Particle Fluids
I tried to follow this tutorial to create a CG Tornado. I'm still trying to replicate the effect in the video but outside of the tutorial I had a play with the Expression editor and things I had seen in the video to create this:
Its very rough around the edges. I wont carry on anymore with this scene file, I'll go back and watch the Tutorial over and over until I can get a good grasp of it.
Doing this has given me another idea for possibly a more simple smoke effect that doesn't use particles