An updated climatology of tropical cyclone impacts on the southwestern United States

A dataset of 167 eastern North Pacific tropical cyclones (TCs) is investigated for potential impacts in the southwestern United States over the period 1989-2009 and evaluated in the context of a 30-yr climatology. The statistically significant patterns from empirical orthogonal function (EOF) analysis demonstrate the prevalence of a midlatitude trough pattern when TC-related rainfall occurs in the southwestern United States. Conversely, the presence of a strong subtropical ridge tends to prevent such events from occurring and limits TC-related rainfall to Mexico. These statistically significant patterns correspond well with previous work. The El Niño-Southern Oscillation phenomenon is shown to have some effect on eastern North Pacific TC impacts on the southwestern United States, as shifts in the general circulation can subsequently influence which regions receive rainfall from TCs or their remnants. The Pacific decadal oscillation may have a greater influence during the period of study as evidenced by EOF analysis of sea surface temperature anomalies.