snowking

That's certainly the one that sprung to mind for me. Along with this (though not as impressive as the '47 chart): But yes I would absolutely agree, it seems a little premature for now. SK

Thought I would drop this in to here rather than clutter up the main thread but - indeed!! Might be a good challenge for someone to find anything close to this in the archives - there are a few examples available SK

Well I'm not entirely sure why this place is as worried as it seems. As BA points out the output is much the same as yesterday's, so concurrent Wave 1 and Wave 2 activity, wave two showing signs of waning just a little as we edge towards day 10. In terms of the questions regarding a 'failure' etc etc - it depends what angle you are coming at it from. If you were expecting a full SSW then yes this impending warming phase will be a failure, and was always expected to be. I can't comment for others but my own expectations are of a far stronger warming occurring during December, timing of this is open to question right now. But to look at this from another point of view we should not view each warming that doesn't produce a cold spell as a failure. Each spell of warming, or wave activity, should be viewed as a little victory. Keep thinking along the lines of the boxing analogies that are plentiful within this thread. Unless it's a very big hit you are not likely to knock your opponent out straight away. So a bit like a boxing match between me and Mike Tyson, the only way I would beat him (and obviously I would beat him...) would be to wear him down over time, throw a few punches to the torso whenever possible. So each little warming and wave break we see, at this stage, is helping to tame the beast, it prevents the vortex from strengthening too much. Will we see it strengthen any more than is is now? In the troposphere at least, almost undoubtedly, and this is well in line with expectations - think of it as Mike trying to take a bite out of my ear through the mid rounds. But this is expected and well in line with the work from Cohen et al. The reason for Ed's comments were the same as everyone else's - the currently modelled split this time leaves too much energy around the Greenland area. That does not entirely prevent cold, but it does make it a lot less likely. But I think the main issue so far has been everyone has been getting themselves a little too excited too early. I think everyone needs to take a step back, embrace the idea that from a stratospheric point of view this upcoming warming is fascinating for those of us who have frequented the thread over the years, but it is not likely to lead to a cold spell for the UK this time around. The story after any potential december warming, should it occur and with the vortex leant against the ropes in the 12th round, may be very different. SK

John - it's certainly very interesting and the most obvious answer, based around Judah Cohen's work, is the feedbacks created by the high Snow Advance Index seen this year, giving us the stronger Siberian high, ridging in to Scandinavia, and the resulting wavelengths producing the Aleutian Low, helping to drive the wave activity seen so far, producing the much more troubled vortex than that of last year. Of course there may be some links with the OPI too (in fact given the current state of play I would say almost undoubtedly - the two seem intrinsically linked) but until we have seen the research here we cannot say with absolute certainty BA - absolutely and I would fully expect it to. Despite the accelerated state of play at the moment I would not expect this to be 'the big one' should we say, merely just another mini attack, and no surprise of course to see the resultant moderation of the AO (and associated winter is over posts across various threads) - the next hit, however, I would think could provide a killer blow if everything goes according to plan through December... SK

Couldn't have put it any better myself The only interesting difference is the GEFS is certainly keen to keep more of the vortex energy towards the Siberian sector - a theme I would like to see repeated. It would be interesting to see some of those WSI ECM EPS charts again today over on Twitter to see if those are still holding firm, but given the output from 12z yesterday one would suspect so. This is probably unlikely to be the main event but once again is shows what a very different situation we are in to this time last year. Up until now (in what has already been a very successful November stratospherically) we have seen obvious signs of an improved Brewer-Dobson circulation, helping to drive ozone up in to the northern hemisphere, then of course we started seeing the fairly consistent wave 1 activity, the only thing we have been looking to join the party is wave 2....not only has he arrived, but it looks like he's bought snacks and a keg with him too SK

