phil nw.

I am not surprised Mike based on the 12z UKMO raw charts. We still have no certainty for Christmas day but no one should dismiss the chance of snow on the day based on a GFS run which historically loves to send energy ne in borderline setups.

It's clear that beyond Wednesday differences between the UK and GFS runs begin.The UKMO shows the Atlantic low disrupting as it hits the cold air whilst GFS keeps a more rounded low.By day 5 the differences are clear in the evolution of the Atlantic trough. and by day 6 The battleground across the borders on the GFS with milder air further south.Eventually the Atlantic wins through. UKMO brings the cold to all by boxing day and looks the best way forwards to prolonging the cold spell.I would like to see some increasing blocking though going forward to help the next low maintain a southerly track.

Just a reminder for those who prefer ,shall i say,less frenetic and more measured discussion on the models there is the other slower moving model thread here- Please try to keep calm and respect each other.We are all here because of our weather interest,especially anything cold and snowy- so let's try and keep it friendly-tis the season of goodwill and all

The last fax from the MO for noon Wednesday. The pattern shows frontal systems trying to make inroads from the south west.Cold air further north as they move into the UK .

Yes a large range there Ali. This one shows the ecm ens.for 850s for Warks on a larger scale. Underlines the large window of uncertainty on where the cold air boundary will lie.Note the operational solution at the very warm end over the holiday.A straw to clutch at maybe.

The concerning trend over the last 24hs or so is the weaker block over Greenland being modeled as we approach Christmas.The whole pattern thereby being allowed to drift further north. A strong Greenland high would have driven a sharp Scandi.trough south and west towards the Uk.Instead we see in current runs a slow moving increasing bloated area of low heights stuck over there.We have also lost the sharpness of any Atlantic trough driving se towards Iberia .The weaker block of course allows the lows from the Atlantic a chance to loiter to our west and south west and combine with the eastern trough further north ushering in milder air. The whole setup is still intact and It's not a done deal yet .There's still time for the models to find stronger heights to the north but we need to see this trend reverse pretty soon.

Yes agree with that Damian. The strength of the Greenland block is key in how far south the Atlantic and European troughs phase.It will much nearer to Christmas for that to be decided. It's exciting to see such a NH pattern like this though,rare for mid December with the tpv shredded.

Marginal conditions are always tricky for snow.I recall the midlands getting snowfall a few years ago with -2/-3c uppers.I guess evaporate cooling is also a factor in some conditions.Of course coastal conditions are at risk to warming of the lower layers off the sea.So many factors but in the right conditions quite modest uppers can deliver given other factors are favourable.

Just shows snowfall is possible as long as 850 are sub zero with a east/south easterly off the continent with low dew points. Edit-snap Kasim

Yes the Icon kept the trough intact but was not sharp enough and phased just too far north.However we can see at the end of that at t180hrs how the Scandi.trough is coming into play and pushing the cold air back south.A fascinating battle coming our way i think.

What we don't want is to see is that sneaky little Azores ridge heading ne through the Canadian trough in mid-Atlantic.This has been modeled on recent GFS runs. Here at t132 hrs on the 06z chart. That will push the main Atlantic low ne turning the pattern milder. We need that trough to remain intact heading se towards Iberia as shown especially on the ecm. Look out for this from around t120hrs.Fine margins as to where the main thrust of the jet goes.

ECM bringing in the cold from the ne.for Christmas . Consistent with it's 12z ens mean from yesterday. Good trend.

That is a decent ECM 850s mean for Christmas day. running through the frames on these we see the cold air hitting the east coast at day 6 and then moving west across the uk until this point.No trend to push any mild in.Cold air would be over us if any Atlantic arrives around this point. Of course lots of detail to resolve before we get there especially wrt to the splitting of the Atlantic jet and the strength of the block. The main thing is the trop.vortex is being torn apart with blocking pushing north on both sides of the pole opening up continuing opportunities for a cold pattern to establish. A pretty good place to be in leading up to Christmas.

