Tropical Cyclone Occurrences in the Vicinity of Hawaii: Are the Differences between El Niño and Non–El Niño Years Significant?

Abstract

Tropical cyclones in the vicinity of Hawaii are rare. However, when they occurred, they caused enormous property damage. The authors have examined historical records (1949?95) of cyclones and classified them into El Niño and non?El Niño batches. A bootstrap resampling method is used to simulate sampling distributions of the annual mean number of tropical cyclones for the above two batches individually. The statistical characteristics for the non?El Niño batch are very different from the El Niño batch. A two-sample permutation procedure is then applied to conduct statistical tests. Results from the hypothesis testing indicate that the difference in the annual mean number of cyclones between El Niño and non?El Niño batches is statistically significant at the 5% level. Therefore, one may say with statistical confidence that the mean number of cyclones in the vicinity of Hawaii during an El Niño year is higher than that during a non?El Niño year. Likewise, the difference in variances between El Niño and non?El Niño batches is also significant. Cyclone tracks passing Hawaii during the El Niño batch appear to be different from those of the non?El Niño composite. A change in large-scale dynamic and thermodynamic environments is believed to be conducive to the increased cyclone incidence in the vicinity of Hawaii during an El Niño year.