Publication Date

Fall 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Meteorology and Climate Science

Advisor

Craig C. Clements

Keywords

Diablo Winds, Downslope Winds, Fire Weather, Foehn Winds, Oakland Hills Fire, Tubbs Fire

Subject Areas

Meteorology

Abstract

Extreme fire behavior in the San Francisco Bay Area (SFBA) has historically been associated with strong offshore wind events referred to locally as Diablo winds. A 17 year surface-based climatological analysis was performed to establish a definition of Diablo winds and to identify their frequency and spatial distribution. Synoptic composites of events were constructed using North American Regional Reanalysis, and high resolution Weather Research and Forecasting (WRF) model simulations were used to investigate the mesoscale dynamics of three significant Diablo wind events. Diablo winds were defined as dry northeasterly, downslope winds that occur in the SFBA with minimum sustained wind speeds of 6 m s-1. Climatological analysis results illustrate that Diablo winds most frequently impact the Coast Ranges nearest the Sacramento Valley and occur, on average, 2.5 times annually. The highest monthly frequency occurs in October when live fuel moisture is at its driest, creating the most severe fire danger for the SFBA during that time. Numerical simulations of significant Diablo events revealed that Diablo winds have complex character with contributions from small-scale downslope winds, as well as large-scale mountain waves interacting with terrain.

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