Here's What Makes the Winds Driving the Kincade Fire So Unusual

Almost a week after it began, the Kincade Fire in Sonoma County is only 15% contained. Emergency officials and meteorologists say this fire has been so hard to control because intense winds have caused flames to spread rapidly and unpredictably.

Last Wednesday evening, high winds predicted for Sonoma County prompted power shutoffs in the region, and PG&E reported that equipment on a transmission tower near the fire’s origin broke right around the time it ignited.

On Sunday, winds blew with speeds upward of 90 mph; a single gust recorded from a PG&E weather sensor in northern Sonoma County passed the 100 mph mark. Fire officials warn that another high-wind event forecast for Tuesday night into Wednesday morning could continue to prevent crews from bringing the fire under control. 

Brian Garcia, warning coordination meteorologist with the National Weather Service for the Bay Area, says several characteristics of the winds in the region make the current conditions “unprecedented.”

Three Events in Less Than a Week 

It’s unusual to log so many offshore wind events (i.e., winds blowing from land out toward the ocean) in such a short span of time, Garcia says. Including the winds predicted for Tuesday night, there will have been three major wind events in fewer than seven days.  

“I’ve never seen it happen this way in my 10 years forecasting on the California coast,” he adds.

Garcia says people in his field don’t record wind records in databases the same way they keep temperature data. Because winds shift constantly they’re harder to monitor. So weather watchers track wind data in “storm reports” that chronicle the effects of extreme weather events.

After the 2017 Wine Country fires, Garcia says PG&E and the National Weather Service have gotten better at tracking the speed of winds in the region.

Wind Speeds Topping 100 Miles Per Hour

An analysis of weather data captured during the Wine Country fires estimated that wind gusts in isolated areas topped 100 mph.

“That event … was the biggest event we’ve ever seen in the Bay Area, at least in recorded history and personal knowledge from various people around the Bay Area,” Garcia says. 

In the aftermath, PG&E increased the number of wind sensors in the region. The utility shares this data with the National Weather Service. 

Garcia says another wind event on Sunday with speeds between 80 and 90 mph eventually crossing the 100 mph barrier, only two years after 2017’s historic wind event, may signal a significant shift in what to expect from now on.

Historic? It’s All About Duration 

In addition to the wind speed Sunday, he says, another factor makes them stand out.  

“The thing that really made it historic and unprecedented is the longevity of those winds. So we went for over 24 hours with very strong wind,” Garcia says. 

That type of high wind event typically lasts for 6 to 12 hours, he says, then adds, “this one was extended by about double of what we typically see as our max.”

While downslope, dry winds are not unusual for autumns in California, the strength of this event was, says Craig Clements, director of San Jose State University’s Fire Weather Research Lab.

“To have 100-mile-an-hour winds, at these mountain peaks, is extraordinary. That’s not common. 75? You know, that happens, not all the time, but it does happen a lot,” Clements observes. “I would say that because these winds were so extreme, that made this event unique.”

Fire crews will have a short respite from windy conditions until Tuesday night. Garcia says weather models forecast the next event to last into Wednesday morning. Then they expect speeds in the 40 to 50 mph range — significantly less intense than Sunday’s gusts, but similar to speeds observed last Wednesday when the fire broke out.