Millions of acres in California have already burned during this year’s California wildfire season. But forecasters say that hot, dry air known as Diablo winds in portions of Northern California could make fires even more destructive.
As the Glass Fire consumes more than 50,000 acres in Napa and Sonoma Counties, forecasters and fire officials, worried that these intense winds could make the fire worse or that others could spread more rapidly, are warning residents to be careful not to spark new flames.
“All we need is one little ember, and we can get a really big fire going,” said Gerry Diaz, a National Weather Service meteorologist in San Francisco.
Here’s what we know about Diablo winds.
What are Diablo winds?
The winds, which take their name from the Diablo mountain range southeast of San Francisco, blow down toward the Pacific Ocean from higher elevations in the northeast, according to Jake Sojda, a meteorologist at AccuWeather. They are similar to Santa Ana winds in Southern California, he added.
Diablo winds can happen at any time in the year, but they typically peak in October and November.
As the winds race down the mountains, they speed into valleys and lower terrain areas, Mr. Diaz said. They blow from hot and arid inland areas toward the coast, getting drier as they move.
Gusts from the winds making their way down Mount Diablo can be rapid, sometimes reaching speeds over 90 miles per hour.
What do Diablo winds mean for wildfires?
Diablo winds have helped fuel and balloon the Glass Fire, according to Roger Gass, a National Weather Service meteorologist in San Francisco. California firefighters are concerned about how the winds could worsen the fire, which started on Sunday and has already burned more than 50,000 acres in Napa and Sonoma Counties.
The Glass Fire was only 5 percent contained on Thursday and its cause was still under investigation, according to Cal Fire, the state’s fire agency. Emergency officials have issued evacuation orders affecting thousands. Over 200 structures have already been destroyed.
Meteorologists said these strong gusts of wind, in conjunction with already precarious wildfire conditions in the state, could make a bad wildfire season worse as the winds fan flames and spread embers.
Diablo winds helped exacerbate some recent fires, including last year’s Kincade Fire and the deadly Camp Fire in 2018.
The Kincade Fire, which burned more than 77,000 acres in Sonoma County, started with already windy conditions and spread rapidly, according to Lynne Tolmachoff, a Cal Fire spokeswoman.
The Camp Fire was one of the deadliest wildfires in California’s history, killing 85 people and destroying more than 18,000 structures. Mr. Sojda said the fire swept through one town in a matter of hours, largely because of strong wind gusts.
“Weather-wise, any type of wind is bad when these fires get going,” Mr. Sojda said.
What are firefighters doing to prepare for the winds?
While the weather was cooperative over the past few days, firefighters focused on containing the Glass Fire and slowing the spread as best they could in areas that would be most affected by the winds, Ms. Tolmachoff said. But the terrain has proved to be challenging, she added.
Once gusts reach 25 m.p.h., firefighting becomes tough, she said, and firefighters typically pivot to work on evacuations until weather conditions improve.
“They will get tested by those winds just like the very first day that fire started,” she said.