OldMetMan

Point taken Phil, sorry I tend to get carried away!

Thanks Linarite, I appreciate your comments, but my main point is how little we truly know of our climate history given its massive length, and our assumptions are based on such little data. We cannot know for sure that CO2 has never, well at least for a long time, been this high, nor can we know how the atmosphere managed to rectify the situation in the past, which given the time of 3 million years you gave, must have somehow happened (not sure how that number was arrived at anyway!). If an imbalance occurs of whatever kind, the atmosphere, being a self-regulating system, will somehow balance it. Correct me if I am wrong, but the climate change advocates seem to think we are heading to a point of no return, if CO2 continues to be produced at, or above current levels. Maybe it does indeed happen in some cases, that a tipping point is reached beyond which there is no going back. One naturally wonders what happened on Mars for example, as it clearly had a very different atmosphere in the past, judging from the evidence for there being water. But we have no way of knowing for sure how these changes occur. One explanation could be a comet or asteroid strike for example. Unless you believe that Mars was once populated by intelligent life, then some other process must be responsible for the change. I agree that true scientists are open minded and only too ready to accept new ideas, based on new evidence. Yet, when it comes to climate change, it has, to my mind, become almost a religion. The scandalous manipulation of data that occurred several years ago among certain climate scientists suggests that the belief had to be upheld at all costs, even if it meant fiddling the data. The reason could be politics, who knows. All the most original scientific thinkers challenged beliefs, challenged dogma and were punished for it. Yet so many new ideas came from their work, that better fit the facts and the evidence. The scientists who pontificate on the perils of climate change when the subject comes into media prominence from time to time( or their mouthpieces) are the ones who seem to think they are beyond reproach. To me, they are not true to scientific principals and it is them I object to. My perception is that the weather HAS changed, even in the 40+ years I have been interested in it. Yet, who's to say that more extreme weather is in fact THE norm. As I said, we are only comparing these events to a miniscule period of weather records, it seems more dramatic and significant for that very reason. Time will tell!

With the extraordinary weather pattern this winter, and especially with the growth in flooding in recent days and weeks, once again the subject of "climate change" is thrust into the headlines, not least because those advocating it came out with an amount of "I told you so" when the question of adequate flood defences was debated, and apparently their advice wasn't heeded. My own view is that we, as a species, are having little significant impact on the evolution of our climate. I say this for a number of reasons, in particular because of the arrogance and dogmatism of certain scientific voices, but mainly because, in the context of the extremely long and complicated history of weather on this planet, it makes no sense at all to me that we can make any assumptions about the future course of our climate, based on what is a microscopically tiny fraction of time when records have been kept, relative to the immense length of Earth's history. Even if ice core samples are included for the purpose of making these determinations, it is still an extremely small set of data. This was particularly brought home to me when I once attempted an Open University course on Climate Change. Not only were the reasons given for how CO2 was affecting our atmosphere unclear and not very convincing, but these vague reasons were then used to project up to 50 years ahead, to produce the most ludicrous predictions. After valiant attempts to take the entire course seriously, I gave up because it was basically stupid! It offended all my years of weather study and insulted my intelligence with its preposterous conclusions. So, any debate or argument that seeks to blame so-called climate change for any particular weather event or pattern, makes me bristle, especially when it is expressed in such a way by anyone who believes they are beyond all criticism. In the vast history of the planet, every imaginable weather pattern must have happened at some time, plus many unimaginable events that we are clueless about. It hardly needs saying but the winter we have been enduring could have happened hundreds or thousands of times in the past, possibly many times worse. We simply do not know and have no way of knowing. Extreme climate variations in the past have been deduced from evidence left behind, such as the Ice Ages, there are theories yes, but unless it happens at a time when we can measure it, we can only speculate at best as to the reason(s). As climate understanding has advanced, a great many indicators, signals, cycles have been discovered, and these are often cited as being reasons for this or that happening. Yet there is still a tendency, I think, to use these in isolation. The atmosphere is a system, an immensely complicated system, and as such, it could be argued that every single event within that system, has an effect elsewhere within it, either in space or time, or both. Models have become extremely sophisticated in recent years, yet for all their cleverness, their use beyond a few days is mostly limited. I accept that never before have so many factors, variables been included in model calculations, but it would be next to impossible to factor in everything. Variations in the Sun's behaviour, not just basic changes in the amount of actual heat we receive from it, but all the many other forms of electromagnetic radiation it affects us with, all this has to influence not only present conditions but future evolutions. I applaud the accuracy achieved in short-term forecasts as a great achievement. This advance has saved countless lives. I love watching how models take a particular situation and then develop it, first one way and then another, and often marvel at how this development can so quickly change. So I have respect for the scientific method as used in this way. Having said at the outset that I do not agree with the assertions of man-made climate change, and then apparently contradicting this by saying that every aspect of a system has some effect of the rest of it, I should make it clear that I think by that reasoning, we must be changing the system somewhat, but I cannot accept that we are doing so to the extent and necessarily in the way the climate change advocates claim. Every natural system has balancing mechanisms that always attempt to restore equilibrium. The climate is such, and although the sheer length of these balancing factors may be over millennia, the fact that we cannot perceive them, does not mean they do not exist. Cycles of climate patterns of this kind must surely exist, or else the atmosphere as we know it would simply have gone, or changed in such a way as to extinguish all life. So, in other words, the nature of climate IS change, but not in the sense it is used these days. Our ruthlessly scientific approach has, in my opinion, robbed us of a more natural relationship with our planet, because we have been unable to see how changing one facet of this system can have many unexpected effects elsewhere. In other words, we are not in tune with our world and have destroyed so much in our ignorance. Our ancestors possessed this relationship, of this I am sure, and were able to work with, rather than against, the planet. We need to find a modern-day equivalent of this. There, that has gotten that off my chest! Learn about our amazing climate and form your own conclusions. Don't let the dogmatists beat you into submission!

