OldMetMan

Thanks Chionomaniac, I notice on the Japanese stratosphere monitoring site, some significant temperature rises over Asia at the 10mb level, and to a lesser extent at 30mb. From reading the posts, and with my limited understanding, there appears to be a growing consensus over the possibility of sudden warming but some uncertainty as to whether it will be sufficient to disrupt the polar vortex.It will be very interesting to see if this trend continues or accelerates. I know that these warmings can proceed with remarkable speed sometimes, from what I have read, but given the extreme cold that has been present at these levels recently perhaps the increase is not as important as it looks, maybe more a case of temperatures rising to more normal levels. But the 1mb temperature is very striking, so who knows!

I'm a complete newcomer to this, but the latest 1MB chart shows temperatures of 27C over Asia. This seems an incredibly high temperature for that high in the atmosphere, could someone more knowledgeable tell me if it is as remarkable as it looks, or do these sort of temperatures occur commonly? Thanks.

Thanks winterof79! You too.

Some subtle hints of a New Year pattern change, but it's going to take its time. First, the 500mb flow is fascinating: The most remarkable feature is the sheer strength of the flow across the Atlantic around the base of the upper low heading towards us, quite rare to see such intensity I think. There are changes upstream as the E Pacific ridge fades and once again Pacific systems are heading SE to re-invigorate the upper trough over E USA/Canada. This suggests, on the face of it, more of the same with the jet continuing to propagate in our direction, with the relentless LPs coming with it. However, note the 500mb high near the Pole that's been there for a few days. It may not look much but if it sticks around, once the pressure field across the Atlantic starts to slacken off, it may just hint at HP building. I mentioned this possibility before, but the ferocity of the jet has obliterated any chance of any blocking pattern forming, let alone persisting so far. But in my experience at least, stormy mobile patterns of this intensity cannot sustain themselves for THAT long. So I am sticking with the story I have been telling for a while now, of LP and the upper vortex sinking slowly S and an accompanying flow of colder air, gradually followed by rising pressure to the N and NE. Well, my very best wishes to you all for a good Christmas and my great thanks for so many of you who have added "Like" to my posts, it is most kind and I appreciate it a lot. I hope Santa brings you everything you want! OMM

I've been following the models, especially the GFS for the last few days, watching for any hints of a change to the zonal pattern and, although there is little to suggest that at this stage, the theme the models seem to keep returning to is to have a deep and complex LP area in our vicinity around New Year with quite a pronounced upper vortex with it. The latest GFS even pulls down some cold air - temporarily - before resuming the unsettled pattern, which is not unusual for the GFS to do. What I find interesting in the latest runs is, firstly the vicious shortwave features shown earlier on the GFS for around Christmas. The 12Z has eased back and personally I wouldn't put any faith in what the GFS says in that regard this far away, but having said that, given the massively strong jet and baroclinic zone that is spawning these LPs, I wouldn't be surprised to see at least one intense LP during the period in question. If, nearer the time, the UKMet picks up on this possibility, now THAT I would certainly take more notice of. Secondly, the large upper vortex I mentioned above, if it has time to hang around before a new, strong jet begins again out of the US, might bring about some ridging to its E and the chance of the high-latitude blocking I am always talking about, especially if the cold air to our NE has time to dig S before the jet sweeps it away again. The GEM model in particular keeps on hinting at this, with pressure builds over the Pole and Greenland, as well as N Europe/Asia from time to time. However, the pattern upstream doesn't offer much encouragement of anything cold that'll last more than a day or two. If the Atlantic vortex does slow down near or to our N, the pattern upstream may start to reflect this with more ridging over the E of N America, and a more noticeable amplification in the flow. As it is, the strength of the flow heading from there right now is very clear in the current chart: In the meantime, some wild and windy conditions until New Year, not untypical for this time of year, but keep an eye on this slowing- down vortex, it might hold the key to a change in January.

