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Eugene -Springfield Area Natural Hazards Mitigation Plan <br />2. Hazard Descriptions <br />Tornadoes <br />Tornadoes are the most violent of all atmospheric storms.33 They are a narrow <br />fiercely rotating column of air. Tornadoes become visible when there is enough <br />condensation of water droplets, dust and debris. Once on the ground, tornadoes can <br />cause significant property damage and threaten human life (Picture 2-1). <br />Tornadoes form at the base of athunderstorm (Figure 2-6). This weather <br />phenomenon can happen any time of the year, but in Oregon they most often occur <br />during the milder months of fall and spring.34 When over water, a tornado is <br />referred to as a waterspout. <br />Picture 2-1. Source: KPTV-Manzanita, Oregon tornado damage October2016 <br />h mammatus clouds <br />line cumulonimbus <br />i <br />cloud base striations shelfcloud <br />SCHEMATIC DIAGRAM OF THUNDERSTORM <br />Figure 2-6. Source: National Severe Storms Laboratory NOAA - <br />httl)s://www.nssl.noaa.gov/education/svrwxl01/tornadoes/ <br />as "Tornado Basics." NOAA National Severe Storms Laboratory. Accessed November 08, 2017. <br />http://www.nssl.noaa.gov/education/svrwxl0l/tomadoes/ <br />34 Livingston, Ian. "Monthly tornado averages by state and region." U.S. Tornadoes. March 16, <br />2013. Accessed November 08, 2017. http://www.ustornadoes.com/2013/03/19/monthly-tomado- <br />averages-by-state-and-region/ <br />2-22 January 2020 <br />