Tamara, I really enjoy reading your well-considered and well-written posts, and through many years of weather study, whilst not having that much technical knowledge myself, I do (sometimes) have a "nose" for weather pattern evolution, admittedly based on past experience, which as you rightly say, will never exactly repeat itself. But I do recognise the persistence factor as a fascinating and intriguing weather pattern phenomenon, having witnessed many such long lasting patterns in the past. I will admit that I do not understand to any degree the mechanisms that lead to any long lasting persistence of a particular pattern and your explanation of this winter's remarkable features makes sense, even with my limited understanding. I have no real scientific evidence to back this, but I do believe that an imminent pattern change is about to occur, based on no more than what my experience tells me and current model trends. I know I have done this throughout the winter at intervals and have been confounded by the persistence you have talked about. I could well be proven wrong again this time, who knows, but, experience of many years' chart studying, using what we currently have synoptically, and what the main models depict for near-term trends, on that basis I see this conclusion of a change happening as plausible. None of the above is meant as criticism of your post. I like your style, to put it succinctly! You have laid out your argument extremely well. Plus I do not claim to have any special power to predict the future, simply because of the length of time I have had an interest in the weather. I know I have more of a tendency to predict change, rather than persistence, just my own predilection I guess. I think my point here is that sometimes reasons cannot be clearly given as to why the weather will behave in a certain way other than what is basically a hunch. Doesn't make it right or wrong, just different, and at the risk of sounding patronising, I detect an element of this is in what you have written. Please keep on writing your interesting posts. There is much there for all of us to learn from.

More definite signs of pressure building across the UK from the models so far today, which is encouraging. Not for the first time in recent weeks, the GFS has HP to the NE in the long term, but as ever, one cannot put much faith in that. Having said that, though, the current pattern, especially at 500mb, does, I think, favour a pattern change, as I mentioned yesterday, and the GFS is a reasonable evolution from where we are right now. Historically, the final LP in a sequence of this kind, tends to be one of the worst, if not THE worst, but it can be followed by a shift in the upper flow, not least because that storm itself distorts the 500mb pattern by itself which has knock-on effects to the overall flow pattern. So, the extensive upper vortex nearby, once more re-invigorated by tomorrow's LP, could encourage heights to build, first to our west, then followed by some progression of the pattern eastwards, so we could end up with an upper ridge close by, building N or NE. In support of this idea, there are also more noticeable signs of upstream troughing over the E of N America, again something to encourage heights to rise further E. Let's face it, the relentless succession of LPs, continuing as it has since before Christmas, barely missing a beat, can only last while the baroclinic zone over NE Canada persists. Yes, the PV still has a foothold in that region, but, if nothing else, the fact we are moving towards Spring, has to have some mitigating effect as temperature gradients reduce, albeit slowly. Tomorrow's LP could indeed be nasty. Certainly on a par with yesterday's. But it really could be the LAST one of that intensity for the winter. I did say "could" because this season has seen unprecedented patterns, so who can say for sure. See if the later model runs continue the HP theme - I really hope so, for everyone's sake.