Many thanks Chionomaniac. I'm beginning to understand the process a bit better and what to look for in the charts.From what you say, it seems the PV will hold its ground for much of the winter, with any disruption unlikely until Spring at the earliest. Not good news for lovers of cold weather! Thanks again, OMM

Hi all, I am a complete novice when it comes to the science of the stratosphere but I am trying to learn the basics at least! I study the various indicators for changes in that part of the atmosphere, and one chart caught my eye this morning, and I was wondering if one or more of the knowledgeable posters could explain the significance, if there is any, of what this chart shows: These are the 10mb temperature changes over the last week and my attention was drawn to the dark red area over Asia which, according to my interpretation of the chart legend, would seem to be showing a substantial temperature rise in the latest chart of the series. I am beginning to grasp the whole idea of stratospheric warming and its impact on the normal cyclonic, circumpolar W-E flow in the troposphere, so is the apparent temperature increase indicative of such a warming? Excuse my ignorance! I doubt if I shall ever understand the physics involved here but I am finding this whole area of meteorology quite fascinating. Any comments would be greatly appreciated!

The GFS today is swinging wildly today, although there is some consistency in the early runs in the last few days, and up to the medium-term, the GFS and other models maintain the zonal unsettled theme, with just daily variations in the timing and intensity of LPs. There are few clues currently as to if and when the unsettled theme will change but the consistency in GFS runs I mentioned I suppose could be called a trend, with gradual falling heights and associated falling pressure over much of the central and eastern Atlantic, as well as falling thickness values and lower temperatures. Further W over N America, there are signs of a more amplified although probably quite transient amplification of the flow. The upper vortex over the E of the US seems vigorous enough to maybe push some ridging up ahead of it in the W Atlantic, which might favour the GFS's idea of falling heights further E in the longer term. The only other configuration I find promising at this stage is there is a certain amount of blocking over the N Pacific as well as quite a respectable upper ridge over the E Pacific, which may, I think, be indicative of a longer term tendency towards more widespread blocking around the hemisphere. But that is a long way off, with so much energy pushing systems towards the UK, continuing unsettled and most probably stormy conditions seem to be the story for some time yet. Indeed, with the very deep LPs we're seeing at the moment, we may well see potentially damaging winds at some point in the next 2 weeks or so. One last thought: continental HP over N Europe/Asia keeps appearing from time to time on the longer term model runs, so once again I am still inclined to believe in the possibility of northern blocking, as I keep on saying! A few more runs from the GFS are needed to see if the trend, such as it is for falling heights, is maintained.

Thank you Cloud 10!

Today's GFS has some bewildering changes, particularly the 12Z but before I go on, here's part of the NWS discussion earlier today: "A RESHUFFLING OF THE UPPER PATTERN ACROSS THE PACIFIC/NORTH AMERICA IS IN ORDER OVER THE NEXT WEEK AS THE HIGH LATITUDE VORTEX REORGANIZES OVER THE CANADIAN ARCHIPELAGO. CONCURRENTLY... RIDGING THE PACIFIC SHOULD BUILD ALONG 150W WHICH FAVORS WESTERN CONUS TROUGHING AND EVENTUALLY EASTERN CONUS RIDGING. A RATHER QUIET START EARLY NEXT WEEK SHOULD STEADILY BECOME MORE ACTIVE BY WEEK'S END." It's clear from today's 500mb chart how the main vortex is transferring from NE Canada to the Atlantic, hence the prolonged run of deep lows forecast to be heading our way in the next 10 days. Fair enough, but today's early GFS runs showed a slow down in cyclonic development with a very large upper vortex over much of the N Atlantic and progressively colder air coming our way from the NW. Further W, HP was shown to be predominating over much of the E of North America, which would seem to match the eastern ridging mentioned in the above guidance. So far, so good, but then the 12Z GFS goes a bit mad, generating yet another massive, deep low pushing back the SW flow over us once again. This doesn't look right to me and certainly doesn't appear to have much relation to earlier runs. Obviously, I shouldn't pay much heed to these variations in end of run developments but it seemed to me that the GFS had been following quite a logical progression earlier then suddenly overturns it. I see that the 18Z is more in keeping with earlier runs! However, all the GFS weirdness apart, other models seem to be settling on this major N Atlantic vortex at the end of their respective runs, and a more direct, colder polar maritime flow as mentioned above. If this verifies, then, as the earlier GFS showed, there would be a very large and broad area of LP gradually sinking S and SE and filling, whilst new cyclogenesis originating off the Eastern Seaboard and heading our way would temporarily stop, maybe with a deeper, more slow-moving LP forming there and helping to build HP north of it. Note too that over N Europe and Asia HP is shown gradually pushing NW towards the Pole. As I mentioned before, I still think that a HP build-up to our N could happen long term. I am encouraged that the NWS guidance is recognising that, in the sort- to medium term at least, the upper flow is changing. We most likely might have to wait until New Year, but I will be interested to see if the GFS in particular revisits the earlier development in future runs. Northerly blocking or not, the prospect of much colder (thickness less than 528) air coming our way seems more likely by Christmas or right after, with wintry precipitation accompanying it.

