Issue Notes

ENSO status: Neutral.
IOD status: Neutral.
SAM status: Positive. Trending positive.

The El Niño Southern Oscillation (ENSO) has returned to neutral conditions, after a short and weak La Niña pattern. Neutral conditions are likely to persist through autumn and early winter.

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 become more negative from late autumn, 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 positive phase, 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 autumn, aligned with most autumns in the last decade. During autumn, a positive SAM increases rainfall over most of eastern Australia, and decreases rainfall for SA, Vi, western Tas, and southwest WA.

Rainfall outlooks are showing below average rainfall for much of Australia during May, then generally returning closer to average by June. There is a increased chance of wetter than average conditions over western WA and eastern NSW with very warm sea surface temperatures near both coasts.