A couple of months ago, BAbloggee Henrik Magnus Ulriksen sent me a link to a video of a cloud that frankly left me — har har — twisting in the wind. When I saw it, I had the strong feeling it was authentic; taken with a hand-held camera, it doesn’t look obviously faked. But what it shows is very odd indeed.
The video is of a cumulonimbus cloud, a puffy white cauliflower-shaped cloud that forms when warm air rises rapidly. The camera view is between two buildings, and you can see the puffy cloud top just below the center of the frame. Keep your eye on the little wisp of cloud just above the cumulonimbus, right in the middle of the frame.
Did you see it? If it helps, the picture here shows you where to look. Starting at 9 seconds in, that little wisp suddenly snaps into a new shape, as if someone had stopped the video, waited for the cloud to change, then started up the video again. But it’s clear that’s not what’s going on; the video is smooth with no transitions.
Assuming the video is real, I had a sneaky suspicion it had to do with the electric currents generated inside the cloud, the same currents that create lightning. Clouds can carry huge electric potentials — essentially, the ability to move charges around — and that stored energy can be suddenly released, creating lightning. When that happens, the electric field resets itself, and starts to store up energy again.
But I had no clue how that would make the cloud appear to dance like that!
As it happens, by coincidence, I met Joel Gratz at the TEDxBoulder talk in September. Joel is a meteorologist who runs websites like Open Snow and Colorado Powder Forecast. I sent him the video, and sure enough a short while later he had a reply for me.