(Los Angeles) – A strong wind event is shaking California in January, with both Diablo and Santa Ana winds taking hold. These winds, which form under certain atmospheric conditions, have contributed to devastating fires in Southern California, where severe drought and dry conditions are exacerbating the problem.
In the hours leading up to the powerful Santa Ana winds sweeping through Los Angeles, there were milder Diablo winds felt further north, in areas like the Bay Area. While the Diablo winds mainly brought gentle breezes, the Santa Ana winds led to dangerous fires, igniting homes and causing fatalities. These winds, both part of the same weather system, differ mainly due to rainfall differences in the two regions.
Southern California has been battling intense wildfires, especially as strong winds have fanned the flames. As of January 11, 2025, the Palisades Fire in Los Angeles County had led to the deaths of at least 11 people and the destruction of 9,000 structures. More than 100,000 people were forced to evacuate, further highlighting the severity of this wind-driven disaster.
Atmospheric scientist Neil Lareau from the University of Nevada explained that the same weather system generating Santa Ana winds also creates Diablo winds, though the latter usually arrives earlier, about 12 to 24 hours before. While Diablo winds are more common in the Bay Area, the stronger Santa Ana winds are more closely associated with Southern California’s dangerous fire conditions.
The winds have a distinct origin. Both the Santa Ana and Diablo winds start in the high-pressure areas of the northern Great Basin, in the deserts of the western United States. These winds build in pressure, race westward, and then move towards low-pressure areas along California’s coast. As they drop down mountain slopes, they accelerate, speeding up through passes like Soledad, Cajon, and San Gorgonio, creating hazardous conditions. Their speeds reached up to 100 miles per hour in some places on January 8, 2025, the strength of a Category 1 hurricane.
One of the most significant dangers posed by these winds is their ability to spread fires. The wind speed and dry conditions combined with low humidity can turn what might otherwise be a minor flame into a massive wildfire. With fuel sources such as dry grass and brush, a fire can spread uncontrollably.
The Diablo and Santa Ana winds are classified as foehn winds, a type of wind phenomenon common in many mountainous regions around the world, including the Rocky Mountains (known as Chinook winds), the Alps (favogn winds), and the Andes (puelche winds). The phenomenon occurs when air, having been compressed and heated as it moves downhill, causes temperatures to rise rapidly and humidity to drop, making the environment more prone to fires.
As the winds descend from the mountains into the valleys, they warm the atmosphere. In places like San Francisco, the temperature reached a warm 73 degrees on January 10, while temperatures remained comfortable in Oakland and San Jose. However, this warming effect is dangerous as the relative humidity decreases, drying out vegetation and increasing the likelihood of fires. This was seen in previous years, such as the Tubbs Fire in 2017 and the Camp Fire in 2018.
Though the winds are strongest in the fall, when conditions are the driest, they also occur in January and other parts of the cold season. A study by San Jose State University revealed that Diablo wind events are most common in October, but January also sees a higher number of such events compared to November, with a frequency of 80% of that seen in peak months.
For those in the Bay Area, Diablo winds typically occur without the same intensity as in Southern California, where dry conditions create a greater fire hazard. The Bay Area has seen more rain than Los Angeles, where the lack of rainfall has left the region vulnerable to catastrophic fires. As California faces a dangerously dry January, conditions are ripe for a repeat of previous devastating fire seasons.
On a broader scale, climate scientists are noting that the planet’s average temperature crossed a worrying threshold in 2024, marking an increase of over 1.5 degrees Celsius above pre-industrial levels. While this data reflects only one year, it adds to growing concerns about the acceleration of climate change, making extreme weather events like these winds and wildfires more likely.
The winds, while predictable in some ways, have also proven dangerous due to their sheer strength and the dry, unrelenting conditions in Southern California. “When the ingredients for these really strong events align,” said Lareau, “we can get very strong winds in places like Pasadena that are often more sheltered.”
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