Thanks Northernlights. The snow sounds incredible! It does still beg the question of what on earth will spring and summer be like? These extremes are bound to have long-term effects throughout the year, not to mention the fact that, sooner or later, there will be a balancing. I hope you don't have to tolerate a wet, cold summer!

My apologies, Northernlights, I should have qualified that statement with "here in the south" or such like. I realise the rainfall anomaly in parts of Scotland is heading in the opposite direction than here in the south. But I do think it's easier for your part of the world to make up a shortfall in rainfall than it is here in the south to lose the effects of so much rainfall.

All credit to the models regarding today's storm and picking it up when they did. I have done a quick browse around the forums and so far have seen no reference to the fact that today's LP would seem to have had a sting jet associated with it. Hence the Met Office Red Alert. Certainly the satellite presentation earlier gave every impression that this was indeed happening. Anyway, the models, this coming weekend's LP does indeed look to be the last major storm for the time being. As ever, the GFS appears to exaggerate intensities, but after today, who can say for sure! Beyond that, weakening flow - gradually - but stronger references from the main models from time to time of more of an anticyclonic trend, although the GFS reverts to its usual zonality on the 12Z. I tend to think we may yet see an easterly, perhaps not much of one, but quite honestly, we just need a break from this interminable rain, so any pressure build would be welcome. We could see more noticeable 500mb height rises spreading from the SW to support HP build up to the NE and N, if some troughing occurs off the US east coast. There is some support from the lesser models for this idea. I think this weekend could see the turning point for a change in pattern so it will be interesting to see model trends at that time. One word I don't expect to hear this year is "drought"!

I don't think there's an easy answer to why so many intense LPs. As I posted yesterday, today's low is the 7th to have a pressure below 950mb - uncommon is putting it mildly. Personally, apart from the enormous temperature gradient you referred to, I think it's the location and persistence of the 500mb vortex and the trajectory of the jet that have brought so many LPS further S than usual and those two factors have been positioned such as to cause the LPs to reach maximum intensity near our shores. But it's mostly energy, the huge temperature gradients have made cyclogenesis more intense. I don't think SSTs are that important when it comes to the development of anything other than tropical systems and hurricanes. Given the havoc this relentless storminess has caused, there will no doubt be many scientific inquiries into the whys and wherefors. That'll make interesting reading as and when!

Searching today for any further hints of an end to our Atlantic battering, but only minimal signs, mostly from the GFS with suggestion of a pressure rise across the south of the country. Tamara's earlier post explained the current position and trends very nicely (thanks Tamara!) in her excellent post so there's not much I feel I could add to that. One factor which is somewhat odd and has certainly done much to exacerbate the rainfall, especially along coastal counties, although not entirely, is the enhanced convection we have been seeing between frontal zones. Especially lately, the LPs have been embedded in pretty cold air, not that unusual for February, but convection has been widespread in the Channel for a long time, an effect that usually wears off as we head out of winter, as the sea temps drop. Clearly, those sea temps have remained high relative to the unstable air moving over it, hence the endless bands of showers that have been forming. Certainly in my location, rainfall from these has been considerable. As Tamara mentioned, the extreme temperature gradient over the Canadian NE is, and has been, exceptional and continues to promote vigorous cyclogenesis, all of which heads our way. Hints from the GFS for this process to stop with the development of a deeper more slow-moving LP off the N American E coast, would be welcome, assuming it is capable of pushing some mid-Atlantic ridging and HP ahead of it. I still think it possible to see heights rising to our N as the elongated upper trough spread out across the Atlantic starts to weaken - if it ever gets the chance and is not continually renewed with all the LP development. If the heights do rise, there may yet be a chance for some late winter blocking to our N but don't hold your breath! I'd be interested to see what the mean surface and 500mb charts will end up looking like at the end of this winter. A pronounced vortex near or over the UK at both levels seems likely, with a corresponding considerable negative anomaly, so maybe if that is the case, it bodes well for HP in Spring and Summer. I think we all deserve that!

