Last night proved how helpful and important some of you can be.
Although neither Ben nor I (nor the National Weather Service) were seeing any rotation on Doppler radar last night, two of you tweeted me about seeing what appeared to be a tornado over Walled Lake. And if you look at the two photos tweeted to me (thanks to Mary Street and Scott Welcer (from Welcer Farms…and the photo Scott tweeted me was taken by his friend Garret Mette), we sure do see a disturbance on the water. Both reported that the circulation extended up around 100-150 feet into the air. And both said it moved across the lake.
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So what is this? First and foremost, it’s not a tornado. Tornadoes originate with strong rotation up in the cumulonimbus cloud, with that vortex stretching and narrowing down toward the surface (by the way, it’s due to the law of Conservation of Angular Momentum that, as the vortex narrows, there must be a corresponding increase in wind speed ... that’s why the wind in a tornado gets so strong). As I mentioned earlier, we weren’t seeing any rotation up in the sky, so this was not a funnel that dropped down from a thunderstorm.
So, again, what is this? It’s called a gustnado. What happens is that the gust front of strong wind that rushes out ahead of the storm (I even tweeted radar images last night showing you the gust front, and cautioning to be ready for very gusty conditions when it arrived) sometimes develops kinks in it, and the change in low-level wind directions so close together can spin up a little circulation.
I was talking about this earlier today with my good friend Rich Pollman, who’s the Warning Coordination Meteorologist at our local National Weather Service Office, and he offers a great analogy: This is similar to those swirls of leaves you sometimes see on your lawn in the fall on a breezy day, except this is on a much larger scale and with stronger wind. Can a gustnado cause damage? Yes it can, and we did have some damage reports last night. But is it a tornado? Not a chance.
After my article was posted this afternoon, I received the best photo yet of yesterday’s Walled Lake gustnado. This photo was taken by Nicole Eleanor Spackman, and provided to me by Scott Welcer. Thanks to you both!
As you can see, the circulation extends up from the water but, if you were to be there in person, it wouldn’t go all the way up to the cloud base. Also notice that it’s not raining. As I mentioned earlier, gustnados form at that lead edge of strong, gusty winds that rushes out ahead of a thunderstorm. That’s why I always tell you not to wait for the rain before taking cover when a severe storm approaches…the dangerous wind gusts (and, occasionally, a gustnado) hit well before the rain starts.