Vol. 129, No. 3 * Pages 241–372 * July - September 2025

The atmospheric teleconnection presented in our former paper (Babolcsai and Hirsch, 2019) shows a particularly strong regularity between the Euro-Atlantic mean sea level pressure anomaly pattern in September and the pattern three months later, in December, in the current positive AMO (Atlantic Multidecadal Oscillation) phase lasting since 1995.
Euro-Atlantic mean sea level pressure anomaly patterns for September were divided into four clusters, whereas cases that could not be classified as any of these, were assigned to a fifth cluster.
Based on the clustering, the December macrosynoptic situation in Europe can be predicted in a significant number of cases, and hence the sign of the temperature anomaly in Central Europe.
In our paper, these regularities are described, as well as their connection to the polar vortex, which is the main factor in forming the mean sea level anomaly of the winter months of the northern hemisphere. In the last 29 years, clustering based on the mean sea level pressure anomaly for September has been able to divide significantly cold and mild December months even better than the state of the polar vortex in December (sign of the AO index).
In addition, a new phenomenon is presented, which might be a sign of climate change and has been interfering in the atmospheric processes since 2019.