I witnessed 1963 and it was certainly the most remarkable winter I have ever experienced. But as Bluearmy correctly points out, this is certainly on course to be THE wettest winter on record, such events are as rare as the '63 winter was. With at least another week of prolonged rain shown by the models to be affecting the worst affected areas in S England, maybe longer, it could turn 2014 into one of the wettest years on record. All this to me begs the question, what on earth will this summer be like?! This amount of ground water is going to take a LONG time to dry out!

This run of extraordinary wet weather shows no real sign of stopping, with perhaps hints of a quieter spell arriving in the long term from the GFS and GEM, with perhaps a more significant drop in temperature according to the GFS. The only sign of real blocking is way west over the NE Pacific, which shows no sign of causing any amplification downstream at 500mb. With the strongest flow at that level fairly well south over the Atlantic, eventually as the strength of the flow lessens, we may see some building of heights to our N, but not before several more vigorous LPs cross over or near to the UK. One promising sign apart from that, is the hint of mid-Atlantic HP late in the period from the GFS at times, which may at long last spell the end of this interminable run of LPs. The cold air over Europe for a while has been well and truly swept way, so I would suggest any cold will reach us from the N, if and when it does come. In 47 years of studying synoptic charts, I don't think I have ever seen so many intense LPs (950mb or less) over or near to the UK. By my reckoning, the present system is the SEVENTH such LP this winter. The LP on 23rd December was an unprecedented 926mb, truly remarkable. Longer term model trends in recent days have occasionally shown higher pressure over the S of the country, which is really what we so desperately need. This winter certainly is one for the record books.

I've taken a step back for a while, as model output has been showing the same relentless onslaught of Atlantic systems, with little to suggest it would change any time soon. The sliding SE LP that's happening now was something I envisaged would happen quite a while back, but it's a pretty lame affair it has to be said, and thereafter it's back to business as usual. The power of the Atlantic jet has been something else this winter so far, indeed I have seriously underestimated its persistence. However, today's output, notably the ECM and GEM, have shown HP sticking around N Europe for much longer than shown hitherto, which suggests to me that maybe, just maybe, the extensive cold air over much of E Europe will find its way here - maybe within 2 weeks. There are features on the 500mb flow I find interesting: There are 2 very persistent upper highs, one NE of Scandinavia, the other over NW Canada. The former has been around for quite some time and if anything it has intensified. In my experience, such high-latitude HPs do tend to retrogress, which as this time of year would have obvious consequences - surface HP moving W with it and attendant E/NE flow. I think the models have been seriously underestimating the depth - and persistence - of the cold air over Europe. But I was intrigued by the 12Z ECM, which long-term is showing a repeat performance of now, with LP sliding away SE, but again quickly followed by yet another intense Atlantic LP, but this time having the effect of putting the main 500mb vorticity much further W than it's been for ages. This suggests the possibility that, even though throughout the forecast period, HP is still too far E, as we move into February, the retrogression I mentioned may begin, IF the European cold air isn't seriously over-run in the short to mid-term. There has been much speculation over on the Stratosphere thread about when, or if indeed at all, a warming will occur, and it's effect on zonality further down on the atmosphere. I accept that there is a link between these SSWs and a switch to colder, blocked conditions, but I do not think it's the whole story, that is, it doesn't mean if no SSW happens, we can't get cold conditions. But I maintain that just as SSWs can happen very suddenly and dramatically, that an equivalent turnaround can occur in the troposphere, with blocking happening quite suddenly, or repositioning of existing blocks. I think we need to see just how much "give" there is in the cold block in the coming days. If it holds fast, then I wouldn't be surprised to see a weakening of Atlantic flow and HP to the N and NE next month. All is not lost cold lovers!

