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NWP viewing a bit gloomy this morning....what's going on further under the bonnet? This is early days - but first chart now identifying the next uptick on MT. Will be keeping a close eye on the trend of that graph, but the red line indicating east asian torque and predicted jet extension is the key one. Model runs today also suggest to me a fairly significant spike coming up in US torque over the Rockies.....so a move back towards higher Glaam should follow. More momentum around those mountain ridges should reduce the momentum up at 55/60N and we will see the benefit with profile in the north atlantic more helpful for blocking. Time line - soon after 15 Dec so I'll stand by the 18 Dec call made yesterday. However - this is the STARTER and not the real deal. For that we need to look at the building blocks. I know that everyone is gloomy at the intensifying trough to our west - but with a stratospheric eye for a moment take a look at the EPS from the side angle this morning for 10 days' time The siberian high, aleutian low combination is very visible here and strong too. What this means is the rate of stress being put on the vortex is going to be cranked higher and higher. Money in the bank so to speak for January. Meanwhile the MJO is reforming in the Pacific as previously advertised. So - wait out the current cyclonic spell, enjoy the flirtation with the scandy high next week that was the product of the last bout of pacific forcing and wait to see what happens with the pressure profile after mid month. More updates to follow as this key phase develops.

Those (like me) signed up to John Hammond's website will have received an email exclusive this morning with his monthly forecast All I'll say is the period from Dec 24th to 6th Jan could be very interesting for our cold folk, impacts might not necessarily be straight away and could be a bit soon for the big day but into the new year may be different... I'll give you a clue SSW

The old reverse psychology delivers again!

I have gleaned enough information via this thread and other sources to hop off my hastily built fence for another memorable winter to unfold. Major warming around exmas now odds on starting to show on the NWP,and we will be deep into winter as it downwells. A RTR most welcome Posted this in media thread too from John Hammond MONDAY 24TH DECEMBER – SUNDAY 6TH JANUARY Signs of major change There are signs of more severe cold as we head into the New Year You’ll have inferred, then, that I am not yet going to commit: Green or White Christmas? It’s simply too far off! However, there are several reasons within the set-up of the atmosphere this winter that suggest the cold air will be back sooner rather than later. El Nino is one; the cycle of spots on the sun is another even more distant influencer. Additionally, in the last few weeks I’ve spoken of signs that the usually strong stratospheric westerly winds that circle the Arctic (know as the Polar Vortex) may weaken markedly as December ends. This signal is becoming more ominous. It’s important because it introduces the possibility of a ‘Sudden Stratospheric Warming’ in which the Polar Vortex goes fully into reverse. Ultimately, it was this which led to the severely cold spell that struck the UK late last winter. From start to finish, this process takes several days, if not weeks, before such a reversal works its way down to ground level. But on balance, there is an increasing chance that cold air will return from the north or the east as we go later through the Christmas period, and more particularly into the New Year. Exciting times ahead – for the child and the weather enthusiast in all of us! EDIT Apologies to Summer Sun didny see you had posted same.

One would think (hope?) that having cold air to both our east and west, ought to presage a better than average winter? Surely we can't stay inside a s**t sandwich for three months?

At least it's cold zonal weather, we might see one flake of snow over Ben Nevis so it's not all that bad

Just to add there is a special discount for those who have been excommunicated or accused of Apostasy.

Looking at the Ecm 12z it's a Mexican standoff between the Scandinavian block and the atlantic, I see lots of potential for trough disruption and some rather cold air in the mix so a chance of some wintry precipitation but especially with elevation...fascinating watching this unfold and to think there's several months of wintry potential for coldies to look forward to!..it's only just begun!!

It seems to be coming Increasingly clear that despite what many hoped for namely some widespread worthwhile prechristmas snow fall that the coming winter is much more likely to follow the pattern of most of our winters that have had decent cold and snow and not really get going until the Xmas /new year period at the earliest. We have a great deal to look forward to with many of our more learned members and some members of the meteorological profession itself. GP Mr Hammond. Met office et al giving good reasons why the Atmospheric dynamics are in favour of something interestingly wintry during the timeframe 19th Dec onward. I know it's an old chestnut but I,m nearly sixty years old and barring 1981 and 2010 all the really cold and snowy episodes I can remember have come in the period from Xmas onwards. Another old chestnut for you and repeated here again because it is true. The coldest winter of the since 1740, namely 1962/63 didn't,t really get into its stride until Christmas yes the first three weeks of December 1962 were cold but cold and quiet not cold and snowy. And the final old chestnut the snowiest winter of the last 223 Years namely 1947 didn't get into its stride properly until 21st of Jan and just days before it had been 14c across Southern England Remember old chestnuts are old chestnuts because they,re true. Let's just enjoy the ride.

