OldMetMan

Yes indeed! I can recall many winters where HP was close but not close enough to give us the full benefit of the continental flow. Ideally, we need blocking to the N as well, but one step at a time! Later runs might give us a clue as to whether this is a viable option. I shall comment in more detail later if the models warrant it!

My feelings exactly Chiono. I was waiting to see what later runs come up with, but current runs do show the Russian HP a little closer. Once any LP over Scandinavia finally fills, now that is the time when HP can form with a vengeance. I have seen such on a number of occasions in the past. Zonal W to NW flows don't often stay as such for long, usually the cold air will win but occasionally, as hinted by the last GFS, there's a pressure build in our area as the pattern amplifies in mid-Atlantic. Cue the (sometimes quite rapid) emergence of the Scandinavian HP, pushing westwards!

Thank you Mark. I doubt if there is much to support any such development in the current output. I have certainly seen similar happening on past occasions but, as they say, each situation is unique in some way. Anyway, here's hoping!

With the major Atlantic storm in the process of brewing up, it's interesting to see how the models are handling developments following on from that. It is tempting to think that such a major upper trough as will develop with this massive low will cause some sort of knock-on effect in the amplitude of the flow, at least in our part of the hemisphere (I have said as much in previous posts) yet there is currently no such indication in model output. Given the time it took the models to firm up this new storm, I might be forgiven for thinking that future upstream developments might be a bit suspect. Here's the GFS at T144: By this stage, there is still a substantial upper trough associated with the deep low, but upstream there seems to be little energy emerging out of the US/Canada. So on the face of it, there seems little to stop the progression of long waves as depicted by the models, well the GFS specifically, However, I am intrigued by the presence of a small but persistent upper high cell over Greenland, that has been there for a couple of days. It's like it's waiting to link up with its larger cousin ridge to the S, and complete an upper ridge block in the mid/western Atlantic. Such a ridge seems possible with the trough further E. Even now, the 500mb pattern, as shown above, shows troughing SE out of the US, so what I am suggesting is the possibility of a more amplified flow within a week, with the major vortex associated with this new storm actually hanging about longer than shown, maybe filling and slowly sinking SE. While this is going on, it means the presence of the cold air over us lasting much longer, maybe with small disturbances joining it from the NW. Within such an air mass, of course, there would exist a snow risk almost anywhere. I say all the above because a) I trust the GFS in this situation less than I usually do and b) the T144+ development just looks wrong to me. I shall give it a few days to see of there are any substantial changes in model output but for now, I am thinking that the cold air might be around longer than is currently expected.

I guess it hardly needs saying, but the 06Z GFS portrays a serious snow situation, especially for the N Midlands northwards, perhaps even further south as the 528dm thickness value plunges down across the whole country. The development of short-wave features looks, at this stage, highly plausible, given the proximity of the powerful jet and very strong baroclinic zone. A lot needs to happen first of course but it would be fascinating if such a pattern or something like it, were to happen. Later runs should prove interesting.

What a difference a day makes! The main models are offering up some very tasty possibilities to come next week. It's quite extraordinary how today all the energy that was shown to be following on from the major storm next week, has suddenly faded away. The aforementioned storm now seems consolidated in the model output, so we are left with a variety of solutions as to what follows it. I mentioned yesterday how storms of this size and intensity can significantly alter the upper flow and this would appear to account for the model differences today. So we have several possibilities here: 1. As per the 12Z GFS, NW turning N with the distinct possibility of polar lows/troughs forming as the cold air floods S 2. A briefer northerly, followed by a fast-moving shortwave running SE, in turn followed by a renewed burst of cold air. 3. A flatter pattern, as was shown yesterday, with further disturbances running W to E but no significant cold air breakthrough or 500mb amplification. It's tempting to think that if the two major models, GFS and to a degree, the ECM are roughly in agreement, then that is what will happen. Still too far off to know with any certainty but if only from an historical perspective, in such situations, the cold air usually wins. If the 500mb flow does weaken over E Canada and US as shown, then I would think cold is inevitable. Being this early in the winter, the sea warmth could create some fascinating situations as the cold air runs over it, with significant snowfall in some places. Let's see how subsequent runs pick up this trend but right now, it sure looks hopeful.

