How Santa Ana Winds Fueled the Deadly Fires in Southern California
This year, however, Southern California has very dry conditions, with very little moisture over the past several months. With these extreme winds, we have the perfect storm for severe fires.
It’s very hard to extinguish a fire under these conditions. The firefighters in the area will tell you, if there’s a Santa Ana wind-driven fire, they will evacuate people ahead of the fire front and control the edges – but when the wind is blowing like this, there’s very little chance of stopping it until the wind subsides.
Other states have seen similar fires driven by strong downslope winds. During the Chimney Tops 2 Fire in Tennessee in November 2016, strong downslope winds spread the flames into homes in Gatlinburg, killing 14 people and burning more than 2,500 homes. Boulder County, Colorado, lost about 1,000 homes when powerful winds coming down the mountains there spread the Marshall Fire in December 2021.
Have the Santa Ana winds changed over time?
Santa Ana wind events aren’t new, but we’re seeing them more often this time of year.
My colleagues and I recently published a paper comparing 71 years of Santa Ana wind events, starting in 1948. We found about the same amount of overall Santa Ana wind activity, but the timing is shifting from fewer events in September and more in December and January. Due to well-documented trends in climate change, it is tempting to ascribe this to global warming, but as yet there is no substantial evidence of this.
California is seeing more destructive fires than we saw in the past. That’s driven not just by changes in the climate and the winds, but also by population growth.
More people now live in and at the edges of wildland areas, and the power grid has expanded with them. That creates more opportunities for fires to start. In extreme weather, power lines face a higher risk of falling or being hit by tree branches and sparking a fire. The area burnt because of fires related to power lines has greatly expanded; today it is the major ignition source for destructive fires in Southern California.
The Eaton Fire, which has burned many homes, is at the upper perimeter of the San Gabriel Basin, at the base of the San Gabriel Mountains. Fifty years ago, fewer people lived there. Back then, some parts of the basin were surrounded by citrus orchards, and fires in the mountains would burn out in the orchards before reaching homes.
Today, there is no buffer between homes and the wildland. The point of ignition for the Eaton Fire appears to have been near or within one of those neighborhoods.
Homes are made of dried materials, and when the atmosphere is dry, they combust readily, allowing fires to spread quickly through neighborhoods and creating a great risk of destructive fires.
This article, originally published Jan. 8, has been updated with new details on the fires.
Jon Keeley is Research Ecologist, USGS; Adjunct Professor, University of California, Los Angeles. This articleis published courtesy of The Conversation. This article, originally published Jan. 8, has been updated with new details on the fires.
