Many studies in the last few years have been dedicated to the increasing temperatures and extreme heat in Europe since the second half of the 20th century because of their adverse effects on ecosystems resilience, human health, and quality of life. The present research aims to analyze the spatio-temporal variations of extreme heat events in Southeastern Europe using daily temperature data from 70 selected meteorological stations and applying methodology developed initially for the quantitative assessment of hot weather in Bulgaria. We demonstrate the suitability of indicators based on maximum temperature thresholds to assess the intensity (i.e., magnitude and duration) and the tendency of extreme heat events in the period 1961–2020 both by individual stations and the Köppen’s climate zones. The capability of the used intensity-duration hot spell model to evaluate the severity of extreme heat events has also been studied and compared with the Excess Heat Factor severity index on a yearly basis. The study provides strong evidence of the suitability of the applied combined approach in the investigation of the spatio-temporal evolution of the hot weather phenomena over the considered domain.

Climate in Bulgaria became not only warmer but also drier at the end of the 20^th century. During the last decade however, precipitation totals have increased mainly due to the contribution of heavy rainfall events which caused severe floods and damages in various economic sectors. In this study a seasonal analysis of heavy precipitation events which is registered during the same process in at least 4 districts in Bulgaria is carried out. All data for extreme precipitation (totals ≥60 mm/24 h) from the meteorological network of the National Institute of Meteorology and Hydrology for the period 1991–2017 are used. An increase of the annual number of days with heavy precipitation is found for the investigated period. About 78% of all days are during the summer and autumn. The classification of synoptic situations connected with 122 days of large-scale heavy precipitation events is also presented for each season. They are divided in different synoptic circulation types, taking into account pressure fields at 500 hPa and sea level pressure. For summer and autumn 4 main combinations of circulation types are defined, which present about 65% of all determined types for each season. The brief analysis shows that more than 80% of all observed cases are connected with varying degrees of damage and even human casualties.

A long-lived supercell developed in Northwest Bulgaria on 15 May 2018 and inflicted widespread damage along its track. The first part of this article presents a detailed overview of the observed storm evolution. Doppler radar observations reveal that the storm acquired typical supercellular signatures and maintained reflectivity values in excess of 63 dBZ for more than 4 h. The thunderstorm was also analyzed through lightning observations that highlighted important characteristics of the overall supercell dynamics. In its second part, the study investigates the predictability of the severe weather outbreak. In the medium forecast ranges, the global European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble indicated the presence of favorable conditions for the development of deep moist convection 4 days prior to the event. A set of three convection-allowing ensemble simulations also demonstrated that the practical predictability of the supercell was approximately 12 h, which is considerably higher than some previously reported estimates. Nevertheless, the skill of the convective forecasts appears to be limited by the presence of typical model errors, such as the timing of convection initiation and the development of spurious convective activity. The relevance of these errors to the optimal ensemble size and to the design of future convection-allowing numerical weather prediction (NWP) systems is further discussed.