When I was at Wichita’s Exploration Place recently, I watched children play with one of those large funnels used for charitable donations. I thought would help me illustrate how supercell-related tornadoes develop.
We often talk about “circulation” in thunderstorms. All supercell thunderstorms have a rotating updraft of modest rotational speed. While dangerous to an aircraft in flight, it usually doesn’t both things on the ground.
When the diameter of the supercell’s rotation is constricted by storm’s “rear flank downdraft” (as the coins’ rotation is constricted toward the bottom of the funnel) the speed of the rotation increases — just as the coins speed up here.
In the meteorology classroom, we call it “conservation of angular momentum.” You can call it part of the explanation of how major tornadoes form.