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So I mentioned earlier on about very high angular momentum levels, which would normally be associated with a strongish El Nino. GWO in high amplitude phase 6 orbit, expected to move towards phase 7 as the MJO component moves through the West Indian Ocean this week. There is a persistent +ve momentum signal across the tropics and sub-tropics which is holding up this unusually high angular momentum signal. Not much scope for a drastic drop in inertia although frictional torques are as expected strongly negative. When the MJO signal swings through the East Indian and Maritime Continent, angular momentum tendency will rise, driving a phase 5 projection in the GWO around 10th December. Composite: This doesn't fully capture the blocking signal over the Eastern Arctic, so some manual adjustment on this required, but the key messages - Alaskan trough, +ve height anomalies to the NE. GEFS for that time alongside the composite: Again, don't get hung upon on exact placement, the broad gist is that at that range, reasonable confidence that the GEFS mean is about right. The strong presumption from there would be for a phase 5-6-7-6 type evolution (herein the beauty of a conceptual model): There is some manual adjustment necessary to these to inflate +ve height anomalies to the NE and reduce +ve height anomalies to the west of Greenland, but some westward pull of the man trough over the North Pacific is the key thing here. That allows any blocking to our NE to manifest itself, and would consolidate a monthly expectation for +ve height anomalies across Scandinavia. Either way, a challenge to any view of returning zonality at any point during December.

One further observation. Both EPS and GEFS very keen to dislodge the Siberian lobe of PV into the Pacific sector and nudge the Canadian lobe further west. Net result - the hemispheric wave number becomes much reduced and aggregated. That's a massive signal for high pressure development in the high latitudes across the eastern side of the hemisphere. Not a lot of change is going to happen to that wave pattern so we are lining ourselves up for the winter pattern here. Slowly slowly catchy monkey.

Same model (with a few tweaks), same data, same run. Two different outcomes: The inherent dangers of using operationals at that range laid bare. What we do glean, and more particularly from the means, is that there is a decent signal for height rises to the north-east. That's broadly in line with thinking. Progression of the MJO signal through the Indian Ocean perhaps a touch slower than EC and GEM forecasts, GFS maybe a bit more on the money. Broadscale hemispheric and stratospheric developments on the back of this as before. One thought to add, angular momentum is sky high (+2.5SD). That's well in advance of the oceanic signal. That limits the scope for large swings in tendency, reducing the scope for amplification signals. That may well mean we head to a destination via a slower, but more steady and surer evolution. That would suggest block to the NE is a long time player which will progressively influence the circulation for our sector. It also means that the atmospheric 'cupboard' is being well stocked to deliver a period of high angular momentum but negative tendency (Phases 7 and 8 of the GWO) for the core of the winter.

..and the value of this approach ? Q: how likely is GFS P t300 ? A: based on reasoned assumptions, likely.

It would help 'yourselves' when referring to back loaded winters & front loaded ones what you actually mean - as some could be referring to cold - Others snow - others blocking... - If one is just referring to 'blocking' positions then a back loaded winter will always be favoured due to the fact that the vast majority of High lattitude blocking scenarios as well as SSWs occur into the new year ( as well as adding average propergation times ) you already at mid Jan- However when your talking about potential snow & or cold then you dont need the huge 'showcase charts' just one mid lattitude block would suffice- That said we are at the tail of November & charts of the 10HPA Zonal wind are being shown to indicate the early season running- well thats totally pointless if the strat is not coupled with the trop- The AO sitting @-4 will be probably within the top 10 of all years for lowest November values ( poss top 5 ) so as far as the actual atmosphere is concerned the NH taken as a total entity is already in a front loaded winter - its just whether the UK gets to benefit - The period Dec 7th-17th will probably be the one that decides people perceptions of that however we as said we are already front loaded bearing in mind the standard Dec pattern is around +1 to +2 AO so currently we are probably 2 standard deviations below that.... Just checked in Heathrow so have a good few days - GFS mean at day 10 & onto day 15 is Easterly @feb1991blizzard

This is the definition of grim... You can see from a N hemi perspective that the set up there is completely different to now... Compare and contrast to the EC day 10 chart and the GFS day 10 chart People use the term 'faux cold'....I would say that what we're going to see over the next 2 weeks or so is 'faux zonal'

Can we drop the petty, mostly pointless argument over the flow on a chart which will be different in 3 hours anyway please.

