The key role of Mediterranean and North Atlantic sea surface temperatures on the 2024 record-breaking Valencia precipitation event

In late October 2024, a well-defined mid-tropospheric cyclone affected the coasts of eastern Spain with record-setting precipitation. The province of Valencia was hardest hit, with 24-hour precipitation maxima above 600 mm, triggering devastating floods. The development of this weather situation occurred alongside positive sea surface temperature (SST) anomalies over the Mediterranean Sea, which are known intensification factors of heavy precipitation over the region. At the same time, the North Atlantic was also anomalously warm, but its role in this type of meteorological events has so far received significantly less attention. In this study we perform global high-resolution experiments using an atmospheric model forced by observed SSTs and compare them against simulations with climatological SSTs over the North Atlantic and the Mediterranean Sea. We find that SST anomalies in both regions have played a significant role on the moisture availability and instability over Valencia, even though the Mediterranean Sea had the largest contribution, particularly in terms of surface-based instability. We also quantify the resulting precipitation in each experiment and find that rainfall totals on the day of the event would have been up to 40% lower if SST anomalies in both regions were suppressed. • Cut-off lows can trigger intense precipitation over the Mediterranean region • An intense cut-off low in October 2024 caused devastating flooding over Valencia • The system was favored by very warm Mediterranean and North Atlantic waters • Numerical experiments quantify the role of both regions on the weather event