08-12-2019 Council Packet - Laserfiche WebLink

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Anoka County 2019 Multi-Jurisdictional All Hazards Mitigation Plan 81 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 88B4.2.1.10 Severe Weather - Tropical Storm/Hurricane A hurricane is a tropical storm with winds that have reached a constant speed of 74 miles per hour or more. Hurricane winds blow in a large spiral around a relative calm center known as the "eye." The "eye" is generally 20 to 30 miles wide, and the storm may extend outward 400 miles. As a hurricane approaches, the skies will begin to darken and winds will grow in strength. As a hurricane nears land, it can bring torrential rains, high winds, and storm surges. A single hurricane can last for more than 2 weeks over open waters and can run a path across the entire length of the eastern seaboard. August and September are peak months during the hurricane season that lasts from June 1 through November 30. The center, or eye, of a hurricane is relatively calm. The most violent activity takes place in the area immediately around the eye, called the eye wall. At the top of the eye wall (about 50,000 feet), most of the air is propelled outward, increasing the air's upward motion. Some of the air, however, moves inward and sinks into the eye, creating a cloud-free area. Tropical cyclones are classified as follows: Tropical Depression An organized system of clouds and thunderstorms with a defined circulation and maximum sustained winds of 38 mph (33 knots) or less. Tropical Storm An organized system of strong thunderstorms with a defined circulation and maximum sustained winds of 39 to 73 mph (34-63 knots). Hurricane An intense tropical weather system with a well-defined circulation and maximum sustained winds of 74 mph (64 knots) or higher. Hurricanes are called "typhoons" in the western Pacific, while similar storms in the Indian Ocean are called "cyclones."