I'm a bit confused as to where you stand Shaftsburysnow, did you not call zonal through Dec yesterday and write off any pattern change? Today you seem to be saying that you favour a back-loaded Winter (Climatological norm) but we can't write off any cold in December? Are you still writing off a pattern change based upon this mornings output or not? This mornings output was disappointing because it did not advance last nights improvements and trended more toward mid lat blocking than high lat blocking but that could easily go back the other way this afternoon and evening. We are currently looking for a blocking pattern to establish as we head into 2nd week Dec, I think that still looks favourite but whether that results in cold and snow is another matter. Personally I believe we will see a pattern change to blocking toward end 1st week Dec which will of course increase the chance of cold reaching us but by no means guarantee it, beyond that the current signals are for another zonal spell before the teleconnections work their magic later in Winter which would go against my idea we will get other blocking opportunities later in the month (Dec) but I certainly wouldn't ever be married to long range generalities either way. I''m much more interested in looking for pattern changes and cold chances within the 2 week time-frame and even those can and do go pear-shaped. It will take more than a few dodgy runs before I wave the white flag (though we do need keep a white flag handy in this game)

Morning all , -4C in the village and snow cannons back in operation on the slopes. Due to open runs this weekend. Picture over looking Katschberg village. Another variation on the model runs this morning but the theme towards a rise in pressure over the British Isles likely in the period day 7 to 10. So a fairly short lived spell of unsettled and relatively mild conditions in your part of the world , although not particularly mild so in the north. The model our expert use still indicate a strong developing ridge over the British Isles for the second week of December and pressure falls in Eastern Europe as the trough starts to sharpen against the cold block. The forecast 300mb flow is indictive of this process over Scandinavia and into East Europe in the longer term charts . C

Exactly what was said by more experienced people yesterday is happening.. The models are throwing out Milder options but also colder options GFS has done this exact thing on it's last 3 model runs in FI. Im not expecting December to be cold or Snowy... It never is.. Apart from the exceptions.. In my short 24 years on this planet ive learnt not to bother myself getting hung up on what happens in December and even let that dictate the rest of winter... Where we sit allows us to flip Milder or colder within a few days/weeks without warning It's very easy to go from "OMG" when the GFS churns out FI stuff like the 18z and 12z yesterday to then be like "oh fk sake" when the 00z comes out.. Its a computer it is randomly creating a scenario each time until the reliable where it firms up. Even then we get some surprises right within the 24-48 hour period! Until a raging Westerly is showing at the start of April Im enjoying the ride so far..

The isoline thats in England traces back to Scandi.

It seems pretty obvious that any relaxation of the jet will allow for an amplification …… whilst some runs were showing that to be early next week, it seems more likely to be later …. if we don't get lucky it may not be at all!, however, i would be very surprised if we have to wait beyond the latter part of next week to see the amplification begin and then it becomes a question of where that will occur - current favourite is to end up over scandi (could be sceuro, could be up through the uk, could even be to our west). so whether we end up in a md dec position where we go proper wintry, surface cold under an inversion, dull and grey or quite pleasant (could be cold and clear, could be mild and clear) remains the big question...……

Thanks. I am just trying to figure out where you are coming from. So yes the bolded part does strongly suggest you were dismissing any idea of a pattern change to those who read it? You have to consider how seasoned posters are going to take that after they have just posted their thoughts on how and why they see a pattern change. it seems dismissive and not based on any current model output for the period being discussed. I don't think there has been any hostility toward you, just strong disagreement with that sentiment an dhow it was expressed. As I said previously it is fine to put up seasonal models and longer range ideas on occasion but the meat and potatoes of this thread is analysis of the daily output with the understanding it chops and changes but attempting to pick the bones out of it. Once we get blocking and the prospect of snow things become focused on shorter term still - just a natural progression for cold and snow lovers. Posting seasonal model output for Jan Feb is not argument for how you see December. The weather will and does make fools of anyone forecasting beyond a few days but there is still a lot of experience and skill that goes into interpreting the daily output. Personally I still think we will see a pattern change which is what you seemed to be writing off - I could well be wrong but for now I believe the weight of evidence suggests that. You have now elaborated upon your position to sate you consider any longevity of blocking will occur in second half of Winter and any blocking first half will be short lived which is welcome and hopefully you see how that is not contentious and people will not pull you up on it. There is of course no need to apologise and I'm sure you weren't trying to upset people. We are all weather enthusiasts here and as such a family, a family that squabbles a lot but still a family Look forward to your future thoughts.

