Dynamic tropopause folding and cyclogenesis in the western Black Sea basin

For Romania, May 2025 stood out for numerous severe and extreme phenomena (abundant amounts of water, medium and large hail, strong wind). Under these conditions, this month rose to 4^th place in the ranking of the rainiest months since measurements were taken. There have been several episodes of heavy rain, but the last one, from June 23 to 30, affected the eastern half of Romania and even caused an ecological disaster at the Praid salt mine located in the central-eastern part of Romania (eastern Transylvania). It was flooded and collapsed mainly due to the rise of the Corund River, whose flow was almost 100 times higher than normal. For this study, the days of May 26 and 27 were chosen because the synoptic and mesoscale context was special, and caused heavy rains. It is about a cyclone that developed over the western Black Sea basin, with the main factor being the folding of the dynamic tropopause. When a potential vorticity anomaly overlaps a baroclinicity zone it makes possible dynamically and thermodynamically interactions between the lower and the upper troposphere. The western Black Sea basin, especially the coastal area, may provide the necessary conditions for such coupling leading to severe cyclogenesis. Under these conditions, very active cyclones are generated over the Black Sea, which when they are close to the shore, cause heavy rains and/or strong winds in the eastern half of Romania. Thus, the aim of this paper is to demonstrate the importance of dynamic tropopause fold in the development of a cyclone over the west part of the Black Sea basin and how strong can affect Romania, even with natural disasters. For the study, ALARO (ALadin-AROme) limited area spectral model analyzes  and ECMWF global model analyes (eg, mean sea level pressure, geopotential high at 500hPa, 1,5 PVU field height, 300 hPa Potential Vorticity, 300 hPa winds,), data from meteorological stations, cross-sections and satellite images were used. The results of this study is important because can be used in operational forecast, for similar situations, and can improve it. 

Keywords: ecological disaster, tropopause fold, cyclogenesis, havy rain