I think we just had a really +NAO earlier in the season.. since it went negative, activity has been way above average.. see how High pressure in the Atlantic is associated with +nao. August was like +3.1 NAO
It's the reason why SSTs cooled of for a little while too.. Some people were talking about shifting to -AMO. The NAO was just really positive.
Regarding regime shifts.. these records in the SW, US are really impressive. And in the next few days Japan is going to be breaking all time high records too. The mid-latitudes around the Pacific are just really hot right now. I don't know that this won't even out as High pressure in the Pacific (-PNA) for the next 5 years or so.. That pattern is associated with more above average tropical activity in the Atlantic.
That cold wave was so intense I can almost forgive the no snow part of it. Just nice to see it can still get that cold. In fact last winter was the third consecutive IMBY to have at least one sub 25 max.