Interesting Pattern Change Coming For Europe, First Big Snows For Alps

Written by on October 6, 2013 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Well we appear to be on our way to normality with the first trough driving colder air south in the Wednesday through Friday period. This shot of chill is by no means out of the ordinary but it will ‘feel’ cold given the out of the ordinary warmth we’ve had of late. How warm has it been? Well nights have supported temperatures more suited to during the day for this time of year at 14-17C.

Last week we saw a strong west ridge-east trough setup but this weekend is seeing height rises right across the continent and with a system crossing the UK Tuesday-Wednesday, so the seesaw flips the other way during the upcoming week with a west trough-east ridge. The ‘extreme’ won’t affect the west as it did the east. In other words we don’t deviate far below normal like eastern areas did, we go to normal or a little below with highs in the 8-13C range whereas eastern Europe has been unusually cold.

SEE YESTERDAY’S POST

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I believe the unusual (late November) chill the east has witnessed is down to a larger snowpack than usual over Siberia, perhaps helped by a larger expanse of arctic sea ice which has helped build the cold pool stronger and more extensive. The warm water stretching from the western Med to Norwegian Sea has kept the ridge firm in the west. All part of a feedback or hangover from summer.

French Pyrenees

French Pyrenees

Last summer was the complete opposite and sure enough, it was colder than normal at this point last year. She mentioned just last night about how she was doing a job outdoors and her and her colleague had to wear gloves. The bulk of last winter saw the worst further east over the continent but that October saw a cold west and warmer east. It’s opposite this year. From what I can recall, October 2009 was similar to what we’re seeing now and that winter was the worst in my lifetime. Sure it was colder in the front end to the following winter (late December through December 2010) but January and February ended up mild.

You can see from the current SST’s where our air has been so mild. Low pressure to the SW and high pressure to the NE has forced warmth from Algeria north, northeast and with warm water, the air moderates less.

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It’s been interesting how the -NAO signal has not supported a cold pattern over western Europe and eastern North America. This is down to feedback from SST’s as well as a lag in the pattern following summer. Keep in mind that we had a strong positive height anomaly in mid summer and this returned frequently, albeit in a more progressive fashion through August and September. This has kept SST’s warmer than normal from the western Med to the Norwegian Sea and as a result the ridge wants to keep going where waters are warmest BUT this will turn around as snowfields expand and Greenland continues to grow colder, so ridges and troughs shift with the season.

This week promises the first slap of reality but it appears progressive as the trough drops initially but as it does so, the axis shifts east then the upper low cuts off forcing the ridge over top. This setup supports cold northerly winds then an unsettled spell into next weekend with a cold vortex spinning over the near continent keeping it cold, cloudy and damp on the other side of the North Sea. Milder air tries to enter Scotland from the north, so there could be a fight between cold to the south and milder air in the north. What interesting is this is a setup supporting the first big snowfall for the Alps and possibly the Pyrenees.

Here’s the current setup according to the GFS. I’ve put up the 850 temps as this shows the temperature of the air masses better.

Here’s Monday and note the general SW flow across the UK and Europe but note the bump in the isobars to the W. That’s a key feature.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By Tuesday it passes with a low pressure centre just north of the UK bringing wetter, windier weather but notice how the cold starts to wrap around the backside of the low. Today has a trough deepening and dropping south over Greenland and Iceland and it’s as this drops south, so the low connects and pulls the cold air south. The connection between the much colder air and the low, allows the development of a deep trough.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By Thursday the deep trough is in place and positioned over the North Sea with cold north winds and 0 to -5C 850 temps driving south.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the ECMWF which shows the same Thursday. Expect to hear reports of snow over the Highlands and possibly on top of the Pennines even. Highs? 7-10C in Scotland with feeling nearer 3-5C in the stiff northerly.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By Friday the upper low cuts off with ridging over top and centred NW of the UK. As the upper low drops towards the Alps, heavy snow will break out.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the latest ECMWF snow projection for the next 7 days.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the GFS which is hinting at snow falling over Belgium and across central and south Germany. I think this is overdone outwith the Alps and Scandinavia.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

What’s interesting about next week is the message this change is pattern may be telling us. In the 7-10 day period, heights remain strongest to the N and W of the UK heralding a more classic -NAO signal. Both GFS and ECMWF are hinting at a stronger drop of cold down over Scandinavia and although it doesn’t show this bodily shifting west, it may be worth watching. We could have some serious winter-level cold and snow on the way to Norway, Sweden and Finland in the period between the 10-17th. Another sign of ‘potential’ for later even if we remain on the warmer side, however with heights on the rise over the Atlantic, I wouldn’t be all that surprised if we get this cold trying to reach the UK. Remember, it’s what the pattern is telling us that’s important.

Here’s a look a little further down the road.

Here’s the 16th and the stronger, cold trough diving into Scandinavia.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Thu 17

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

All in all, I want you to keep in mind that any cold shots that come down over the next couple of months is NOT the winter ahead but mere indicators, insight and teasers of the season ahead. Let’s watch how this pattern evolves in coming weeks.

Be sure to watch the video I posted earlier.

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