Interesting changes in model output in recent days, in particular with regard to the predicted development of a major storm system next week. From being a smaller short-wave development, particularly from the GFS, it is now shown as a very intense LP, pushing some very wet and windy weather our way. Although it's not a done deal at this time distance, given the VERY strong temperature gradient over the E of Canada in a few days, it seems quite likely. The other models are gradually coming into line with this projection but developments beyond the middle of next week are pretty varied, and thus best ignored I think. What always occurs to me in these situations is the possibility of a major distortion of the upper flow developing in response to such a powerful system, enough to have a knock-on effect downstream. We still have a very slack 500mb flow over and to the E of us, which I find rather odd because it's been that way for quite a while, so I am inclined to think that will soon become better defined. There has been a persistent cold pool over S Europe and the European/Asian HP is still there, waiting in the wings, but we need a significant amplification of the upper flow for that to have any hope of influencing our weather. A more noticeable upper ridge is needed, to the N. Not much sign of that happening yet. Maybe we could see the LP sliding away SE into S Europe, that is hinted at by the GEM model, and to some extent by the ECM, opening the door to pressure rises to the N. Lots of "ifs" and "buts" admittedly! However, over so many years of studying charts, I have learned to never say never, as sudden change can and does occur in what would appear to be quite normal synoptic situations. So, by way of illustration, and (hopefully) with the mods' indulgence, here are 2 charts of the pattern just days before the outbreak of some record cold. Obviously, the whole hemispheric pattern needs to support such a radical switch in pattern, but - it can happen! I remain convinced that, while it won't necessarily be on the scale of the winters above, significant cold will be a feature of this winter, maybe starting this month, maybe early January. The clues will be there when the time comes.

Some interesting remarks spotted this morning in the NWS forecast discussion. It's not exactly clear to me what the implications are for the circulation pattern here, but it looks significant: "...AND WHAT IS BECOMING MORE EVIDENT...IS THE LATITUDE FOR THE WAVE TRAIN MIGRATION. TO ME---IT'S DISPLACED SOUTH OF A 'TYPICAL' LATE-AUTUMN LATITUDE---CLOSER TO 40N-42N THAN 47N-48N ALONG 140W LONGITUDE. IF THE ECENS MEAN IS ANY INDICATION OF WHAT CAN BE EXPECTED...ITS 1/12Z DETERMINISTIC RUN AND 250MB JET FORECAST SHOULD BE NOTED FROM THE SOUTH COAST OF JAPAN TO 40N 140W BY THE END OF DAY 7. A SECOND FEATURE OF THE PACIFIC---IS THE EARLY EMERGENCE OF THE SUBTROPICAL JET...AND ACTIVE OVER NORTHERN MEXICO SO EARLY IN THE LOW-SUN HALF OF THE YEAR. THIS IS USUALLY MORE A LATE JANUARY THROUGH FEBRUARY OBSERVANCE. AND WITH THE DETERMINISTIC GUIDANCE SUGGESTING NOTABLE INCREASES IN THE PACIFIC BRANCH OF A JET NEAR 25N...IN CLOSE PROXIMITY TO HAWAI'I NORTHEASTWARD INTO NORTHERN MEXICO BY THE END OF DAY 7...AM THINKING THIS MEDIUM RANGE FORECAST PERIOD IS TRYING TO TELL US SOMETHING---AND PERHAPS THE PATTERN IS CHANGING IN EARNEST...WITH THE DOWNSTREAM EJECTION OF THE CLOSED LOW OFF THE CALIFORNIA COAST SETTING THINGS INTO MOTION." I mentioned the unusual appearance of what seems to be some sort of sub-tropical feature by the GFS for this coming weekend, and with each run, the GFS has maintained the formation of this significant feature but has changed it's development. The latest run shows it becoming a major storm system next week. There has been a great deal of change within the longer term trends of the model output, even more than usual it seems to me and I can't shake the feeling that something important is going to happen within the next couple of weeks. What NWS are saying about the sub-tropical jet suggests to me a weakening of the northern stream, and subsequent reduction of zonal activity at our latitude. Others more knowledgeable about such things are welcome to comment. The model output is, in my view, even more unreliable in the longer term than is usually the case and I am struggling to see any consistent trend emerging from recent runs of all the major outputs. The storm system I mentioned above, well the projected development just looks plain wrong to me. As I mentioned in my last post, it looks more likely to introduce a greater amplification to the flow upstream and may be what the NWS is getting at. For now, things look pretty "normal" but by the end of the week, I suggest we may see the first signs of a major pattern disruption and change towards a colder and more blocked one. I shall have to mull this over in the coming days and come up with a less vague prediction than this! But I will say that when it comes to cold and snow, be careful what you wish for....!