No great changes model-wise today, still the relentless procession of LPs heading our way for some time. The main issues will be determining timing, strength and track of the lows. The GFS seems to have backtracked somewhat by keeping the jet further N than earlier, but I am intrigued by the end of the run, as far away as it is: This is the kind of development I was talking about yesterday, for when the jet finally runs out of steam and the last LP in the train heads SE as the upper vortex extends and disrupts. Further west, HP begins to take over on the E of N America, this is the kind of configuration that could favour high-latitude blocking. It will be interesting to see if the 18Z maintains this idea. Of course, as its so far off, that could quite easily disappear next run! Meanwhile, some lively Atlantic weather for a couple of weeks, possibly some noteworthy gales in the N and W particularly. With the strength of this jet and the baroclinic zone associated with it, some ferocious LPs seem possible.

Thank you Tamara, that's much appreciated.Let's see what later runs today come up with. OMM

On the face of it, model output in general favours continuing SW flow, vigorous LP activity over much of the Atlantic, and HP near enough to the SE to minimise any rainfall there. However, there are some interesting hints of changes for later in the month: 1. The US/Canada upper vortex is gradually pushing E, whilst the jet is moving progressively further S. 2. Although much of Europe is shown by the models to be HP dominated for the foreseeable future, an interesting feature appeared on the 12Z GEM with HP building over the Pole. 3. When LP activity starts to decrease in the longer-term, with a very large upper vortex likely covering much of the central and eastern Atlantic, as I mentioned the other day, it sometimes happens as the main LP fills and any frontal activity is travelling E on a low latitude, pressure starts to build to our N, as suggested by the latest GEM. 4. The GFS is showing the polar vortex WAY south at the end of the run, so, should that prove to be the case, intense HP seems likely to form over much of Canada and the N USA. This does I think, favour keeping the polar front and jet a good way S. So, as I see it, 2 weeks of mobile and mostly mild weather then a gradual shift to northerly blocking taking place, and we know what that could mean! The position and strength of the jet will need watching through. If it stays well south then when the final LP of the current stream heads E to the S of the UK, it might pull the old Atlantic LP SE with it, with LP transferring to the Mediterranean, followed by N or NE winds over us. A long way off yet, yes, but it remains a possibility I think.

Nah, I wouldn't know where to start!The 18z seems to be continuing the 12z trend, with LP taking a more S track. In the past, from about this point in winter, I always keep an eye on cooling trends over N Russia, to see if increasing surface pressures are in evidence, in association with intensifying cold. The GFS seems to think this is likely to happen, albeit a long way off. On its own, it's not I think that significant. All too often, intense HP in that region just stays there with little influence on our weather. But occasionally, the cold air spreads further SW and W as the surface pressure builds with it, as had already been mentioned regarding what happened in Dec 1962. The key item of interest right now as I see it is that deep cold over the US, pretty early in the season I think for those sort of temps. This has got to distort the upper flow, and could do so in our favour if, as I mentioned, the jet gets shunted further S. Bear in mind too that the GFS likes to keep things zonal, especially in the long-term of each run, so this is quite an intriguing possibility it's showing. If it continues for a day or two, well, we might be in business!

