Interannual variability of near-coastal eastern Pacific tropical cyclones

Interannual variability of tropical cyclones affecting the west coast of North America is shown to be modulated by the ENSO cycle and by Pacific decadal variability. More tropical storms affect the Pacific coast during La Niña years (when equatorial Pacific Ocean temperature is anomalously cold) compared to El Niño years, although previous research suggests that the overall number of Pacific tropical storms is not significantly related to the ENSO cycle. The difference between La Niña and El Niño years was particularly pronounced during the mid-20th Century epoch when cold equatorial temperatures were enhanced, as described by a standard index of the Pacific Decadal Oscillation. Composite sea level pressure maps of warm seasons with high and low landfall counts show that the SLP anomalies associated with the "cold" phase of ENSO and PDO are consistent with tropical storm tracks preferentially steered toward the west coast.