Downslope Windstorms in Coastal Santa Barbara from Observations and Numerical Simulations

Downslope windstorms occur when atmospheric flow interacts with sufficiently large mountain barriers. Under influence of downslope windstorms, wildfires may grow to apocalyptic proportions as was shown by recent major wildfires in southern California. Understanding the main mechanisms controlling downslope windstorms is therefore crucial to advance the understanding of wildfire spread and increase resilience of communities residing in the wildland-urban interface. In this work, we investigate the influence of convective boundary layer development in a valley upstream of the Santa Ynez Mountain (SYM) on the onset development of downslope windstorms in coastal Santa Barbara, CA. Downslope windstorms in this area are known as Sundowners, indicating their relationship to sunset. We show from numerical simulations that the presence of a valley and a higher mountain range north (upstream), but also the Pacific Ocean south of SYM range may contribute to the diurnal manifestation of Sundowners on the leeside of SYM. Additionally, some instrumental platforms are being used to determine the importance of convective boundary layer development in the valley upstream of SYM to the onset of Sundowners on the leeside of SYM from an observational perspective. This work advances new theories related to downslope windstorms in coastal areas, and aids in the better prediction of wildfire spread.