Thank you kindly EML Network. I could just be talking a load of rubbish (not for the first time!) but I tend to trust my instincts when I spot something unusual or in some way significant in the model runs. You make some valid comments in your post re the movement of HP over the next week or so with cold fronts in between. I think we tend to forget sometimes that a great part of our day-to-day weather is pretty ordinary, but with, it seems, increasing incidence of more extreme conditions. Half the fun of model watching is being able to detect real signs of such events in advance as well as significant pattern changes, which the models don't often do in the >5 day range. But it's all good fun!

Although the recent model runs have produced some tantalising possibilities of a northerly blast in the coming days, there has been no consistent trend in that direction. However, the current setup has some intriguing potential which is worth mentioning. Before I do though, I must say that this last week the models over overestimated the eastward progression of Atlantic systems, with the European HP holding its ground quite well. The upper vortex to our south will, while it lasts, inevitably lead to some form of upper ridge to the W, and the models take this and predict some transient HP for much of the coming week, which is fair enough. However, 2 things: there is currently a significant influx of very cold air heading in N Russia which would, I think, favour strengthening HP NE of Scandinavia. The models appear to brush this feature aside. Second, over several runs, the GFS has been developing what appears to be some sort of sub-tropical low towards next weekend moving N from N of the Caribbean, which if it were true, would be most unusual this time of year. But crucially, if it happened, a lot of very warm air would be pushed NW towards the US/Canada east coast and there would be, I think, a distinct possibility of a major upper vortex developing which would amplify the flow. As a result downstream, this could allow significant troughing into our area from the NW, perhaps feeding into what's left of the upper low to the S, which would pull in significantly colder air from the N. Fanciful speculation? Maybe, but as I mentioned on Friday, such troughing as I discuss has certainly come about in the past on a number of occasions. It just needs some decent upstream amplification to occur. The model output beyond the end of this week looks sillier than usual so I am inclined to ignore it completely. As I see it, even right now, there are still significant features in the upper and surface flow to suggest a much colder trend later in December. Where that cold comes from remains to be seen. I am keeping a close eye on 500mb developments in the coming days for a clearer idea of what's to come.

No problem Knocker. It's a very tough call at the moment really. The only other thing that has caught my attention today is the tendency for a more amplified hemispheric 500mb pattern. But that in itself only hints at possible future blocking. So much depends on the long wave locations. But it sure looks a lot different from this time last year!

HP has been present to the NE and E since the middle of the month. The upper pattern is, as I mentioned, admittedly somewhat ill-defined over N Europe, but currently Atlantic systems are sliding away SE as a result of the high, so I think that constitutes a block. Such patterns of HP to the NE do have a tendency to recur. Some models have been showing the Azores HP actually linking NE to Scandinavia, but there is too much day-to-day variation in that scenario to put much faith in that happening. I think the next few days should give us a clearer idea of whether blocking as I mentioned will re-develop.

In the midst of some fairly mediocre model runs today, the GEM midnight run stands out as the most interesting. Given the fact that this model is quite often out on its own, too much credibility shouldn't be given it at this stage. But the evolution shown is certainly possible. Historically, with HP near or to the W of the UK, change often occurs in this way with an amplifying upper trough extending SE from the NW as shown. But it does depend on there being sufficient amplification upstream too, else the mobility and transient HP as shown on the other models is a more likely outcome. Nevertheless, this development is certainly worth watching. Note the extreme HP over Greenland especially. Whilst the current setup with HP blocking to the NE is interesting in terms of its likely recurrence as we head into winter proper, what's needed first is a significant influx of polar continental air over Europe, rather than this murky tropical continental stuff we currently have. On that score, I am intrigued by the 500mb flow across Europe and much of Asia in that it is a fairly flat arrangement, apart from a weakish upper low and I can't help but feel that this state has already lasted too long and something more definite needs to happen. I mentioned before the possibility of a more pronounced upper high to the N & NW which if it happens, would certainly favour what the GEM says as the upper high retrogresses westward. All in all, despite the current mostly HP trend shown by the majority of models, this scenario does, I think, have serious potential for some notable cold within the next 2 to 3 weeks, either from the N or from the E.

