Long-range flood outlook for strategic preparedness - final report

This report examines the feasibility of introducing a long-range flood outlook for Australia, targeting the sub-seasonal to seasonal (S2S) timescale. Developed by the Bureau of Meteorology and Natural Hazards Research Australia, the study used co-design workshops with end users, selected 20 flood forecasting locations nationwide, and applied a Bayesian Joint Probability (BJP) statistical model to hydrological and climate data. Case study sites spanned diverse climate zones, and forecast verification included comparison to observed events and skill metrics such as the Brier Score and Cumulative Rank Probability Score.

Key findings demonstrate that targeted long-range flood outlooks—quantifying the likelihood of threshold exceedance at flood forecasting locations—can provide valuable lead time for preparedness. The results show that forecasts can identify periods of elevated flood likelihood weeks to months in advance, enhancing operational readiness and strategic planning for emergency services. Authors recommend further development through pilot studies, integration with existing Bureau forecast and impact mapping services, and clear communication of probabilistic flood risk and uncertainty. This approach aims to fill gaps in current flood hazard information and support improved community resilience, advance preparedness, and enable multi-agency coordination across Australia.