The Influence of El Nino-Southern Oscillation on Tropical Cyclone Activity in the Eastern North Pacific Basin

The interannual variability of tropical cyclone (TC) activity due to El Nino-Southern Oscillation (ENSO) in the main development region of the eastern North Pacific basin has received scant attention. Herein the authors classify years of El Nino, La Nina, and neutral conditions using the multivariate ENSO index (MEI). Storm measurements of the net tropical cyclone activity index and power dissipation index are used to summarize the overall seasonal TC activity and TC intensity between 1971 and 2012. Both measures are found to be statistically dependent on the ENSO phases in the basin's main development region. However, when the area is longitudinally divided, only the western portion of the development region experienced a significant difference (p < 0.05). Specifically, El Nino years are characterized by more frequent, more intense events compared to La Nina conditions for this subregion. Correlation analyses on the relationships between the MEI and both TC indices demonstrate correlations between ENSO and TC activity and intensity that are statistically significant (p < 0.05) only in the western region. These relationships have the potential to improve the short-term forecast of the local TC activity and intensity on a seasonal basis for public awareness and disaster preparation.