From Greenland to the Mediterranean: Unveiling a new cascading atmospheric circulation mechanism promoting extreme convective activity?

On 17 August 2022, the western Mediterranean experienced an unusual thermodynamic environment with extremely high unstable atmospheric conditions, combined with strong wind shear. These conditions, with the help of a shortwave trough, led to the formation of a bow-shaped system of thunderstorms, which developed into a derecho, very rare in the region. This system produced a long path of severe winds, stretching from the Balearic Islands to southern Czech Republic on 18 August. The strongest wind gust reached 62.2 m s⁻¹ at Corsica, where numerous records were beaten. Unfortunately, 12 people lost their lives, and 106 were injured during this event.

A record-breaking marine heatwave (MHW) was present in the western Mediterranean simultaneously during the summer of 2022, peaking in July. The extremeness of the summer 2022 MHW is evidenced by the high SST anomalies in the first half of August 2022, ranking first among all years since 1940. An attribution exercise with numerical experiments and novel results (González-Alemán et al., 2023) indicated that this derecho event was substantially amplified by the extreme MHW and suggested that current anthropogenic climate change forcing contributed to triggering the severe storm by creating a thermodynamical environment more favorable for convective amplification.

However, no answers can be obtained regarding its dynamical contribution. Thus, to further investigate this event and the dynamical role of global warming in it, we explore the atmospheric circulation mechanisms that can lead to such a record-breaking event and other years with extreme convective activity over the western Mediterranean.