This cumulonnimbus cloud formed over Williams Lake, BC, on the afternoon of June 19th, 2010. It was an interesting formation because of the wedge shape to the lower portion of the cloud, a shape that may be called tuba (a formation sometimes associated with tornadoes). Fortunately it did not appear to be rotating. Further, the cloud quickly lost stability, as just five minutes later (see below), you can see the cloud beginning to fall apart. Five minutes after, this the cloud had completely disappeared.
Cumulonimbus clouds are usually associated with thunderstorms. I'm guessing that flying into a cloud with such a precise shape would not be a good idea, as the edges probably represent serious wind flow.
Photo Credit: Me