And the EC follows suit. Probably as good as we could've possible hoped for today from where we were 24 hours ago. Clearly, if the 'upgrades' stop here, it won't be quite enough. But another day or two of this and things are going to start to look very rosy indeed for many. Who is going to go and fetch BA back from the other thread?

Hi I think I said over this last 4-5 days I was expecting to see the energy transfer SE- & despite run after run of that not being shown ( plus some mild panicking from this winters usual culprits ) - suddenly today we are on the cusp again What the UKMO looks like today @144 is exactly what I said & proposed would happen * BUT * the finer detail on how things actually slide & happen have big impacts on snow or rain- Heres the zoomed in UKMO 144 & ECM 144 I have reviewed the thicknesses - the scaling is different on UKMO & ECM but they work out the same - both are hitting around 540 DAM which just about supports a marginal snow event- ( no 850-1000 Thickness yet ) Remember Colours different but thet are actually identical charts !! ECM is just a bit more progressive in the south with feeding through atlantic air - As as result south of M4 is to warm- Projected frontal snow chart is below* UKMO again is ok, marginal & ive annotated the ideal flow as opposed to the marginal one- Hope that helps S

I will admit I had a look earlier but knocker was being rude about this thread so i decided not to bother

ECMWF in a Christmassy mood tonight! Nice surprise to see the Scandinavian block next week putting up more of a battle against the big, bad, Atlantic. More pressure put on the Lows trying to reach the U.K from the West. The Atlantic does still sorta win the boxing match (and to be honest, still think the block will lose some of its power, for now). However, the Lows struggle to penetrate far enough East through the U.K, with some of the Low Pressure disrupting and dropping to our South-East into mainland Europe. Even if the cold weather fans have to endure another spell of Atlantic weather, hopefully no chance of this happening soon: But this would do:

I would much rather see cold zonality that the extended Ecm 00z ensemble mean shows than mild benign or sw'ly zephyrs cr*p..

That is one hell of an Aleutian low too - combine that with the resilient Scandinavia/Siberian high, and what do you get? The atmosphere is cooking up something tasty, it’s in the prep stages at the moment, but it’s getting ready to turn the oven on....

Ironically, stronger stress on the vortex than previously modelled has as a by-product increased the modelled stretching across the N. Atlantic next week, likely giving the N. Atlantic troughs an extra boost just when we really didn't want to see that. While model bias still suggests that the W. Eurasian blocking should prove more resilient than currently modelled, I'm sadly getting the impression that the cold boundary will end up hanging around just out of reach to our east. Could be only some 750 miles in it. The big flip-side is of course that the stronger disruption of the vortex is tied in with increased SSW probability for late Dec or early Jan. How much correction toward less Atlantic mobility we see next week will be important for whether we can achieve that from our very encouraging, but not guaranteeing standpoint; more fight back from the blocking will further increase troposphere-stratosphere transport and hence the magnitude of warming + geopotential height rises int he stratosphere.

The change back towards the block over Scandi extending further west and Atlantic trough disrupting due to the jet stream positioning further south highlights how despite some success in predicting broadscale patterns in the longer range based on MJO phases in combination with other drivers, models can often struggle with the finer mesoscale detail of the positions of low and highs beyond day 5, which is important for our small chunk of NW Europe. 12z EC indicating snow event this time next week across the north and east, as the Atlantic frontal system bumps into colder air moving over the North Sea from the southeast. However, 7 days is a long way off to forecast such detail, so subject to change and often we won't know until 36, sometimes 24 hours out where it may snow in such knife-edge marginal situations. Given the Met Office in the their 6 days+ forecast mentioned "Through the remainder of this period there is a fine balance between colder air to the east and milder air in the west" - highlights that the battleground between milder Atlantic air and cold continental may end up closer than we previously thought. The Atlantic may eventually break through and increase mobility, but next week increasingly likely to feature slowing / stalling fronts as they head east, bringing a threat of snow in places as the rain bumps into cold air from the east.

Well there you have it northwestsnow. Colder 850mb flow moving back into NE Britain on Tuesday. So could yet still be colder East v Milder west scenario to develop. Not all lost yet. C

The GFS is now in the sub 144 timeline working towards the Euro solution- This is because its woeful at energy seperation- Which in this scenario is the defining point of difference... NB 12z v 18z with the 18 beginning to see more seperation..