After last week's near miss with the Arctic plunge, largely due to the upper flow being too flat, NOW it decides to turn meridional, with a sharpening upper trough over much of the central and eastern Atlantic, with a corresponding upper high over and to the SE of the UK, probably the worst arrangement for those of you who are on the look out for snow and cold. The models are showing little variation in output; HP gradually easing away E and the GFS bringing LP ever closer to us with typically increasingly stormy conditions associated with ever deeper lows, getting into the N and W. The latest 500mb suggests little in the way of change for some time yet: However, there is always the possibility that we will gradually see the jet taking a more southerly track, with heights starting to rise between Greenland and Scandinavia. In fact, at the end of 12Z GFS, with a very intense LP over much of the N Atlantic, such situations have, historically, led to the last and most intense LP spiralling SE as pressure builds to the NE of us, gradually bringing the air from the Continent. With such a sharp upper trough to our W for a while to come, it could also help build heights over the E US/Canada, up towards Greenland, perhaps encouraging surface pressure rises to our N. One other possible indicator for future developments does I think lie in the fact that some pretty intense cold air has dug in over much of the US, which has been around for some days now, this could be a factor in taking the jet further south, as the upper trough there digs ever further S and SE. However, in the meantime, mild, quiet weather gradually turning more unsettled and stormy seems to be the general message from much of the model output, but the jet location needs watching. It's early days yet for wintry weather!

Thanks NNW, we won't know for a day or two yet, but like I said, developments in the W Atlantic will certainly influence whether any cold is short-lived or not. A lot of what I say is based on how similar situations have developed in the past, not that any two situations are ever exactly the same, but it does quite often happen that HP positioned where it is now, will pull away to the W and NW. One other point I forgot to mention is how the Greenland HP has been forecast to grow pretty intense, something else which suggest to me that HP will link N/S across the mid-Atlantic, at least for a few days. The models should prove interesting this week!

I have watched the models flip-flop over the forecast N blast at the end of the week, for the last few days, and with the latest run, they seem to have opted for this northerly merely giving us a glancing blow. Something doesn't look right to me, so let's look at the current position: Strong upper ridge still over us - yes. But what's happening further afield? A vigorous upper low heading into the Pacific NW with very cold Arctic air spreading SW across the W USA. All this suggests a likelihood of amplification of the flow, as indeed the NWS guidance in the States has been talking about for some days. Strong troughing then over the W US, adding amplitude to the Canadian vortex, helping our upper high to retrogress into mid Atlantic - down comes the upper trough at our longitude along with the Arctic flow. But instead, the models push the HP back over us again - peculiar to say the least, not impossible, but to me, it just looks all wrong. I think the crucial development point will be at around T120, in terms of how the cyclogenesis actually takes place S of Greenland. Given the strong baroclinic zone that seems likely to develop at that point in that area, it seems quite likely that a vigorous LP will peel off south-eastwards and fully engage the cold air, and pull quite an intense cold pool towards the UK. As I said the other day, developments over, and to the east of the Canada/US east coast will clearly have a big impact on this development, and to what follows from there, but I don't see the models have got a proper handle of all this, as of yet. Signs of more pronounced upper flow amplification around the hemisphere have been there for some days. An interesting twist has come with the 12Z GFS suggesting HP blocking starting over Scandinavia, but that is very long term. It still needs to get a grip on more immediate developments. It will be interesting to see how the Met O FAX handle it later. I suspect they will go for the glancing blow, but we'll see.

Yes, it was a Friday, a polar low tracked SSE across Wales and Central S England, with snow starting where I was (the Isle of Wight) about 9am and lasting about 4 hours. Shortly after the snow started, there was a terrific flash of lightning as the convection was enhanced hitting the warm Channel waters.The enhanced convection produced huge snowfalls along the immediate S Coast, Sussex mostly, which, given the time of year, was pretty remarkable.

For those of you who may not have experienced a "proper" northerly blast in early winter, this is one of the best examples I can remember. The polar lows it spawned dumped up to nearly a foot of snow along parts of the south coast. This looks pretty benign, somewhat similar to now, but within a week, it became this: Note the slow down of the upstream pattern with large LP off the Us E coast, powerful HP over Greenland and a distorted upper flow. This is the kind of development being hinted at by the GFS, well, not so the 12Z. As has been said, it's all about timing and system spacing, sometimes it works out perfectly, as in this example, but it's pretty rare. We'll see!

