South Pacific Tropical Cyclones and the Southern Oscillation

Abstract

A 40-year sample of tropical cyclone origin points in the South Pacific region has been studied in relation to the Southern Oscillation. The area in which origin points tend to be concentrated varies with the phase of the Southern 0scillation, being farther to the north and east when the phase is negative. This broad-scale relationship is consistent with the behavior of the principal synoptic controls on tropical cyclones. Least squares regression analysis shows the same underlying pattern for individual cyclones in all months and for the data stratified by month. Time series analysis reveals that there have been periods when the correlation was weak and even changed sign, particularly during the 1950s and in the late 1960s.