Characteristics of Diablo Winds from a Climatology of Surface Observations

Diablo winds are generally considered to be dry and gusty north-northeasterly windstorms that affect the Northern Sierra Nevada and Bay Area. On the evening of 2017 10 08, Diablo winds contributed to the ignitions and spread of the “Northern California Firestorm”, including the Tubbs Fire, which burned 2,800 homes in Santa Rosa, resulted in 22 fatalities and $1.2B USD in damages. Although Diablo winds and Santa Anas are often compared to each other, very little is known about dynamical mechanisms that cause Diablo Winds, their frequency of occurrence and their general characteristics. Here we use a record of surface observations from all NWS and RAWS stations in California to build a climatology of Diablo wind events, including providing a definition of what a Diablo wind is, and discuss dynamical coupling between synoptic and mesoscales, which, in conjunction with localized terrain induced non-linear flow, provide the requisite preconditions for Diablo winds to occur.