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Anoka County 2019 Multi-Jurisdictional All Hazards Mitigation Plan 98 104B4.3.1.4 Severe Weather - Tornado Tornados are violent windstorms characterized by a twisting, funnel-shaped cloud. Spawned by a thunderstorm (or sometimes as a result of a hurricane), the funnel does not need to reach to the ground for a tornado to be present. A debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado. The damage from a tornado is a result of the high wind velocity and wind-blown debris. The intensity, path length, and width of tornadoes are rated according to a scale developed by T. Theodore Fujita and Allen D. Pearson. The Fujita-Pearson Tornado Scale is presented below. Tornadoes classified as F0-F1 are considered weak, those classified as F2-F3 are considered strong, while those classified as F4-F5 are considered violent. Enhanced Fujita Tornado Scale Description Table EF- Scale Damage Winds (mph) Description EF-0 Light 65-85 Chimney damage, tree branches broken EF-1 Moderate 86-110 Mobile homes overturned EF-2 Considerable 111-135 Considerable damage, trees downed, mobile homes demolished EF-3 Severe 136-165 Roofs/walls torn down, trains and cars overturned EF-4 Devastating 166-200 Well-constructed walls leveled EF-5 Incredible 200 + Homes lifted off foundation and carried considerable distances The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of 1 mile wide and 50 miles long. Even with advances in meteorology, warning time for tornadoes is short or impossible. Tornadoes can occur in any state, but are more frequent in the Midwest, Southeast and Southwest. Tornado season is generally March through August, although tornadoes can occur at any time of year. They tend to occur in the afternoons and evenings. Over 80% of all tornadoes strike between noon and midnight. There have been 24 tornado events that have impacted Anoka County and participating jurisdictions since 1961. In some cases, the same tornado may have impacted multiple jurisdictions and was reported more than once.