Severe convection event in southeast of Bulgaria on 17th September 2022

The Knowledge of the development of the severe thunderstorms is crucial for improvement of weather forecasts which are provided to air traffic control (ATC) units. Intense thunderstorms, strong winds and hazards such as severe turbulence and icing, lightning activity, microbursts, and hail are very important for the aviation safety.

The present work focuses on the study case of atmospheric conditions preceding and during the development of unusual severe convection over southeast Bulgaria on 17^th September 2022. when the squall line passed through the airport of Burgas bringing a lot of damage to the airport and surrounding towns.

On this days the weather was dominated by the presence of a very unstable air mass over Southeast Bulgaria, ahead of the atmospheric frontal zone. As convection continued its development, it moved east/northeast forward Burgas with overshooting cloud top height up to 14 km, cloud top temperature of -70C and maximum radar reflectivity of 60 dBz. In the late afternoon the process led to formation of gust front that reached the Burgas airport with the record for the past 50 years wind speed exceeding 45 m/s that damaged the mast of the airport's instrument landing system. At the same time heavy rain and intense lighting activity are reported. For analysis of the severe weather conditions are used weather satellite, radar and lightning data, Mode-S aircraft wind data and surface observations. In addition, information provided by the ground based Global Navigation Satellite System (GNSS) network is used. Integrated water vapor shows a sharp increase several hours before the convection developed. As moisture is one of the main ingredients for intense thunderstorms formation, GNSS tropospheric products are used together with other surface data to help the process of deep convection monitoring and forecasting.