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.
Source for the explaination