The Sundowner Winds of Santa Barbara, California

Abstract

Significant downslope wind and warming events periodically occur along a short segment of the southern California coast in the vicinity of Santa Barbara. This region is characterized by a unique mesoscale topography:over a length of about 100 km the coastline is oriented approximately west?east, with the adjoining narrow coastal plain bounded by a steeply rising (to elevations greater than 1200 m) and coast-parallel mountain range. Called Sundowner winds because they often begin in the late afternoon or early evening, their onset is typically associated with a rapid rise in temperature and decrease in relative humidity. In the most extreme Sundowner wind events, wind speeds can be of gale force or higher, and temperatures over the coastal plain, and even at the coast itself, can rise significantly above 37.8°C (100°F). In addition to causing a dramatic change from the more typical marine-influenced local weather conditions, Sundowner wind episodes have resulted in significant property and agricultural damage, as well as extreme fire danger. They have, in fact, been associated with many of the most destructive conflagrations that have occurred in the Santa Barbara region. In the present study, three different Sundowner wind episodes are examined. These include midsummer and midautumn events primarily manifested by extremely warm temperatures, and a winter season event notable for its damaging winds. The associated meteorological conditions are examined, and possible physical mechanisms responsible for these episodes are discussed. In at least two of the three cases considered here, mountain wave development appears to have played a significant role.