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  1. 59 points
    The idea that the signals 'have gone wrong' and previous posts don't tally with earlier posts would be laughable, if it wasn't so misleading and demotivating to (all) those who have made those posts. For my own part, I'm very deliberately posting 'the whole book' written one month past which assessed the possible problems the patterns this season might encounter in terms of the favoured cold weather this thread (largely) craves. Its staggering, frustrating, very annoying and equally demoralising that so much time can be wasted attempting to provide so much information in voluntary time but to persistently find a name banded around with quite different interpretations - and especially an inability to take one post in context of the next - some simply lazy and glazed over and can't be bothered to read, and others which are frankly trolling deliberate misinterpretations. So, another long one (I'm afraid) of intending to manage expectations before returning back to the rollercoaster sidelines My own perception of the start to winter. (like any other season in terms of weather preference), largely differs from most because I am far more interested and curious how the signals play out (either way) and not how cold and snowy it might get. So I will have to be forgiven for a different tone that frankly intends to neither optimistic or pessimistic, but simply hopeful objective how I see it. There is neither the time or inclination to get absorbed in the daily swathes of NWP operational and ensemble suites - but instead the usual non NWP approach is most helpful to me. In the final analysis anyway, the signals dictate the models, not the other way around. Apparently consensual ensemble suites gauge assessment based on a moment in time captured, but they are prone to switch direction like shoals of fish when they realise something different may be going on... So, for what it may be worth: Sorry no time for links. Atmospheric angular momentum tendency (essentially in context referring to the turning force of the jet stream) has tumbled back with lack of tropical convection (MJO) focus allowing easterly wind inertia to return to control the atmospheric circulation in line with La Nina consolidating at all levels in the Pacific. The SOI is consistently +ve and there are colder waters to upwell and strengthen La Nina into the close of the year The Global Wind Oscillation (which represents a plot representation of global wind flows as referred to above) in reflection of all this, has progressed from quite an amplitude Phase 8 and is set to hover around Phase 2 for a while. This slow/stationary orbit underpins the modelling over the coming days in terms of the very big signal for a very amplified holding Atlantic ridge - and certainly favouring a cold pattern sustaining into the medium term as the vacuum occurring upstream slams on the brakes with jet flow rapidly decelerating In terms of the stratospheric feedbacks though, the question mark in my mind is the extended hints of the Pacific pattern starting to show the first signs that La Nina is going to tighten its control from upstream with the building of the Alaskan ridge. On that basis a highly anticipated two week stratospheric forecast is just that, and on the basis of potential upstream changes that ultimately spell return of the jet, it cannot be wholly assumed it will automatically favour this side of the pole as the Pacific pattern starts to take control. So I don't personally agree with some of the views being expressed that this is a "good thing" for downstream prospects in terms of sustaining a cold weather pattern beyond the early to (possibly?) mid December period. Its a typical La Nina development that often happens as wavelength cycles occur with the change of month and season and has the effect of increasing Canadian cold and re-booting the energy into the downstream polar jet. Such inications are minority model solutions at the moment that show increased upstream flow in FI, but I think its not a case that they are automatically wrong, simply maybe on the progressive side. And I would be highly cautious of 100% confident assumptions then return energy will automatically split and encourage trough disruption under the Atlantic ridge On that basis I'm not sure that any equal assumption (however valid) can be made that the present amplified pattern has a sustainable feedback. Or at least not sustainable without a further eastwards moving MJO catalyst, to engineer further tropics>extra tropical rossby wave train and set up further downstream amplification via +ve MT and then, just as importantly in turn externally pressurise the polar stratosphere. Even the freeze of 2010 ended on the basis that no follow up occurred to the high amplitude MJO event of October and that led to the rapid taking of control of the default La Nina Pacific ridge and return of polar jet flow after Christmas So the La Nina default will not favour any undercut of -NAO automatically. The upcoming pattern is a traditional (extra amplified) mid latitude ridge pattern. The irony is that the higher AAM pattern we have been seeing of late has actually featured something of a Greenland High and an attempted -NAO (albeit west based). Its no coincidence that falling AAM redistributes the blocking pattern into the Atlantic. I think this has already been forgotten by quite a few because of the pretty charts at the moment However much the warm air advection from this ridging may perturb the troposphere/boundary and help prop up the poleward nature of the ridge in the short and medium term, the increasing upstream amplification in the Pacific that will carve out the default La Nina ridge will, eventually, increase cold air advection upstream and focus jet energy into the polar branch. That is not going to assist cold air advection downstream and both negate stratospheric destabilisation this side of the pole, and transfer the weakness to the Pacific side. This is an old and familiar story, and though we are certainly in a different place to last winters weak La Nina, the possibilities remain the same with the arctic in such an alarmingly fragile state. Its getting increasingly hard for the whole hemisphere to be cold - there is simply not enough cold air to go around. Something, and somewhere, has to give The importance of the Aleutian Low and Siberian High moving forward in terms of cold air feedbacks have been identified a few times on here as a means to sustain a cold pattern into winter proper. Any Pacific heights, as a key part of an arrangement of circumglobal La Nina mid latitude ridges and polar jet flow, are counter intuitive to this. The stratospheric pathway can certainly override the tropospheric winter La Nina effects, but its going to require tropical forcing to play ball and come into play just at a time when the upstream pattern shows signs of coming back to life once more. Strengthening La Nina and changing seasonal wave length changes are going to become increasingly resistant to this the further we head towards January and especially beyond. There is no certainty either way, and whilst the pattern could sustain in a few ways yet - the "quick fix" I spoke of in the MOD a couple of weeks could easily still be just that. At the moment I see things much as I would at the end of a warm La Nina Spring, that so often does not transfer to a warm La Nina summer. That said, there is more to encourage a cold pattern, certainly to start, beyond what the weak La Nina went on to deliver last year - but I don't see the straightforward path to sustained cold nirvana many others see. Ciao I could have posted much more from various other posts which have gravitated and returned back to this theme, but it still wouldn't increase the chances of having them put in the right context. Now, a whole lot of signal evolution and model output has obviously gone under the bridge since even the last week of November and many, many others have contributed large amounts of time to try to give best perspective. Lots of different posters, some with great NWP insight, others using non numerical methods. But in between the ever increasing signs of a theme towards possibilities to cold weather as a recurring theme this winter, there have been REPEATED posts that have returned to the early cautionary theme of the whole bolded post above. Simply speaking, there are still uncertainties ahead which some are rightly referencing, but that crossroads I banged on about is arriving and frankly there should be no surprise that the signal, tea leaves, teleconections (call them whatever) have come to roost