Australian East Coast Cyclones III: Case Study of the Storm of August 1986
Amanda Lynch
Abstract
The Australian east coast cyclone of August 1986 caused the worst flooding event in metropolitan Sydney in over a century. The formation and evolution of the system is described in detail, with reference to the general classification of Australian east coast cyclones presented in Holland, Lynch and Leslie (1987).
The performance of the operational numerical weather prediction (NWP) model was inadequate for this event. Hindcasts are presented using the research version of this model to demonstrate the predictability of the cyclone, and to identify mechanisms contributing to the development. It was found that the research model produced much better guidance, especially at higher resolution, although it is considered that sub-grid scale parametrisation is still inadequate for such an event. The model hindcasts reflected the cyclone's failure to intensify explosively, and the placement in time and space of the maximum precipitation. The amount of precipitation was severely underestimated, however.
The formation of the system was consistent with a large-scale baroclinic process, with minimal convective activity which was identified with the explosive intensification in an earlier case study. These results are compared with the conclusions of this earlier case study to determine the applicability of these conclusions to the east coast cyclone of August 1986.