I'm finding it hard to put much faith in the mid- to long-term model trends at the moment as there have been quite a variety of solutions, and changes of direction within different models. So, what we have now is an amplified 500mb flow all the way from the E Pacific but the long-waves are not well placed from the cold point of view. We have the axis of the upper low near the UK, stubbornly refusing to either disrupt or move away. Just across the North Sea, maddeningly close, the cold air is stuck, unable to make any westward extension, as LPs continue to feed SE into the upper low over us. As I see it, towards the end of this week, with a more vigorous LP heading NE across the Atlantic, although the models simply push it eastwards, there remains a possibility, albeit a slight one, of this LP pushing a warm ridge NE ahead of it towards Iceland, finally inducing the upper trough over us to disrupt, whilst at the same time, letting the cold air to the E break through westwards. The ridge meanwhile, would link to the existing upper high NW of Scandinavia. Unlikely but possible, check out December 1962 for a great example of this happening. Longer term, there have been some interesting signals for a cold February, not least of which is the intense polar HP that's been showing up on the models, notably the ECM, in recent days. I find it hard to accept that we will merely see a resumption of intense Atlantic systems again after the briefest of lulls. The GFS has been showing a more NW-SE LP movement from time to time, which always raises the possibility of a northerly breakthrough, but none of the longer term model solutions looks convincing, given where we are now. If we do indeed see a return to mobility, then once again we need to watch out for cold air pooling to the N or NE as we approach February. I remain convinced that winter is far from over!

Yes you're right TT, January 1947 had a lot of HP to the NE - for most of the first half of the month in fact - but too far off at the time to bring in the cold air properly. In 1962, the 500mb flow was quite amplified in December, but HP was absent from Scandinavia until around 17th. However, the switchover, when it did happen, did so in a few days quite spectacularly. I think the main point I am making here is that the pooling of cold air over NW Europe, for several days can quite rapidly lead to a significant rise in surface pressure, and this is happening now, albeit not that intense a cold pool. But there is an upper high to support it, which is encouraging.

I agree, I kept copies of all the N Hemisphere 500mb charts from that time! It was awesome! Two of the most famous cold spells began pretty abruptly; December 1962 and January 1947, but on those occasions, everything worked out perfectly - not something that happens very often! We too often are right on the edge of the cold, with it maddeningly close across the Channel, or lurking just to the north. I am still amazed at the strength of the mid-level flow across the Atlantic that we've been having. But given the intensity of the polar vortex, as evidenced by the extraordinary cold in the States, it's hardly surprising we've had such a powerful jet. Stratospheric temps have been remarkable too - minus 90C at one point last month at 30mb! However, things across the US are a bit more temperate, one can only hope the jet either weakens considerably or changes trajectory - to our south!

No doubt many would disagree, but I am finding current model output fascinating, as it continues to tease with hints of a colder continental flow. Yes, it is also frustrating, looking for some development that might clinch the deal, so to speak, but so far, nothing is there that qualifies, I think. However, there are still some promising signs, if not within the current model timeframe, but for later this winter. But for now, I am still intrigued by the changes occurring at 500mb, especially upstream: : First that mid-Pacific troughing is still amplifying - a little - whilst the E Pacific ridge looks a lot stronger than it did. Downstream, the trough over the E US/Canada has certainly amplified a good bit. But I am still watching that persistent upper high off NW Scandinavia, plus the ridge way off to the SW of it. As it looks now, it would seem to take very little to join up these two features, to form a really solid SW/NE block across the W Atlantic, whilst our own upper vortex to the W sinks away SE. This, in my view, would certainly allow the cold air floodgates to open, as troughing extends SW out of N Europe. Yet again, we have that fearsome jet to take into account, plus the overall hemispheric flow which remains pretty potent. Just a bit more troughing off the N American E coast and a slow down in the flow, that to my mind would be a clincher. After the preceding weeks, it seems as if any chance of that happening is remote, in the model timeframe at least. But not impossible I would say. The model output has continued to be vague as to what will happen to our 500mb vortex, and what will follow. Inevitably, the GFS launches straight back into zonality, as it likes to, but both the GEM, the ECM and even the UKMet have toyed with at least a temporary disruption of the zonal flow in recent days. Nevertheless, I find it encouraging to note the changes we already have in terms of how the upper flow is amplifying. Whether that will translate into the scenario I described above is highly debatable, but, like I said, not impossible. I would suggest anyone interested to go and look at the buildup to the famous cold spell in November/December 2010, to see a classic example of how a real block develops - and I think that occasion IS classic. Whatever happens this time around, I believe that the mere presence of a Scandinavian HP in January, with that persistent upper high accompanying it, is an excellent sign for its recurrence either later this month or early next. Meanwhile, I shall continue to watch how the models grapple with this scenario, with great interest. So much potential here- let's see what happens!

