Final answer:
Tornadoes form when the horizontal rotation at the periphery of the rear flank downdraft tilts, making it the most common way tornadoes are formed.
Step-by-step explanation:
Tornadoes form when horizontal rotation at the periphery of the rear flank downdraft tilts, resulting in the process of tornado genesis. This is known as the most common way tornadoes form. In severe thunderstorms called supercells, the column of air rotates around a horizontal axis. The difference in wind speeds between the jet stream and winds from the Gulf of Mexico causes the rotating air to shift and spin around a vertical axis, creating a tornado.