The eastern North Pacific (ENP) basin boasts a high density of tropical cyclone (TC) formation compared with other ocean basins in which TCs occur. Since ENP TCs can form near or otherwise impact land, they serve as an important yet variable source of summer and fall precipitation in southwestern North America. Higher sea surface temperatures (SSTs) and reduced vertical wind shear associated with El Niño events tend to support increased TC activity, exemplified by the very active 2015 ENP hurricane season. Yet the 2018 season eclipsed that activity despite the absence of El Niño, likely influenced by a positive phase of the Pacific meridional mode (PMM). In addition, though La Niña conditions can decrease overall ENP activity, shifts in the atmospheric circulation can increase the likelihood of land impacts from TCs that do form.
This talk explores the ENP TC record with consideration for the satellite era (1971-present) and National Hurricane Center era (1988-present). By quantifying the patterns that affect TC behavior from season to season and acknowledging uncertainty in past TC observations, future work can evaluate how TC activity may continue to evolve in a changing climate. The presentation will also provide historical context for unusual events in 2023 such as Hurricane Hilary, a storm that prompted the first tropical storm warning for California, and Hurricane Otis, which unexpectedly hit Acapulco, Mexico, as a category 5 hurricane.