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I'll do an update with the 500 mb anomaly charts later today, not all gloom and doom for you coldies though!

Catacol very much on the right lines with his recent posts I believe. Resonating to with a good deal of recent GP input too and it looks like tight isobar is also seeing similar potential (as far as can be reliably interpreted). It pays to remember that that models really struggle to resolve the tropical-extratropical-stratosphere sequence of interactions sufficiently well for them to be of much use beyond 5 days or so when those interactions are in an excited state (high amplitude events). Stratosphere looking the most interesting for this time of year since 2009 if I'm recalling correctly. Scope for a mid-Dec taster and the main course by January? Hmm... cautious it may be, but I'm becoming optimistic too!

Worth pulling this post out from 11 days ago - because it has proved overoptimistic though not totally incorrect in perceived development. The pattern has in fact "relaxed" a great deal - calculated tendency of AAM has started a sharp fall Why? The simple answer is that overall Glaam hit such a height (+3SD) that there had to be a reaction....and therefore the downward phase of the to and fro nature of the momentum budget has been strong. I was guilty of not, perhaps, placing enough emphasis on that +3SD peak of the global momentum budget, largely because I didn't expect it to get quite so high. But - hold on. This is not a post of resignation (from an openly slightly biased snow lover...) - quite the opposite. The pattern was always going to relax at this point, and we have ended up with a trough that appears to have blown away the blocking pattern and led to gloom on here. But remember that these cycles are predictable - and while the current phase has proved to offer more atlantic south westerlies than were hoped for the medium term prognosis is still very good. Note the cyclical nature of momentum budgets...and the certainty that an upwards trend will return before too long. Key to this will be the MJO. We continue to see forecasts of a strong MJO wave and without doubt the signal for blocking to return under a Nino base state will return: Meanwhile the very favourable positioning of blocks through November is having the expected impact on the vortex as we enter December - this is a strong wave 1 attack and is sustained for many days What do these signals therefore suggest? Frictional and then mountain torques will reengage in the next 5 - 10 days and this will initiate a surge in momentum as the pacific jet extends, and poleward wave energy forces a much more meridional pattern to the north atlantic. With increased westerlies over the tropics, sub tropical ridges will be undermined and the signal for falling pressure over the azores and/or Europe will increase. We will see ridging return. Given the pattern at present I will hold to the timetable advertised previously - mid December for the true start to winter, and if we can get engagement with the pool of very cold air that is concentrating over Russia then some snowy fun for some is certainly a possibility. The extent to which the vortex is impacted will have a bearing on where we then go forward. I don't think we have a serious chance of a full reversal in December - but perhaps we are setting the vortex up for a lethal blow in early to mid January. If the blocking pattern that returns mid month sets a scandy/russian ridge up once again, then this will initiate the second phase of necessary warm air attacks on the vortex, with a lag effect impact into January. So - cold in mid December, and the potential for winter to accelerate into January. There will always be ebb and flow within this broad scale pattern - but right now we are still on course for some great model watching kicking off early next week as NWP picks up on the mid December signal. Optimism still in place.

Sorry I posted in the wrong thread but hope a mod will drop it and its links in here, Met O 6-30 day area, but the words below, sorry not got time to do the links at the moment So what was the reason for the post I made earlier? As someone kindly pointed out it is rare for me to give support to you coldies. Believe it or not I am one myself, in moderation though having lived and remembered 47 and 62-63. Anyway below are the usual 500 mb chart links First the NOAA from last evening; this shows the Atlantic fairly strong flow all of you are so happy with. Look NW of the UK though, Greenland area and you will notice the very first signal of height rises coupled with a ‘bulge’ in the 500 mb flow also over Iceland? Far too early to get excited BUT it MAY indicate a change in pattern. Looking at the 8-14 day version and it also shows such a signal. To be honest it is not that often that both pick up on any marked upper flow change on the same day. So to the ECMWF-GFS from this morning. Both these have a similar slight suggestion of ridging/height rises in a similar area. One other thing to watch on these two charts is the tendency (over the past couple of days), for the flow into the UK on the EC for the flow to veer just north of west. So there is a glimmer, no more than that for the possibility of a change in pattern. I would want to see 2 or perhaps 3 more outputs emphasising this before I would believe it is a ‘real’ probability. Currently 15% perhaps. What we will have even if this does not occur is a more general Pm air mass more often than a Tm air mass. This will mean some colder if brief interludes over the coming week or so. As the Atlantic upper flow is so strong further spells of wet and windy, possibly very windy in exposed W/NW’ern areas is going to occur. I’ll keep you posted but DO NOT get excited yet!

warning ! File contains weather porn ...