in the way described above and are not necessarily following the 'straightforward path to sustained cold nirvana many want to see' that was posted 4 weeks back Please, to those with lack of attention span, note the italics in the previous sentence. There is of course a whole lot of this season to go yet, and much can still (and will) happen either way - and who knows sooner or later. But please no-one act surprised or blame the 'tealeaves' for being wrong. Blame a skewed, frost tinted or addled mind instead - the pendulum has swung to and fro with the upsides and downsides (this is the UK after all) but don't anyone tell me (or anyone else) they have been misled. Its not my fault (or anyone else) there are selective agendas and a few who are so insecure they need constant 'will it snow' updates who only want to hear what they like. There is the weather, and there is also a life. One that is often more serious, more problematic and can have much greater repercussions than whether or not it snows. I've seen it said that weighting two different scenarios is some kind of ploy so as not to be wrong either way. Er,no - its simply saying things as they are and giving an honest opinion. Like lots of other opinions. Its not about right or wrong, its meant to hopefully be about informative contributions, and not to pander to tribal allegiances. I'm not wasting any more time and energy with further explanations or even current analysis - its a hiding to nothing continually having words put in mouth by a vocal percentage who keep acting bemused or even cheated because (allegedly) they had been promised their cherished weather and its disappeared, or hasn't happened yet. Whatever. Or who offers nada themselves but sit and carp at others efforts. Why bother? But there are plenty of very good (also equally non-egotistical) posters on this forum, many of them on this page each day. I suggest keeping looking out for who they are and those referred to above maybe who, either deliberately or simply lazily have selective thinking, paying them the respect they deserve. Otherwise they too are going to get fed up very fast and not bother also. I know some who already feel that way - so this is not just another one-off paddy fit. To the rest (of the large majority) on here, I hope you all have a lovely Christmas
  2. 34 points
    Please note: I started working on this post this morning but I had to break off for a few hours. Then Paul closed the old thread where much of this post and all the charts were sitting in that thread's browser. I thought that I would loose it all ,especially the charts but the whole lot seems to have copied across okay into this thread's browser (whilst still in "pre-submit mode"). I just hope that all the charts are easy to view (in the quick/move across mode). EDIT: they seem to be ok, phew! TIME TO TAKE A STEP BACK, ASSESS THE VERY MIXED SIGNALS AND TRY TO MAKE SENSE OF IT ALL Well, they say that 24 hours is a long time in politics and for all of us model watchers 24 hours can sometimes seem to be an eternity when the output can swing quite widely from run to run. In this post I will try to address some of the comments from a few of our most experienced and well respected posters and examine many of the conflicting issues and "possible" changes in the background signals that drives all the model output (usually with a time lag of at least a few days). As I always remind everyone, I am definitely not an expert and I only have a limited understanding of the key teleconnections. I use the simplest terminology just as much for myself as for the majority of readers on this forum. My strength is my study of charts and interpreting what we are looking at and how they "might" evolve, which I have been doing for over 56 years since the age of 8. Over the years, I have also read many papers on various aspects of meteorology but I am the first to admit that this knowledge/understanding/experience is not nearly enough on its own and I'm fully aware of my limitations. Nevertheless, I will attempt this overall assessment and I will have no problem with any one "respectfully" commenting on or correcting anything that I say (with at least a short explanation). Most of you who read my posts will know that I'm very much one of the "coldie" brigade and I do spend a lot of time searching for possible changes to colder patterns. Some might dismiss this as "ramping" but I always try to provide a degree of balance and often use "CAUTION" statements to put what I say into context. Quite a few (certainly by no means all) of our much more experienced posters also have a strong preference for cold (and snowy) evolutions and they can sometimes get just as excited or as disappointed as anyone when they see possible changes in the background signals and the output. Most of them and the professionals do try to manage their expectations and still provide realistic and honest assessments. We must all exercise considerable restraint - so no throwing the toys out of the pram, no blaming anyone for simply "being the messenger" of any disappointing news and definitely no ridiculous arguments about dismissing the relative merits of teleconnection science (there is a tiny minority on here who often express highly disrespectful and nasty comments and criticising the post contents can be just as bad as criticising the poster especially without any real evidence to back it up (not just conveniently quoting several sentences completely out of context which almost always misses the very caveats and caution that was expressed elsewhere in the post; I do wish that the moderators would clamp down on this dreadful practise - otherwise we will lose some of our very best and most valuable contributors). Having said all that, I still remain pretty bullish about the overall prospects for this winter (may be just timing issues - more on that shortly) and the output for the period just after Christmas looks much more interesting (for coldies) than it did only a couple of days ago. When we see the likes of @Steve Murr start to tell us that any signs of a decent cold spell in January have all but gone we should sit up and listen. When one of our professional and highly respected posters @Glacier Point explains why things have changed we must pay even closer attention. Then we have some highly experienced members who mostly post on the stratosphere thread and rarely post on the model thread. So when, for example, we see @KyleHenry bothering to take the time today to post on here we can only show our appreciation and pay careful attention to what he says. Now an amazing coincidence - just as I am writing this (currently 1110) @Tamara has posted. Regular readers of my posts will know that I often refer to Tamara as I have the utmost respect for her dedication and how she explains how the background signals are behaving. Just as she "always" does, I never forget to stress that anything that she says should not be taken out of context and the downside risks must be taken on board. I urge any of you who have not yet read Tamara's post to study it very carefully indeed. She again stresses the uncertainties and describes what "might" go wrong as well what "might possibly" still fall into place (she stresses that bit in italics but with caution) . It is a terrible shame that the tiny minority that I already referred to above are responsible for Tamara deciding to take a break from this forum. It happened last year too. I will just say publicly how sorry I am that it has come to this and of course I wish her a Happy Christmas. (I rarely use these but a one off one today to cheer up Tamara and all her supporters). So, no more bursts of unwarranted emotion from anyone please (let's have some Christmas spirit). Now on with my post. I know that looking into deep FI can sometimes be about as reliable as picking the winning lottery numbers but there are important occasions when we need to get an idea of future "possible" pattern changes and if a new direction might just be starting to be sniffed out in the distant model output. As always, remember it's the background signals that drive all the model output not the other way around. Unfortunately, we only have the GFS and GEFS models going out that far (plus the extended EC46, monthlies and ens etc). Knowing that the 6z runs would be coming out while I'm writing this, I deliberately saved the 0z for making an important comparison. I had noticed several comments that the GFS 0z operational run was completely out of kilter with the GEFS control, mean and ensembles. This does not mean that it's wrong, of course. In fact it can be the Op run that latches on to a possible change