Yesterday morning my friend Kurt Hulst called to say, “Grab your camera. There’s a great shelf cloud coming your way. It passed my location before I could get a picture.”
Okay, then. My apartment faces east, and all I could see was blue sky. Not even a hint that a storm might be approaching from the west, and usually one gets at least some kind of a clue. But I snatched up my camera and car keys regardless and headed outside.
Yes, there it was–a hazy arcus cloud moving my way from the west and northwest. I hopped in my car, with the intention of finding a better view for taking photographs than my parking lot afforded. But the cloud was moving faster than I realized, and by the time I reached 108th Street, it was almost on top of me. So, with the wind kicking up flurries of leaves in front of me, I headed east, thinking to put a little distance between the shelf cloud and me.
Several miles down the road, I turned north, parked by a buffalo farm, stepped out of my car to get a look, and realized immediately that my cause was lost. The cloud was right overhead. It had to have been moving at least 60 mph. So much for weather photos. Within seconds, I was looking at the backside of the arcus, and it wasn’t particularly photogenic.
For that matter, there wasn’t much to it. No ensuing rain, no lightning, no thunder, no storm at all, just blue skies. I can’t speak for other parts of the country, but here in Michigan it is an odd thing to observe an impressive-looking shelf cloud with absolutely nothing behind it! The cloud evidently had formed as the isolated effect of cold outflow from dissipated storms back in Wisconsin, in conjunction with a closer, severe-warned MCS to the north. Back at home, I could see the outflow boundary arching southwest all the way down into Indiana and moving rapidly east.
Yesterday seemed to be the day for such phenomenon to be clearly defined on the radar. Later in the afternoon, GR3 showed a similarly highly distinct outflow boundary down in northern Indiana. The source of this one was easy
As an item of curiosity and an example of a highly defined outflow boundary–I suppose you could call it a runaway gust front–I captured a screen shot. Click on the image to enlarge it.