Just a gentle reminder to use the Met office thread for discussions on their outputs please folks. Ta.

Logically you would think the likely temporary interference in the mjo has created changes in the medium term outlook. Probably this being the reason recent modeling shows blocking relaxing enough to permit the Atlantic to try and move in. Taking this reasoning further once the mjo resumes it's forecasted movement east we would see the blocking signal strengthening. The 06z gfs seems to show this quite well.We see the Atlantic attacking then being repelled by a reinvigorated block. This creates the chance of a classic old school snowy pattern. Exciting stuff and would be great if it verified over Christmas .

GFS 12z Not a bad run with the cold air from the east arriving at t168 and across the country by T192.

Comparing yesterdays 12z ecm mean 850s for 22/12/21 with todays-Europe view.T240 now T216hrs So 24hrs later the ens mean shows sharper ridging north and cold pool to the east broadening and a little closer,Little steps in the right direction.

The overnight clusters showing the Ht anomalies for Christmas day. No surprise the 3 scenarios all go for the block but interestingly the 2 biggest go for ridging nw towards the Greenland/Iceland area. Cluster 2(33%) entertains the idea of a high centre around Iceland which would usher in the cold from the east,One to watch.

A promising ECM mean at tt240hrs -850s-European view That cold from the east getting very close.If that Scandinavian trough broadens a little more we could well be seeing deeper cold across us by Christmas.

A new thread to continue model output discussion. A change to a high pressure pattern is expected to develop through the coming few days as pressure rises from further south .We can see this well established around our shores by the end of next week. Cold air by then is coming south over Eastern Europe and parts of Scandinavia with the Atlantic blocked off.Any drift off the continent will cool things off at the surface for the Uk but detail like this is best left until nearer the time. Latest 2m temp. ens graph does show a steady cooling trend though. As ever the position and orientation of the block will make the difference to ground conditions,let's hope a drift further north appears where we can tap into colder upper air in time. Ok on we go then please keep just to model output discussion in this thread and use the other threads for anything else. Thanks all.

Ok folks whilst it's quiet i will lock this now and will open a new thread ready for the 12z charts. New thread here

Iirc !962 saw a November Canadian warming which had weakened the vortex .We saw a strong wave 2 attack by mid December that then shredded the tpv to enable the high then around W.Europe to shoot up to Greenland. This time we have plenty of waa being modeled in the medium term from as far south as the Canaries but we do have a stronger pv to combat this year. An interesting period ahead to see if the high can gain further traction north.

As expected the UK block starts to set up shop around day 6 and then looks to become a very familiar resident .I fear we will start to weary of this pattern if it hangs around at mid-latitude until well beyond Christmas as extended ens suggest.Let's hope we can squeeze some frosty conditions out of this pattern at least. A small difference in it's positioning even by a 100 miles of so could make a difference to surface cold development and cloud cover as we know, so that sort of detail will became clearer as we go forward. I do hope we get it further north.Even a modest move will bring more of us into at least a colder drier continental flow, with the probability of less cloud and therefore more night time cooling,A more southerly position of the high risks bringing in a moister and milder Atlantic drift around the top and we would be chasing cloud amounts and the attendant risk of Anticyclonic gloom.

The common theme is a high looking to be around the UK as we approach Christmas. Whilst gfs in particular tries ridging further north the core of the high remains too far south so no Greenland block yet.There is till enough energy running over the top hindering further movement north. This pattern could well develop towards N Y if the mjo moves further east in the Pacific ie phase 8. Forecasting the mjo movement and strength is tricky though so I am always wary of changes in this. At least the first stage towards blocking seems pretty solid now we just need some good fortune to see that regress north.

Wise words Catacol. Us cold lovers would love to to see blocking up north but I was surprised to see recent gfs operational runs developing this so soon. Ens. guidance is certainly strong on a devolping high somewhere around the UK or nw Europe from mid month. A frosty Christmas looks quite possible with the hope that we see the high build north as we head towards NY.