Just a PS before I go to my bed! The 120H FAX has a classic look of HP pushing everything W and SW and the LP track going further S. And that's the FAX chart saying this! We'll see if it continues tomorrow.

Cheer up, we're not even half-way through January yet! As I am always saying, blocking to the NE can sometimes develop very quickly and catch the models out. Keep watching and you may be pleasantly surprised!

I wasn't going to post today until I saw the 12Z ECM - back to easterlies again. On closer inspection, some subtle upstream developments hint at a possible upper flow amplification - the factor I mentioned the other day as being lacking and therefore not favouring any significant blocking. Over the central/E Pacific, there are definite signs of a deeper 500mb vortex developing, in what has been a pretty flat flow. This is what we need! That, with a stronger ridge off the N America W coast, would I think ripple downstream and amplify the Atlantic upper vortex, sending LPs further S. The upper high to our N is still there, and on watching the IR satellite imagery N of Iceland, it is clear there is a significant westward flow, pushing frontal zones W and a little S of W, suggesting to me that the GFS has overdone it again with the persistent zonality. The GEM, and also the UKMet to an extent, show more of a stalemate situation, with the GEM especially having slack LP in our vicinity. This is a very hard one to call, with so many mixed messages. If anything significant is really going to happen with blocking, the upstream pattern is crucial. Little or no amplification then I think little likelihood of blocking just yet. If nothing develops this time around, I feel sure February will provide some interest for cold lovers.

Thanks John, this is a very helpful and informative description. Anomaly charts are not something I refer to as a matter of course, although I can clearly see the benefits and what you explain makes much sense. With me, I tend to look at the overall current pattern and for features that stand out, based on what I have seen from historically similar situations, and compare to the model output to see if it looks realistic. Not exactly scientific I readily admit! You make some very valid points on model reliability beyond a few days. I never cease to be amazed at how quickly the output can change, that together with the remarkable differences in output between the different models themselves sometimes. These last few weeks have surprised even me in terms of the intensity of both the jet and attendant LPs. In 47 years, I don't ever recall seeing a 926mb LP that close to mainland Britain, as happened last month. Although I have no scientific rationales for saying this, it inclines me to think the pendulum will swing to the other extreme before the winter's out. Maybe it's just my own perception, but it seems as if extreme weather is becoming more common. But that's another subject altogether! Thanks again for taking the trouble to explain anomaly charts, I shall refer back to your postt in future.

Just some early thoughts on the fickleness of the models! In only a few days, we have seen a pretty good consensus on a blocking easterly, degenerate into a bit of a shambles, with the Atlantic flow ultimately winning again. However, what strikes me most is that, even though we have the right combination of upper air factors already forming - upper high to the N, disrupting trough to the W, very cold air continuing to feed SW over Scandinavia - what seems to be lacking is a real and significant amplification of the upper flow, from N America all across to Europe. Having said that, the GFS so far today, shows a very interesting potential development when it gets to T120, with a respectable HP over Scandinavia, and LP lining up over and to our W, giving every impression that the upper trough associated with it is going to disrupt, as earlier charts in this run have been predicting to keep on happening prior to that point. This is, I think, the pivotal time where the pattern could shift dramatically in favour of some real blocking plus cold continental flow. But, as I say, not enough upper flow amplification showing for anything persistent - not yet at least. I still think it will, but the upstream flow especially needs to change in that regard. As I said the other day, modelling this kind of development is not easy and changes can and do happen very quickly sometimes, catching the models off guard. Later runs may give us a clearer picture, but it sure looks interesting!

