The first link I bookmarked the other day but the second link I had not seen yet.
Thinking about this for Terragen, it has been quite the challenge to even remotely recreate such cloud structures. The extreme convection, the striations, the mesocyclone vortex features, and lest we forget the fantastic colors with such storm systems.
For example, I read that the tallest clouds known can be up to 22,860 meters tall but accurately representing that scale and look within Terragen is very hard to achieve.