Quasi-linear convective systems and derechos across Europe: ERA5 convective environments and synoptic-scale patterns

An average of 184 quasi-linear convective systems (QLCSs), including 6 derechos, occur every year across different parts of Europe, posing significant socioeconomic impacts. In this work, we analyzed convective environments and accompanying synoptic patterns associated with QLCSs, considering their intensity and spatiotemporal variability. For this purpose, we used the database with manually identified QLCS cases based on the OPERA radar data. In total, we investigated 1469 cases over a period of 8 years (2014–2021), and for each case, we assigned a representative ERA5 vertical profile sampling the pre-convective environment. We found that warm-season cases develop primarily in a large atmospheric instability setups and are often driven by strong cold-pools, whereas during the cold-season, synoptic-scale lift with marginal (but non-zero) CAPE and high vertical wind shear is the most common environment. The mean vertical profiles indicate the dominance of westerly and southwesterly flow during QLCS development, accompanied by steep mid-level lapse rates. Except for warm-season QLCSs over the West and cold-season cases in the Central region, QLCSs are associated with clockwise-curved hodographs. Our results indicate that the intensity of warm-season QLCSs is well represented by downdraft-related metrics such as downdraft CAPE (DCAPE). Marginal and stronger QLCSs can be distinguished using atmospheric instability (CAPE), especially across Central Europe. In the cold season, kinematic parameters were found to discriminate well between the severity of QLCSs. Observed storm-motion of QLCSs was typically faster than the 0–6 km environmental mean wind vector in the warm season (65% of cases), while in the cold season, it was opposite (84% of cases).