Almost to be expected, backtracking from the models today, with even the GEM producing only a weakish cyclonic easterly. I have to say that the evolution depicted by the GFS in particular next week does not, to my mind, follow from where we are now. Yes, I know of the problems in modelling developing blocking patterns of this kind, but, as I mentioned yesterday, there are some significant signals for a block developing at the moment. The 500mb pattern is revealing: 1. We already have a 500mb high cell to the N, admittedly not very strong. 2. Trough disruption has already occurred to our W and, as I said yesterday, the main vortex action is now over the Atlantic and gives every indication, by its orientation and location, that it will move and extend SE under the high cell. There are greater heights E of the disrupted trough that could quite easily link to the high cell, Apart from that, the most potent signal is the cold air pooling and starting to spread SW over Scandinavia. Very low thickness values are involved here, plenty cold enough to encourage significant pressure rises. As is quite often the case, this could easily turn into the forecaster's nightmare scenario - Atlantic versus Continental - and at this stage it's impossible to tell if this is likely, even harder to know which would win. But I still favour the blocking developing. Future runs will most likely flip-flop for some time yet but I would add that, historically, major blocking can develop very quickly, in a couple of days even, in this situation and I doubt the models could accurately pick up on that more than a few days ahead. I said yesterday not to underestimate the Atlantic jet but we are seriously overdue a lull and a weakening of the Atlantic flow, quite apart from what I said above. This is going to be a fascinating few days to see how the models handle the situation.

At long last, we seem to be seeing some consensus amongst the models for HP to develop to the NE, with some pretty cold air spreading into the UK. The main question of course is, how long will it last? That's assuming it does actually materialise! The GFS as you might expect is returning us to mobile conditions quite quickly. On the other hand, the GEM keeps us in the E flow right to the end of its current run. The ECM does rather similarly. What signals are there at present to suggest a more sustained blocking situation? The 500mb flow has some clues I think: The much publicised (and misrepresented by the media) polar vortex over the E of N America is heading further E, whilst the upper trough to our immediate W has extended and is disrupting. Further W, much more energy is heading in off the E Pacific, to steadily erode the cold block, and helping to keep the main upper vortex further E. This suggests to me rising heights in the E Atlantic and northwards. Cold air is heading S into Scandinavia. All these factors do, I think, support a blocking pattern. However, after the remarkable mobility of recent weeks, I don't think it wise to underestimate the reassertion of the jet, such as shown by the GFS, although I think it unlikely we will get storminess on a scale of these last few weeks, if that is what does happen. On the other hand, the overall look of the Atlantic flow at the moment does have a much weaker look in the shorter term. Also, as I posted last time, such a ferocious jet and attendant LPs do not continue indefinitely, even this time of year. Stratospheric developments, incidentally, are showing mixed signals I think, although a couple of minor warmings have already happened, and a third appears to be underway at the very highest level. Not enough - yet - to disrupt the PV. So, at the moment, a welcome break from this incessant rain seems likely soon, with a good possibility of cold continental air early next week. The ECM seems to have picked up on the blocking trend most consistently in recent days, so I am inclined to go along with its future runs, as opposed to the GFS. I can almost see the next headlines: "After the floods, now comes the Big Freeze".

Morning folks, and a Happy New Year to you all. Although we are still very much in the throes of a relentless Atlantic progressive flow, a couple of things in recent runs of both the GFS and ECM have caught my attention. But first, today, I notice that we once again have a small 500mb high stationed near Iceland. Admittedly, it's a weak affair, but I think it has significance: The persistent upper vortex responsible for this prolonged unsettled spell, and the many shortwave features running around it, seems to be displacing further S, along with a gradual shift of the jet likewise. The feature on the model runs I mentioned is the intermittent appearance of HP near Scandinavia, plus in recent GFS runs, cold air has been getting dragged S to the NE of Scandinavia. There has been signs of a weakening in the flow late in the period too, which suggests an opportunity soon for finally some northerly blocking to set itself up. I think the remarkable strength of the jet these past weeks has precluded any possibility of this, even keeping the European HP well SE, but in my experience, these hyper-active phases can only ever last a limited time, before they fizzle out and I suspect that time is soon. The temperature gradient across the US is evening out a bit more which also suggests a weakening flow. As an aside, the stratospheric thread is rife with speculation, based largely on model output, of a sudden warming arriving, which if it happens, could have major implications for blocking and Atlantic flow reduction, but it's by no means a done deal. However, for now, looking at regular tropospheric model output, there is definitely a changing trend to quieter conditions later this month, and if the GFS continues to show cold air pooling to our NE, maybe some blocking and cold E/NE winds, once this jet burns itself out and the Atlantic vortex finally disrupts and moves away. If such a trend is real, then I would expect the model output to pick it up more consistently over the coming days - we'll see!