I'm not so enthusiastic as I was a week ago that we'll see proper blocking anytime soon, i.e. next few weeks, as there just looks like too much El Nino westerly momentum and a trop PV too close to the NW to allow blocking to form near enough to the UK or position ideally for any deep cold to spread across the UK. Looks like the models are picking up some transient eddies in the generally fast zonal westerly jet stream ploughing across the N Atlantic into western Europe, which may form some transient ridges that could pull down some cold arctic air to bring a brief 1-2 day cold snap, with snow for northern UK a real posibility. But I do feel that there is not going to be enough amplification in what is an enhanced jet stream over the N Atlantic - fuelled by cold over NE USA/E Canada over the next week or two and strong westerly momentum over the Pacific. I did think we may get some help from MJO, which is headed into phase 1 to start December, but it does so at low amplitude signal on most model forecasts, so unlikely perhaps to create enough amplification in the upper flow to allow high latitude blocking. Plus the recent record high AAM / growing El Nino (Modoki) is creating poleward flux of westerly momentum which in turn is creating a strong zonal jet stream across N Pacific, N America and N Atlantic - which will not allow for much amplification. The MJO will quickly orbit through to phases 3 and 4, which are even more hostile to high latitude blocking as we head towards Xmas. However, the state of the stratospheric polar vortex remains intriguing as we head through December, with forecast pulses of poleward wave activity hitting the PV over the next few weeks according to 10hPa wind/height forecasts, so be interesting to see how this impacts the sPV, i.e. displacement later in Dec or SSW in the New Year perhaps.

The Netweather winter forecast is online: https://www.netweather.tv/weather-forecasts/uk/long-range/seasonal Discussion thread here:

Hot off the press (the site links aren't even live yet!) - The Netweather winter forecast for 2018/19 is now online - written once again by Ian Simpson aka @Thundery wintry showers. The headline is "As the days grow longer, the blocking and the cold grow stronger"... You can read it in full here: https://www.netweather.tv/weather-forecasts/uk/long-range/seasonal Thanks, as ever to Ian for his efforts in putting together the forecast. He's had a great year in terms of accuracy of the LRF's and was close to spot on with last winter as well, so it's well worth a read

I should write blocking off more frequently given this afternoons runs. Think I will stay quiet for a little while, keep the reverse jinx going.

Morning - The pendulum has swung back a little more towards cold today with again some transitory snow episodes in the mix- at this stage difficult to pinpoint any of these but somewhere around up towards the England / Scotland border could be a good shout ( with the premise that corrections south do occur ) We have a right old mix of solutions out there - The very worst could see the mild air cover the UK, the very best sees the lows track well south leaving the majority of the UK in the polar air- The ECM in particular tries to hold the atlantic up with some wedging of high pressure over Scandi - This is great, & whilst this initially wont create masses of deep cold the opportunity does arise again of low pressures undercutting into colder air - especially if we get some amplification behind - A bit of a rollercoaster at the moment & probably another 24-48 hours to resolve how much high pressure we get ahead of the first low which in turn creates a domino effect down the line - An interesting period coming up!

Tbh honest john..your a fantastic man of overall..-meteo,knowledge-. However.. a lot is now swayed on human input (imo).. Which is increadable 'given' the advances in scope/computer accom. But as we gain in tech...we also do in the way of thought/decipher 2 compete with the tech-analysis!!.. And 4 that im sure..more precise forecasts will be both..challenging..and to the marker!!.. If we take LRF-MODS-throughout a 12 month equation/analysis... And breakdown verbal input/output via person interp.... The man chatting...is likely 'closer the mark'. ...lol...but not 4getting..computer in-out is/was in-design by .....man himself!!! I have different devation/interps/outs.. And i won't change that 4 any1!!!.. So- nor should yourself!!!.. Full respect for persons like yourself...whom minamal-or major..have got meteor/atmos-science...2 where we are now!!!..

Just @ JFK - Seen the Debilt T2Ms- biggest signal yet for cold...

Yes as others have said , this evening 12z’s are better . The GFS only has around a week of zonal and then high pressure takes over until the end . The only annoying part about that run is the PV over Greenland, it stops the high from building further north , but it gets there in the end . A better run from what we’ve been seeing .

Here comes the bluearmy march Westward!

It's been a funny few days on here with emotions seemingly running high in some quarters, which seems a bit strange since winter only starts tomorrow (well, in about 2 hours time actually!). Having spent far too many hours studying winter models and learning from those far more learned than me on here, it's clear that trying to predict anything more than 7 days into the future is a fool's errand. As today's models have shown, pattern changes can crop up at very short notice. Not saying 'snowmaggedon' is on the cards for 10 days time, but small changes at day 3 mean big changes at day 6 and so on. Let's hope the momentum towards cold is continued over the days ahead, and if not, it's only the weather after all. Let's have a pub run special to kick-start the weekend.

