. Which tropical Pacific convective regions are most influential on US West Coast marine conditions?

Abstract
El Nino Southern Oscillation is the leading mode of tropical Pacific climate variability at interannual timescales, with important societally-relevant impacts. Canonical El Nino events achieve their largest sea surface temperature (SST) anomalies in the eastern Pacific, and that area is often considered responsible for the ENSO atmospheric teleconnections with the largest global impacts. However, other studies have highlighted the key role of the central and western equatorial Pacific regions for producing heating anomalies that can effectively alter the Pacific North American (PNA) pattern, the leading mode of geopotential height variability in the North Pacific. Here we present evidence of the important role of the western equatorial Pacific in controlling marine warming along the US West Coast (USWC), an area that is strongly influenced by variations in the strength and position of the North Pacific Aleutian Low, a surface expression of the PNA. Using a statistical approach, we identify sensitivity patterns of SST and sea surface height (SSH) anomalies that are conducive to USWC warming at some later times. These sensitivity patterns do not coincide with a mature El Nino pattern, but highlight the important role of subtropical and western equatorial Pacific SST anomalies. While the marine heat wave that took place in the northeast Pacific and USWC during 2014 was not associated with a strong El Nino event in the equatorial Pacific, the weak equatorial SST anomalies during 2014 had a very large projection on the sensitivity pattern, indicating the relevance of that pattern for the northeast Pacific marine heat wave.