Synoptic analysis of Medicanes based on ERA5 reanalysis data

Medicanes are a small, cyclonic systems which develop over the Mediterranean Sea. They are most frequent in the autumn and early winter months, when the sea surface temperature is still quite high, around or above 20 °C. Their development is mostly influenced by baroclinic effects as upper-level troughs or cut-off lows lead to extratropical cyclogenesis, but later, thanks to the warm sea, the cyclones appear as self-sustaining convective structures, often with an eye-like feature. This process is similar to the tropical transition process in the northern subtropical Atlantic Ocean, where they are officially classified as subtropical or tropical cyclones. In the affected areas, significant damages can occur due to medicanes. The heavy rainfall often causes flash floods or landslides in mountainous and arid areas, while strong winds cause damage and coastal flooding along the coastlines. We built a database of medicanes from the recent years, which includes intensity and track estimates using available satellite and land-based measurements. Additionally, all cyclones were analysed using ERA5 reanalysis data to determine their synoptic characteristics in the development and mature phase. This data allow a possible categorisation of the medicanes according to key meteorological parameters, which differ between their initial extratropical and mature subtropical or tropical phases.

In our presentation, we will briefly introduce our Medicanes database, highlighting the most extreme examples. Thereafter, we will present the key synoptic parameters defined by the ERA5 reanalysis and the main characteristics of the selected medicanes, followed by a possible categorisation by clustering the similarity attributes into subtropical-type and tropical-type categories.