Extreme heat has worsened the conditions driving the flames. The fire is chewing through dense forests and drought-induced twists on steep terrain in the Tahoe National Forest, and is threatening the nearby towns of Foresthill, Georgetown and Volcanoville. Cal Fire said the blaze has grown to about 23,000 acres and advanced yesterday, pushing into Volcanoville and destroying structures but not the entire community. No September in the West has seen such a heat wave “It’s the hottest fire of the season in Northern California,” Craig Clements, a professor of meteorology and climate science at San Jose State University, said in an interview. “These really extreme temperatures caused extensive drying of dead fuel.” Because of “continued dangerous fire weather,” California Gov. Gavin Newsom (D) on Thursday declared a state of emergency for counties affected by the Mosquito fire and also declared a state of emergency for the Fairview fire, which is burning in the South California. Regarding the Mosquito fire, Clements added that there is a “high risk for much of the area as this fire progresses, primarily due to dry fuel conditions.” He said the fire reminded him of the Creek Fire, which tore through the Southern Sierra Nevada in September 2020 and sparked two wildfires. Clements students were studying the Mosquito Fire on site as part of the National Oceanic and Atmospheric Administration-sponsored California Fire Dynamics Experiment and had a front-row seat when the fire exploded in size Thursday afternoon. Kate Forrest, a graduate research assistant at San José State’s Interdisciplinary Wildfire Research Center, described the fire as having strong, warm updrafts that penetrate the atmosphere and condense into huge clouds, also known as cumulus clouds. In this case, the plume of smoke reached so high—about 40,000 feet—that it formed a cloud of pyroclastic or pyroCb—a sure sign of extreme fire behavior. Forrest, whose research focuses on the factors that lead to fire-generated tornadoes, said the Mosquito Fire had a rotating column that was confirmed visually and by radar. “The fact that it was still putting up a pyrochlore after sunset was an indicator of how much heat this fire put out,” he said. “I was surprised”. The cause of the fire, which started on Tuesday, is being investigated. This week’s record-breaking heat was likely a catalyst for the extreme burning conditions seen yesterday. The major utility company Pacific Gas and Electric also reported that electrical activity on its equipment “occurred near the time of the fire report.” The area has been classified as “high risk” for fire all week for hot, dry and unsettled weather and highly flammable vegetation. “This is leading to extremely long burn periods and significant slope and fuel fires,” Brent Wachter, a fire meteorologist at the Northern California Geographic Area Coordinating Center, said in an email. Data shows fire danger in the Northern Sierra has skyrocketed in recent weeks, with vegetation nearing record lows for moisture content. Some areas, such as the Sacramento Valley and its foothills, have already reached that point, according to Wachter. An extreme heat warning continues Friday for the region, where the National Weather Service in Sacramento expects temperatures between 100 and 114 degrees in the valleys and foothills and up to 105 degrees in the mountains. An all-time high temperature record of 116 was set in downtown Sacramento on Tuesday. Rare tropical storm brings heavy rain, strong winds to California Because of the unsettled conditions, forecasters are also closely monitoring the remnants of Kay, which was downgraded from a hurricane to a tropical storm, given concerns that the surge of tropical moisture could unleash dry lightning and spark new fires. Forecasts show that dry lightning is possible in the Northern Sierra this weekend. There was also concern that strong winds from Kay could push the Fairview Fire farther into residential areas before significant rain reaches Southern California on Friday. The 27,319-acre fire has claimed two lives and destroyed a dozen buildings. According to the National Interagency Fire Center, 71 large wildfires are burning, mostly in the western United States, including 28 in Idaho, 12 in Montana, 11 in Oregon and eight in California. Red flag warnings for strong easterly winds have been issued for western Washington state and Oregon on Friday and Saturday, raising the risk of additional fast-spreading wildfires. Smoke from several wildfires in the West has compromised air quality in California and the Intermountain West and is expected to linger through at least the weekend. Unhealthy to hazardous conditions are in the Sierra Nevada, central Idaho and eastern Washington and could worsen for major cities along the West Coast. The National Weather Service in Medford, Ore., said smoke from the wildfires was drifting westward on easterly wind flow and warned that “the risk of rapid fire spread is significant today through Saturday.” Research has shown that climate change has contributed to an increase in the frequency of large wildfires and the size of the area burned by wildfires, as fire seasons become longer and more dangerous. In California, fall is also warmer and drier, with an increased risk of extreme fire weather. High tree mortality due to drought and high temperatures as well as overly dense forests from a long history of fire suppression are also important factors. “The fires are burning hotter and more intense than we’ve ever seen,” Forrest said.
