. That was the (approximate, eyeballed, from my safe office in Atlanta Georgia which won’t get hit with this thing until tonight) storm tide.

Storm Tide is the combination of Storm Surge and the local tidal effects in place before the storm hits. NOAA’s National Hurricane Center explains the difference. And while the tides in the Gulf of Mexico are generally relatively low compared to many other places, they do play a factor.

Here’s a tide table from Willy Weather, url: https://tides.willyweather.com/fl/bay-county/mexico-beach.html

A foot of our water in our estimate comes from the alignment of the sun, moon, zodiac, or magic space turtles on which the flat earth rests, depending on your chosen scientific epistemological framework, and the rest comes from Michael. So 16 feet, give or take.

Did We Predict This Correctly?

Not too badly, I think. This is from the 7AM National Hurricane Center Public Advisory:

DISCUSSION AND OUTLOOK

----------------------

At 700 AM CDT (1200 UTC), the eye of Hurricane Michael was located

near latitude 29.0 North, longitude 86.3 West. Michael is moving

toward the north near 13 mph (20 km/h). A turn toward the north-

northeast is expected later this morning, with a turn toward the

northeast expected this afternoon or tonight. A motion toward the

northeast at a faster forward speed is forecast on Thursday and

Friday. On the forecast track, the eye of Michael is expected to

move ashore over the Florida Panhandle later today, move

northeastward across the southeastern United States tonight and

Thursday, and then move off the Mid-Atlantic coast away from the

United States on Friday.



Reports from an Air Force Reserve Hurricane Hunter aircraft

indicate that maximum sustained winds have increased to near 145 mph

(230 km/h) with higher gusts. Michael is an extremely dangerous

category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.

Some additional strengthening is possible before landfall. After

landfall, Michael should weaken as it crosses the southeastern

United States.



Hurricane-force winds extend outward up to 45 miles (75 km) from

the center and tropical-storm-force winds extend outward up to 185

miles (295 km). A wind gust to 56 mph (91 km/h) was recently

reported at Apalachicola Regional Airport.



The estimated minimum central pressure based on NOAA and Air Force

Reserve Hunter aircraft data is 933 mb (27.55 inches).





HAZARDS AFFECTING LAND

----------------------

STORM SURGE: The combination of a dangerous storm surge and the

tide will cause normally dry areas near the coast to be flooded by

rising waters moving inland from the shoreline. The water has the

potential to reach the following heights above ground if peak surge

occurs at the time of high tide...



Tyndall Air Force Base FL to Aucilla River FL...9-14 ft

Okaloosa/Walton County Line FL to Tyndall Air Force Base FL...6-9 ft

Aucilla River FL to Cedar Key FL...6-9 ft

Cedar Key FL to Chassahowitzka FL...4-6 ft

Chassahowitzka to Anna Maria Island FL including Tampa Bay...2-4 ft

So they were off by two feet at the eyewall. Pretty good job sciencing, there folks.

Instead of posting the photos of Mexico Beach, which is (was) (hopefully will be again) a beautiful vacation destination with wonderful people who I pray are all okay, I’ll leave you with a beautiful animated image of the thing coming inland and about to wreck Bainbridge Georgia as a Category 3 or 4 depending on who’s talking.

GOES Satellite images from NOAA are super cool

Alright, I was kidding, here’s some video from Mexico Beach. Yeesh. I used to anchor up off of there.