Understanding and predicting the extreme wet conditions over Australia in 2010 spring

The 2010 spring hosted a near-record strong La Nina and a record-breaking positive SAM, both of which played key roles in the extreme wet conditions in eastern Australia. In this study, we attempt to understand the predictability of the extraordinary climate conditions in 2010 spring by assessing the prediction skill of the Australian Bureau of Meteorology's dynamical seasonal forecast system (POAMA2) and by conducting forecast sensitivity experiments to the atmosphere and ocean initial conditions.

POAMA2 skilfully predicted the spatial pattern and magnitude of the tropical ocean temperatures associated with the La Niņa event at lead times of at least 4 months. Importantly, POAMA2 also predicted the key variations of atmospheric circulation during spring 2010 associated with the positive swing in the Southern Oscillation as well as the strong positive excursions of the SAM out to a lead time of 3-4 months. Consequently, the wet conditions over eastern Australia in 2010 spring were skilfully anticipated from the preceding early winter. Results of the forecast sensitivity experiments suggest that POAMA's ability to predict the 2010 strong La Niņa and its teleconnection to Australia was the key component for the success of the prediction for 2010 spring rainfall at up to a season lead time. On the other hand, realistic atmospheric conditions played an important role in predicting the large-scale atmospheric circulation and the associated extremity of the rainfall event at short lead time.