prior to the other output. Update: in fact we now have the 12z rolling out but this comparison is purely to make my point. So, let's have a closer look: T+384 0z Run: GFS Operational GEFS Control GEFS Mean Run GEFS Ensemble Panel The GFS operational run does show a somewhat strengthened and rather more organised PV but not particularly vigorous. There are no Arctic HPs and and only a "Cold" faux Greenland HP. There is still a little amplification. HP has built north-eastwards from southern and central Europe towards north-west Russia (not a Scandi HP but equally not a flat pattern with a "Euro-slug" at the D16 stage). The GEFS control is more amplified with HP drifting into Scandinavia and still pretty high pressure over the Pole. The mean (caution: remember this averages out all the 20 ensembles, the op and control runs and can be misleading) actually has a broad band of HP extending from central northern Canada, through the Pole and across into Siberia/northern Russia. The average depth of LP is very weak and far from a raging PV. There is an even bigger spread in the ensembes. Anything from a stronger PV to a fully split PV and a cut-off proper Greenland HP - for coldies is that as close as we get to something very special? There is a larger group of ens with disrupted PVs. So, yes the op is out on its own with a stronger PV, the mean paints a very different picture and many of the ensemble members showing continued disruption and the control run is somewhere in between. All this being clearly reflected in the 850s chart below (unfortunately, it was too late to get the 0z surface temp and pressure ens charts as the 6z ones were already showing). GEFS Ensembles - London: 850 Temperatures Moving on to the 6z run, let's look at the same charts and then look for any possible trend (far too early to draw any meaningful conclusions but just a possible indication). T+384 6z Run: GFS Operational GEFS Control GEFS Mean Run GEFS Ensemble Panel Well, seeing as the 6z run was still rolling out when I was writing up the 0z analysis, I was pleasantly surprised. The GFS op run has back-tracked to some extent although it is still one of the warmer runs (see 850s below) but it shows only a moderately stronger PV and much higher pressure over the UK and ridging through southern/central Scandinavia, northern and north-eastern Europe and right through to north-west and north Russia. Is that merely a GFS "dead cat bounce" or are they dropping the hints of a much flatter pattern set up? The GEFS control run still shows WAA through Alaska and towards the Pole with HP there and some HP in north-east Russia. The mean (which would never show a split PV unless almost all the ens showed one and in very similar positions) still has HP from central/northern Canada, through Arctic, across the Pole and right through to northern Russia and Siberia. Now, we are back to an even better set of ensemble members. We have three with fully split PVs through the Arctic, one north to south but two more east to west. Steve Murr alluded to the latter pattern being of interest and dismissed the former but I will focus on this below as I have several important points to make. The ens charts below show the spreads nicely. The 850s are not indicating much in the way of upper cold with only a few members below or well below 0c. The op and control are amongst the warmest towards the end of the run. The mean surface temps are mostly around 5c with some of the ens up to 10c and some closer to 0c. The op is around the highest at the turn of the year but falls away thereafter. So mostly temps look close to or slightly below average. With warmer 850s and rather lower surface temps mostly shown, that might indicate some higher pressure around (with some surface cold). The op and control have us under HP (as mentioned above) around 1030 mb but there is quite a spread with the mean closer to 1016 mb. GEFS Ensembles - London: 850 Temperatures 2m Surface Temperatures Mean Sea Level Pressure Overall, if this run was any indication to go by at all (very unlikely to be accurate) this would be far from very unsettled and very mild by January 5th. Before some of you think that this exercise is a complete waste of time (some will of course!) let me remind you why I bothered to show it. Firstly, I was looking for any very early hints of the GFS picking up on us moving away from the possible change to a colder regime - just as I was looking for any pointers supporting this change. Only on this very scant evidence, one might say that the GFS is pulling in both directions! The op in the 0z and the op and control in the 6z are amongst the warmer evolutions but the mean, supported by many of the ens charts, suggests otherwise. As we always say, far more runs needed (and you will have had a chance to comment on all the 12z output when this post goes live) and will the output from the other models start to move away from the WAA and HP into the Arctic pattern in the middle term (say D7 to D10)? This gives an idea of what to look for in the longer term and then the route taken by all the model output towards or away from that destination. We will need to look at many more runs and as @johnholmes often reminds us, it is often a good idea to compare like with like and not the changes in every run (eg: every 24 hours with the same run each time like the 0z or every 12 hours with say the 0z and 12z runs) as this often achieves better consistency with the same new (latest) input data becoming available in time for certain runs. CAUTION: remember the lag time for the models to start factoring the possible changing background signals - this can take a few days. Unless those signals improve, there may well be some significant downgrades in the extended model output. I am still taking my more optimistic approach and some of my points below "may" address a few of the issues. Timing Issues: If FI is unreliable then mid to late January is even more unreliable! We need to turn towards the broader background signals. When the majority of our specialists (teleconnection including "some" from the strat thread) were talking about a "possible" change to a more amplified and colder regime for some parts (a few weeks ago) not only did most of them mention the downside risks but also uncertainty on just when it might occur and how long would any transitional phase take. I've picked up on this in several previous fairly recent posts. Originally, the period from after Christmas through to early January was mooted as a possible period for the changes to start. The models were late to pick up on this and then we started to see some interesting Arctic patterns merge, initially in deep FI but then quite suddenly into the middle term (D6 onwards) with all the models coming on board eventually. The PV coming under attack is one thing and delivering a cold spell is quite another (again I'll look at this towards the end of this post but I was going to do a current and predicted temperature analysis which will have to wait for another day or two). Might it be a case that there'll be a move away from this pattern change but with a move back slightly later on and we merely end up with a delay to a possible colder regime?. To understand this we need to recognize just what has been happening and, in particular, some of the conflicting signals. Conflicting Signals: Our teleconnection specialists and quite a few others have told us how this could be a "winter on a knife edge". I'll list some of the issues here (with the simplest of comments): 1. The ENSO state - La Nina conditions but not a particular strong one would usually signal a colder run into winter with early blocking, giving way to much flatter patterns in mid-winter as the PV goes through its typical strengthening phase and the jet stream usually gets to around its strongest at this time of the year. Then it looked like a more unusual Nina signal with it becoming an east Pacific based event (the colder currents and upwellings in the east and warmer currents in the west, perhaps allowing for a more extended period of blocking; then very recently a suggestion that the La Nina might be strengthening and moving into its more usual central Pacific position with a more typical La Nina winter impact - then back to timing issues of whether the impacts of this could take hold before or after an increased amplification (favoured until recently) despite a strengthening PV and jet stream (the latter "could" still be the case). 