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• <br />• <br />Anoka County Multi - Jurisdictional <br />All Hazards Mitigation Plan <br />in the course of a few hours. Most severe weather occurs when thunderstorms affects one <br />location for an extended time. <br />All thunderstorms contain lightning, an electrical discharge that occurs within the clouds or <br />between the clouds and the ground. A bolt of lightning reaches a temperature approaching <br />50,000 degrees F. In the United States, 75 to 100 Americans are hit and killed each year. <br />Hailstones are products of thunderstorms and are developed by downdrafts and updrafts that <br />develop inside the cumulonimbus clouds of a thunderstorm, where super cooled water droplets <br />exist. The transformation of droplets to ice requires a temperature below 32 degrees and a <br />catalyst in the form of tiny particles of solid matter, or freezing nuclei. Continued deposits of <br />super cooled water cause the ice crystals to grow into hailstones. Hail can be smaller than a <br />pea or larger than softballs and can be destructive to property, crops, livestock, and people. <br />Straight -line winds, which have exceeded 100 miles per hour, are responsible for most <br />thunderstorm damage. One type of straight -line wind, the downburst, can cause damage <br />equivalent to a tornado. Thunderstorms are also associated with tornadoes and heavy rains that <br />can lead to flooding. <br />WIND ZONES IN THE UNITED STATES" <br />406 24.1111.1. <br />Rig.r• 1.2 Wi »d on <br />n.ed <br />HAWAII <br />OTHER CONSIDERATIONS <br />So.CNal Wind Region <br />M{.Fmcane S49b9abbla Rogan <br />WINO ZONES <br />ZONEI <br />(130 mph., <br />ZONE 11 <br />(Ica "c' <br />ZONE 11 <br />goo ''pit <br />_ ZONE N <br />(250 mphl <br />• Design Mind Spnadd (JYeecand gu 1) nons.smna with ASCE 7.95 <br />All of the jurisdictions of Anoka County have experienced occurrences of severe thunderstorms <br />accompanied by high winds, lightning and sometimes damaging hail. <br />The city of Anoka experienced an unusually severe storm in September of 2005. There was <br />damage to homes and trees, streets were closed due to flooding, and septic and drain field <br />failures occurred. Extensive debris removal was required. <br />104 <br />