Apologies for the lack of charts as I am on my phone and so they are difficult to post. Needless to say with continued (and slightly increased) Wave 1 and concurrent Wave 2 activity shown on the Berlin strat charts this morning from day 8 onwards, the vortex is going to come under some real pressure. By day 10 it becomes very stretched and distorted, with zonal mean winds dropping all the way through the forecast period and looking as though it wil have a tendency to split a little later on beyond day 10. Current forecasts suggest once again that the main bulk of the stratospheric vortex will end up in Siberia. Interestingly the profiles would also favour a ridge over the UK towards the day 10 period to perhaps offer something a little more settled. Big attack approaching I suspect , though within the reliable timeframe this appears limited to the stratosphere...deciphering what happens further down the line troposphericallty should keep us entertained in the weeks to come SK

I refuse to provide a link to the newspaper in question as the more of us that visit their website, the more revenue they generate to continue paying their under qualified, over oxygenated, crackpot gaggle of so called 'journalists' (should read: numpties) to keep spouting this utter tripe, so I will just leave you with the headline: POLAR VORTEX WARNING: Latest winter weather models show UK faces MONTHS of heavy snow *sigh* And they still can't get their tiny little brains around the fact that Judah Cohen is neither Italian nor an author of the OPI. What irritates me about this constant barrage of bull**** is this - if I went and published a story which suggested David Cameron, Ed Milliband and Nick Clegg had spent a romantic night together, I would likely be taken to court for defamation of character and numerous other charges, when in all reality all I have done is print the same sort of story the likes of these tabloid newspapers have been printing for years now. Yet as soon as anyone approaches such organisations about their actions all they have to say is 'freedom of the press' and off they go on their merry little way. Anyway, it is what it is - as for madden (amazed that's not in the swear filter yet), I think if we all donated £5 we could afford a pretty good straight jacket to put him in to prevent him from being able to communicate this nonsense year after year SK

The only caveat I would add is that I can't make out whether the analogue provided is their actual forecast, or whether it is just highlighting what happens in deeply negative AO years - I suspect the latter Of course either way with their expectation of a negative AO it bodes well, but I wouldn't be necessarily taking the composite charts at absolute face value. From their text it looks as though they certainly expect it to be below average overall in NW Europe, but not necessarily severely so. Still great to see a forecast from them and certainly what many of us were hoping for

Interestingly though, if you take the three closest OPI years... Not an exact match but certainly gives the right sort of idea SK

It think it is worth picking up on this point over here, just incase some do not venture over to the stratosphere thread (it is understandable - I can imagine it may be a little daunting at times especially for newer members) Whilst we have experienced a high SAI this year, in fact the highest on record (though this only stretches back as far as 1998), high SAI years do not tend to favour a cold first half to the winter for Western Europe. Occasionally this may happen as a consequence of the strengthening Siberian high nudging slowly Westwards, but it is not the most common of occurrences for us here in the UK. However, what seems to be apparent this year is that the 'normal' timeline of events - i.e. the Scandi high/Aleutian low combo, and consequential wave breaking in to the Stratosphere is happening a little quicker than usual. Remember the mentioning of the failed Dec '12 Easterly, well this year that potential (or potentially failed) Easterly looks to be happening towards mid-November instead. You may remember from 2012 that we saw a period of a return to Neutral/Positive AO before the Negative AO returned towards January. You may also have noticed in recent days many of the more seasoned members have been trying to temper expectations a little. The two are not mutually exclusive events. As Cohen has put it in his recent blog entry for this year: (I have omitted the final part of that quote so as to avoid an outbreak of mass hysteria in here) So as per Nick Sussex's excellent assessment above, yes there is a possibility of (perhaps even a likelihood of) a return to less negative AO conditions. However, I would also add that any calls from current GEFS runs that we will be seeing a return to any sort of intense vortex in the next couple of weeks look very wide of the mark. Just taking a look at the panels from the 6z: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384 We have perhaps two out of 20 members suggesting anything nearing a 'traditional' (perhaps should read 90/00's) polar vortex - and I would put that down to the standard variability we have come to expect from the GEFS at such range. So I think the point to take from all of this is that yes there is a chance of something cooler towards the middle of this month, equally should it not come to fruition do not become disheartened, and as we see an almost inevitable return towards a more neutral AO later this month bear in mind this is an expected development. Hopefully by this time we will all be a little more distracted by activity way above our heads up in to the stratosphere. SK

