National Weather Service report shows strong winds played major role in California wildfires
A recent report from the National Weather Service in Monterey, California, revealed that extreme wind conditions were a major factor that contributed to the spread of wildfires that tore through northern California in October.
The National Weather Service (NWS) report from incident meteorologist Matthew Mehle addresses how weather-related conditions in Sonoma County were ripe to fuel the spread of the fires.
“The thing that’s most remarkable from a weather standpoint is how events unfolded during the fires,” Mehle said in an interview with Daily Energy Insider. “The wind conditions stuck out. It was such an extreme event.”
In fact, the NWS put out a Red Flag Warning in the lead up to the wildfires in October, due to humidity being around just 10 to 20 percent and gusting winds. Mehle said even National Weather Service models didn’t forecast winds hitting the 80-90 miles per hour gusts they did. The NWS had predicted winds of 60-70 mph, which would still have been incredibly strong for the area.
Three main factors contribute to the spread of wildfires, he explained: fuel, topography and weather. In this case, “high winds led to actual spread of the fire itself in such a short amount of time. In less than 8 hours, it burned most of the acreage that burned over the whole course of the blaze,” Mehle said.
The wildfires, the most damaging in the state’s history, killed more than 40 people and damaged over 8,000 structures, according to the California Department of Forestry and Fire Protection (Cal Fire). Statewide, insured losses from the wildfires in October total more than $3 billion, the California Department of Insurance said.
The official cause of the fires is still being investigated by Cal Fire, the California Public Utilities Commission (CPUC) and others.
Wildfires themselves also create wind, Mehle said, fueling a fire’s spread, and in northern California that was coupled with already excessively high winds in the area at the time of sparking.
The strong winds caused trees to topple and knock down power lines throughout counties in northern California.
Pacific Gas & Electric Co. filed 21 safety incident reports with the CPUC, which showed the widespread nature of the windstorm and its damage to trees and power lines during the fires that started on Oct. 8. In one such filing, PG&E reported that a 100-foot-tall Douglas fir tree uprooted and fell near Santa Rosa in Sonoma County, damaging electrical equipment on Oct. 8.
Mehle’s report noted the five years of record-breaking droughts the state has suffered. Although the state experienced rains more recently, that rain had a negative effect on fire conditions by contributing to an increase in undergrowth, Mehle said. So-called finer fuels like grass improved with the rains, even while larger fuel sources such as trees were still dry, having lacked sufficient time to soak up all that moisture and make up for years of sustained desiccation.
“Because we had a lot of rain over winter, the smaller fuels were rising, which would allow the fire to spread across the ground,” Mehle said. “We have larger fuels that are stressed, and finer fuels that grew because of all the rain. There were discussions nationally of potential for larger fires due to the green-up, the carrier fuels, and the five years of drought.”
“We knew something like this could happen,” he said.
Preparation would not be enough to deal with storms of that magnitude.
“There’s going to be a lot of research being done on this on the ground, the conditions of what actually happened,” Mehle said. “A lot of local universities are doing research on what caused this freak wind event.”
