Fujita Throwback: Snow Devil Swirl Trail in My Driveway
It's 5:00 in the morning and I can't sleep, so I'm going to tell the weather enthusiasts who are here an interesting story that happened to me this week. As long as I can remember, I've been interested in the weather, but even after 30+ years of observing it, I still sometimes run into something I haven't seen before. Such was the case when I checked my home driveway cam Monday morning and noticed a strange swirling pattern in the recently-fallen snow:
I took some pictures of it to confirm what I thought it was: A "snow devil" swirl trail. We've talked about snow devils before. There are always minature vortexes of wind around us -- but we can't see them until dust, leaves, or snow gives them form. Local storm chaser Ron "R-Factor" Shawley got some great video of one last week near Johnstown, Pennsylvania:
Dry snow and high, gusty winds are most conducive to snow devils, and they can often be found near corners of tree lines or buildings where the wind tends to swirl. Like tornadoes, they leave a swirling track behind them, and if conditions are right, snow gives it form. Here's a higher-resolution panorama photo of the trail in my driveway:
I thought at first that it might have been just a piece of trash (for example a bottle) blowing along the driveway, but on closer inspection there was a clear source and termination spot, and no object that could have caused it. As you can see from the closeup below, the snow was pushed to varying heights in the swirls as it moved along. Which way did it move? Since I didn't see it on the live cam, I have no idea. The fact that I couldn't find these in the other driveways or streets in my neighborhood, and that this tiny little vortex chose my home to leave its mark, is amusing.
The interesting thing here is how similar these vortex trails are compared to their larger cousins - tornadoes (rarely photographed but documented first by famous tornado researcher Ted Fujita (R.I.P.), one of my heroes). The aerial image below, from NOAA, was taken by Fujita in 1965:
Even more interesting is that these marks, said to be the evidence of multi-vortex tornadoes (tornadoes which have small twisters circulating in their outer wall that cause massive damage), indicate that there also multi-vortex snow devils, and if you look at Ron's video above, it's obvious there are some there. Whether large scale or small scale, vortexes in nature behave the same. I see why Fujita was interested in observing small tornadoes in the laboratory (AP Photo):
Like the Glass Bead Rainbow I photographed earlier this year, I was thrilled to have documented yet another interesting bit of the science in the world around us.
