12-Month Rainfall Forecast

Issue Notes

ENSO status: Neutral. IOD status: Neutral. Negative possible. SAM status: Neutral. Trending positive. The El Niño Southern Oscillation (ENSO) is in a neutral pattern. Neutral conditions are likely to persist through 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 a negative phase, with some clear building of ocean heat starting near Java, and increased convection near Sumatra. Slightly more than 50% of international models forecast a negative IOD to develop this year. 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 neutral phase, meaning cold fronts are generally reaching as far north as you would typically expect at this time of year. Forecasts are indicating a positive phase to be more dominant during Winter (at least June and July). During winter, a positive SAM increases rainfall over most of Qld, NSW and the Nullarbor, while decreasing rainfall for SA, Vic, 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.