Subseasonal potential predictability of horizontal water vapor transport and precipitation extremes in the North Pacific

To make informed decisions based on forecasts, it is important to determine the extent to which they could be skillful. This study focuses on subseasonal forecasts out to a lead time of four weeks.

We examine the differences between the potential predictability, which is computed under the assumption of a " perfect model, " of integrated vapor transport (IVT) and precipitation under extreme conditions in subseasonal forecasts across the northeast Paci fi c. Our results demonstrate signi fi cant forecast skill of extreme IVT and precipitation events (exceeding the 90th percentile) into week 4 for speci fi c areas, particularly when anomalously wet conditions are observed in the true model state.