Perhaps all tornadoes form on the ground, as horizontal wind tunnels that, for whatever meteorological reason are pushed upright and become vertical. From this point, perhaps they touch down at certain points, then go up into the clouds again. This might account for the linear paths of destruction tornadoes usually take. Quite possibly, destruction in different areas are caused by the same tornado, touching down here, then thirty miles down the pike, etc.

Just a thought. I realize it's not about earthquakes, but I'm always fascinated by things I don't understand, which is a LOT.

Cathryn