I will try to ansver as good as I can with my bad English.
My stormchasing can't be compared with Discovery's at all!
I mostly follow storms on the internet, watch from my windows at home or drive a few miles to get better sight, take poto's or film..
I have small children and that limits my possibilities to chase.
Very briefly:
LI the lifted index indicates air instability
Cape measures it
Dewpoint above +10 degrees means a higher risk for thunderstorms.
Well... Don't bother.. Guess I'm the only stormfanatic here anyway.