What are Diablo winds fanning California’s fires?

Just as Southern California has its notorious Santa Ana winds, Northern California’s most infamous winds are known as “Diablo” winds. These are the winds that are fueling the Kincade Fire, now raging in California’s wine country.

Like Santa Ana winds, Diablo winds originate hundreds of miles inland in the desert regions of the Great Basin, according to the Los Angeles Times. There, circulation of air around a strong area of surface high atmospheric pressure flows over the Sierra Nevada, heading toward lower pressure at sea level.

The resulting flow from high pressure inland to lower pressure off the California coast is warmed and dried by compressional heating as the air sinks from the Great Basin, which is 4,000 to 5,000 feet in elevation, down to sea level, said meteorologist Jan Null of Golden Gate Weather Services.

The dry, northeasterly offshore flow clears out the marine fog and stratus clouds that usually drape the San Francisco Bay Area, and it can create extremely dangerous fire conditions throughout Northern California because of the strong winds and low relative humidity, the Times said.

The seasonal timing of Diablo and Santa Ana winds is extremely important in regard to wildfire danger, Null said. One of the chief characteristics of California’s predominantly Mediterranean climate is its extended dry period from about May through October.

Consequently, in the fall, these strong, warm and dry winds occur after months of very little, if any, precipitation and when fuels (such as grasses, shrubs and forests) are at their driest.

The term “Diablo Winds” dates to shortly after the 1991 Tunnel Fire, which devastated a large area of the Oakland and Berkeley hills, according to Null.

“We somehow fell upon the name Diablo Winds as a double entendre,” Null said, “because they generally blow from the direction of Mt. Diablo in the far East Bay, and ‘diablo’ translates from Spanish as ‘devil’; thus, devil winds.”

Doyle Rice