On the Dynamics of Extreme Rainfall in Tasmania

Although small in size, the island State of Tasmania is Australia’s largest producer of renewable electricity from hydropower. The hydropower storages are located in the west of the State and given the sensitivity of the industry to rainfall (and subsequently streamflow) variability and extremes, it follows that skilful climate forecasts may assist in water resources and hydropower planning. The skill of rainfall forecasts lies in the ability of forecast models to simulate the climate processes that influence the rainfall variability in the region at relevant timescales. Climate in western Tasmania is unique from both eastern Tasmania and indeed the rest of Australia, due to local topographical influences and its location in the path of the prevailing high-latitude westerly winds. Beyond this knowledge there is a limited understanding of the synoptic and dynamic processes influencing rainfall variability and extremes. This study addresses this gap through characterisation of rainfall extremes in the region and their relationship to catchment runoff, the construction of atmospheric flow composites around these extreme events and the assessment of the relationship between large scale climate processes and rainfall. This analysis will ultimately help to outline the deficient process representations in the climate forecast models and in interpreting model forecasts.