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LLNL Emergency Management Plan Rev 24 January 2019 1.4.2.4 Meteorology The climate at both sites is characterized by mild, rainy winters and warm-to-hot, dry summers, with strong seasonal wind and rainfall patterns. Wind patterns at both sites tend to be dominated by the thermal draw of the warm San Joaquin Valley that results in wind blowing from the cool ocean toward the warm valley during the warm season, increasing in intensity as the valley heats up. During the winter, the wind blows from the northeast more frequently as cold, dense air spills out of the San Joaquin Valley. The meteorological conditions at Site 300 are also strongly influenced by higher elevation and more pronounced topological relief. Approximately 55% of the rain at both sites falls in January, February, and March and approximately 80% falls in the five months from November through March, with very little rain falling during the warmer months. The average wind speed in 2017 at Site 200 was 2.2 m/s (4.9 mph); at Site 300 it was 5.5 m/s (12.3 mph), based on data from the LLNL Environmental Report for 2017, Table 1-1, dated October 1, 2018 (UCRL-TR-500027-17). 1.4.2.5 Natural Phenomena Tornadoes/High Winds Tornadoes and high winds are not major concerns for emergency planners at LLNL because they are rare events and historically have not caused significant damage in Alameda or San Joaquin County. Since 1950, only three tornadoes have been recorded in Alameda County, CA, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center Storm Events Database, all of which were rated as FO tornadoes on the Fujita Scale. In San Joaquin County, where Site 300 is located, 18 tornadoes have been recorded since 1950, fourteen of which were F0, two of which were F1, and two of which had an unknown ranking on the Fujita Scale. The Fujita Scale (F-Scale), or Fujita—Pearson Scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation, where FO represents light damage, F 1 moderate damage, F2 considerable damage, F3 severe damage, F4 devastating damage, and F5 incredible damage. Earthquakes A major earthquake is a credible disaster caused by a natural phenomenon that is likely to involve the entire Laboratory and the entire surrounding community. Hazard mitigation at LLNL is achieved by complying with building codes, applying good engineering and housekeeping practices, and providing training programs required for managers and workers. LLNL's approach to responding to a severe event is discussed in Section 1.3.3 of this Emergency Plan. The Livermore valley is bounded in part by active faults (Figure 1.2). The Greenville Fault zone bounds the Livermore valley on the northeast. The northeast-trending Las Positas Fault zone forms the boundary of the southeast corner of the valley. The Mount Diablo Fold and Thrust Belt, north and west of the site, includes the Williams and Verona faults southwest of Livermore 18