Multiyear flood predictions are possible for watersheds in which the magnitude and frequency of flooding can be related to an atmospheric pressure see-saw in the North Atlantic region.
Examples of predicted extreme streamflow in catchments (locations shown in the lower right panel) where flooding conditions can be related to variations in the large-scale surface pressure gradient in the North Atlantic. The black line is the observed streamflow. The solid color lines are the median forecasts (i.e. 50th percentile), with confidence bands representing 25th-75th percentiles of the complete, raw (grey color) and filtered (orange) sets of ensemble climate model outputs used as input to the dynamical-statistical model developed in this study. The filtered set of the ensemble only includes models that can reproduce surface pressure conditions in the Northern Atlantic. Credit: Moulds et al. [2023], Figure 3
Predicting flood likelihood over the next decade can inform preparedness and water management sectors, but such predictions are currently lacking. Moulds et al. [2023] show how skillful decadal climate predictions can be used for that task.
By focusing on winter flood conditions for watersheds across the UK, decadal (2-5 years) flood predictions are feasible, but their robustness depends on whether catchment flooding severity and frequency can be related to the intensity of the westerly winds blowing across the North Atlantic Ocean between 40 and 60°N, known as the North Atlantic Oscillation. The new dynamical-statistical approach developed by the authors can provide a useful decision-making tool for flood risk managers and water resource planners.