Wildfire — East Bay Hills and the Diablo Range, California
2020-08-16 to 2020-08-31 · East Bay Hills and the Diablo Range, California
Event narrative
After multiple lightning strikes across the region and breezy erratic winds, approximately 20 separate fires broke out across counties (Santa Clara, Alameda, Contra Costa, San Joaquin, and Stanislaus) the morning of August 16th. These fires were later re-named the SCU Lightning Complex Fires https://www.fire.ca.gov/incidents/2020/8/18/scu-lightning-complex/. This complex became one of the top 5 largest fires in California State history prompting numerous evacuations, destroying nearly 400,000 acres and destroying over 200 structures. These fires resulted in 6 injuries (Civilian and Fire Personnel). The fires came dangerously close to the historic Lick Observatory on Mount Hamilton https://arstechnica.com/science/2020/08/a-california-wildfire-nearly-destroyed-the-historic-lick-observatory/. The fire was still burning at the end of August.
Wider weather episode
A prolonged and oppressive heat wave swept the Central Coast and Bay Area for almost a week from August 14th to August 19th with widespread record breaking temperatures observed across the region. This was caused by a strong high pressure system over the Desert Southwest that expanded westward into California. This dome of heat brought hot temperatures to the area for several days. Multiple days of triple digit afternoon highs were recorded inland with some coastal locations even reaching the mid 90s. Several days of hot and dry weather further dried fuels over the area increasing fire danger. During this event, a surge of monsoonal and tropical moisture from a former Tropical Storm advected northward with sufficient instability to generate multiple high based and dry thunderstorms that produced several thousand lightning strikes over the Greater Bay Area. Many locations saw wind gusts of 40-50 mph with isolated areas seeing gusts of 60-75 mph. This prompted the San Francisco Bay Area forecast office to issue a rare severe thunderstorm warning. These lightning strikes in combination with gusty and erratic outflow winds sparked hundreds of wildfires across the state of California. Several smaller fires combined to form complexes some of which are now among the largest wildfires in state history. Most of which were still actively burning at the end of August. Hundreds of thousands of acres have been burned with several hundred structures destroyed as well as a handful of deaths and injuries. Tens of thousands of residents were also forced to evacuate. Additionally, all of these wildfires burning simultaneously across the state gave the Bay Area the worst air quality in the world at one point.
Source: NOAA Storm Events Database, event_id 912890. Narrative written by the NWS forecast office that issued the report.