Winter 2014/15 coldest in 100 years?
Posted Fri, 10 Oct 2014 14:43:50
It’s October so inevitably the speculation about the coming winter is reaching fever pitch and there are press reports suggesting winter 2014/15 will be the UK’s coldest. Never mind the fact that most UK winters are damp affairs which bring little snow to the majority of Britain there’s always the chance the next one could be the ‘big one’. Quite why it should be is rarely explained in any detail and the evidence used to support the idea is often sketchy at best and at times appears to be non-existent.
Nonetheless, it’s impossible to categorically say the coming winter won’t rival the big freezes of 1947 and 1963. It’s of course very unlikely in any given year, but as they say, a stopped clock is right twice a day. Keep saying the same thing and eventually you’ll probably be right.
What’s my view on the prospects for the coming winter? I’ll add the usual caveat that on TWO the full winter forecast is issued in late November because my belief is it’s important to see how the autumn pans out in full. On balance I’d say the pattern we’ve seen during September and the early part of October is more likely to be followed by a milder rather than colder winter.
Do the seasonal models give any guidance? They shouldn’t be ignored but they still demonstrate a low skill level for our part of the world where we are on the border of different air masses. The September raw output from the UK Met office global model points towards a milder than average winter. On the other hand JAMSTEC which is a Japanese global model is pointing towards colder than average conditions. The latest runs I’ve looked at from the US CFSv2 model are suggesting a cold February with close to average conditions in December and January. You can really take your pick from these, but perhaps the conclusion at the moment would be ‘no strong signal’.
Another input being widely discussed this year is the October Pattern Index (OPI). My understanding is this is based on research done in Italy which has found a link between 500hPa heights in October and the development of the polar vortex in the winter months. A negative OPI apparently correlates with a weak polar vortex. A weak polar vortex increases the chance of cold arctic air being displaced down to our latitude in the winter months. The OPI is today running at -3.91 which is strongly negative, but this changes daily and we’ll need to wait until the end of the month before knowing the final figure. Nonetheless, if you’re hoping for a cold winter this may be the most encouraging signal right now.
There are many other things which can be looked at such as the ENSO cycle, other teleconnections, solar activity and stratospheric temperatures. Also lets not forget the great hope from early years of this century, the expected North Atlantic Oscillation (NAO) index based on the forcing mechanism of sea surface temperature anomalies. There are also the more esoteric indicators which I always enjoy reading about such as the wax wings, squirrels and berries.
Where does all this leave us? Well not really much further down the track and there is the added complication of whether we’re currently in a period of colder or milder winters. In 2008 after a long run of predominantly mild winters things flipped and we had several cold ones. Last year of course brought one of the mildest winters on record and temperatures this year have been running well above average. Have we flipped back into a period when mild and wet winters are the norm with just an odd colder exception? Possibly.
Finally then, if I was forced to play my hand now and make a call on winter 2014/15 what would it be? It would be a very tentative call and not one I’d have too much confidence in. Nonetheless, I’d go for an average to mild winter again, but with most place seeing at least some snow. That in itself would be a big change from last year.
http://www.theweatheroutlook.com/twoother/latest.aspx
I'd say the cold winter phase has passed now, sadly
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