The influence of tropical cyclones on heat waves in Southeastern Australia

Abstract

Heat waves in southeastern Australia in summer are commonly associated with slow‐moving surface high‐pressure systems, which result in warm northerly flow from the continental interior. The underlying dynamical pattern of heat waves in this region is associated with propagating Rossby waves, which grow in amplitude and eventually overturn, forming an upper level anticyclonic potential vorticity anomaly. The influence of tropical cyclones on the development of these anomalies is investigated here. Tropical cyclones may affect heat waves in this region indirectly, as the divergent outflow at upper levels perturbs the Rossby wave guide, leading to downstream development. However, the effect may also be direct, through the advection of anomalously anticyclonic potential vorticity from regions of deep convection in the vicinity of tropical cyclones into the upper level anticyclone. Our research shows that this direct reinforcement of the anticyclone is likely to be more important in the formation of severe heat waves in southeastern Australia.