A tornado is a violently swirling column of air that is formed in severe thunderstorms and contains a hollow core. It is characterized by rotating air that often contains dust and debris and quickly spirals upward. The column’s bottom touches the ground, while the top extends five or more miles into the sky.
A tornado usually moves from southwest to northeast. The length of its path averages 4 miles but reaches up to 300 miles, and the width of this path averages 400 yards. Tornadoes travel at a speed of 25 to 40 miles per hour. It typically originates from dark, heavy clouds with a swirling funnel-shaped pendant that extends to the ground. Preceding the storm, precipitation, hail and a heavy downpour usually occur. Tornadoes are generally characterized by a roaring, rushing sound like the noise made by airplanes or trains speeding through a tunnel.
Most tornadoes in the United States occur from 4-6 p.m. in March and through July. Conditions necessary for tornado development include an unstable atmosphere with a strong thunderstorm, a lifting force and a vertical wind shear pattern that provides rotation. The clash of air masses is a major contributing factor in tornado formation. A tornado’s strong winds often destroy houses and buildings, uproot trees and cause loss of life.