Tropical cyclone track direction climatology and its intraseasonal variability in the Australian region

Abstract

Aspects of tropical cyclone (TC) activity, such as the influence of the El Niño-Southern Oscillation and the variability of TC genesis location, have been examined in numerous previous studies. However, relatively few studies have examined aspects such as the influence of intraseasonal variability on TC track direction. Here we focus on a number of knowledge gaps relating to observed TC track directionality and intraseasonal variability in the Australian region. Climatological examinations are presented for TC track directional variability throughout the Australian region. In contrast to previous studies that have focused on the mean direction of TC movement in this region, TC tracks are examined here based on the full spectrum of track directions for a given location or region. Variability in initial TC track directions is investigated, including an examination of the influence of the Madden-Julian oscillation (MJO). It is demonstrated that there is a considerable degree of seasonal and intraseasonal variation in TC motion in this region. These variations result from variations in genesis location throughout the TC season, as well as zonal wind anomalies associated with the influence of the MJO on the steering flow winds. Anomalous westerly steering flow occurs during MJO phase 4-5 and anomalous easterly flow during phase 8-1 in the western basin, with resulting changes in the proportion of TC tracks in each direction during these phases of the MJO. The results presented here are intended to provide improved seasonal TC activity guidance and enhanced resilience to TC impacts.