Purpose. This paper aims at identifying and studying the cases of steady winds of one direction over the Black Sea and analyzing the accompanying conditions in the surface atmosphere and middle troposphere in winter (December–March).

Methods and Results. The situations with extremely steady winds of persistent direction, namely, when the prevailing wind over the sea does not change its direction for 5 days or more, are considered. The analysis is based on the 6-hour data on wind speed at the 10 m height, the 500 hPa geopotential height and the surface pressure from the ERA5 reanalysis of the European Centre for Medium-Range Weather Forecasts for 1979–2021. Within the analyzed period, 10 cases of steady, mostly north-eastern, winds were identified. At the same time there were 3 recorded cases of the eastern, northern and south-western winds. The empirical orthogonal function analysis performed for a set of steady wind cases shows that distribution of the first modes of the geopotential height and surface pressure fields has a spatial structure with a stable high-pressure area over the European territory. The contribution of these modes to the total variability is 65 and 47%, respectively. Analysis of the revealed situations with steady winds shows that in all the cases with northern and north-eastern winds, there was a blocking process in a form of a quasi-stationary anticyclone in the middle atmosphere located over the Northern Europe/Scandinavian Peninsula. In the case of northern wind, an extensive high-altitude anticyclone was located over the northern part of the European Russia. Values of the Tibaldi and Molteni blocking index confirm the fact that the considered cases of long-lasting north-eastern and northern winds correspond to the blocking conditions over the European region. A steady eastern wind was observed when the extensive anticyclone in the middle troposphere was actively moving from the north of the Scandinavian Peninsula to the south-east. In the case of a long-lasting south-western wind, a subtropical high-pressure ridge was presented in the middle troposphere as well as an intense transfer of cyclones took place over the European region that created a prevailing steady wind over the Black Sea.

Conclusions. The analysis results indicate that the considered cases with steady north-eastern and northern winds over the Black Sea are related to the blocking processes in the European region atmosphere.