How do mechanical forces help produce a tornado?
Mechanical forces acting with energies other than thermal can help produce a tornado in areas where the air is already unstable. These forces include air flowing in from the sides, rotation of the earth, and the sweep of high-powered jet wind streams aloft. These factors slowly constrain the rotating air currents already set in motion by differences of temperature, density, and other things. As the radius of circulating winds is decreased, the speed of rotation increases, just as an ice skater spins faster by drawing in his arms, thus contracting his body radius as much as possible. These converging, rotating, accelerating winds all help set the tornado vortex in motion.
