phil nw.

Yes Don that's what we are all watching for I think.

Looking at the latest Strat.outputs and like Blue said signs of increasing mean zonal winds at 10hPa. These are gradually downwelling towards mid-level but not yet affecting the troposphere much. Images below. In short the vortex is roaring away at the top but down near the surface we still have very light or zero westerly momentum winds. Currently the trop with it's blocking pattern is still just about holding sway and up to now has been leading the dance.An interesting battle ahead as to whether this continues into the second half of the month.

Just for information folks any posts regarding met o/bbc forecasts please use this thread Just so we keep this thread on topic. Thanks all.

Signs from the gefs 850temp.ens graphs that the cold air does gets south of the Uk in the medium term. A look at the London and Paris ens graphs shows a mean of -5 into London by the 10th and Paris 3 days later. Good signs that if any battleground develops near the south the cold air would prevail,based on this. Overall the trend continues for a nicely aligned Scandinavian trough heading our way for the middle of next week. Plenty of wintery interest to follow.Just waiting to see what disturbances may develop in the flow which won't be picked up yet. It's all lining up nicely.

I am late to the party tonight and can see from quickly reading the later posts we have a nice upbeat mood tonight and quite rightly after viewing the charts. No grumbles from me wrt t the 12z outputs.Chilly until mid week and then colder from the north east still well supported. Mean charts for next Friday A solid cold pattern establishing and by then feeling quite Baltic.

Some trough disruption is likely as it comes south as the Arctic air runs over the warmer sea I guess. We are seeing various solutions on this now as the higher resolution of the operation runs are now picking these up as we get closer. The overall pattern though is still good for cold and being consistently shown. We will get a better idea of snow possibilities from the weekend when the shorter range models become useful.

Consistency again from ECM with the angle of attack from Scandinavian trough. Looking good.

What a run from both models si but tbh no less than the Ecm suites have pointed too for a few runs now. A great angle of attack from the dropping Scandinavian trough. If we get to this point Arctic air over a warm sea should induce disturbances in the flow giving areas of snow heading south west into the UK. The first half of December promising to be increasingly exciting for cold lovers I think.

A little bit of model comparison information for the upper air temperatures ging into next week. It's a graph from NWxtra showing the projected 850hPa temperatures from the most recent operational and ens.runs. I have used my own location-Warks. as it is pretty central. Pretty good agreement now for a drop by the weekend as the colder easterly is felt.Divergence shows it's hand by the 5/6th December though as we can expect having viewed the latest runs. This is likely as a result of a possible approach by the Biscay low around a week away and how far north it can bring any milder air into the UK. The cold appears to win out in the end though by varying degrees,looking at the graph.How cold we get later remains to be seen,if this setup holds for a couple of weeks then we should see the fall in temperatures continue.

Yes GFS06z is ok until around day 6 and is close to the ECM.After that though the trough from the north east disrupts all over the shop and halts the cleaner feed of colder air that is shown on the ECM suite.

The first thing I did when I logged in this morning was look at the ECM mean. Those are day 8. A perfect angle of attack of cold from the north east with a solid Greenland block. Again remarkable consistency following previous runs which increases confidence.

I am sure in this case it has been a help as it has been quite amplified.There are other factors of course but this pattern coincides with the recent track of the current MJO.

Yes Blue it's been forecasted for a while. There's usually a lag effect of a 10/14 days hopefully we have time to see a decent cold spell.

The ECM mean charts continue with their consistency with a solid Greenland block and dropping down the Scandinavian trough. Very reassuring output after the GFS op runs earlier threw a few doubts into the mix. We are now entering the transition phase where the Atlantic is stopped and the easterly sets in. Next week looks to be where we see another step forward as the cold builds towards us. Too early yet to pin point any detail.Low pressure towards Biscay next week may move north and create a battleground setup across the Uk but modeling will pick this up nearer the time. What a NH pattern to start Winter though.Plenty of interest to come I think.

