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2025 Hazard Mitigation Plan <br />Kittitas County, Washington <br /> <br /> <br />Chapter 4: Hazard Identification and Risk Assessment 152 <br />damage path extending hundreds of miles.187F <br />187 Table 4-96 outlines the different types of strong winds.188F <br />188 <br />Strong winds in the State of Washington are often associated with atmospheric river events. Atmospheric <br />rivers are long, concentrated regions in the atmosphere that transport moist air from the tropics to higher <br />latitudes. The combination of moist air and high wind speeds produces heavy precipitation upon landfall, <br />especially over mountainous terrain. As atmospheric rivers move over land, conditions can be similar to <br />a tropical cyclone leading to flash flooding, landslides, cyclone force winds, increased wave heights, and <br />catastrophic damage to life and property.189F <br />189 Refer to the flood and landslide sections of this Plan for <br />further details on these hazards. Over the last 20 years, studies show that globally half of the most <br />extreme mid-latitude windstorms were associated with atmospheric rivers, causing billions of dollars in <br />damages.190F <br />190 <br />Table 4-96. Types of Strong Winds <br />Type Description <br />Straight-line Wind Term is used to define any thunderstorm wind that is not associated with a rotation and <br />is used mainly to differentiate from tornadic winds. <br />Downdraft A small-scale column of air that rapidly winds towards the ground. <br />Macroburst <br />An outward burst of strong winds at or near the surface with horizontal dimensions larger <br />than 2.5 miles and occurs when a strong downdraft reaches the surface. Macroburst <br />winds may begin over a smaller area and then spread out over a wider area, sometimes <br />producing damage similar to a tornado. Although usually associated with thunderstorms, <br />macrobursts can occur with showers too weak to produce thunder. <br />Microburst <br />A small, concentrated downburst that produces an outward burst of strong winds at or <br />near the surface. Microbursts are small (less than 2.5 miles across) and short -lived (five <br />(5) to 10 minutes) with maximum windspeeds sometimes exceeding 100 mph. There ar e <br />two (2) kinds of microbursts – wet and dry. A wet microburst is accompanied by heavy <br />precipitation at the surface. Dry microbursts, common in places like the high plains and <br />the intermountain west, occur with little or no precipitation reaching the ground. <br />Gust Front <br />The leading edge of rain-cooled air that clashes with warmer thunderstorm inflow. Gust <br />fronts are characterized by a wind shift, temperature drop, and gusty winds out ahead <br />of a thunderstorm. Sometimes the winds push up air above them, forming a shelf clou d <br />or detached roll cloud. <br />Derecho <br />A widespread, long-lived windstorm that is associated with a band of rapidly moving <br />showers or thunderstorms. A typical derecho consists of numerous downbursts and <br />downburst clusters. By definition, if the wind damage swath extends more than 240 miles <br />and includes wind gusts of at least 58 mph or greater along most of its length, then the <br />event may be classified as a derecho. <br />Haboob A wall of dust that is pushed out along the ground from a thunderstorm downdraft at high <br />speeds. <br />*A downburst is the general term used to broadly describe macro and microbursts. <br /> <br /> <br />187 NOAA, National Severe Storms Laboratory. (n.d.). Severe Weather 101: Damaging Winds Basics. Retrieved <br />from https://www.nssl.noaa.gov/education/svrwx101/wind/. <br />188 NOAA, National Severe Storms Laboratory. (n.d.). Severe Weather 101: Types of Damaging Winds. Retrieved <br />from https://www.nssl.noaa.gov/education/svrwx101/wind/types/. <br />189 National Oceanic and Atmospheric Administration. (2023). Atmospheric Rivers: What are They and How Does <br />NOAA Study Them? Retrieved from https://research.noaa.gov/2023/01/11/atmospheric-rivers-what-are-they-and- <br />how-does-noaa-study-them/. <br />190 Buis, A. (2017). In Atmospheric River Storms, Wind Is a Risk, Too. Retrieved from <br />https://www.jpl.nasa.gov/news/in-atmospheric-river-storms-wind-is-a-risk-too.