Even better run I think in terms of longer term potential on the FV3, signs at T228, then the big Scandi high following at T300, looks better placed too. As you can see on the T850s, good angle of attack for the cold air

Great ECM this morning. The Atlantic is going to have its time over the next 7 days, quite possibly two week but my thoughts remain positive thereafter. Are we looking at a similar Jan'13 wedge situation perhaps? Here's the chart two weeks before that memorable cold spell kicked off... Hardly the polar opposite to the ECM's take on proceedings at D8... Food for thought, that's all.

Much better run from the ecm. Look at the 1010mb low forming in the mid Atlantic at t144. Then look at t168 and you will see that it is acting like a cut off low and has actually moved back north westwards. This is what we need to see. The t192 chart then shows the fruits of this. Much more amplified.

At 600 feet up in west yorks, you can be more sanguine than most ! but you're right, the other thread is more relevant for model discussion which is based on the stronger likelihood of mobility verifying - that's just basic stats. if i thought there was no chance of cold within the next 2/3 weeks then i would be discussing the nwp on there and keeping knocker company!

I'd trust a zonal chart at day 15 more than an easterly chart at day 10, unfortunately.

The atmospheric/dynamics have/are being underestimated- via miss overlooking! The momentumn-and shrug- has been of MASSIVE shout...and the annoyance of upper layers are showing now!!! Some will have to re-alaborate there mid term- deciphers/forecasts!!..

Another run and the developing Scandinavian Block comes back on the scene again. Each time it brings it a little nearer to a more liable time frame. Maybe it will be dropped again in consequent runs but it is a reappearing theme. You may have noticed in the above post , the forecast of the important 300mb jet has been all over the place in the period 10- 15 days, varying from full on Atlantic zonal to being split to pieces as shown on this latest run. No wonder models are all over the place at the moment but something must be stirring to keep showing these charts to flip -AO in a instant. All very interesting. In the short term the wave track still not settled for early next week, UKMO moves its a little further north but could easily take a route into the continent. Our outer perimeter snow model does have some snow on its northern edge for a while, especially over high ground , maybe from the borders to the North Midlands but this will change on a hourly basis. Have a good weekend ,out on the slopes tomorrow! C

Morning all. Really excited about the start of the new ski season tomorrow. All piste groomed and ready to go. As every year passes ,I get more excited at the prospect of being in snow and surrounded by beautiful scenery . Right the charts, interesting feature the wave or low development over Southern Britain at 120t. GFS has this passing further north into the North Sea, whereas UK has a more southerly passage , similar position as highlighted below from Winter View chart below. The thought from over here at 120t, much of the UK will be in a Polar Airmass with the track of the low over Southern Britain to move towards the Alps ( hence we have now a snow alert here for next Wednesday) . So there remains some variability in the short range model forecasts but basically all fairly fluid from west to east. Medium term ,picks up high pressure to SW of Ireland with developing longer wave trough over Central Europe. Thereafter, uncertainty remains as to what extend the Atlantic push into Europe, zonal or more meridional . The forecast jet pattern at 300mb seems inconsistent out in medium longer term forecast models but our experts expect more of a wintry theme to development over The British Isles but cannot say whether this will be sustained. All very interesting. Notice the snow spikes increasing over parts of Britain early next week. C

Given a pacific pattern that feels more super Nino than weak Nino at the moment - I'd say a substantive torque event is not out of the question, though it requires a bit of luck to get the tropospheric pattern just right. We saw a +1SD east Asian torque event in mid October and another in early November. We ought to see another in about 10 days' time, but it would need to be a bit special to knock the vortex into touch in December. More likely we see a hit that knocks it back a bit further in mid December with the potential then for a more deadly blow in early January. But there is a lot of water to flow under the bridge before then - and there is no guarantee that a knock out blow will be landed at all. However a powerful east Asian event would certainly substantially increase the chances. They are, however, fairly rare.

It’s you ..........

GFS would see temps plummeting in the run up to christmas,struggling to get above zero through the day by the very end.. Of course it will likely be different tomorrow, but if we can just eeeek out a little break in the jet then its not out of the question...

ECM day 5 snow zone somewhere about here...

this is never going to be an evolution where the mean will pick it up ahead of the ops …….too much volatility in the nwp

Plenty of vava voom in para seems like a light switch was turned on today..

gfsp on board at day 10 - waiting for ecm to give a full house !

Ecm..gaining.. The nuances gaing also... Turning point ALSO 'OF GAIN'..as we note atmosphetic tranfer!! Block formats 'still' not modeled correct.. However...the big picture formats are of note!!!.. Pacific punch is the daddy of evo!!!. The russian-pen ridge..will likely become bullied/and of lighter gain...as we progress... And the damage- @the upper layers..becomes present!!! Edit..suttle but -of note.. The 10hpa (strato)-rapid notion.. Is a classic' notion"..of upper sheet destruct-..and quick transfer- of the atlantic achillies heel..@point tip greenland...and typical of downwelling!!.. A point of note after initial wave dynamics!!! The power jet reliance of the atlantic..also looking 2 be tested...as we gain!!!

