This study newly accepted in Geophysical Research Letters examined why California experienced extremely wet winter and spring conditions during the 1997-98 and 1982-83 El Niños, but near normal rainfall during the extremely strong 2015-16 El Niño. Statistical data analyses and simple model experiments were used to show that sufficiently warm and persistent sea surface temperature anomalies in the far eastern equatorial Pacific are required to excite an anomalous cyclone in the North Pacific that extends to the east across the US west coast, in order to increase rainfall over California. During the last 69 years, only three El Niño events (i.e., 1957-58, 1982-83 and 1997-98) clearly persisted in the far eastern Pacific, which explains the fragile relationship between El Niño and California rainfall.
Lee, S.-K., H. Lopez, E.-S. Chung, P. N. DiNezio, S.-W. Yeh and A. T. Wittenberg (2018), On the fragile relationship between El Niño and California rainfall, Geophys. Res. Lett, doi:10.1002/2014GL0076197, accepted.