Thank you kindly PM, hope I will be around more from hereon, had a few health issues earlier this year, gradually getting back in circulation!OMM

Hi folks, As we approach the official start of winter, I thought I would weigh in with some thoughts on where we are and what the current model trends are showing. Looking at the current hemispheric 500mb flow, what strikes me is the number and amplitude of vortices and of course, the strong upper ridge over us. Very meridional I think for this time of year, and gives me the impression that large-scale blocking may be the trend in the next few weeks. I am intrigued by the northerly the GFS has been depicting for several runs, for around the end of the first week of December and, given the current upper ridge position, looks to be an entirely plausible development, as upper highs positioned as of now, have a strong tendency to retrogress with LP and an amplifying upper vortex forming and heading down into Europe. As to the axis of the coldest air and its persistence, much depends on whether the upstream pattern supports it by increasingly amplified long waves, which is what I was suggesting may happen above. In my view, the current corresponding jet positioning, structure and strength is quite distorted and again suggests to me the possibility of widespread hemispheric blocking: It all looks rather fragmented, the strongest areas being in the W Pacific and NW Atlantic, but with weakish flow over the E Pacific and much of N America, also a quite pronounced sub-tropical jet crossing N Africa. Assuming the GFS is picking up on a definite cold trend here, (and the ECM as well) which of course is by no means certain this far off, I think we need as ever to closely watch upstream developments, particularly in the E pacific and over the E US/Canada, to see if the upper flow is amplifying noticeably, and thus whether any cold Arctic blast will persist near or over us, as the wave pattern becomes more static. Mid-latitude HP across the Atlantic this time of year has a number of possible outcomes, one of which is the persistence of what we have now, with minor shortwaves heading SE around the E fringe, or the HP could just slip SE to bring us a mild SW flow. However, given the strong NW Atlantic jet, some strong cyclonic development looks likely in the short- to mid-term, with LP heading E and then SE, making the Arctic blast a strong possibility as the HP moves W. One other thing that has caught my attention is the depth of cold air over Greenland and the Canadian Arctic. Quite intense for this early in the season. Some interesting possibilities for early winter blocking I think.

Morning all. Well, the wind here wasn't so bad as to keep me awake! Looking at the official data for wind gusts overnight, it seems the coastal areas picked up the highest values, as you'd expect but with some fierce gusts inland, most likely ahead of, and during the passage of the low's cold front. It could have all been much worse I think. The 99mph at the Needles isn't surprising, it usually claims that title for highest gust in these situations given its location as the wind gets funnelled up the Solent. 75mph at my nearest station (Solent) is not that surprising either, as it's pretty exposed there. Outside locally I see no sign of any damage. All in all, quite a vigorous LP but not that exceptional, only inasmuch as it's quite early in the season for it. Certainly, not on a par with 1987. Still, all credit to the Met, not a bad job I think, although inland sustained wind speeds not as high as they thought. I expect we may hear of more damage on the near continent, maybe Denmark, as this LP reaches its peak later. 07H pressure is 976mb so it's probably got a bit more deepening to do. Looking ahead for this week, the powerful Atlantic jet would seem likely to bring further LPs in our direction so it still has the potential for some strong winds to come. Interesting autumnal weather!

Hi GTLTW, I don't know about this one, the deepening should be a whole lot quicker if we are going to see the kind of pressure gradients that produce 80mph gusts, and the 22H chart doesn't really have that look. Pressure has fallen a fair bit, yes, but nothing excessive, not what you'd expect for explosive deepening. I reckon this LP must be travelling at 40kts or more, so I'll stick my neck out and say the most rapid deepening will most likely be as it approaches the E coast later in the night. Anyway, I may yet have cause to eat my words! We'll see. I'm off to bed and if the telephone wires outside start whistling in the wind, I'll get up early and get my video camera out!

Thanks Peter, much appreciated! OMM

Thanks Peter, much appreciated! OMM