Storm Daniel fueled by anomalously high sea surface temperatures in the Mediterranean

Abstract In September 2023, Cyclone Daniel formed in the Mediterranean, severely affecting Greece and Libya, and becoming the deadliest storm in Mediterranean history. The Mediterranean’s unusually high sea surface temperatures (SST) likely contributed to the cyclone’s intensity and extreme rainfall. Greece saw over 700 mm of rain in 18 h, while Libya experienced daily records exceeding 400 mm, leading to catastrophic infrastructure failures. Our hypothesis is that high SSTs provided additional energy and moisture fueling Daniel’s intensification. Using the Weather Research and Forecasting model, we conducted numerical experiments to quantify the role of high SSTs during the event. Comparing actual conditions with a counterfactual scenario, we found that the long-term global warming signal in SSTs significantly increased the storm’s intensity and precipitation. This study underscores the need to understand rising SSTs contribution to predicting and mitigate future tropical-like cyclones as global temperatures increase.