Let's put an end to the snide remarks and personal insults now, shall we?! Thank you!

I think I might actually self combust if I read Met Office says xyz again , they have been wrong before and will be wrong in the future, as will the Italian Met, Meteo France, Met Murr etc etc etc. They update there forecasts almost as often as we all change the weather patterns in here ? Especially for D15-30! Meanwhile no ECM yet, which means it’s going to be amazing (at D10) Looked at GFS rolled my eyes, then saw the GEFS ........ not to shabby at all towards the end.

The other point for all of the doom mongers is that it's still late November - even if nothing comes up in the next 14 days we will only be 10% through winter. It'd be the equivalent of writing of summer because the first week of June was bad.

I normally agree however with a Scandi block at 348 which is day 14 you would expect a mean to reflect the long term average as by then most ENS have filtered out the blocking 'noise' - so to have a fairly solid Scandi high & continental cold pool means that there cannot be much 'opposing' data otherwise the signal would be weaker... Anyway - looking forward to the next couple of weeks, all the info & data highlighted in the Winter forecast is very much live & relative to where we are on todays date stamp- ! Best S

^^^^ Genoa low will do us just fine...

This thread is getting perilously close to farce , last nights sniping by grown adults was embarrassing , sadly the theme is continuing today !

Based on what? Last nights models had sub -8c over much of the UK, the models this morning now show mild, sure. But that’s what I and others have stated would happen, wild swings in the models were expected by a few of us on here and that’s whats happening. Further flip flopping from mild/cold/mild is expected whilst the models deal with the evolving forecast. GEFS ensemble mean as high pressure moving Northwards from Iberia across the UK, look at the Eastern Hemisphere across the Arctic, also filling up with high pressure EPS mean similar, high pressure filling the Arctic Extended EPS shows the Atlantic trough that’ll be with us this week backing out West with a signal for heights to build across Scandi day 15 Certainly far, far from “bog standard”. Continued flip flopping expected but note the likelihood of increasing cold runs towards the end with milder runs becoming fewer and farther between as this week progresses and into next week. The Strat isn’t an issue. There is no downwelling, it’s not influencing our weather at the moment. Sig wave 1 activity continuing with further Heat Flux into the Strat from the Trop in the forecast, the Strat is very much under attack from a couple of different angles right now. The expected developing Scandi Ridge/Arctic High into Dec could be the nail in the coffin anyway. 15-20th December < That’s the timeframe for the pattern switch.

Certainly is (moreso latter dec).. As GP- NOTES, some getting far too hung up on placements-at afar! The overiding factors all there.....

It seems to me that we may well end up with a Scandi high at some point after mid December, it keeps popping up on the runs regularly now and I noticed the other day when the Italian Meteo guys were doing their winter outlook that they were suggesting what looks like a dominant Scandi block and LP towards the Med, by the look of the anomaly charts that they had up anyway.

Its there follow it back - crystal clear

The mean slowly heading down in the extended ENS.. nothing dramatically cold, but certainly not much screaming mild there! December certainly holds interest as it stands, in my mind at least. Operationals seem to have a decent grip on the D5/6 period, but other than that they are clearly struggling. So looking to far ahead using the Ops is futile in my opinion, especially as they are flip flopping between solutions regularly at the moment particularly in the low res. But will that stop me having a peak, or raising an eyebrow when I see a cold run.....? Not a chance PS MetO 15-30D outlook is just short of useless in these situations. They have a responsibility to the public, so aren’t going to jump off the fence at that range unless it’s utterly inconceivable that anything else might happen. So the 15-30D forecast will generally follow climate norm for our island on the edge of the Atlantic! Note they use the word “Should” several times... that’s not definitive!