2. The various oscillations and how they interplay - we have an eQBO, tropical forcing, the GWO, angular momentum (possibly a less favourable phase); the MJO might be moving into more favourable phases to enhance HLB patterns. There had been talk that the MJO signature may have been masked by other signals. Will it move quickly or slowly on through the key 7.8 and 1 phases and at a decent or lower amplitude, will it actually play a major role in assisting or is it less relevant right now. I have just noted another excellent post from @Singularity and a similar comment from @nick sussex who both both that there may be continuing uncertainty in the progression of the MJO. This could prove to be a very important ingredient down the line. (UPDATE: just read Nick's fascinating post with the NOAA report - possibly encouraging for coldies) It strikes me that if all the ducks fall into a row to assist each other rather than compete that this would make predictions a lot more straight forward! LOL. Just what are the more dominant forces in any particular situation? - way beyond my limited understanding. 3. The near record low Arctic sea ice build up and very high anomalous sea surface temperatures there. The cause and effect relationship with these favouring split or disrupted PVs (see my post on page 72 of the now closed 9.12.17 winter model thread). 4. Very high Asian snow cover. Judah Cohen has conducted extensive research into this and believes that this combined with the Arctic profile (above) can favour strat warming events (more on this shortly). 5. Solar weather - very low (zero for several months, I believe) sun spot activity, solar bursts expected this week with uncertain impacts. 6. The conditions in the stratosphere and the stratospheric/tropospheric relationship (more below). 7. The PNA - was positive, briefly negative and was expected to go positive again but has this/will this change? Impacts for favouring amplification and down the line possibly leading to a mid-Atlantic ridge and some HLB nearer to us and/or sending the jet stream further south with a potential for a build of heights to our north-east (might this still be on the cards, delayed or far less likely?). 8. Probably various other factors but I'll leave the list at this point. The Stratosphere: As I said at the opening, this is getting way out of my comfort zone but I'll make a few points, some of which I suggested in some of my recent posts. I'm a reader and (slow) learner when I look through some of the highly impressive posts on the strat thread from an array of often highly knowledgeable contributors. I have noted that some of the conflicting signals have been part of the recent discussions. Until perhaps only several days ago, there were indications of warming in some layers (whether a brief early to mid-winter warming or the precursor to a sudden stratospheric warming - SSW). Then there was discussion of whether the changes both warming and cooling were propagating up or down properly through the layers. I thought that the consensus "was" that changes in the stratospheric PV were not imprinting on the tropical PV. Some commentators pointed to a strat/trop disconnect and I thought (perhaps quite incorrectly) that some of the tropical forcing might interfere with the usual processes - again way out my depth here but has this happened or changed recently? What does occur to me is that it can take some time for any reconnection to have an impact through the lower layers and down to the surface. We "had" been expecting a flatter surface pattern for the run into Christmas and on into the New Year and much of the output started to reflect that change. More recently, we have just seen some traces of moderate amplification again in the middle term (say D6 to D10+ period) and possibly beyond. Could this in part be due to some of the earlier amplification signature still embedded in the lower layers and/or could it be due to the MJO being more active than recently recognised and held back for longer in the key phases (7/8/1 or at least the 8/1). One or both of these might be sufficient to produce at least some further HLB and perhaps that build of heights to our north-east and even a Scandi HP. Yes, clutching at straws here. Many posters have been pinning their hopes on a strong warming or even a full on SSW. In a recent post I said that many cold winters have been achieved with little or no warming events. We know from past experience that predicted SSWs do not always propagate down to the surface or they do so in several stages, delaying the full impact (I'm not going to discuss wave 1 and wave 2 or multiple events). Then, even with a strong mid-winter warming or full on SSW, the associated HLB and the expulsion of Arctic cold towards the middle latitudes only sometimes falls into place to bring that cold into western Europe and the UK. The GFS model has been quite consistent with showing strat warmings towards the end of each run, then sometimes bringing that forward close to the more reliable period, then, more recently dropping the notion almost altogether and finally today's 12z runs brings it back strongly. Is this just GFS natural variabilty? I thought that the modelling of stratospheric changes was more consistent than modelling the layers nearer to the surface. It probably is but I assume that occasional unexpected upticks or coolings do crop up. Just how confident are you guys of the current signals and particularly the impacts playing out down the line. The Tropospheric PV: Now I'm much more confident with this part of my post! In my post last week (page 72 of the old thread) and in a number of other posts, I have been monitoring the state of the PV and the Arctic pressure patterns. I produced an analysis looking into just how rare split PVs are. I found several interesting papers (all the links are in that post) which demonstrate how split or at least thoroughly disrupted PVs have been becoming much more commonplace in recent winters and there is the cause/effect relationship with the reduced Arctic sea ice extent and the anomalously high sea surface temperatures there. These events displace the Arctic cold, often to North America but less frequently towards Asia and Europe and only occasionally towards the UK. As these events are seemingly becoming much more frequent (at the expense of the warming Arctic), the UK's opportunities should increase. I researched previous cold winters using the re-analysis archives and came up with some quite unexpected conclusions. Fully split PVs are actually very rare (probably modelled far more often but without actually verifying). When they do occur they hardly ever last for more than a couple of days. What happens in some winters is that the PV comes under attack from various angles over a period of time. I would not normally disagree with @Steve Murr.as he is so much more experienced than me but my research suggests that the angle of the split may not be the important part of the event. The split is the result of WWA into the Arctic. The warming from the Pacific side through Alaska as shown on quite a few models on successive runs during the last few days, typically produces a cut-off Arctic HP or on the odd one or two even a cut-off "warm Greenland HP. I agree with Steve that this angle of attack may not be the best but I also do not believe that an east-west attack would be either. The evidence (which I can easily reproduce) would suggest that any full split or partial split thoroughly disrupts the PV for a short period but it's the multiple attacks (from any angle) over a few days or several weeks, which disrupt, disorganise, displace and weaken the PV for an extended period. The impacts from this are usually delayed by a week or two. I showed this in some of our notable cold winters. The PV sometimes tries to reform (probably due to the natural seasonal climatologocial strengthening processes) but then comes under further attacks. Disrupted PVs were a lot rarer back in the 1960s and 1970s! Quite a few cold winters were achieved with quite strong PVs. Even 1962/63 only saw occasionally disrupted PVs.. Turning to this winter and the currently modelled patterns. If we can get these patterns (for only a week or so away) to verify, then we might be able to disrupt the PV sufficiently before the anticipated strengthening. This could have significant affects down the line and might really put the spanner in the works and interrupt the more natural climatological patterns that the changing background signals may now be indicating. So, I will continue to focus on the Arctic charts and monitor what is going on. This and the MJO behaviour may be at least two factors that do confound some of the expert opinion. If this winter is still on a knife edge, then perhaps I've just sharpened the knife! That's enough (or too much) from me for now!
