Predicting regional gray swans via translocation: AI weather models and Dubai's unprecedented 2024 rainfall

Artificial intelligence (AI) models have transformed weather forecasting, but their skill for unprecedented weather extremes is unclear. Here, we analyze GraphCast, AIFS, and FuXi forecasts of the unprecedented 2024 Dubai storm, which had twice the training set’s highest rainfall in that region. GraphCast and AIFS accurately forecast this event up to 8 days ahead. FuXi forecasts the event but underestimates the rainfall. Fine-tuning and receptive field analyses suggest that these models’ success stems from “translocation”: learning from comparable/stronger dynamically similar events in other regions during training. Evidence of “extrapolation” (learning from weaker events) is not found. Even events within the global distribution’s tail are poorly forecasted, which is not only due to data imbalance (generalization error) but also spectral bias (optimization error). These findings demonstrate the potential of AI models to forecast “regional” gray swans and the opportunity to improve them through understanding the mechanisms behind their successes/limitations.