Try Stormchasers...they usually have good quality footage. Check out some of the science channels...as you probably already know a tornado is actually multiple entities. It does have some interesting properties for a natural phenomena. I remember a show proving a single tornado actually had up to 12 satellite (mini) twisters which were generating the vortex...quite interesting.
I would like to see what you can engineer mate...interesting stuff
cheers bullet
bullet1968
"A Darkness at Sethanon", a book I aspire to model some of the charcters and scenes