  3. 32 points
    This isn't specifically aimed at you, but way too many are falling into the trap of expecting a silver bullet when it comes to forecasting - short or long range. The MJO is an indicator, one possible signal to use in amongst 100 others. It's never been and never will be the single answer to the weather forecast, so to say it's useless because it can be over-ridden or muted is pretty much the equivalent of saying using air pressure in forecasts is useless because you expect it to always be sunny when pressure is high. If forecasting were that simple, we'd have next to nothing to discuss in here! Weather is complex, rather than railing against the complexities and difficulties of forecasting, i'd recommend embracing it, and trying to learn why things over over-ridden, why some indicators fair well sometimes and not at others, that's the challenge and interest of it all. Failing that, there's always the moans thread
  4. 28 points
    So if your so certain of a mild and wet January, and now Glacier point also saying a similar theme yesterday, why was in only a week maybe 2 at the most that him and others were posting very good reasoned out posts all pointing to our north east in the new year, very confident forecasts explaining why it looks nearer enough a dead cert??? This happens every year and it seems peeps never learn. Signals and teleconnections seem to be as fickle as anything else imho. Can you or glacier point explain what's suddenly gone wrong on what seems to be a chatostrophic scale? Cheers
  5. 20 points
    It really is sad when a weather forum with enthusiastic folk, most wanting cold, quite often end up bickering with one another. No one, and I mean no one, person amateur or professional, is correct all the time. We all have our favourite models/outputs for short or longer term forecasting. Again NONE of them are correct all the time or as Paul commented a little way above, this forum would be not required. How about we all try to learn and respect one another, no matter who posts. If you do not agree with someone, hit the report and let the team sort it out. Respect each other. In the12-13 years I have been on here the knowledge some of those with no professional training is close to amazing in my view. I write as one of the few, I think 3 of us who post on this weather site, with Met Office professional training as well. The site is first class, okay it has imperfections but so have we all. Trying to predict the British weather is, take t from me, much much improved from 40 years ago, in any time scale, but it is still far from perfect. Just to pick up on one moan fairly regularly in here, snow in 'my' back yard. 'They' cannot get it right, model or whatever, and even at short time scales. Why? Just think of the summer when the rainfall prediction is wrong, at similar time scales, wornt time, wrong place wrong amount. In winter trying to predict will it be snow not rain needs at least 8 other predictors, with at least 5, depending on the circumstances, sometimes 7, to get the prediction corret. that is fact, please remember this when the next prediction of snow for your little area is wrong. Sorry to have gone on for so long but it does need us all to be more respectful of each other. Send a polite pm and ask that person to explain why they have a different take on yourself., Think would you say the same thing if talking face to face rather than over the web. end of sermon. You all know my hobby horse, the 500 mb anomaly charts! Oh and of course, post 144 h then compare like with like run=00 or 12 z for instance. 'night folks.
  6. 19 points
    I wonder whether my pension will be affected now that I've succumbed and gone over to the dark side.
  7. 17 points
    That’s a great shame Tamara. I find it quite disturbing how an individual who has done extensive reading, starting from nothing, has such a wealth of knowledge. And is ridiculed you can’t argue with the science, Tamara, always highlights the caveats - no wonder she doesn’t forecast what makes it all more baffling. This one-upmanship needs to stop at once, and TEITS I’ve seen very little signal of very mild SW’ly so a bit of a cherrypick 10 days out.. I’ve read it’s a bad as it gets? Hyperbole quite frankly a 3-4 day cold snap/spell is now firmly agreed upon and with that the chance of snow even possible away from usual places.
  8. 17 points
    Let me see if I can help, the cyclones that they are referring to regarding interference are those occurring in the Indian Ocean. That body of water is included in forecasting MJO phases. What we have are several cyclones moving poleward, it is unclear what amount of energy is contained in these storms, therefore difficulty in calculating effect. Initial forecasts stemmed from that enormous Pacific energy wave in mid October as shown below This in turn due to its magnitude created a split in PV via Tropospheric upwelling. It was a very large sigma event. Since then the Pacific had went dormant until now. Typhoon Tembin has now formed as forecasted. It is this typhoon that will create the modelled Pacific WAA and upcoming -AO. Models have forecasted a 2nd Pacific NW Typoon which has not materialised as yet. There will be two pulses of significant statospheric energy waves. The issue now is what magnitude of energy will they contain. At present they look to not contain enough to attain a full reversal at 60N @ 10 hPa level. Hence the readjustment of GP’s and S Murr’s thoughts. There will be cold incursions from this event but unlikely to hold unless energy contained inside these wave breaking phases is misjudged by models. Finally January is not a forgone conclusion until we reach the 20th day of the month, but the remainder of December is. The Pacific could very well go into full activation mode and create a SSW. Energy contained and storm activity are the unknowns, hence the readjustment to forecast. Personnally I’ll be looking at the next phase of Typhoon/cyclone activity after this one around the 10th Jan 2018. Then we will have a better understanding of what’s to come for the UK.
  9. 16 points
    Glad to see the moods picked up after the wake like atmosphere in the previous thread! Can you imagine spending Christmas obsessing over another possible slider low! Oh well if we must! Still a lot of uncertainty with that and also how quickly the PV ejects east from Canada. It would help if the models could squeeze out a bit more amplitude upstream to hold back that chunk of PV. Its still going to be difficult to keep the UK on the polar side of the jet with so much energy heading east but tonights outputs so far at least give some interest in the medium term.
  10. 15 points
    You miserable bunch this morning. Don't give up hope, nothing is set in stone regards early - mid January. Pret15 keeps the faith 😁
  11. 14 points
    Think the time has come to lock this one and start a fresh thread. Will post up the new one shortly. just trying to decide whether to stick to calling it model discussion or whether a change of name to the willy-waving thread may be a better fit? New thread here: https://www.netweather.tv/forum/topic/89032-model-output-discussion-heading-into-christmas/
  12. 13 points
    I sort of tend to agree with you - The problem with global teleconnections is that at best you are hoping to second guess what ‘influence’ will be in charge 10-15 days down the line. Some signals are more pronounced for NW Europe, others less so. The issue being though that nearly all cold forecasts are based on a deck of cards usually relying on either the MJO aligning into the right phase or the strat decelerating so that it either reverses or becomes a decoupled feature. The reason the cold forecasts appeared on here generally related to the fact that thus far through December the Troposphere was running the show not allowing the Downwelling strat winds to penetrate down past 10MB however in the past 5-7 days the GFS peak forecasts for the zonal wind have continually increased - & now see the crest just 2 or 3 M/S slower than the all time strat record- in this case then its total wipeout for Northern blocking- you can liken the speed to the most positive AO phases of the 90s or the December not to remember a couple of years a ago. So the expectation has changed now & the GFS 16 day ensembles all have a high peak of zonal winds for the start of Jan - however a sharp gradient of decline in Jan back to below ave levels.. so based on that week 2/3 may yield a high prospect of HLBs until then - continual battering of westerly winds will be in offering often storm force straight through the nose of the UK. No planned cold other than transient events ( although globally we could get 1 MLB ) so an outside chance of a scandi week 1 Jan but unlikely- More chance of persistent Azores high ridging East.. As Mentioned the zonal wind drops off sharp so all is not lost for Jan- it could be the reverse of December.... S
  13. 13 points
    Nevermind 80% of the mood in here, what are the models showing
  14. 13 points
  15. 12 points
    I share your frustration Tamara and cannot pick fault with anything you said in your post. I really do hope you continue to contribute on this forum as your analysis and expertise is second to none as far as I am concerned.
