Predictability of Interannual Variations of Australian Seasonal Tropical Cyclone Activity

Abstract

The number of tropical cyclones observed in the Australian region during a single cyclone season has ranged from one to nineteen since 1909. Previous studies, using limited data sets, have suggested that interannual variations in the number of cyclones are related to the Southern Oscillation and that an index of the Southern Oscillation (e.g., Darwin pressure) can be used to predict the number of cyclones expected in the coming season. This study uses a 74 year time series of tropical cyclone numbers, from the 1909/10 season to the 1982/83 season to confirm this. Strong and stable correlations are found between cyclone numbers and Darwin pressures before and during the cyclone season. Even stronger relationships are found between Darwin pressure and the number of cyclone days in a cyclone season. The correlations are strong and stable enough to allow prediction of seasonal cyclone activity from several months prior to the start of the tropical cyclone season. A simple equation for predicting seasonal cyclone activity is derived.