Just reading through Cohen's blog, and had to pull out a few tidbits of interest. The first one is this: Of course we are starting to see this appear now in both the ECMWF and GFS suites, and it also confirms recent discussions regarding the unusually early nature of the repercussions from a high SAI. Whilst a few days out of date, the below chart from the blog also looks pretty useful: In short it shows vertical propagation of wave flux - and as you can hopefully see, there appears to be particularly strong propagation through much of the stratosphere forecast through the next couple of weeks. I am anticipating a barrage of 'winters over' posts over in the MOD thread if we do indeed transition back towards a neutral/positive AO state towards the end of the month, but I am hoping the sensible posts from some of the more seasoned members are helping to temper expectations a little. The truth is following a high SAI, early winter is not a favourable time for Western European cold - there is always a slim chance that this occurs consequentially given the strengthening Siberian high, but generally speaking I hold more interest in seeing the cold air pool to our East as opposed to watching and expecting it to be advected our way early on. But it should be noted once again that we do seem, at the moment at least, to be working on an accelerated timeline. My personal expectations following the SAI/OPI final figures had been that we would not see anything too significant cold wise until January. But given where we find ourselves right now, I cannot disagree too much with the below: So what am I personally looking for with the upcoming -AO period? Simply to start building a cold pool to our East, ready for us hopefully to 'tap into' a little further down the line. At this stage the only factor I can see counter to the theory of a -AO this winter is the average to slightly above average sea ice extent around Barents/Kara, as Cohen mentions too, but on the grand scale of things and given that this is a very recent theory with little conclusive supporting evidence for the moment it does not concern me greatly. Even if we do not hit the holy grail here in the UK, stratospherically this is going to be another fascinating season and thankfully should provide a stark contrast to last 'winter' SK

There is discussion of the PRX here: http://www.americanwx.com/bb/index.php/topic/44784-t1534-gfs-gfs-at-13km-along-with-other-upgrades-can-be-found-here Haven't got time to discuss in detail but in short it is another parallel run initialised by NCO on a semi-lagrangian grid at 13km forming part of the 30 day evaluation period Should essentially be same as current GFS(p) with a few tweaks SK

I think we need to bear a few things in mind here folks... First of all with regards to the apparent shock at the Met Office figure of only 10% chance. The Met Office is a scientific organisation, and as such they will only generally comment upon what the data provided to them shows - sure, there will be a certain level of human input too, but at that sort of range their forecasts will be based upon what I would term Model Facts. In terms of this specifically, the 10% chance is not a figure that would have been arrived at randomly, it suggests that out of the suite of 51 ECM EPS members (whether there might be some integration with MOGREPS too I could not say), only 5 or 6 members show a scenario reflecting that of the operational run. Now of course it is also true that the operational runs, running at a higher resolution, should in theory resolve features better than the ensemble members (I do not know whether perhaps operationals carry greater weight in probability statistics), and often we do find that to be the case, but the beauty of posting on an open forum, as opposed to forecasting to a scientific standard, is that we can play devil's advocate to a certain extent and theorise scenarios that might occur based upon previous experiences...but there is a reason ensemble suites are run at that range. I would also caution, and I believe there was a post a short while ago from I'm Dreaming Of confirming this, that there has been a very noticeable trend over the past couple of years to raise heights in the vicinity of Greenland at day 9/10 incorrectly. I also usually find it concerning when the UKMO GM does not back a scenario whole-heartedly, particularly when it comes to blocking to our North and any sort of trough disruption accompanying this. So whilst the excitement is understandable, I would urge members to wait until such charts begin coming in to the 120 hour timeframe before lighting the cigars and bringing in the overweight contralto. You are probably sick and tired of me saying this, and I know my keyboard letters are getting worn out writing it, but just remember back to December 2012 and the trouble caused there even inside 144 hours. Though to finish on a ramp, stratospherically things are certainly becoming interesting... SK

Just seen this posted by Michael Ventrice over on twitter from the 0z ECM ensemble mean: Split up to 50mb with a ridge around the Greenland vicinity, apparently elongated as far up as 10mb but no split above this level just yet. Bear in mind that chart is an ensemble mean, and things start to look positive. And that's before the strongest of the warming towards Asia has appeared... SK