  16. 12 points
    Im not sure I agree with some of the posts this morning. Between Xmas and the New year its likely to be unsettled with snow on higher ground in the N. Im not sure I would refer this as stormy though just bog standard typical zonality. Worringly if you're seeking a cold spell for the New year the outlook could become even worse.as I can see pressure rising from the S with the jet taking a SW-NE trajectory. This will result in very mild temps spreading across the UK into Europe. I continue to be amazed at just how much warmth is being predicted especially for Scandi, Siberia. Only positive for the New year is the ouput can only get better because it cannot get any worse.
  17. 11 points
    Good heavens a former met office man showing a chart at 11 days and expecting it to verify. Whatever next
  18. 10 points
    For reference sake this is glaciers very good post from the 13th dec, what's changed so much since then? From what I can tell the GWO isn't reaching phase 8 like expected and this could be the biggest driver? Thanks
  19. 10 points
    Latest MJO and PNA Charts: Just a short one from me, for a change! I don't think anyone posted the recently updated MJO charts today. SOURCE: NCEP/GEFS - NOAA SITE SOURCE: http://www.njstrongweatherforum.com/t511-what-is-the-mjo-really Still a lot of uncertainty regarding whether the true MJO signature is being masked. I'm a little baffled by the different GEFS traces on the two charts (the green lines on both of them). I put the sources up but all the data comes from NOAA. The amplification in phase 1 is greater in the second chart! For the same index surely one of them must be in error? Anyway quite a mess overall. I'm sure that @nick sussex will shortly find a report from NOAA on this or at least their thoughts on the current state. SOURCE:- NOAA I copy the Dec 20th chart and it keeps reverting back to Dec19th. My comments are correct! Most of the PNA ensemble members are going positive again towards the New Year, having been briefly negative for a few days. I think that this is bang in line with part of what @Tamaraand @Catacol were predicting in their recent posts towards the end of last week.This is what is starting to show up in the model output with fairly low pressure close to the Aleutians and a strong ridge through Alaska and into the Arctic - a classic +PNA signature. Any more on this will be beyond my pay grade!
  20. 9 points
    It's always a shame that we have to remove posts. I am sure we can all have different views on the models and background signals and post them in a friendly and constructive way without the need for showing disrespect to other members.
  21. 9 points
    What's going on tonight? Can we not treat eachother with a bit of respect and discuss our shared interest in the weather in a friendly way? If some can't, then please hit the report button (you can also report pm's btw), rather than responding in here. Thanks!
  22. 9 points
    Indeed, plenty of potential for snow around from boxing day right through to late next week, good stuff from the Gfs 12z with a return of wintry weather bringing sleet, snow, frosts and ice..not just to the north either!
  23. 9 points
    Yes i was just flicking through those Frosty and some places could see a 5 day cold spell.These are 2m temperatures from the 06gefs C Scotland C.England Certainly a colder period creeping up on us between Christmas and New year.Maybe no deep freeze but as i posted yesterday the further north and higher up the better chances of seeing some snowfall. The jet coming much further south next week as the Azores high is flattened Some quite cold polar maritime air being brought further down by a couple of secondary wave depressions with -3/-5C uppers. Certainly the further south these disturbances track the more chance of snow further away from the usual favoured locations.Looking at those gef 2m temperatures daytime maxs close to freezing in C.Scotland and below 4C for C.England for 4/5 days should maintain some interest for Winter lovers.
  24. 9 points
    Today's (GFS) tropical outlook underscores why we are heading for a substantive drop in angular momentum. The only bit of forcing being 60W, lots of easterly wind addition across the Tropical Pacific and northward momentum transport. To rub this in, GFS also predicting a -ve zonal winds developing in the upper stratosphere over the Equator, which will add easterly inertia to overall angular momentum budgets. Net result is that were are heading for GWO phase 2 New Year onwards. As a basic template, low to the west, ridge to the east but not far enough west or north to bring about an easterly flow and not conducive for cold outbreaks to our east.
  25. 8 points
    The bottom of the pile CHAVgem...but worth a butchers! 😃
  26. 8 points
    Anyway, an increasingly cold, complex, unsettled spell next week as these Gfs 12z charts show which follows on nicely from the GEFS 6z mean which also indicated something similar..so, some potential for wintry surprises from around the 26th through towards the end of next week with snow, ice and frosts in the forecast during that period for much of the uk, especially further north..hopefully the models can build on this idea and extend it further!
  27. 8 points
    According to the GEFS 6z mean, next week indicates not only an unsettled spell but also a rather cold period for most of next week, cold enough for snow in places, especially further north and with elevation as well as night frosts and ice..so, potentially some wintry weather to look forward to during christmas week!
  28. 8 points
    @tamara - you shouldn’t be surprised that much of your posts are not read properly. I think the problem you had over the past few weeks was that it was ‘cold on the ground with snow’ and some posters here and the met Office were seeing cold ahead in their models etc for jan. You wanted to remain on the fence but I felt that developments in the Pacific pushed you into landing on the ‘cold side’ going forward. Whether that’s the right or wrong decision remains unknown but some are bound to sadly react badly to ‘apparently ‘having their snow taken away’ from them !
  29. 8 points
    I don't blame Tamara for giving up at all. If I was her I'd do the same. The teleconnections are what drives the Nwp. All Tamara has ever done is give her honest opinion of what they are suggesting at any given time along with what could scupper that outcome. The same as GP. This forum will be very very much the poorer without her.
  30. 8 points
    Thanks! Me, HC, Northern Strath, Northern Lights etc away out to Chanonry Point later to sacrifice Sean Batty to the snow Gods.