Just seen 1 run today UKMO 12z

The models are currently very keen to take the atmospheric state into a temporary Nina-like condition next week with a broad N. Atlantic trough and rising heights through Europe being the general response. However, with the El Nino event now well connected to the atmosphere this isn't likely to take place in reality, and while the models continue to insist otherwise in the longer-term - just look at ECM days 9-10 and how awkwardly it suddenly changes track - there comes a point at which the reality of observation data forces them to make adjustments toward lower Euro heights and a less broad, more disrupted N. Atlantic trough. I still feel that it's going to be a big ask to get the overall battleground line wholly west of the UK, but I'm less resigned to it staying just out of reach to the east next week as I was this morning; the fight back by the blocking highs during the second half might have enough to it after all (to produce at least one appreciably-sized snow event in the UK... somewhere! Eastern parts having the better chance as things currently look). Regardless, there remains good teleconnection support for that blocking high to make a move toward Greenland (but at how high a latitude, it's unclear) by early the following week but at the moment, the models are still turning things too Nina-like for that to be depicted properly (this being why you see some runs going with mid-Atlantic ridges instead; these are the most Nina-like). A really interesting question going forward is then whether that stage of high-latitude blocking sticks around long enough to merge with the impacts of a major SSW... presuming that does occur. I expect that'll be the main deciding factor in what manner of weather we experience during the festive week this year. Seeing a very wide range of possibilities for that one!

Oh my can't believe it. Just look at the charts had to check the time and date twice. That's why I love this place what a turnaround. Alarm set for 4am

No band - house music and ecstasy.

While a SSW doesn’t guarantee cold for the UK (around 70% of the time it does bring cold), a lot points to blocking in January and February being favourably positioned for the UK. A lot to be positive about. A winter of patience but hopefully with rich reward.

In a nutshell, it's a finely balanced outlook, not seeing a full scale unsettled period, there should be some frosty icy nights, especially further e / n...not seeing any mild sw'ly trash which pleases me the most!...I feel it won't take much to tip us into a proper wintry pattern.

Think UKMO run is the best run again in the hunt for cold especially in the medium term. I noticed on the chart below that the flow backs during the period 120 to 144T and introduces colder uppers back into Eastern Areas. So still clinging on to the prospects of some type of undercut. Longer term , you would expect the Atlantic troughs to be driven through on a fairly strong 300mb jet that heads for Southern Britain and deviates into Europe. However, looks like the UK will be on the slightly colder side of the Polar Jet, so never that mild. One features that is still resilient throughout the runs is the high block to the NE and could easily force its hand again in later runs. In the meanwhile, the main models show a deep Atlantic system fuelling a returning Pm into much of NW Europe. C

At least the Ecm 00z shows cold zonality later on with 526 / 528 dam which is much better than sw'ly zephyrs!!!

Latest 96 FV3 - jet stream at 96- 18z on the left means increments leading to a sharper pattern & also westward shift... look at the near vertical jet on 18z & the weaker but sharper atlantic jet.. also the developing jet off the states is alligned more SE than the 12z which has more Easterly component...

Well this is turning into a real nail-biter (for you up north, not expecting anything for myself ). When it's on a knife-edge like this, expect to be in the "snow-zone" on one run, then out of it the next run ... but that won't tell you the outcome just yet!! Anyway, onto another interest of mine, the potential for height rises in the Atlantic around 18th December. You can see something starting if you look south of Greenland on this chart (17th Dec) Will it turn into a more significant rise and potential northerly for the UK? Or will the jet ride over the top? Or will the signal just disappear altogether (it's been there 5 days and still going, so not expecting that really). Plenty of time to go before this one gets firmed up.

If you look carefully at the 00z run, it was very odd in the central Atlantic and didn’t repeat on the 12z the disruption we now see at day 6 showed on the day 7 chart @carinthian posted so we must indeed give it kudos for placing the trough disruption where it did plenty of gefs members were playing with this solution though lets see where gfsp goes later on this ..... the eps control has been messing around with these runners in the base of the trough so no surprise on that theme

ECM 192 so close with deep easterlies We need about ~2/300 miles out of the continent...

Initiation of the potential SSW is now heading towards the day 10 time frame 12z gives us a bigger warming late on than the 6z did

INSTANT TROP RESPONSE ALERT!

I advise all members to not be despondent, there's still plenty of interest around the 8-12 day period. In the immediate, cold zonality under light winds can bring bitterly cold nights with hoar frost. It can also bring (with the right ingredients of course) snow to many. The Jet Stream is forecast to track south of the UK so anything can and will happen. In short, reading the models today, we may not see significant snowfall but I don't think we will see just one flake on Ben Nevis either Looking more seasonal going forward after this horrible wet and mild period. That's still better, isn't it?

Yes, that's what my money has been on for a couple of days now. Several runs have shown this. The main interest in future runs re the shorter term is not whether the Scandi high will hold on for ages, just whether it will hold on long enough for a battleground snow scenario as the Atlantic system pushes across us. That's knife edge but underdog for the moment, especially for the south, but who knows how that might change in the next day or so. Thereafter that potential for height rises to the NW is relevant.

