Visualizing Updraft Rotation in Supercell and Non-Supercell Thunderstorms

To visualize the horizontal spinning effect caused by wind shear, roll a pencil along a table top with the palm of your hand. Now put it between your hands, tilt your hands vertically and slide your right hand away from you. You have just created a miniature rotating updraft!

To illustrate the way non-supercell tornadoes are formed, put a pencil between your hands, and place your hands perpendicular to a table (the table represents the ground, your hands represent wind coming from different directions at ground level, and the pencil is a parcel of air that gets caught and starts spinning). The spinning at the surface is drawn into the updraft of a developing or mature thunderstorm and is stretched into a tornado.

Images adapted from "Thunderstorms... Tornadoes... Lightning: Nature's Most Violent Storms"