I've been following model developments these past few days and it has been interesting to see the presence of blocking HP to our NE quite regularly run to run. Although the GFS, in longer term, is being relentlessly mobile, as it often is, we are still seeing repeated trough disruption over or to the W of us, as has been happening and as is being shown to continue for a while yet. The N hemisphere 500mb "shape" doesn't look particularly amplified at present, but there is still the rather weak Rex block over N Russia, which has been quite persistent - hence the trough disruption. It looks to me that we will see a large, slow-moving vortex to the W and SW before long, which might enable a more pronounced upper ridge downstream. I think in 2 or 3 weeks would could be looking at a very different overall pattern, with the Atlantic mobility heading SE into the Med, and significant HP to the NE pulling in some real coldness. I just have a feeling about this - not exactly scientific!

Thank you Tamara, I would like to thank you for your eloquent, well-reasoned and informative posts. You add great insight to this forum.

Hi folks, time for me to chime in as we are approaching winter proper. One thing I have noticed in recent days is the similarity of the upper air pattern to late November 2010 and we all know what happened after that! All the longer term models I have looked at today are showing blocking to the E and NE (well the GFS does its usual return to zonality long-term) but I think there is a certain ambivalence shown as to the future of this blocking in terms of where exactly it will be located. Another interesting sign for more pronounced blocking is the presence of a significantly amplifying upper trough over the E US, such as hasn't really been seen this winter so far. Also, the weakish upper high to the N and NE would, I think, become stronger with that trough amplifying. Given that we have had a series of disrupting upper troughs over us for a while, I think it reasonable to assume the large scale pattern will retrogress, and this seems to be the model trend. The main question in my mind is whether the upper high/ridge will strengthen and shift to the NW of us to a position S of Greenland. That would favour a NE flow in our locality, which is the coldest direction this early in the winter. I've a feeling this coming winter will be very different from last and I shall keep a close watch on the longer term trends of the models, as well as what's happening in the stratosphere. Could be interesting times ahead once we lose this rather boring E/SE drift off the Continent.

Here is what the Met O said on 7th regarding the uncertainty over the future of Bertha: "The transition from a tropical to an extra-tropical feature is a particularly hard one to forecast with confidence, so there are still some differences in the location and intensity of the resulting depression, which is expected to pass over, or close to, the UK from early on Sunday." However, this is what the NHC in Florida said in its last advisory on Bertha on Wednesday 6th at 11am: "Satellite images indicate that Bertha has become associated with afrontal system and has acquired extratropical characteristics. Thelow-level center is devoid of deep convection and is on the cold airside of a frontal cloud band or trough extending from Nova Scotiasouthwestward to the Bahamas. In addition, there is a strongwesterly upper-level jet over the system.The low is moving toward the northeast or 055 degrees at 27 knotssteered by the mid-latitude westerlies. Most of the global modelskeep the post-tropical cyclone moving rapidly northeastward andthen eastward over the North Atlantic." So it seems the transition from tropical to extra-tropical had already occurred by the time the Met O decided to discuss it on their website. It looks to me like the NHC's forecasters had a better handle on Bertha's future than our own forecasters did, yet both presumably had access to the same data. It'll be interesting to see how the forecast develops over today and tomorrow

Hi everyone, just dropping in after a long break. I hope the variable summer weather (especially the thunderstorms) has kept everyone entertained. I must confess that I am finding all the forecast dithering over the fate of ex-hurricane Bertha rather baffling. Admittedly, forecasting potential storm tracks this time of year is somewhat difficult, owing to the lower jet speed. Yet, as I see it, the case for Bertha turning into quite a potent storm looks quite compelling. I notice that for at least 5 days, the GFS has consistently shown Bertha developing into an intense LP, keeping fairly close to the same track from run to run. That in itself suggests it is entirely possible that the track will be across England as it has been showing. That apart, the NHC, even when Bertha was still tropical, showed the expected track to be straight out into the Atlantic, south of 50N. The storm is currently very well placed to engage the jet off the E coast of Canada. There is always an abundance of very warm, moist air associated with these ex- tropical storms, which by itself increases the temperature gradient and favours substantial deepening. I think the ambivalence concerns whether Bertha will actually engage the jet or not. Well, as I said, the GFS hasn't had any doubts on that score. The latest MetO thinking gives a 60% probability of Bertha crossing S England, heading NE. Herein lies the greatest risk, I think, with a strong possibility of the storm developing a very tight gradient on its W and SW flank, as pressure rises sharply behind it. Not to mention copious amounts of rainfall, although with the likely speed of the system, that seems to preclude any significant rainfall issues. August storms of this kind are not that unusual, although this is pretty early in the month for one. Personally, I feel this storm could be quite notable, with the wind being the most potentially damaging feature. I shall watch with great interest how the situation develops and how the forecasts change in the next couple of days.

