Squall line in the Balearics producing extreme wind and meteotsunamis

On 22 January 2021, an active squall line embedded within cyclone Hortense swept across the Balearic Islands, significantly impacting Mallorca and Menorca. The event was characterized by extreme wind gusts, including a 130 km h-1 peak at Palma airport, an intensity breaking the 50-year record. Consequently, the squall line induced an outstanding long-lived pressure perturbation, which triggered moderate meteotsunami activity across several harbours and coastal inlets. Notably, a sea-level oscillation of 60 cm was recorded in the Port of Ciutadella (Menorca). The main objective of this paper is to investigate the coupled atmospheric and oceanic dynamics underlying a squall line event that produced extreme winds and meteotsunami activity, focusing on the role of an associated atmospheric pressure surge. In particular, we provide a comprehensive observational description of the combined event -squall and associated meteotsunamis- using land-based meteorological and oceanographic data, remote-sensing imagery, and ERA5 reanalysis products. Furthermore, the predictability of the event’s key dynamical features, including wind extremes and meteotsunami generation, is assessed through high-resolution atmospheric and oceanic numerical simulations. These findings highlight a rarely documented mechanism of compound atmospheric-oceanic hazard in the Mediterranean and underscore the critical need for improved mesoscale forecasting capabilities to support coastal risk mitigation strategies