How Wind-Driven Wildfires Storm the LA Area
The Unprecedented Weather Phenomenon
A look at how intense gusts rarely seen in Southern California stoked blazes in urban areas in and around Los Angeles.
What Causes Santa Ana Winds?
Santa Ana winds occur when there is high pressure to the east, in the Great Basin, and a low-pressure system off the coast. Air masses move from high pressure to low pressure, and the more extreme the difference in pressure, the faster the winds blow.
Topography Plays a Role
As the winds rush downslope from the top of the San Gabriel Mountains, they become drier and hotter. This is a function of the physics of air masses. By the time the winds reach the point where the Eaton fire broke out in Altadena on January 7, they were reported to have reached 60 to 70 mph.
Have the Santa Ana Winds Changed Over Time?
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.
The Impact of the Wind on the Fires
With the winds so strong, there was little firefighters could do to control the flames. Jon Keeley, a research ecologist with the U.S. Geological Survey and adjunct professor at UCLA, explained that the strong, dry winds are often around 30 to 40 mph, but they can be stronger. The winds in early January were reported to have reached 60 to 70 mph.
What’s Ahead?
The Santa Ana Wildfire Threat Index is reporting moderate Santa Ana wind conditions continue Sunday, January 12. There will be somewhat of a lull later this afternoon through Monday morning, then another long-duration moderate event will begin. Exceptionally dry fuel conditions are present over Southern California.
Conclusion
The recent Santa Ana wind-driven wildfires in the Los Angeles area have brought devastation to the region. As the winds continue to pose a threat, it is essential to understand the causes and impacts of this phenomenon. The changing weather patterns, population growth, and infrastructure development have all contributed to the increasing risk of wildfires in the region.
FAQs
- What is a Santa Ana wind?
A Santa Ana wind is a type of strong, dry wind that occurs when there is high pressure to the east and a low-pressure system off the coast. - What are the causes of Santa Ana winds?
Santa Ana winds are caused by the movement of air masses from high pressure to low pressure, with the more extreme the difference in pressure, the faster the winds blow. - Have the Santa Ana winds changed over time?
The timing of Santa Ana wind events has shifted from fewer events in September and more in December and January, but there is no substantial evidence to link this to global warming. - What are the impacts of Santa Ana winds on wildfires?
The strong, dry winds can spread fires quickly, making them difficult to control. The recent wildfires in the Los Angeles area are a prime example of this. - What’s ahead for the region?
The Santa Ana Wildfire Threat Index is reporting moderate Santa Ana wind conditions continue, with a lull expected later this afternoon through Monday morning, followed by another long-duration moderate event.
