Dan Cayan Scripps Institution of Oceanography, UC San Diego USGS Water Resources Discipline much support from David Pierce, Mary Tyree, and other colleagues Sponsors : California Energy Commission NOAA RISA program Southwest Climate Science Center U.S. Army Corps of Engineers El Nino 2015 will it alleviate the drought? CEC Workshop Sacramento 8/28/2015

Highest sea levels occur during big storms, high waves During high sea levels, the sea is often not quiescent January 1983 Monterey Bay, California

Extreme sea level occurrences San Francisco observed at or above 99.99% historical hourly threshold 1.41m above mean Highest California sea levels have mainly occurred in a few stormy years, especially during large El Niños (e.g., 1983 and 1998) from hourly sea level record at Ft Point, mouth of San Francisco Bay 1983 El Niño 1998 El Niño

Global SST Departures ( o C) During the Last Four Weeks During the last four weeks, equatorial SSTs were above average across the central and eastern Pacific and the Indian Ocean, and below average in the Atlantic Ocean. NOAA

Niño Region SST Departures ( o C) Recent Evolution The latest weekly SST departures are: Niño 41.1ºC Niño ºC Niño 32.2ºC Niño ºC NOAA

Sub-Surface Temperature Departures in the Equatorial Pacific Most recent pentad analysis Recently, negative anomalies were evident in the far eastern Pacific and western Pacific, while positive anomalies have persisted across the central and eastern Pacific. During the last two months, positive subsurface temperature anomalies were observed across most of the equatorial Pacific NOAA

Central and Eastern Pacific Upper-Ocean (0-300 m) Weekly Average Temperature Anomalies During January – March, a significant sub-surface warming occurred across the eastern Pacific. Since March, sub-surface temperature anomalies have remained large, but with some minor fluctuations in strength. Following a drop in June, the anomalies increased in July. Since early August, positive anomalies have persisted. NOAA

8

SUMMARY Rather strong El Niño conditions have developed in the tropical Pacific. El Niño will likely remain in place through winter If winter El Niño is strong, we could see above normal storminess in Southern California and maybe Northern California. Historical El Niño’s have resulted in a wide range of California precipitation during the water year. Strongest odds of wet winter in SoCal. Historical El Niño’s have produced large Pacific storms along with high waves and high sea levels along the Calfiornia coast. Periods with highest tides would produce strongest impacts if large storms were present SUMMARY Rather strong El Niño conditions have developed in the tropical Pacific. El Niño will likely remain in place through winter If winter El Niño is strong, we could see above normal storminess in Southern California and maybe Northern California. Historical El Niño’s have resulted in a wide range of California precipitation during the water year. Strongest odds of wet winter in SoCal. Historical El Niño’s have produced large Pacific storms along with high waves and high sea levels along the Calfiornia coast. Periods with highest tides would produce strongest impacts if large storms were present Frank Gehrke, California Cooperative Snow Surveys, DWR 10

11