Yeah Liverpool Istanbul 2005. Can the cold pull it back from 3-0 down at HT. Hope the 18z isn't an anti-climax.

After what seemed relentless dowgrades a change of fortunes on especially the UKMO . More trough disruption and very close to importing some cold air to undercut any fronts moving east. Still time for more changes and I’d be dubious of anything post day 6 as the models might still disrupt more energy as the next low moves in after that .

Straggler pack is growing The Mean moving around 150 miles west shown by the easterly isoline- The atlantic bomb further NW as well... 18z first

Plenty of Atlantic trough disruption SE into mainland Europe on the 18z GFS which follows the 12z EC, just when we had given up hope of the cold to the east having any say. Always fun to have these twists in the models when it seemed, for a time, we would be starring down the barrel of a week or two Atlantic mobility. The trough disruption next Thursday may improve further in favour of stalling frontal zones, given that the deep low to our NW is a long way off undergoing cyclogenesis and may not deepen as much, with less WAA towards UK and more disruption as a result. It is still just a wave leaving the U.S.Eastern Seaboard early Monday - same feature bringing a winter storm to southern Plains and southeast of USA this weekend.

Personal view - NWP take snapshots of readings and then applies algorithms based climatological norms to interpret the way ahead. I would imagine by now that the best computer minds have applied machine learning to the process - so as we move forward NWP will learn. But currently I suspect there is a reliance on normalised processes. And this is where the human ability to interpret can have an edge. And the mountain torque charts have updated. As expected a steep climb has begun Cue - move away from the apparent passage towards a Nina-like state in the atlantic and a return to a more Nino meridional outlook. Humans 1, NWP 0. = Scandy fights back. (At least a bit....because expected processes would still say this phase next week is not going to produce full on goods. Need a bit more time for developments to work their way through for that....)

Welcome back from the dark (mild) side!

Another slight correction west and it's a potentially snowy Thursday for some

Or we could look on the positive side and realise we got a bullseye after the last SSW in Feb Here are before and after stills After Before

Am i the only one buzzing in here? i am really happy with the output, i would rather an absolutely blistering spell further down the line than a half baked one now, perhaps its because i only really very fleetingly and usually only for 1 run or 2, actually bought into anything significant in December, January was always the one that was going to bare fruit.

Things look to turn a slow moving and quite banal later on the ecm run. That sturdy high pressure on the eastern seaboard of the US gives me some hope. Looking at the later frames of that run and I cannot see a return to mild dross anytime soon. In fact you could bet on quite a cold run up to and probably including Christmas based on this.

Have I ever said how much I love and rate the EC46?! I'd imagine we'll be getting a pretty wintry long range update from the Metoffice pretty soon if that sticks.

Not often one sees such a marked positive height anomaly over Greenland and Iceland at week 5 but more strikingly at week 6 in EC weeklies, normally the anomalies are muted at that range. EC longer range smelling the SSW coffee?

Now that's an interesting chart at 168t from UKMO extended . C

Outlook - wet and windy becoming calmer, drier and cooler The NH 500mb profile and surface analysis for midnight and euro chart for 0400 The frontal system associated with the deepening low adjacent to the Hebrides, is currently traversing the country accompanied by heavy rain. Particularly down the western half of England, and all of Wales, associated with the cold front. This will clear from the west during the morning giving way to squally showers which will be very frequent in the north, even coalescing into longer periods of rain, where the strongest winds will also occur with gales and severe gales in exposed areas. A very mild day. The strong winds will continue this evening and overnight, but moving a tad further south, with a continuation of the squally showers which will gradually become more concentrated in the north During saturday the low is filling and moving to a position south of Norway thus the wind will abate and veer with the showers eventually dying out but more cloud and rain will start effecting south western areas courtesy of an occlusion associated with another low out to the west. All of which is under the auspices of the upper trough. Temps still okay. Over Saturday night and through Sunday the pattern change gets underway with the subtropical high amplifying to the west and the upper trough dropping south to the east. Thus again the wind will veer northerly and cooler air will be introduced behind the occlusion which is traveling south. Any showers confined to coastal areas or perhaps the odd snow flurry over the Scottish mountains. During Monday and Tuesday the ridge, now over the UK, comes under increasing pressure from the complex upper trough in the Atlantic and the massive amount of energy exiting the eastern seaboard. The detail of this has been touched upon in previous posts so will leave it there. Suffice it to say this results in a couple of dry days for the UK with weakening fronts gradually encroaching from the west. And the NH profile for T120 which illustrates the last point very well