A sundowner is a northerly offshore wind in Santa Barbara, California. It occurs when a region of high pressure is directly north of the area, the coast of which trends east–west. This contrasts with the more typical onshore flow. The winds blow with greatest force when the pressure gradient is perpendicular to the axis of the Santa Ynez Mountains, which rise directly behind Santa Barbara. These winds often precede Santa Ana events by a day or two, as it is normal for high-pressure areas to migrate east, causing the pressure gradients to shift to the northeast.
Sundowners are particularly dangerous during wildfire season because the air heats and dries as it descends from the mountains to the sea. Gale force hot, dry winds can make firefighting impossible. A sundowner quickly burned a swath from the mountains through populated areas and across Highway 101 into Hope Ranch during the 1990 Painted Cave Fire. The most intense periods of the Jesusita Fire's destruction have also been blamed on sundowner winds. The Sherpa Fire grew to 4,000 acres (1,600 ha) overnight due to the sundowner winds, destroying the water system for El Capitán State Beach at the beginning of the 2016 fire season.
The etymology of the word sundowner is uncertain, but it may derive from the Spanish term zonda, or from the Arabic simoom, which are both similar wind phenomena.. It is also typically the case that sundowner winds commence in the evening right around sunset, when onshore sea breezes abate, and offshore flows, such as the sundowners, pick up.
- Ryan, G., and L. E. Burch, 1992. An analysis of sundowner winds: A California downslope wind event. Preprints, Sixth Conf. on Mountain Meteorology, Portland, Oregon, Amer. Meteor. Soc., 64–67.
- Serna, Joseph; Fernandez, Alexia (June 17, 2016). "Santa Barbara County declares state of emergency after wildfire grows to 4,000 acres overnight". Los Angeles Times. Retrieved 17 June 2016.
- Pine, Stephen J. (2016). California: A Fire Survey. Tucson: University of Arizona Press. p. 66. ISBN 0816532613.