This article studies the life cycle of the well-organised mesoscale convective systems (MCSs) that affect Catalonia and surrounding regions, using a weather radar composite with sophisticated corrections and lightning data over a full period of five years. Nearly 350 MCSs were identified and analysed for the 2012–2016 period after applying size and duration criteria to 438,000 radar composites. MCSs are responsible for the majority of flood events in the region of interest and in many other areas around the world. We have analysed the main radar parameters and lightning properties, looking for differences between the systems depending on the season of the year. Autumn and spring show the highest frequency of MCSs, but there are considerable differences between their properties for the two seasons. More specifically, lightning activity, maximum reflectivity and duration are higher in autumn than in winter, although the total accumulated rainfall may be lower. This higher convective activity is associated with the warmer sea surface temperature of the Mediterranean and a large number of cyclones that affect the region of analysis.

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