Even with all of that, is there any direct connection with the SSW event in Winter 2013 and the pattern in the following March? Could not this have occurred independently of SSW?
Hi CP; the fact is, for a host of other reasons, just about any setup is possible without a SSW event. SSW, it seems, increases the probability of certain conditions occurring and persisting.
This link gives a summary of N Hemisphere SSW peaks (go to p66) and you can see that some very cold spells with Ely and Nly components, some well quoted, precede SSW peaks.
Some are surprising: 23.1.87; 22.2.79; 28.1.63.
Others seem much closer to surface cold than the oft-quoted 2 week downward propagation period, including 4.12.81 and 1.1.85- in the latter case, the cold setup was red-carpeted on New Year's Day with an elongated Atlantic HP, and established 3 days later as LP to the NE began pumping cold air out of Scandinavia. In the 1981 case, there was a distinct line marked by a far-reaching frontal boundary behind which a very distinctly different airmass brewed.
Point here being to illustrate not the obvious- that some SSWs do not deliver, which I think everyone knows; but that some macroscale setups involving reversals in long- and broad-fetch prevalent airstreams are not SSW dependent.
The link:https://www.earth-syst-sci-data.net/9/63/2017/essd-9-63-2017.pdf
Bertie, Itchen Valley.
'We'll never see 40 celsius in this country'.