A Climatology of Extreme Heating ‘Sundowner' Events near Santa Barbara (CA) Based on Surface Observations

The Sundowner events in the region of Santa Barbara are characterized by extremely high temperatures and dangerous wild-fire conditions. In some cases, such as the 1985/07/03 event, temperatures in Santa Barbara increase by 20 deg F over 1-2 hours in late afternoon, while at the same time, temperatures at nearby stations decrease from their usual mid-day high. Despite the influence that they have on weather conditions and historical wildfires in the area, the cause and frequency of occurrence of Sundowners are not well known. In this study, we analyze historical observations in the area of occurrence of Sundowners based on a number of criteria related to temperatures at KSBA vs other stations. We find that Sundowner events are: • much more common than has been previously reported • characterized by various signatures in time series data, aside from the classic late afternoon temperature increase • often limited in spatial extent to the foothills of the Santa Ynez range to the north of Santa Barbara, and thus not present in analysis of KSBA observations • characterized by Internal gravity wave (IGW) breaking over the Santa Ynez range and adiabatic warming of air parcels as they descend from the North to the South over the city of Santa Barbara