Atmospheric drivers and climate change attribution of the October 2024 Valencia flooding

On 29 October 2024, Valencia experienced one of the most catastrophic flood events in Spain’s recorded history, resulting in 232 deaths and widespread damage to infrastructure and property. This event raised urgent questions in science and society on the atmospheric processes that led to this extreme event and the influence of climate change in shaping its severity. The purpose of this study is twofold. First, using observation-based datasets, we investigate the large-to-local scale atmospheric processes leading to this extreme event. Second, using pseudo-global warming simulations with the Weather Research and Forecasting (WRF) model, we quantify the influence of climate change on this extreme event and determine how similar events may unfold in the future.

 

By identifying and tracking potential vorticity (PV) streamers and cut-off lows as 3-dimensional objects in ERA5, we show that this extreme event resulted from Rossby wave breaking over the North Atlantic nearly a week prior to the event. The cut-off low moved southwards and persisted over northwest Africa and the Iberian Peninsula for four consecutive days. The cyclonic circulation associated with this cut-off low initiated and sustained the transport of warm and moist air masses towards the eastern coast of Spain, generating favorable conditions for deep moist convection.

 

Present-day WRF simulations generally reproduce the extreme precipitation event well, despite a shift in its location and an underestimation of the highest rainfall amounts as observed at some stations. The consistency of simulated heavy precipitation across different initialization times further supports the robustness of the model results. While spatially aggregated daily precipitation amounts show little sensitivity across pre-industrial, present-day, and future scenarios, the most extreme sub-hourly precipitation intensities systematically increase with warming levels. Therefore, our findings suggest that flood events similar to the October 2024 Valencia flood are likely to recur under future climate conditions with comparable or greater short-duration precipitation intensity, underscoring the need for improved early warning systems and flood risk management.