Sundowners: Santa Ynez Mountains Downslope Lee Heating Wind Events

Sundowners are a local term for northerly, downslope winds in the lee of the Santa Ynez Mountains that cause anomalously high temperatures in the Santa Barbara area. Historically, these lee heating wind events may occur every few years, have severe wind gusts, and cause temperatures at the coast to exceed 38°C. A new study focused on lee heating wind events occurring from September 1995 through August 1997, based on surface stations throughout the Santa Barbara Channel, a radar profiler at Goleta, and National Weather Service surface and upper air analyses. Statistics were developed on the occurrence, strength, and aerial extent of lee heating wind events. These were mesoscale events influenced by the coastal topography, and the strength of the marine layer. They occurred mainly between 1300 LST and 1600 LST, lasted a few hours and might be referred to as "afternooners". The maximum temperature for an event was 37.9°C. Although National Weather Service analyses were consistent with northerly, offshore flow over the entire Santa Ynez Range, downslope, lee heating wind events occurred only over a very limited aerial extent, most frequently at Gaviota, a coastal station downwind from the Santa Ynez Mountain range minimum height. From Gaviota, the winds extended a short distance offshore and deflected to the east towards Santa Barbara. They were occasionally measured at a platform 6 km offshore, but never at the mid-channel meteorological buoys. There was also no systematic correlation of downslope, lee heating wind events and synoptic scale pressure gradients. The temperature inversion and wind structures at the Goleta radar profiler were not consistent with mountain wave dynamics or National Weather Service upper air analyses at 850 hPa and 700 hPa.