From my perspective it's all about learning something new every season. I remember back in 2011 when @Glacier Point did Netweather winter forecast and he mentioned that seasonal forecasts are like A+B+C = D - forecast. If one presumption doesn't happen according to it then whole forecast will most likely be more wrong then right. For example which teleconnection drives weather on our side of Atlantic in western Europe mostly: is it tropical forcing(MJO),low solar,stratosphere, or SST? We know some are conductive to blocking and some are not this year. Looking at MJO and forecast from NOAA yesterday they are anticipating robust event through phases 8 to 3. If we look at re-analysis of phases 8 and 1 they show blocking and cold singal in Europe generally. Zonal winds also do not look like interfering much over the coming weeks as they might even trend below average. So in my view if this mornings GFS and ECMWF deterministic outputs pan out correctly then MJO presumption will be wrong as they do not show HLB, barely MLB. After this I personally would consider not favorable SST as most important driver for our weather, where the Atlantic energy coming from eastern CONUS takes over with lows spinning across sometimes cut off sometimes part of vortex that loves staying between Greenland and Hudson bay.

As we look deeper past 144 for a look at possible blocking heading up towards Scandi the UKMO day 6 highlights that there is 'some' potential coming in the shape of a NNW from Iceland gradually bringing in sub -5c air into Scotland, could be some wintry showers day 7 & some welcome snow for the scottish mountains - Also the atlantic low may track across that cold bringing further wintryness however its a long way out ATM - ECM also has colder air south @120 with a shallow slider moving across the UK may prompt some wintryness At 144 the pole & AO is tanking with high pressure

FV3 at T360 is absolutely immense... Plenty of mileage left in December for me...

gfs parallel leading the way again.Another run showing an Easterly again. Bitter cold over siberia moving westwards,need to see this consistency continue.Would expect a change from meto extended if this continues White christmas anyone?

This latest 300mb wind flow pattern out east would be indictive to sharpen the trough (under cut process) against the cold block to the NE . This split in the main polar jet helps ridging, as in this case over the British Isles. Where we end up from there is another story ? but this set up usually leads to a colder outcome in days 10 -15 Hope this helps. C

Personally, I probably would have left the posts unhidden as I didn’t feel there was anything too wrong with them really. (I guess us admins/mods/hosts all see things a bit differently at times and doing what they feel is appropriate). But maybe it might just be best to drop the Easterly debate. Thanks guys!

I like this mean Look at the size of that huge Russian ridge. Pretty sure that is usually a SSW precursor. We could still be on for that late Dec SSW

I'm guessing this is the source: It's the DJF mean SLP from the Italian Met.

Jet way south into Europe. That’s what we want .

So, before the 18z(s) roll, what has today told us? Yesterday's 12z suite offered a smorgasbord of possibilities mostly with a strong element of high latitude blocking, although not all beneficial as far as UK cold is concerned. 0z were a letdown (as usual - I'm sure there must be a scientific reason for this due to when the data is collected, I'm not imagining it...). Moving on. Some sort of Arctic high looks highly probable. Which means there is no coherent trop vortex, phew! But a lot of runs seem to invigorate the jet across the Atlantic, without an obvious zonal pattern, these look (slightly) suspect to me. A few runs, more so on the ens, push Atlantic heights north towards Greenland, the earlier evolution of a Scandi high looks more probable maybe? And then there's the strat, FV3 has the best chart for that T336: But no obvious SSW yet, weakens vortex a bit. In my view the days ahead hold very interesting model viewing indeed.

To be honest Im not here to make enemies - when I wrote the below post yesterday it was exactly in context with other discussions at the time such as blocking etc " On ‎26‎/‎11‎/‎2018 at 16:18, Shaftesbury Snow said: GFS keeping things mild up to 144hrs The pattern is unlikely to change until late January in my opinion based on all of the long range models and the fact that we are continuously chasing FI" I definitely don't take long range models as gospel but I also observe sun spot predictions, look out for SSW, MJO and lots of other things. I think many others on here today are now following the idea of a pattern change (blocked and cold) into January. Much of the talk on this thread has not been about day to day models and many have spoken about the bigger picture etc. No one else has been slated today for saying similar to me. Maybe they have better reputations and people don't want to offend them. My previous post to this is exactly what I said and I stand by that. If you follow the day to day models for the hunt for cold it will drive you mad, I just look for tends and broader NH profiles and the day to day models have moved away from a blocking scenario at the moment going into December. Anyway, apologies to any offence caused to anyone

I'm getting the impression that this year we may get a spell of winter weather that will coincide with the coldest part of the year...and that will be utterly amazing if it were to happen, given the crud we've had over the past few years.

