If you want to know the reason why Moscow was so mild during December 2019 then look no further than the mean surface pressure chart for the month and you’ll see a straight W’SW flow from 60° west right across to 50° east. That’s because pressure was over 10 hPa low to the northwest of Scotland during the month and around 3 hPa higher close to the Azores, between them this tightened the W’SW flow across the Atlantic, especially between latitudes 45 and 55° north, and that’s why the UK was around 1 or 2°C milder than average and much wetter especially in the northwest at the beginning of the month. Interestingly the pressure anomalies across much of Greenland again managed to remain positive.