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LLNL Emergency Management Plan (EPlan) <br />Rev 27 <br />January 2022 <br /> <br /> 18 <br />The average wind speed in 2020 at Site 200 was 2.1 m/s (4.7 mph); at Site 300 it was 5.5 m/s <br />(12.3 mph), based on data from the LLNL Environmental Report, Table 1-1, dated <br />October 1, 2021 (UCRL-TR-500027-20). <br />Wind roses in Figure 1.2 show wind direction and wind speed frequencies at the Livermore site <br />and Site 300 during 2020. The length of each spoke is proportional to the frequency at which the <br />wind blows from the indicated direction. Different line widths of each spoke represent wind <br />speed classes. <br /> <br />Figure 1.2 2020 Wind Roses <br />1.4.2.5 Natural Phenomena <br />Tornadoes/High Winds <br />Tornadoes and high winds are not major concerns for emergency planners at LLNL because they <br />are rare events and historically have not caused significant damage in Alameda or San Joaquin <br />County. Since 1950, only three tornadoes have been recorded in Alameda County, CA, <br />according to the National Oceanic and Atmospheric Administration’s National Climatic Data <br />Center Storm Events Database, all of which were rated as F0 tornadoes on the Fujita Scale. In <br />San Joaquin County, where Site 300 is located, 18 tornadoes have been recorded since 1950, <br />fourteen of which were F0, two of which were F1, and two of which had an unknown ranking on <br />the Fujita Scale. The Fujita Scale (F-Scale), or Fujita–Pearson Scale, is a scale for rating tornado <br />intensity, based primarily on the damage tornadoes inflict on human-built structures and <br />vegetation, where F0 represents light damage, F1 moderate damage, F2 considerable damage, <br />F3 severe damage, F4 devastating damage, and F5 incredible damage.