Good tweet above from Anthony. The papers linked include the Matthewman one which is essential reading imo, also exciting to think ahead for final third of December with another impactful event in the post so to speak. Such a good watch just now and I think the killer question is around just how much resilience the vortex has this winter. To my eye it absorbed the W2 from the Scandinavian block readily, however the compounded impact of the current wave 1 looks notable. Plus, this should be followed by well mapped impacts as noted via AAM and MJO cycles and further torque events. With hints of further W2 visible across many layers. Will it absorb these or has there been enough preconditioning of the vortex to allow what lies ahead to deal a killer blow for end Dec. From looking through previous animations to my eye the most dramatic changes feature some form of block in the Scandinavian/Greenland locale, almost the last piece of the puzzle' that finally creates capitulation. All this versus the canonical vortex intensification phase makes this season intriguing.. Also, if not end of December period will this mean its game over in the hunt for technical SSW this season....

This one's for that cheeky monkey

The 18z GFS looking identical to the 12z FV3 at 192 - so expecting a decent amount of amplification similar to the ECM EPS...

Really strong signal here on the ECM ensemble mean for the kind of ridge we've been seeing on the op runs this evening, T240: The spread interesting at the same time: 2 points here, the uncertainty extending into Southern Europe would suggest low pressure systems headed here on some members - this would be a welcome trend, and the massive area of uncertainty upstream of the UK is interesting, this looks totally up for grabs and I would expect a range of options for blocking and the track of low pressures in this area on the clusters.

You can`t trust anything at day 15, it`s just unfortunate that the default pattern we live in most of the year is zonal which makes posting that a little bit of a cop out tbh.

You posted a 360hr chart earlier on to show how zonal was likely..

Thank you Ian for a very well prepared forecast. As with any of us on any time scale we have to wait to see how close to the actual But thank you.

GEM also sniffing around an easterly at day 10 this evening..

And we end the run with a 1045mb scandy high- Nice to see but i think most of us realize its going to to take a bit of luck getting there- atmosphere seems pre disposed to NH blocking if we can get the Atlantic to play ball, it did on 12z and the end result is what i want to see in the run up to christmas..

Not bad at all. Compared to the 0z.

Nope. Just going to be wet and windy for a few days. I’m starting a petition to sack their editor.

Lol..some refer to the synop..as the PIZZA SLICE/OR NO MANS LAND!!.. OH WELL EVERY 1 2 THERE OWN... 'However'..the pac ridge..and brother russian arm are imo..modeled too' clockwise!!!.. And evolution..is'/will now become favourable...as the alarm bells ring in the upper thermos!!! Its a very strange set of miss-/de sheveled dynamics... Atm. But we-are close as-close to something notable... And earlier than diog'ed!!!.. Imo!!

EC more amplified than GFS at 168-

Ens mean is of catch up here... Check the supports for full 12z...after ec-12z.. Will speak volumes!!.. @i think!!@,? We are gaining!!! RAPIDLY....

Much improved GFS too! although takes a little longer here T240, T312: Builds the Scandi high, and if we're seeing this sort of output, upgrades always possible as we get closer in time. Good start this evening.

Yes, clear amplification signal from day 8 on most of the NWP this evening. Thank God - even if it gives us a short break from the wet and windy regime. Sunny days and a touch of frost will do me for now!

To tell you the truth, it's not always a clear picture how strong the MJO wave is, the RMM plots show low amplitude, the VP200 and other variables combined suggest more amplitude/stronger MJO through 8/1 as below plots show So I can see why there may be some enthusiasm for blocking to develop given the above plots. However, I would have expected the models to have churned out some stronger hints of blocking in the ensembles and operationals for week 2 of Dec if the MJO wave was strong, EPS clusters and EC weeklies not on it yet. Given the forecast strength of the upper westerlies over the N Pac, NAM and N Atlantic - see little signs other than transient cold shots for now. But worth seeing if the trop PV retreats poleward over Canada, as some models hint at, which may ease up the strength of the jet stream. Certainly there looks like signs of a relaxation of cold over eastern N America by mid-month, which may allow the jet stream to weaken.

A feasible-outcome !!. With date exactions, on stills about the turning point!!!

Seriously Ed, you need to stop using day 16 op charts to make a point, whichever direction they are headed in ....... eps clusters are now five again in extended so the mist which was possibly clearing is maintained .... looks like plenty of possibilities at day 10/11 for coldies