Influence of the Madden-Julian Oscillation on multiweek prediction of Australian rainfall extremes using the ACCESS-S1 prediction system

We assessed the ability of Bureau Meteorology’s ACCESS-S1 dynamical forecast system to simulate and predict high rainfall extremes for each season over Australia, especially focusing on role Madden-Julian Oscillation (MJO). Using retrospective forecasts period 1990–2012, we show that simulated observed modulation extreme weekly mean by phase MJO reasonably well; however changes in probabilities tended be weaker than those observed, across far north during austral summer season. The model (i) (ii) a lead time four weeks, translated enhanced skill predicting occurrence much Australia at times when was strong, compared weak, spring seasons weeks 2 3. However, reduced central suggesting is not good depicting MJO’s convective phases as it protrudes southward northern Australia. During autumn winter, there little indication skill, depending strength MJO. results this study will useful regional applications strong summer, particularly where swing probability large specific