Origins and variability of extreme precipitation in the Santa Ynez River Basin of Southern California

On average, a wet year features three or more extreme events, a normal year 1-2 events, and a dry year 0-1 events. We identify four distinct synoptic-scale weather patterns associated with extreme events and find that 74% of events are associated with atmospheric rivers. El Niño years tend to have a greater number of extreme events, though this relationship is not dependable. The reliance on just a few extreme precipitation events and diversity among these events highlights the challenges of seasonal prediction and resource management in this area. This novel approach to defining variability on a watershed scale can support ecological, geological, and hydrological studies as well as regional water resource management.