An examination of tropical cyclone activity near the Western Australian coastline during the cyclone seasons from 1960/61 to 1996/97 inclusive showed distinct seasonal and regional characteristics consistent with variations in the average value of the Southern Oscillation Index (SOI) during the months prior to the cyclone season, as well as changes in the average SOI value from the previous year. Important findings of this study were: an overall increase in tropical cyclone frequency (and coastal impacts) with strong positive SOI values; a greater number of coastal impacts when the SOI value was positive together with a large positive SOI change; a large increase in probability of early season (prior to Christmas) activity with positive SOI; and a preference for more late season (April/May) events to occur following negative SOI years. Although there were fewer tropical cyclones in the negative SOI years, a higher percentage of these were severe. As a result the number of coastal impacts by severe tropical cyclones was similar following both positive and negative SOI years.
Broadbridge et al. (Tue,) studied this question.