In terms of records being broken, that by itself suggests longer cycles of change for that to even happen, such as this winter and another example, the extreme cold of December 2010.This is why I think we can learn much from these long patterns when it comes to model output. Maybe other factors can be brought into model development, ones that were either previously unknown or not given enough emphasis, who knows!But certainly in my experience, I have never seen so many extremes in such a relatively short space of time as has happened in recent years.

Hi all, Now that winter is officially over (although I doubt if it is in practice!), looking back through it shows, quite apart from the massive rainfall totals, an almost complete absence of high pressure anywhere near us from about mid-December onwards. According to most of the model output these last few days, we seem set for a return of the absent HP, with any differences in model output mostly of a timing nature. So after these endlessly cyclonic weeks, at last something to help dry things out! It's interesting thinking back how at various times the models tried to build pressure over or near us yet it never happened. We were often surprised at the incredible persistence of the run of LPs. What comes into my mind is that, for now at least, we seem to be in a pattern of longer cycles of weather type, weeks or months rather than days at a time. If this is so, perhaps the pendulum will swing the complete opposite way, and bring lengthy HP spells in Spring and Summer. It would be nice to think so. We had a fair amount of anticyclonic weather through early autumn, although not as persistent as the opposite has been this winter. My impression of model output is that, by and large, it has been pretty good at predicting the continuing cyclonic pattern, apart from the failed HP trends I mentioned above. But I am wondering if this extraordinary winter will provide new data to incorporate into model calculations. I am sure there will be a great deal of research into the mechanisms at work and maybe some new discoveries that could advance the science of weather prediction. Meanwhile, one thing is for sure, if we do indeed get more HP than LP in the coming weeks, it is going to take a very long time to bring ground water levels back to more like they should be and that by itself could affect the kind of temperatures we get going into summer; that plus the sea temps being kept well up due to the almost complete lack of any cold. I really do hope the model trends are right for the coming days. I think most of us just want to put this horrible winter behind us now and look forward to some Spring warmth and dryness!

In my experience, the position of the jet has always been variable, and has also stayed in the same relative position for extended periods, hence the extreme summers/winters there have been. They are talking about it as if it were a new phenomenon, when it isn't. It just happens that the location this winter has been to such as to bring LPs on a more southerly path, just as it did in summer 2007, when all the floods occurred then. You're right next winter could be completely different. Who knows also whether the jet may shift again this year before it warms up too much. The US forecast guidance today is talking about a marked change from a zonal to a highly amplified pattern across the US in the next few days - that's bound to affect us downstream. If there is one thing I have learned over so many years of watching the weather - never say never!

Thanks Mushymanrob, I just get p'd off with the same old stuff being trotted out. I feel better for writing that!

I suspect that they are saving that actual headline to apply to the Summer, only in place of "in sixty years" it'll be "ever", knowing them. I like that they take an interest in the weather, but it would be nice to see, now and then, something they write which is even remotely near the facts. Exaggeration doesn't really cover it!

A few glimmers of hope today for something drier in the coming days. After today's LP, the next system coming in from the W has been shown consistently as a filling system by the models, becoming absorbed into the main LP to the N and NE. As I see it, we have a small window of opportunity the middle of next week with a chance for HP to nose down from the N and NW. This ties in with what John was saying about anomalies, and also with the fact that we currently have a small 500mb high cell over SE Greenland. It all depends on whether the LP in the W Atlantic mid-week next week develops and turns N rather than NE and some 500mb troughing occurs behind it. This might be enough to increase heights ahead of it to support rising pressure. The 120H UKMet chart today shows this possibility: The other models are kind of vague at this point, showing no real amplification that might help, but it might become clearer in future runs today. As I recall, the GFS had suggested this on and off for some days, but, as ever, high uncertainty remains. I remain convinced that a pattern change is coming, slowly to be sure, but on its way. Even the possibility of a pressure rise over the Continent would be welcome right now, as shown by the ECM. Anything to stop this never-ending rain!