The Atomic Cloud

As I was digging trough my photography Archive, I've found a very interesting shot. The image is 2 years old, I remember a heavy summer rain that day and at sunset as the sky cleared out this very interesting cloud formation formed. I've never seen anything like this, It's pure coincidence, luckily the camera was there to take the shot. The image went trough some very basic post processing.

http://i.imgur.com/vAI4N5P.jpg As you can see the cloud formation really looks like a "atomic cloud" or a cloud after a big explosion. But there was no big explosion, it's a pure random cloud formation. The one below has heavy contrast applied, it looks even more dramatic. http://i.imgur.com/gAvPjw1.jpg

Technical info
A57	WB/Auto	55mm focal length
ISO 100	f6.3	1/125