A nice clean vortex split by the ECM. That would lock the cold in for a while.

Well the generally colder outlook seems to be still on track with a new much different NH pattern set to show in the near term.A complete switch to a -AO/NAO setup. A couple of images just to simply illustrate the effect of a negative AO/NAO 500hPa pattern,taken from the latest gefs day10.This may be helpful to folks new to chart watching perhaps. The first image is the height anomalies and the second the 2m temperature anomalies. The first image shows the +ve hts to the north(red colours) and the blue lower heights to the south. The second image is showing anomalous cold pushed out of the Artic into mid-latitudes by the warmth headed into the polar regions at the 500hPa level. reflective of a solid -AO setup. This is quite a stark move away from our normal westerly Atlantic pattern and shows at quite short range now- in fact the change gets underway this week with the development of a blocked Atlantic and the onset of the easterly as temperatures drop. We can see this from an overview chart for Friday This is a very uncommon early Winter setup and very promising for cold lovers with all the main landmasses going colder than normal down to those middle latitudes. As we look further out then the ens. guidance continues to show a Greenland high developing in week 2. Yes there may be blips on the way such as the Iberian low in the medium term but really the bigger picture couldn't be much better than what is modeled currently.

That Iberian low bringing milder air into the south of the UK had support from the ooz and 12z eps.The 12z Gefs and Geps also show a temporary incursion,all from around day 7 to about day 11. All the above suggest the cold air comes back south though. It looks like a temporary blip at the moment with the ongoing support for blocking centered around Greenland continuing beyond that.

A nice summary Cambrian. Looking at the EPS charts a similar picture between days 8-12 where the milder air tries to encroach around the Iberian low from the south.There may be a bit of a battle across the the UK around this period. but the cold air wins on this one as it returns from the north east. We are going to see ebbs and flows whilst we enter this transition as the blocking develops so beyond a few days the operationals will vary but overall the trend to northern blocking is still very much on track along with a stalling Atlantic.

Something we don't see very often. Two separated vortex's with independent jet stream flows. This is inevitably sending cold air into mid latitudes. Some good points being made though about so many paths this could follow.Bearing in mind it is early in the season so the upper temperatures are still cooling. If the pattern remains as ensemble guidance suggests then as we go further into December we should start to those 850 hPa coming down further. It's a case now of seeing if the blocking aligns in our favour.It will be some days yet before we get some certainty on this I think. Looking at the trend for the main block to head towards Greenland we would be very unlucky not to see a decent cold spell from this. Whatever happens though there's plenty to interest us going forward.

Not much to add this morning just to note as Matt H posted that we have good support for the transition towards the block building next mid week. That's the first stage ie stopping the Atlantic and reversing the the flow to a continental one. It will naturally cool off as we wait on the development of this pattern. As ever we see slight variations on this but overall the ens.are looking good.

Yes on this run an almost classic retrogression from a Scandinavian easterly to a Greenland north easterly. Not perfect would like the high further north but that type of evolution would prolong the cold pattern.

If the block does retrogress towards Greenland or even part way watch that Siberian lobe head this way clockwise around and under the block Air from the coldest source across a colder landmass by then.Then we really are talking bitter cold and snow. It is another step but the way the ens are heading quite possible.

Another decent set of runs from the 12s and the trend for the Atlantic to be halted is still on track by around what is day 6 now. I like the ECM run this evening showing the Scandinavian/Siberian block building nicely towards us. The easterly setting up with cold air arriving this time next week .A nice clean evolution on this with deeper cold waiting upstream.

Just a reminder guys that the real move to the pattern amplifying is from around day 7. It will take a some days to develop the pattern from there,that's why the really interesting stuff is still beyond the reliable. So really the trend is still the same.

Yes keep focusing on getting the high first. We know from experience how we get different solutions in later time frames. Undoubtedly we are now at the stage where we will get a block of some sort so that the first hurdle.