The Climatology and Seasonal Forecasting of Santa Ana winds across Southern California

The season for Santa Ana (SA) winds (common to Southern California) typically begins as early as September and can last until early June.  During the fall months when the native vegetation tends to be the driest, these dry offshore winds can lead to catastrophic wildfires. The Santa Ana Wildfire Threat Index (SAWTI) is an index that quantitatively measures the severity of SA winds based on the potential for a major wildfire to occur.  During the SAWTI development phase, a high resolution 30-year weather and fuels climatology was created to help put current and future SA wind events into historical perspective.  We now leverage the SAWTI to produce an authoritative and descriptive climatology of SA winds for multiple regions across Southern California.  Using this climatological dataset, we will investigate any inter-annual cycles and trends, and differentiate SA wind types.  We have found multiple statistically significant relationships between standardized SA wind days per month and publicly available climate indices including the Pacific Decadal Oscillation (PDO) and the Ocean Niño Index (ONI).  Using this unique data set and these discovered relationships, we are producing forecasts of SA wind day frequencies for one month and three month time periods through a forecast ensemble framework consisting of ARIMA time series, machine learning, and analog models.  These forecasts will help fire agencies make better long-term staffing and resource decisions in the preparation for future potential catastrophic wildfires.