The Franklin Fire – Are Santa Ana Winds Getting Worse?

Santa Ana winds intensified the ongoing Franklin fire in Malibu, California, forcing mass evacuations and valiant firefighting efforts. These hot, dry, powerful winds desiccate vegetation, carry embers, and increase flame length, accelerating wildfire spread. From 1990 to 2009, 50% of burned area and 80% of wildfire economic loss in Southern California was linked to Santa Ana winds (Kolden et al., 2018). More recent examples include the 2017 Thomas and 2020 El Dorado fires, which together burned over 300,000 acres.

Climate change is increasing annual average air temperatures and wildfire burned area across the Western US (NOAA, NIFC), but its impact and Santa Ana winds is uncertain. These winds are generated by pressure gradients between the warm Great Plains and the cooler Pacific Ocean that typically form during the autumn months. Reanalysis of weather data from 1979-2020 reveals that strengthening temperature gradients between coastal California and the continental interior may be increasing the frequency of these events (Thompson et al., 2023). However, global climate model outputs suggest that the frequency of Santa Ana winds may decline over the 21st century as the annual window of favourable conditions narrows (Guzman-Morales and Gershunov, 2020).

Though the evolution of Santa Ana winds as the climate changes is unclear, their devastating effect on wildfire activity continues to increase. California’s rainy season arrives ~27 days later than it did in 1960 (Lukovic et al., 2021). A extended wait for wildfire-relieving rains prolongs the period where vegetation dried over the summer months is exposed to Santa Ana winds. As a result, we may see an increasing number of late-season Santa-Ana-fuelled fires like the Franklin fire in the future.

Solid and dashed blue lines show the mean monthly precipitation for California between 1943-1963 and 2010-2023, respectively (National Oceanographic and Atmospheric Association). Yellow bars show the monthly average number of Santa Ana events recorded between 1948 and 2012 (Guzman-Morales et al., 2016).