Battle Between Atlantic And Arctic Air Over Europe This Week

Written by on October 14, 2013 in Rest of Europe, United Kingdom & Ireland with 0 Comments

The next spell of -NAO, AO is setting up and yet another shot of arctic air is diving into Europe. The models are in pretty good agreement that the bulk of the arctic air dropping south over Scandinavia will stay north and east of the UK as yet another ridge tries to fight back the cold over the UK and western mainland. In saying that the cold appears to reach the north coast of Scotland indicating somewhat of a late week battle between Atlantic and Arctic.

One key difference between this shot of cold and the last is the North America pattern is shaping up differently. This time around, cold air will dive into the heart of the continent and should eventually spread EAST and not hold in the west. This should teleconnect to the Europe pattern and one would expect the cold to attempt to push further west. Modelling has more of a Greenland block late week which we didn’t see with the last -NAO.

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The latest GFS NAO, AO, PNA ensembles indicate a cold signal for eastern North America and Western Europe but as stated in recent posts, the PNA has been the fly in the ointment and has held the North American cold further west which lead to cold diving into eastern Europe as a result. This time around the models show the cold over more central and eastern parts of the US and so we should watch carefully more next week’s pattern. As for this week. The Atlantic appears to fight back the next batch of arctic air trying to drop south over Scandinavia.

Here’s the latest indexes.

nao_fcst

ao_fcst

pna_fcst

By late this week you can see the cold air is close to the UK but notice the ridge to the south stopping this from dropping south. Low pressure to the NW of the ridge will throw unsettled, mild weather across the UK.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By Saturday the cold tries to push south but both low pressure and ridging to the south stop the southward progression of cold.

120 hrs (Sat)

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By Monday of next week, the model continues to show both ridging and low pressure but it will be interesting to see what happens once the cold begins to spread east over North America and this reacts to the downwind upper pattern across the Atlantic.

168 hrs (next Mon)

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

As for the surface pattern, the UK looses the stubborn low that’s been locked in place over the past 3-5 days by surrounding high pressure but this opens the door to a low waiting in the wings to the southwest. The fight continues with either ridging or Atlantic weather trying to hold back descending arctic air. We saw a batch of arctic origin air drive south over Scandinavia at the end of Sept, early Oct only to be deflected east by ridging and this time around it appears a large area of low pressure which pushes into the UK from the southwest will do the same this week.

It’s funny to watch this and I believe this battle of air mass will eventually breakdown. The PNA is playing an important role as well as the summer pattern which is feeding back. I’m noticing with this next shot of cold, it’s creeping ever closer to the UK as you can see from the above 850mb temperature charts and if you notice the PNA does go positive. It should get to neutral this week, hence colder air reaching northern Scotland but by next week don’t be surprised if we turn much colder here in the west with the deeply negative NAO and if the PNA does get to positive territory which it’s likely to given the models have a strengthening western North America ridge and the AO should hold negative too so the arctic air should still exist within the mid-latitudes.

If it doesn’t happen then I am too quick. The interesting thing is that the trend is now for blocking and this should now progress into the winter months. Soon enough we will loose the ridging and arctic air will dive into western Europe. It’s all in the timing.

What’s important to remember about October patterns is that often a COLD OCTOBER in the UK leads to a not so cold winter and often where it’s mild but wet, particularly so in November, that’s where your winter trough tends to aim for. Something worth keeping in mind.

Here’s the ECMWF surface chart for the next week.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Note by Friday the 540 line hangs over the north coast of Scotland but plenty of wet weather dominates western Europe into central and northern areas.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Little chance by Sunday.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

And by Monday. The low southwest of Ireland is acting as the block but notice the 540 line is sagging further south over Europe. With low pressure over Russia, expect to see some decent snowfall over Scandinavia late week into the weekend.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Hope you got a chance to watch yesterday’s video as I explain a few things but don’t be surprised to see any cold that’s on the way, disappearing into November as I believe we warm and turn considerably wetter with the NAO, AO turning back positive for a time. It’s all part of the downward spiral into winter.

Be sure to remember, often where your autumn trough is positioned, that’s where your ridge is during the winter and think about it. Wouldn’t it be rather interesting to have a ridge over Scandinavia??

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