Multiple Supercell Thunderstorms on 11 August 2021 Following an Extreme Heat Wave in Greece: An Unusual Event

Abstract

Greece was hit by an extreme heat wave, with a significant impact on human health and natural ecosystems in the period between 28 July and 11 August 2021. After the end of this unusual warm period, a rare occasion of multiple supercell storms was observed on 11 August 2021 in northern and central Greece. The synoptic conditions indicated embedded short waves in a northwesterly flow and significant thermal instability across the regions of interest was evident. In conjunction with the strong vertical wind, shear organized convection was released. At least six long-track supercells were documented and the onset, evolution and specific characteristics of them are presented. All supercells moved from NW toward SE, accompanied by large hail, intense rainfall and destructive wind gusts, producing widespread damage along their track.

Keywords

• supercells
• heat wave
• radar
• severe convection
• hail
• strong vertical wind shear