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Lamar County Multi- jurisdictional Hazard Mitigation Plan <br />HAZARD PROFILE: SECTION ONE - TORNADO <br />1. Description <br />Chapter Three <br />Tornadoes are earth's most violent storms. With an average of 139 (1953 -2004) tornadoes <br />touching down each year, Texas ranks first in tornado occurrences. A tornado is a brutal <br />windstorm characterized by a twisting, funnel- shaped cloud. Tornadoes occur in association with <br />strong thunderstorms and commonly are accompanied by lightening, heavy rain, and /or hail. Note <br />that although tornadoes are associated with thunderstorms, tornadoes are profiled in this plan as a <br />separate event. <br />Data on tornado events was gathered from various sources including the Hazard Mitigation <br />Planning Team, local emergency officials, NOAA, and the Hazard Assessment Survey. <br />2. Location <br />"Tornado Alley" is the term used to describe the region of the U.S. where the strongest tornadoes <br />occur most frequent. "Tornado Alley" does not have an officially defined area but includes eastern <br />SD & CO, NE, KS, OK, and North Texas. This area has a reported concentration of five or maore <br />tornadoes per 10,000 square miles. Lamar County is located in this "Tornado Alley" and the entire <br />county is equally susceptible to tornado damages. Due to the county wide probability of tornado <br />every structure has equal probability to be struck by an eF0 tornado or higher. <br />3. Extent <br />A tornado has intense wind speed normally from 40 miles per hour to more than 300 miles per <br />hours. Although a tornado is usually on the ground for a short time the damage that it can do is <br />severe. Until February 2007 tornadoes were rated on the Fujita Scale (F- Scale). Using the wind <br />speed and the type of damage they were giving a rating of F -0 to F -S. <br />The Enhanced Fujita Scale was enacted in the U.S. on February 1, 2007. This new version of Dr. Ted <br />Fujita's 1971 classification system accounts for different degrees of damage that occur to different <br />types of structures. It is thought to provide a better estimate for winds speeds and sets no upper <br />wind speed limit. Although the U.S. is officially using the new standard most of the world is still <br />using the former Fujita Scale. <br />54 <br />