  31. 8 points
    An interesting comment that, re the output from Glosea, how do we know what it was suggesting as we have no sight of it? In the fairly reliable time frame, and already commented on re the 500 mb anomaly charts. They, that I can get hold of, other than NOAA, both 6-10 and 8-14, have changed emphasis somewhat but in general a strongish westerly Atlantic flow from the bottom of the main Canadian trough into the UK then on into a relatively shallow European trough, on some, into the Mediterranean. So other than the 2-3 day colder spell post Xmas, and quite probably similar developing in the 2 week period behind deepish surface lows then no major cold outbreak seems likely. beyond 2 weeks I leave to folk with a much greater understanding than I have. If I may as an old 'un, make an observation on some of the posts re deep cold, what interests me is why, with UK Met models being constant in the 2-4 month outlooks re overall temperatures, upper air patterns, is why we got such a fairly deep cold outbreak this month. Nor have I any idea why UK Met, went fairly consistently for the colder option in their 6-30 day outlooks, in spite of what their 2-4 month input must have shown. Quite intriguing but I no longer have any contacts in the senior man's area so I will probably never know! usual links below along with the ECMWF 500 mb anomaly charts via Meteo-c http://www.cpc.noaa.gov/products/predictions/610day/500mb.php http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=101&map=0&type=0&archive=0
  32. 7 points
    After much consideration, I figured it was better to keep the thread title as is, in the hope that we can just get on with chatting about our common interest in the forecasting models in a friendly and reasonable way, especially as Christmas is coming Want to have a bit of banter or a ramp and moan only loosely related to the models? The banter thread is for you: https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/ Want to talk about the weather in your part of the country? The regional threads are the place for you: https://www.netweather.tv/forum/forum/142-regional-discussions/ Want to view the model outputs? You can get all the major ones here on Netweather: GFS GEFS Ensembles ECMWF ECMWF EPS NetWx-SR NetWx-MR Met-Office Fax GEM GFS Hourly Snow forecast and precip type Model Comparison Global Jet Stream Stratosphere Merry Christmas
  33. 7 points
    NOAA have just issued their January forecast and seem uncertain because of the MJO with apparently a conflict between the longer range modelling and the lagged response to the MJO. The main section important for us in Europe: THE MJO WAS RELATIVELY INACTIVE IN NOVEMBER BEFORE BECOMING MORE ACTIVE DURING DECEMBER OVER THE WESTERN PACIFIC. MJO FORECASTS INDICATE A SIGNAL MOVING ACROSS THE AMERICAS AND EMERGING OVER THE INDIAN OCEAN BY EARLY JANUARY 2018. LAGGED COMPOSITES BASED ON AN MJO OVER THE INDIAN OCEAN WOULD FAVOR RIDGING AND WARMTH OVER THE EASTERN CONUS WITH TROUGHING AND COLDER TEMPERATURES OVER THE WESTERN CONUS, AT ODDS WITH TRENDS AND MOST MODEL OUTLOOKS FOR JANUARY, SO THE MJO IS A POTENTIAL SOURCE OF UNCERTAINTY DURING THE OUTLOOK PERIOD. THE ARCTIC OSCILLATION (AO) IS FORECAST TO BE NEGATIVE AT THE BEGINNING OF JANUARY. THAT WOULD IMPLY A COLDER SOLUTION FROM THE NORTHERN PLAINS TO THE GREAT LAKES AND SOUTHEAST. THE STATUS OF THE AO BEYOND 15 DAYS IS UNCERTAIN, SO THE AO WILL LIKELY BE MORE OF A FACTOR IN THE END-OF-MONTH UPDATE TO THIS OUTLOOK. That MJO induced upstream set up would normally see high pressure east USA, troughing in the Atlantic to the west of the UK, higher pressure to the ne however whats uncertain is whether we'll see a more digging amplified trough set up to the west which would help disrupt energy se and perhaps bring something colder from the east/ne. So as you can see from NOAA they really aren't sure whats going to happen so its a case of seeing how things unfold as we head into January.
  34. 7 points
    Afternoon Some quite varied interpretations of the model output so I thought I’d summarise my interpretation of the output in the simplest way I can to aid new members. A few days ago I mentioned the possibility of a split in the polar vortex from the high pressure cell over NW Canada. Indeed that now looks to be happening with this synoptic picture at T96. The PV is split like a knife through hot butter. Now this is no guarantee of a sustained cold spell over our part of the world, indeed it depends on whether the blocking can sustain itself and where the lobes of the polar vortex fall. Here is the synoptic picture another 2 days later, unfortunately two things go wrong: - Although pressure is encouraged to build over Greenland, the mild air doesn’t reach this area. It is a cold based high and therefore pressure only really builds over Greenland. - The cold shot of air heading into Canada moves ESE instead of S due to the high pressure sinking to the south-east USA. As a result, the lobe of the polar vortex over Russia moves into the arctic and the Atlantic fires up due to the cold air leaving NE Canada. The result is that the vortex is fusing back together and our chance to build some good northern blocking in our part of the world is gone. Where does this leave our longer term prospects? Well the Atlantic will probably be quite active due to all that cold air over the NE of Canada spilling out into the ocean, so it may be a little while till we get another blocked pattern. I wouldn’t get too despondent though unless we start seeing height rises to our south and south east. A possibility but quite a few ensemble members don’t build heights there. With that in mind we may get transient northerlies or ridges of high pressure coming in. Something may pop up at short notice. So fingers crossed we don’t get the height rises to our immediate S/SE, no white flag waving from me yet. December 2015 this is not, it ain't ideal but that’s the British climate for you!
  35. 7 points
    I would say large parts of the UK have snow next week on many of the runs including the most recent GFS 06z
  36. 7 points
    Barring a few GEFS which survive the zonal onslaught the SS Save Christmas has now sent out an SOS! The surface temps though dont look that mild , looking at De Bilt and given the set up which would mean northern parts of the UK would be colder there still could be some snow during Christmas week. There are still differences in the medium term between the big 3 with how low pressure exits the ne USA and the speed of that . So not great this morning but the jet still remains on a more southerly track upto T240 hrs and there’s always a chance of a surprise with that.
  37. 7 points
    Today Not much change from yesterday with the high pressure remaining to the south much of England and Wales and N. Ireland will be mild and murky with the odd spot of rain in the latter and one or two other places in the north. Much brighter in Scotland. Tomorrow a similar picture except light rain may well encroach western coastal areas. By 12 Saturday the high cell is coming under pressure from the east bound energy and a shallow wave depression is just north of Scotland with the front trailing away to the south west and rain already affecting the west coast of Scotland. Further south a brisk westerly is in place but still dry and mild. Over the next 48 hours the front and rain move slowly south as far as N. Ireland and the north of England but to the west it is still under pressure from the eastbound energy and by 12 Xmas Day is orientated over Ireland and a wave has formed on it and popped north east to be over southern Scotland. This could well produce some snow in central and northern Scotland. All the while England and Wales remaining dry in the brisk, quite mild, westerly which gradually backs.south westerly. This really heralds the start of a much more unsettled period as the front and rain traverse the the UK overnight, there could well be some more snow in Scotland and perhaps northern hills, before clearing the south east early Tuesday. But this is a very brief respite as the next low tracks quickly in from the NNW on a very strong low level jet and is 987mb over the Midlands by 1800 bringing a fair bit of rain the the south. Once more perhaps some snow on the northern edge of the front but best left to nearer the time. The low quickly moves away to the east but meanwhile another intense depression in mid Atlantic has undergone explosive cyclogenesis courtesy of 160kt jet and is situated north west of Ireland with associated front just encroaching the south west by 06 on Wednesday. Fortunately the low is filling by this stage but it tracks into the Irish Sea during the day and this could bring severe gales the the SW and Wales and perhaps a fair amount of snow in Scotland The low quickly moves east initiating a transient cool northerly flow over the UK but out in the Atlantic the 'bombing' scenario is being repeated, albeit the low taking a different track, and by Friday more fronts are approaching the south west. The GEFS anomaly this morning is not adverse to this scenario.
  38. 7 points
    We only have to look roughly 5 days back when folk were on the cusp of putting out the white flag. Euro slug appeared to be in full control things have changed considerably. Cumbria can do quite well away with these set ups away from the coast inland with some good elevation. GEFS shows lows taking a more southerly track this is a good thing to see, we need further corrections for more than usual suspects to see some wintry weather. Half baked? Nothing is in the flaming oven yet. D16 GEFS mean definitely looks wintry for Scotland. I’d be quite happy if I was up there!
