As we head into September I continue to watch the overall global pattern and the primary drivers. The El Nino is strong and influential to the global circulation, however as I’ve pointed out previously, there are competing factors which suggest there’s nothing obvious as of now. By that I mean we can’t just look at this El Nino, assume it’s the same as 97-98 and therefore we’re heading for a warm, wet winter both here in Europe and on the other side of the Atlantic.
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If you want me to commit to where I think the upcoming winter is heading, based on the still warm water in the North Pacific which tends to promote an Alaskan ridge, I think at least SPELLS OF COLD dive into the Eastern USA and this suggests a stronger trans-Atlantic jet stream like we witnessed the last 2 winters.
Another significant factor is that the North Atlantic remains cold and is likely to remain that way into the winter months. What does this suggest? An active +NAO pattern which frequent low pressure hits on the UK and Northwest Europe but crucially, cold air over E North America combined with colder-than-normal waters in the Atlantic makes me believe a similar winter to last year. A MIX OF MILD ALONG WITH SPELLS OF SNOW AND COLD.
In saying that, the warmth off both sides of Iberia is likely to promote a stronger and potentially further north than normal Azores high which may promote unusually mild days all the way up to Scotland but I suspect a battle of air masses type winter in which some very cold days/nights along with spells of decent snowfall is also quite probable.
Current global SSTA.
Change within the last 7 days over the North Atlantic.
Project SSTA’s during the upcoming winter.
CFSv2
Jamstec
My theory is that if waters go above normal around the UK then there’s more chance of a warmer than normal winter.
Positioning of the El Nino warm pool is critical, a more centrally based Nino would support a better chance of cold for both US and UK but in close to South America and there’s more ridging and warmth. Warm and cool ocean temp anomalies ultimately determine where the mean ridge and trough pattern settles.
We’ve a colder than normal and warmer than normal SST profile that’s likely to bring big back and forth flips this winter. I don’t see a warm winter like 97-98 nor do I see the winter of 09-10 which was a moderate El Nino year but the solar cycle reached it’s lowest values in 100 years. This winter, it’s half way between a maximum and minimum. By around 2020, I suspect another 09-10 style winter.
Cycle 24 continues to fall from it’s peak back in March 2013 following a warm winter which led to the warmest summer for the UK since 2006.
Until we reach the minimum, expect our winters to be mixed but cold, snowy spells have been known to turn briefly extreme. 1995-96 saw one of the coldest spells on record in Scotland when Glasgow hit -20C and we tied the UK record of -27C in Braemar. That winter overall wasn’t particularly cold and this was on approach the cycle 22’s minimum.
We saw extreme winter weather in 2000-01, this hit just off cycle 23’s maximum.
IF ‘cold lows’ ride a stronger than normal jet, driven by a large North American thermal gradient across a cold North Atlantic into the UK, enough cold may be in the pattern to bring us snow and cold rather than mild and rain.
Another aspect worth considering. While I believe we’ve another +NAO winter, the warm water surrounding the northern side of Greenland may be worth watching as spells of -NAO and blocking highs to our west can’t be ruled out.
Of course the same drivers which bring a certain type of summer does bring a different signal in the winter. Last winter was strongly positive while the summer strongly negative.
The latest CFSv2 shows a warm winter particularly for Southwest and much of mainland Europe.
Note it’s got the classic colder back end El Nino winter with North Atlantic blocking and colder scenario.
Jamstec still shows a colder than normal winter for UK/Ireland and France, warm elsewhere.
Hope to have a video for you this afternoon!
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