Is there an increase in favourable conditions for the development of cyclones with tropical characteristics in the Mediterranean basin? A study of Potential Intensity in the Mediterranean Region over the last 70 Years

In recent years, an increase in the frequency and intensity of cyclones with tropical characteristics has been observed in areas of the Mediterranean Sea (De la Vara et al., 2021). The rise in this type of cyclones has triggered extreme weather conditions in many Mediterranean coastal regions (Romero & Emanuel, 2013). With the increasing focus on the study and characterisation of these types of cyclones (Gutiérrez-Fernández et al., 2024), numerous research efforts have employed different methodologies to investigate the favourable conditions for the development of cyclones with tropical characteristics in the Mediterranean (Romero & Emanuel, 2017). Among the methods used to study the favourable conditions for the development of tropical cyclones, one of the most widely applied is the Potential Intensity (PI; Holland, 1997). This index measures the theoretical maximum intensity a cyclone with tropical characteristics can achieve under specific atmospheric conditions. This method has been investigated in numerous studies on tropical cyclones and demonstrates that high values of this index are associated with a higher likelihood of intense tropical cyclone development (Emanuel, 2005; Wing & Camargo, 2007).

Therefore, the main motivation for this study is to analyse the evolution of the Potential Intensity (PI) over the past 70 years in the Mediterranean region. For this purpose, ERA5 reanalysis data (Hersbach et al., 2023) covering the period from 1950 to 2023 over the Mediterranean basin were used. The results indicate an increase in the values of this index, particularly during the autumn months, when most cyclones with stronger tropical characteristics occur. Finally, an individual analysis of this index was conducted under pre-development conditions for recent cyclones with tropical characteristics in the Mediterranean.

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