Hi there, long time no see. It certainly has been a while since we last did a Winter analogue. I have not made much progress on the analogues because I have been either busy or have no ideas for analogues. However, I have now come up with an idea and that is Winters which followed on from positive NAO Summers and specifically the top 20 positive NAO Summers back to 1865.
To start off, let's look at these Winters as a whole. There is a deep area of below average heights just to the southwest and over the UK and Ireland with weak above average heights over the northeast of Canada and to the northeast of Europe. As there is no real blocking around Greenland or the Arctic, it is a mild and wet setup. It may look like a straightforward mild and wet Winter setup but if you notice the Winters in the analogue, there are a few indifferent ones. Most notably the top year of similarity in positive NAO to 2018 was 1946 and the Winter that followed (1946-47) was a very severe Winter with a ton of Scandinavian blocking bringing in constant easterly winds and the coldest February on record back to 1659. 1894-95 featured a severe February too. 1890-91 featured the coldest December on record for the CET (beating 2010 by 0.1c) and a notable blizzard in March. 1961-62, 1933-34, 1953-54 and 1954-55 all had notable cold spells or snaps at some point in them especially in the Februaries and Marches. They were also relatively cold Winters overall.
In terms of December, it looks very similar to the Winter overall but perhaps even more of a stronger signal for a wet month, maybe not overly mild due to the meanders in the jet stream. Not overly cold either mind you. Some of these Decembers were chilly but most do not really stand out.
The Januaries once more show a similar signal to the Decembers and the Winters overall with well below average heights over top of the UK and Ireland. More of a signal for mild too.
The Februaries get more interesting than the preceding two months. With weak above average heights to the north and deeper below average heights to the south and west of the UK, it's mostly a signal for wet and mild month. However, there are a couple of very cold Februaries or Februaries that contained at least one notable cold spell in this analogue as mentioned above including 1947.
The blocking to the north strengthens over Greenland in the Marches of the analogue with below average heights to the south of the UK. This is a proper cold setup with northeasterlies being the mean wind direction in such a scenario. 1947 and 1962 are two examples in this analogue of severe Marches that support this reanalysis. 1955 was very cold but dry and sunny.
Not the best or most exciting analogue in the world for cold lovers but it does get more interesting in February or March. Stay tuned for more analogues as we get ever closer to the Winter 2018-19 forecast which will be released on Tuesday, November 27th.
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