Officials and experts say low humidity, high fuel load and sloping topography create a “perfect recipe” for extreme fire behavior at Oak Fire in central California.
The fire exploded overnight in Mariposa County after starting Friday afternoon, spreading to 6,500 acres by Saturday morning. The fast-moving blaze, about an hour from Yosemite National Park, exhibits “extreme” fire activity, Cal Fire said in a morning incident report, and has destroyed 10 structures and threatens 2,000 more. .
Sierra National Forest spokesman Daniel Patterson said Saturday the fire appeared to be due to weather and topography. A “full combination of factors” led to explosive growth on Friday and overnight, including dry, hot weather, and rugged terrain with an abundance of dry trees and grass.
“There was decent wind yesterday, and we’re in a 1,200-year drought,” Patterson added. “And all of that is the perfect recipe for extreme fire behavior. We have seen this in California in recent years.
Oak Fire displays unusual nighttime behavior
California fires tend to slow overnight when temperatures drop and humidity rises. But the Oak Fire burned actively through the night, Cal Fire said, amid poor moisture recovery and warmer than normal temperatures.
Crews working to establish containment lines must contend with steep topography that allows the fire to spread quickly. Crews also have to deal with abundant sources of fuel. The area in which the fire is burning – near Jerseydale and Bootjack – has not burned since 1924, Crystal Koldenpyrogeographer and professor at UC Merced, said Friday.
Kolden, who studies wildfires, added that the Oak Fire spread so quickly due to three main factors: fuel load, heat and very dry air due to a 108 degree day.
The fire spreads in all directions
Daniel Swain, a climatologist and fire expert at UCLA, wrote on social media on Saturday that an “interesting and complicated” aspect of the initial Oak Fire explosion is that it was able to spread to all areas. directions, both uphill and downhill. Swain attributed the phenomenon to the dry fuel load of the ongoing drought.
The blaze was caused by windy conditions on Friday, which died down on Saturday, Patterson said. But Swain said on social media that the lack of wind may not slow the blaze, which appears to be “heavily fuel and topography driven”.
“With (the Oak Fire), the series of relatively small, non-destructive wildfires in California so far this season appear to be over,” Swain said. wrote in a social media post. “It continues to be an intense and rapid fire.”
Fresno Bee’s Bryant-Jon Anteola contributed to this story.
This story was originally published July 23, 2022 1:10 p.m.