[important] London’s Temperature Is Set To Drop 13 or 14C From Today’s 28/29C To Tuesday or Wednesday’s 15/16C [/important]
Yesterday saw a respectable 28.2C in London and with a reading of 25.3C at barely 11.30am this morning, readings are well on their way to 29C somewhere in Greater London or the Southeast. The east of England should see the 26C line reach Yorkshire again but cloud and rain is advancing southeastwards across Northern Ireland, Scotland, Wales and NW England and this is the boundary which brings us all our first taste of autumn in the coming days. Today will be the last VERY WARM day of 2012. Yes we’ll probably get another few days of 22-24C but there’s growing limitation in daytime heating as we progress towards mid-Sept.
Next week will be a wake up call as to what’s ahead. While Iceland shivers in an early season arctic blast, so this cold air will sweep down over the British Isles and Ireland in modified form, even reaching into northern France mid next week. Tomorrow will see the first of the cool air over Scotland and Northern England with heavy showers piling in on a stiff, chilly northwest wind with snow is possible above 4000 feet in Scotland. Look for highs of only 14C in Glasgow, 16C in Carlisle but though cloudier with a few odd showers around, the South of England remains fairly mild with the main boundary still to the north. By Tuesday and especially Wednesday, the trough covers the UK and highs in Scotland and N England will have a tough time getting above 12C with some possibly rising to only 7 or 8C in the Highlands. The breeze will feel nippy providing a real sense of autumn. If we manage to get clear skies for long enough Monday and Tuesday nights then frost is quite likely in areas away from the coast and urban areas but even in towns and cities, lows could push frost level.
London may have a tough time hitting 16C on Tuesday, 15C on Wednesday and this will likely be the coolest day since May in the Southeast.
Have a look at these upper level charts off the ECMWF to compare today with Tuesday.
Next week’s turn to cooler, stormier is likely the sign of seasonal change
As well as showing the trough and turn to much cooler across Northwest Europe, the models have also been showing a tightening of pressures across the Northeast Atlantic during the second half of next week and following a chilly Monday through Wednesday period, we are likely to see an increasingly windy, even stormy, leaf stripping setup develop Thursday onwards.
The pattern this summer has been a very active one with deeper than normal lows crossing the Atlantic (thankfully their centres have tracked further north and nearer to Iceland, the fronts associated with these lows have been a frequent visitor to the UK though) and as the cold builds across the arctic and with very warm sea surface temperatures over the North Atlantic and Greenland, this suggests a continuation in this pattern.
As the seasonal shift begins and it could well be next week, I believe a wetter and windier period is upon on during the second half of this month with perhaps a cold spell to end Sept and start October. Next week’s increase in storminess will likely be a sign of the type of autumn we can expect with warm surges ahead of these deepening lows and cold shots on their backside.
A weak Nino, positive NAO and warm N Atlantic likely means a warm, wet autumn with brief cold shots in between
All in all, I continue to go for a warm, wet autumn despite some short shots of cold which mainly come down on the backside of a storm system exiting and sliding into Scandinavia. When might they occur. I think late Sept and early Oct as well as during November but it won’t last. Will we see any unusual low level snowfall this October like we’ve seen in the past? Unlikely, but what we may see is some wild storms as we progress towards the later of October and through November, perhapos taking us into December.
A wet, windy and warm end to November and start to December is sure to get those routing on a warm winter excited. However, what’s important to keep in mind is that where the trough and wettest compared to normal is in late autumn, this often tells you where the cold pool in winter will be. It was Joe Bastardi who alluded to that theory a few years back and it played true in the autumn of 2009. Remember the harsh cold and snow we got that Christmas? That year, winter struck after a very wet, warm November and the el nino and temperature profile in the North Atlantic is similar to this year. 2002-03 also plays similar though the Pacific was warm.
With regard to the NAO, the majority of the summer has been mainly neutral or negative but this autumn I think it could hold neutral or positive through November with a flip in both the NAO and AO by December. Just in time for a white Christmas for many, hehe… Hey, ya never know right?
What about the Greenland Block This Year?
We us here in the UK and the eastern US to get nice cold blasts during winter, we need a Greenland block to develop. That’s a high pressure system which parks itself over Greenland and occurs during negative NAO’s.
What might suggest more blocking this winter like we saw during the 2 winters of 09-10, 10-11 which brought us plenty of snow and cold, could be a TRIPOLE over the North Atlantic of warm over cold over warm. So warm-cold-warm, can lead to more in the way of high pressure over the very area we want it to be.
What’s the JAMSTEC model saying?
First and foremost, take a look at where the warmest waters are in the equatorial Pacific, they are well off South America. Had they been nearer the coast then this would have suggested a stronger El Nino signal and more ridging and warmth over much of North America as well as the UK for autumn and winter.
BTW, those warm waters surrounding the UK and across the North Atlantic should support wetter, milder and stormier conditions through November for us and Scandinavia.
Now the water temps for winter.
Now that’s looking good for blocking during the winter plus the nino holds out over the central Pacific. That is a good signal for ridging over the North Pacific and West Coast North America and troughiness and frequent cold shots into the Central and Eastern US and Canada, reinforced by possible enhancement of blocking over Greenland with the tripole of warm, cold, warm. This should bring us here in the UK a decent series of cold spells like we encountered back in 2009-10. Keep in mind that although the cold spell was longer and stronger in 2010-11 than in 2009-10, the winter of 09-10 was worse in that we saw repeat spells of harsh cold and snow in Feb and March. Following the brutal cold from late Nov through New Year, after that, winter was over.
As for what this model shows for temperature.
Here’s what it has for autumn. Note the warmth it has for the UK and much of Europe.
Now for winter. Notice the majority of Europe is warmer than normal but the UK is either normal or below with most of it below normal.
More later!
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