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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br /> <br /> <br />Chapter 4: Hazard Identification and Risk Assessment 151 <br />hailstone. There is much uncertainty in the average speed hail falls; however, NOAA developed the <br />estimates shown on Table 4-94.184F <br />184 <br />Table 4-94. Hail Speed Estimates <br />Hail Size (inches) Fall Speed (mph) <br />Less than 1 9 – 25 <br />1 – 1.75 20 – 40 <br />2 – 4 44 – 72 <br />4 or greater Over 100 <br />Tornado <br />A tornado is a narrow, violently rotating column of air that extends from a thunderstorm to the ground. A <br />tornado is hard to see unless it forms a condensation funnel made up of water droplets, dust, and debris. <br />Tornadoes are among the most violent phenomena of all atmospheric storms and atmospheric scientists <br />continue to conduct research to better understand how tornadoes form. Tornadoes come from mainly <br />two (2) types of thunderstorms – supercell and non-supercell.185F <br />185 Table 4-95 outlines the types of <br />tornadoes.186F <br />186 <br />Table 4-95. Types of Tornadoes <br />Type Description <br />Supercell <br />The most common and destructive tornadoes occur from supercells. A supercell is a <br />rotating thunderstorm with a well-defined radar circulation called a mesocyclone. <br />Supercells can also produce damaging hail, severe non-tornadic winds, frequent <br />lightning, and flash floods. The rotating updraft from a supercell is the key development <br />for a tornado. One way a column of air can begin to rotate is from wind shear when winds <br />at two (2) different levels above the ground blow at different speeds or in different <br />directions. Once the updraft is rotating and fed with warm moist air flowing in the ground <br />level, a tornado can form. <br />Non-Supercell <br />Nearly 20% of all tornadoes are associated with lines of strong thunderstorms called <br />quasi-linear convective systems (QLCS). QLCS tornadoes frequently occur during the <br />late night and early morning hours. These tornadoes, however, tend to be weaker and <br />shorter-lived on average than those associated with supercell thunderstorms. NOAA’s <br />National Severe Storms Laboratory (NSSL) researchers are looking for ways to detect <br />QLCS tornadoes more effectively. <br />Another type of non-supercell tornado is a landspout. A landspout is a tornado with a narrow, rope-like condensation funnel that forms while <br />the thunderstorm cloud is still growing and there is no rotating updraft - the spinning motion originates near the ground. <br />Strong Winds/Damaging Winds <br />Strong winds/damaging winds are classified as those exceeding 58 mph and are often called “straight- <br />line” winds to differentiate the damage they cause from tornado damage. Damage from strong <br />winds/damaging winds accounts for half of all severe weather reports in the lower 48 states and is more <br />common than damage from a tornado. These types of winds can reach up to 100 mph and produce a <br /> <br />184 NOAA, National Severe Storms Laboratory. (n.d.). Severe Weather 101: Hail Basics. Retrieved from <br />https://www.nssl.noaa.gov/education/svrwx101/hail/. <br />185 NOAA, National Severe Storms Laboratory. (n.d.). Severe Weather 101: Tornado Basics. Retrieved from <br />https://www.nssl.noaa.gov/education/svrwx101/tornadoes/. <br />186 NOAA, National Severe Storms Laboratory. (n.d.). Severe Weather 101: Types of Tornadoes. Retrieved from <br />https://www.nssl.noaa.gov/education/svrwx101/tornadoes/types/.