Encouraging to see ec mean taking the mean ridge west out of Europe by day 10 ...... that allows for it to ridge a little to our west and for the sceuro trough to back further west

While we are waiting for ECM may as well do some in depth analysis of GFS ensembles. Looking at the 850 temps maybe a bit misleading if use them to consider a pattern change other than letting us know there is no upper cold is yet programmed. However if we look at the pressure and ground temp charts we see signs of a pattern change. We see a typical zonal pattern out to around 4th/5th Dec where upon we start to get a lot of scatter but the mean climbs and although it isn't a solid signal it never drops back down below the point it begins to climb. And the 2m temps also suggest the flow will not be zonal falling away around the same period pressure rises which suggest high pressure will be close to or over the UK We can also see a few colder runs appearing but the mean is around average to little below.

As BA pointed out earlier, that is the bias corrected version, use this.. . Low amplitude but scraping round the edge at least. As for your comment. Eh? On that basis, what is the point of any weather chart?? The MJO will change in the same way as any computerised weather chart changes, every time new ‘start data’ gets entered.

I Think the GFs(p) will lift the mood in here shortly. It’s actually showing some consistency now if you compare it to it’s 6z run

I appreciate that and points well made. I don't think there will be a pattern change in December as such, not a lasting one, but my gut feeling is that it will start to take place after new year and set us up nicely. Unfortunately I don't really see much cold until then. I would love to be proved wrong though big time!

Oh! that's it then... the next four weeks are settled and we can dismiss the next two weeks of GFS / Euros and start over Mid December! - Darn right we will F5 clicking from 4:00Pm daily at least, looking for those 50 mile swings in the right direction or not! and is that not half the fun :):)

Looking back last nights sniping was out of order andif repeated posts will be removed and if necessary warnings given. Nothing of that scale noted this morning though.

Not necessarily IMO. I’ve seen the meto outlook flip very quickly. They are using mostly the same models as us. If this signal continues they will change that outlook

This time yesterday I reported that the ECM ensembles were all at sea from D8 onwards. Have they caught up yet? Maybe just maybe - but also maybe not. Here's D11 clusters for last night and this morning: Still rather split but slightly more emphasis on ridging trying to get north from the Azores (so back to the position the EC clusters held a couple of days ago on the 6th-9th December period) By D15 though 60% of runs have fair height anomalies to our north around 11th-12th December. This opens up several possibilities, but none likely to be particularly mild; 1. if heights get far north, southerly tracking jet firing lows directly through the UK 2. if heights can't get too far north UK high 3. middle ground option, heights to our north but not so far to allow Atlantic lows access to the UK, resultant easterly flow.

Hi, Shaftesbury. I'm not sure that 3 snapshots from a single op run of the 4th-best performing model really indicates anything, but for what it's worth I'm not overly optimistic for December either (the first half more so). This is based on all the output out to 12 days or so. Beyond that there's a ton of scatter on the ens, but there are still a significant number showing high lat blocks and a negative AO: https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&amp;mode=6&amp;ech=300 So not an overwhelming signal for anything, but I've looked at hundreds of these GEFS panels over the years when they are showing nothing but 100% zonal out to 16 days.

like backloaded winters, more effective, last years was good

Indeed SS. As Gavin's video showed, signals now suggest that a 'back-loaded' winter is more likely...

Just come in from work and said W.T.F,wow some good charts/models tonight yes the mean at 240 has more troughing in the atlantic than the 12z the latest from cpc 8-14 shows a much bigger arctic high than last evening and the eps at day ten also picking it up now http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php https://www.tropicaltidbits.com/analysis/models/?model=ecmwf-ens&amp;region=nhem&amp;pkg=z500a&amp;runtime=2018111712&amp;fh=264 and finally,has anyone seen an L for low pressure on the charts before!!! here is ukmo 144 hrs(i have circled it in red) i have never seen that before p.s,i see that the arctic rabbit is appearing in the models,i know what happened when that was showing i think last year. a couple of tweets i find interesting.