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<br /> <br />Figure 14-2. Tornado Risk Areas in the Coterminous United States <br />Severe Weather <br /> <br />14.1.6 Tornadoes <br />A tornado is a violently rotating column of air extending between, and in contact with, a cloud and the surface of <br />the earth. Tornadoes are often (but not always) visible as a funnel cloud. On a local-scale, tornadoes are the most <br />intense of all atmospheric circulations and wind can reach destructive speeds of more than 300 miles per hour <br />(mph). A tornado’s vortex is typically a few hundred meters in diameter, and damage paths can be up to 1 mile <br />wide and 50 miles long. Tornadoes can occur throughout the year at any time of day but are most frequent in the <br />spring during the late afternoon. As shown in Figure 14-2, California has a relatively low risk compared to states <br />in the midwestern and southern United States. Tornado severity classified on the Fujita Tornado Damage Scale is <br />shown in Table 14-1. <br />