Purga this is not meant to be a dig at all so please don't take it to be, but I am just interested. I have seen you post about this quite a lot during the past couple of days, but I have yet to actually see any sort of powered up jet stream chart to accompany it, only something very weak and not particularly zonal such as this: And that's actually one of the stronger frames on offer. I think it is important to bear in mind that the jet stream is generally measured at around 200-300mb, and so in fact whilst we might be seeing the potential for a sharp thermal gradient at 850mb, this is not the be all and end all in terms of how strong the jet stream is. As I said, please do not take this as a personal dig because that is not my intention at all, just that I like to see the physical evidence of what is being suggested coming to fruition what we are seeing right now is not all that different to many other years gone by. Here's 2009 for example: I think all in all there is still a heck of a lot of over-reaction going on right now on either side of the equation for the time of year. What we are seeing right now is fairly typically what was to be expected from the best fit analogue years, and indeed from the climatology provided by Cohen et al. Like I said yesterday everyone will be sick and tired of hearing about this, but Scandi High, Aleutian low and most pertinently, troughing centred just to the West of the UK. I also take on board Cloud 10's comments from yesterday regarding last winter too - unfortunately what was expected to develop later in the season got close but not quite close enough for us. It also hopefully goes to show that no forecast nor forecaster is infallible - in fact, very much the opposite! There is absolutely no guarantee that this year my expectations (or indeed the chosen analogue years) will meet reality. Trying to take a balanced view of things right now out to the middle of this month: And the key features outlined previously are pretty much what we see, and the implications for the UK? Pretty unsettled mostly, with an alternation of slightly below to slightly above average likely temperature wise. No absolute signs of being sent in to the freezer, no signs of me having to get the shorts out again (ladies of the UK will be thankful I'm sure), and certainly no signs of a rampant jet stream any time soon. Regards, SK

That's got it! Many thanks SK

Might just be me but I can't get that link to work for some reason, just get taken to a 404 page Regards, SK

Right, I am going to try and calm things down a little in here, as well as answer a few questions that I have seen along the way hopefully. The over-riding message from this post is this - Calm Down! We approach November with two things which are a recipe for over-excitement, mood swings and plenty of toy throwing. These two ingredients happen to be: - Something that can barely be described as a 'Winter' from last year - A Polar Vortex this year more absent than UKIP at Notting Hill carnival So, let me start by addressing the misery of last year. I have seen some occasional posts asking whether what we are seeing right now is 'normal', both in this and other threads. My assumption is that by normal, they mean preceding a mild winter. Below are some mid-November charts from what we might consider to be some of the milder years of recent times: A very random assortment and chosen for a very specific reason. Whilst not all of them feature hugely organised vortex's necessarily (and that in itself becomes a point - just because right now there is little organisation to the vortex does not mean it can't still become more organised and vulgar) they all lack a crucial ingredient in something we now know, thank's to Cohen, is a crucial ingredient in SOME colder winters, and something you may be sick and tired of hearing about by the end of November - The Scandinavian High/Aleutian Low combination. For example, here are some of the colder winters of recent times: Notice in all of these years we end up with a Scandinavian High and Aleutian Low combination during November. Now this is not me saying that before every cold winter we have to have this setup, but in the majority of years we have seen this setup occur it has lead in to a colder winter. This is all linked in to Cohen's research on the Snow Advance Index, with the rapid snow advancement (and interactions thereafter given the rapid cooling of the surface) giving us the stronger than usual Siberian, and eventually (hopefully) Scandi/Sceuro ridge. If we have a look at the forecast setup for the middle of November this year: We see something fairly similar forecast. I think this serves as an important point heading forward for those of you impatient to get the cold in as soon as possible. The best case in point for this is the now infamous December 2012 failed Easterly - the whole idea here was that yes as nice as it would have been to get the cold in as soon as possible, it was not vital that we got the early season cold. It was once again then a Scandinavian high that initially looked to retrogress to advect the bitterly cold air across Europe Westwards in early December, before some more shortwave drama lead to record sales of Nick Sussex's prozac. But the point is, we had the Scandinavian high/Aleutian Low combination at this time, which helped to drive wave activity in to the Stratosphere and ultimately led to the cold JFM 2013 period which we saw. One final addition to make before we take a look at current forecasts, here was my analogue for this November, based around OPI, eQBO and El Nino matches: Notice a few key things which this picks out which we already know to be true: - Trough to the West of the UK - Aleutian Low - Scandinavian Heights - The cold pattern across the USA with a West Coast ridge and East Coast Trough. If you try and match that to the 8-10 day height comparisons posted above, you'll notice a pretty good match overall with just a few minor tweaks. Roll that forward in to the winter months and you get this: So, the overriding message I have for you all is this: Whilst we are seeing some wonderful synoptics on show which at least makes a nice change from last year, it really is not imperative that we get the cold in this early. Even the greatest winters of '47 and '63 did not get going until after Christmas, hang tight and try not to get aboard the rollercoaster too early. Get outside, head down to the pub, go see some friends and family etc. because we all know that once the truly cold charts start showing none of us on here are going to have any sort of life outside of the area between our laptops and our lamp-posts. So, back to the future... If we keep the above in mind and search just for the Scandi High/Aleutian Low combination for now: We can generally still find that combination in the outputs through to around day 10, and if you want to make it easier to spot this, try using the anomaly charts instead: ECM Ens. Day 5: Day 10: And if you head over to the stratosphere thread and take a look at some of the posts from this morning, you will see some wave activity starting to rear its head once again, which is most welcome. So as we are only 5 short days in to November, this is all I will be looking realistically for now, the Scandi High/Aleutian Low combo, and anybody expecting anything other than eye candy in the next couple of weeks may be a little misguided. Let's wait until the end of November before we start getting too excited about anything potentially good synoptically, hoping that in the meantime we can start bringing some of that colder air in to Europe. SK