  39. 7 points
    I have to say, HC, that I read Ruzzi’s post as purely about challenging people to be inclusive in their MO discussion, not with any sense of there being anti-English content. In years gone by I used to post on TWO but one of the reasons I moved over here to this thread was simply that there was more local input about the weather where I live (and of course the banter is of a high quality ). This thread is inclusive, it’s friendly and it’s not too precious about the weather. Other aspects of life (politics, religion, etc.) are bound to come out in conversation now and again but I think the contributors to this thread do an admirable job of keeping it light, informative and entertaining....while still stamping their personality on their posts. Since it’s the season of goodwill, I’d like to thank you people for making this thread such a good read.
  40. 6 points
    i have never seen a scandi high in the eps ..... actually possibly never ever thinking about it ! Sceuro ridge last year but never a true cut off upper ridge over scandi. Not never. Im with mwb - the extended eps are are tremendous aid. The fact tha we now see the Icelandic clusters make them even more useful. From my memory they have flipped twice this last eight weeks - one occasion when they dropped a euro trough/low anomoly as they approached day 10 and the other when they found a one approaching day 12. Both times they were right to flip as the solution then verified.
  41. 6 points
    I think they have been very good, actually. All through November they churned out a majority of blocked runs to the north or west, and what did we get? Blocked to north and west. They went AWOL for a couple of days at the end of November where there forecasted a return to average conditions too soon, but shortly after they correctly nailed on a renewal of north Atlantic amplification for the 16th-17th December extremely consistently from two weeks out and correctly called the end of the cold period shortly after, again from two weeks out. Since about the 12th December, they have been forecasting strong troughing close to the UK between Christmas and New Year with just enough potential in the pattern for a marginal snow event and, guess what, it is now the 21st December, 9 days on and they are still forecasting this for the same period. Actually just recalling what has happened, they've been better than good in the D10-D15 period - they've been brilliant. I've followed them avidly since the start of November and they've rarely led me down the garden path in either direction.
  42. 6 points
    I've seen worse and of course a lot better but whilst the jet is tracking south theres always the chance of a surprise or two. In terms of any slider low still up in the air. These are the ingredients we have to work from so its unrealistic to expect something outlandish to pop up given the models are generally agreed on the overall pattern. However the exact track of the jet could be modelled further south or north nearer the time. A suggestion at day ten on the ECM that we might see more amplitude towards the east USA. Regarding the MJO still uncertainty as to whether this scoots into the COD and straight out into phase 2 or whether this goes into phase 1 then phase 2. Overall its not the Christmas weather many might have hoped for but it is what it is. We rarely see the Christmas cards scenes at this time of year but at least we don't have a raging Bartlett high.
  43. 6 points
    Periods of really wetting drizzly rain today fields are just like bogs again.Ground conditions in these last few months are really as bad as I have ever seen them with just odd days dry enough to spread dung,plough or lift turnips. Will be glad to see the back of this year as it feels its been a constant battle with the weather since July with only my interest in Netweather helping us to get on the ground just when conditions were right as they could be. Currently wet and 6c May I take this opportunity to wish everyone on the Scottish thread a very Merry Christmas
  44. 6 points
    Let's hope the Ecm builds on the Gfs idea and brings us another taste of winter between xmas and new year!..we will soon find out
  45. 6 points
    Just looking at the 500hPa temperatures we can see the warmer air getting right into the centre of the Polar Vortex (552 thicknesses) and this pushes out the cold upper air south around the edges thus the Atlantic jet heads south of the Uk whilst this effect lasts. With time without that strong Pacific ridging we can see on this run how the PV gradually cools and contracts( lower thicknesses) and the jet starts to move back north with sub-tropical ridging moving north with it. Not expecting the latter chart to verify like that of course but just to illustrate another way of seeing the varying strength and depth of the pv and how it expands/fragments and then reforms/contracts with the changes of temperature.This even on a modest scale shows how some cold air can move south with very modest polar heights-just the odd wedge! Of course for a more notable cold outbreak we require more than what is showing currently but never the less some interest next week,especially for the favoured areas and certainly colder for most.Worth watching out for the track of those wave depressions that run along the jet across our locale after Christmas.
  46. 6 points
    With the jet temporarily diverted south by the upper trough the front with little developing waves stalls over the UK. Possible white out in the Pennines ? .
  47. 6 points
    Lots of negativity this morning. It’s not a poor outlook it’s just average IMO. Not sure how anyone can say it’s a poor for the next 10-15 days if you like wintry weather. Large parts of the UK will see snow next week, perhaps some are being very IMBY ?
  48. 6 points
    Those 10 hPa zonal mean charts are very sensitive to the movement of the vortex at the moment - the big rise occurs as it drifts across the pole having been displaced for some time; there's little or no strengthening of the circulation itself being indicated. Only longer-range hints from GFS of further stratospheric warming of any note to come though. How much and how soon varies with reach run depending on how the Arctic blocking aligns itself and to what extent it connects with mid-high latitude features. Seemingly a bit of a jackpot situation there. Somehow posted this early when pressing 'enter'? That's not normal! Here we can see the observed atmospheric state still edging toward the transitory state that could lead onto a renewed rise, but also clearly evident is the point at which GEFS decays out the Pacific MJO activity and the atmospheric state snaps back into a La Nina-like state. Shows just how close we've come; it would not have taken a lot more MJO amplification or duration to achieve the upward kick scenario with downstream amplification in useful places for us. It has been tense to watch us come closer and closer, only now reaching a point where a shortfall looks the more likely outcome. The subsequent IO emergence of convective activity is probably being overdone by GEFS though, hence the GLAAM drop as well, so beyond a week's range I'm inclined to treat it's output with even more suspicion that usual. Best chance we have later next week and a bit beyond is if the stratospheric forcing can tone down the westerlies sufficiently for the jet to dig further S into Europe, but the modelling currently favours this to happen in the middle of the N. Atlantic, which has the opposite effect on temperatures to what is desired by most on here. After that, we're back to trying to modify the pattern toward allowing a well-placed Scandi high, as GP has been alluding to as the best bet for good results next month. Unless, that is, a major stratospheric warming comes about after all.
  49. 6 points
    Noooooooo Fundamental points of model discussion Not even 1/3rd of the way through winter so all to play for More runs need More amplification needed GFS trending cold will do so again and ECM will come on board. If it doesn't its a crap model Look to T240 for things of beauty but they never verify of course Never look out of the window keep your eyes down for GFS12z and GFS 18z In May a full easterly will come along
  50. 6 points
    Its coming ' i tell you not ' its coming ... I feel it and i smell it ' after the 27th of this Month its going to get COLD i tell yah i tell yah ' you never Listen though ' i feel it in me bones and i am 78 and still smoke a splifter . Have a spliffy Crimbo to you all x