Can seasonal forecasts be used to quantify the hazard of extreme meteorological droughts?

The characterization of hydrometeorological extreme events can be hindered by limited availability of observations of past meteorological conditions. Seasonal forecasts, commonly used to represent the temporal evolution of predictable components of the Earth system over periods of a few weeks or months, have recently been applied to obtain information about extreme events and their dynamical mechanisms. These forecasts typically have higher spatial resolution than climate projections and can provide a better description of the complex and nonlinear interactions among Earth system components. This study presents an application of seasonal forecasts for studying meteorological drought across Europe, with a focus on precipitation deficits over Germany. Following a rigorous workflow, the realism of seasonal hindcasts from five contributors to the Copernicus Climate Change Service (C3S) is assessed through various steps including bias correction, statistical characterization and stability check of the outputs. When examining physical credibility of simulated extremes, the mean 500 hPa geopotential anomaly field associated with the most intense meteorological droughts over Germany shows common large-scale features across different models, suggesting that seasonal forecasts can serve as a powerful tool for better understanding the drivers of climate extremes at the regional scale and the role played by the involved teleconnections. Furthermore, chance assessment for the period 1993-2016 indicates that harmful and unprecedented meteorological droughts, such as those observed in 2018 and 2022, could have been anticipated using seasonal ensembles. The refined methodology can be successfully downscaled to various regions of the European domain, providing hydrologists and engineers with an actionable tool for evaluating regional drought hazard.