. Absolutely Phil and I think that will make this a really fascinating winter. IF, and it's still a huge if, the competing background signals do indeed prove to have correctly indicated a colder than average winter, some serious re-evaluation will surely be needed on the initialisation data for many of these models. Of course conversely it may throw out a lot of 'alternative' theories if we do see another milder than average season. All theoretical right now, but a fascinating background story to what I'm sure will be another rollercoaster of a season!

Just posted about these over on the model output thread too, but thought I would drop them in here too for reference for any keen stratosphere readers. If you ever wanted a clear example of Cohen's SAI theory in motion, this is it. SK

If ever you wanted an example of Cohen's theory in practice, those charts would be it. Big Aleutian low, Scandinavian/Sceuro high. The result (if it were to come to fruition of course - this is still a set of forecast charts) would likely be some impressive wave activity heading in to the Stratosphere. SK

I would have thought the raw data presented in the table is the evidence - as stated before, that is making assumptions with a small sample size, which is never overly-scientific, but the evidence presented is that so far (sorry for sounding like a stuck record) every time we have seen an OPI above to below the 1/-1 range, it has resulted in an above/below average CET. You are correct IF you include all the years in between that range there is then no correlation evident, but the point I was making (and I think we are both making the same point but with different mindsets) is that up until now the 'extreme' ends of the OPI scale result in predictable results...allegedly at least. SK

If you take the dataset as a whole, certainly yes. However once again if you take the <-1, >1 stance, all winter CET's finished below/above the 71-00 average as a whole, and that is what I was trying to get at - which has been the suggested use of the OPI ever since Steve Murr's initial research earlier last month. SK

You're right, there is none other than the raw statistics. Unfortunately with such a small sample size the evidence is not absolutely compelling, but I am talking purely from a face value point of view, and within this the suggestion of <-1, >1 (though this could be taken down to 0.7 strictly speaking) clearly works. Had the OPI this year finished at say -0.7, I don't think that anybody would be expecting a cold winter outright. But we can only go for now with the limited data we have, and that certainly suggests cause for optimism. SK

My expectation for January at present is somewhere around the 3-3.5c mark as an upper bound. There is the potential for this to slip a little lower, but as a nice round figure I think 3c would be where my thoughts are right now, given data from previous eQBO, El Nino years. SK