Analysis of the severe thunderstorm in Croatia on September 15th 2022.

On September 15th 2022, in the afternoon hours, central part of Croatia was hit by a violent thunderstorm, with gale-  and possibly hurricane-force winds, hail and heavy rain - and caused severe damage to properties and particularly to the forests. Testimonies of local witnesses pointed even to possibility of occurence of a tornado. A comprehensive synoptic and mesoscale analysis was performed, including radiosounding, satelite and new radar observations from the recently established radar network.  

Synoptic situation was characterized by the passage of a cold front, bringing cold air in the upper layers of atmosphere which enhanced  atmospheric instabiliy. Sounding analysis pointed out high value of most unstable convective available potential energy, accompanied by pronounced deep layer wind shear, as well as significant low layer shear (0-1 km) which is quite favorable for the formation of a tornado. Severity of the phenomenon was confirmed by lightning and satelite measurements (overshooting tops) and particularly by the radar image, pointing to hail areas and exhibiting so-called 'bow-apex' feature, indicating development of a supercell. 

In order to clarify some doubts - for the first time in our practice – a detailed in situ inspection of damaged area was also carried out, and aerial footage was also consulted. Although the atmospheric conditions were prone to development of a tornado, no material proof lead to presence of a tornado vortex, since no evidence of wind spinnig was found, and trees were usually knocked down in the same direction. 

The risk for severe thunderstorm activity was well forecasted, and corresponding operational alert was issued by the Met Service. Furthermore – as an early warning for the incoming weather change - a special announcement was issued on our web page.