12-Month Rainfall Forecast

Issue Notes

ENSO status: Neutral. IOD status: Neutral. Negative possible. SAM status: Positive. Trending positive. The El Niño Southern Oscillation (ENSO) is in a neutral pattern. Neutral conditions are likely to persist through autumn and early winter, and the vast majority of international climate models expect neutral conditions in 2025. The Indian Ocean Dipole (IOD) is in a neutral phase, but the Indian ocean overall is much warmer than average. The IOD is forecast to tend towards the negative from late autumn, with early signs already being observed (i.e. northeasterly trade winds rather than southeasterly, and increased rain and cloud near Jakarta, and an increase in warm water from the Indonesian flow-through), and is a higher than normal chance to develop in 2025. A negative IOD typically increases the amount of northwest cloudbands that cross Australia, increasing rainfall from northwest WA through to southeastern Australia during winter and spring. The Southern Annular Mode (SAM) is in a positivephase, meaning cold fronts are further south than they typically would be at this time of year. Forecasts are indicating a positive phase to be more dominant during Winter (at least June and July). During autumn, a positive SAM increases rainfall over most of eastern Qld and NSW, and decreases rainfall for SA, Vic, western Tas, and southwest WA. Rainfall outlooks are showing below average rainfall over eastern Australia and increased rainfall for WA in June. In July and August, models show above average rainfall over WA, central Aus, Qld and NSW, and the Alps (August only), with below average rainfall for SA, Vic and Tas.