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Everything posted by stodge

  1. Afternoon all As we await some eagerly-awaited 12Z output, just a look at some of the current output 10 days or so away: The GFS 06Z suite was one of the most remarkable I've seen for a very long time: Control: Parallel: OP: It's the first time I can recall the three main players in the GEFS suite all looking so strong for cold. Add to those ECM GEM: It's of course worth saying this is emphatically NOT a done deal at this time - experience taches us that and while cross model agreement at T+240 is nice it's so much better at T+0. The key for me has always been whether we can catch enough of a break as the trough disrupts SE into NW Europe to enable height rises into the stagnant cold pool of Scandinavia. This is the critical point in the evolution: OP (T+150): Parallel (T+144): For those who have been whingeing on about the Azores HP, it becomes our friend at this point as it holds the Atlantic energy up long enough for the heights to build to the north and later north east. Very cold spells are vulnerable at two points - at the very start and at the very end. As we've often seen, it can be quite hard to shift a cold blocked pattern once established and the OP is a wonder of longevity. For now, I'd like to see UKMO heading in the "right" direction this afternoon and models like JMA and ICON come more firmly on board. It's hugely unlikely the 12Z GFS will be an "upgrade" on the 06Z (I don't know how it could be in all honesty) and we will see some OP runs which will have the usual suspects reaching for the whatever but I'm cautiously optimistic this time next week many of us will have snow but for now cautious optimism is as far as I want to go.
  2. Afternoon all As we await the next instalment of the roller coaster, a thought or two from me as to where we might be going. Last evening's ECM 12z got a lot of people very excited but this morning's offering more disappointing. The GFS 06Z OP once again promises bounty at the very end - the T+408 chart would be worth seeing while the NAVGEM 00Z output was well worth a look for cold fans. The notion of "cold zonality" gets people agitated as it often leads to marginal set ups at low ground for snow. Yes, if you're up high and up north it usually delivers and it may be true some low ground will also get a covering but for the bulk of us in England and you'd better believe that's true of lowland East London, it's cold rain and unpleasant cold winds. IF the trough digs south, we really need to see the heights respond to the NE but we continue to have upstream dramas. GFS 06Z Parallel maintained a strong PV right through firing off vigorous LP one after another but the Control drains away the PV letting a more amplified scenario evolve while the OP hints at the PV moving to the west also allowing amplification.and the resolution of that which is beyond my comprehension at this time. As Johnny Nash said in 1972 "there are more questions than answers".
  3. Evening all For all the talk of snow from the ECM 12Z OP I think the key point, as alluded to by Knocker, would be the ferocity of such a storm were it to verify. That's a 951MB storm off the west coast of Scotland "filling" to be a 967MB storm over northern France 24 hours later. As Steve Murr rightly says, no storm of that ferocity has traversed the British Isles from north to south but then again there's a first time for everything. The winds from such a storm would be extremely strong and damaging and that damage intensified by the fact we've had so little real wind this winter. It probably won't verify like that and that may be a blessing.
  4. Afternoon all Onwards, upwards and downwards goes the rollercoaster it seems and one or two nerves getting a little frayed because we're not seeing storm force easterlies with -20c uppers or 1070MB Greenland HP cells at T+6. The signal for the trough to disrupt SE into NW Europe has been there for a while and the 06Z Control was a very good run for cold fans after a pretty decent set of 00Z output to be honest. 06Z Parallel keeps the theme of "cold zonality" while 06Z OP has disappointed many as it seems to default back to an Atlantic-based regime (wow, GFS reverting to an Atlantic regime, that has never happened !!) One or two comments on the Azores HP and some seemingly wanting it to "do one" (whatever that means). The Azores HP is of course a vital ingredient in the progression toward cold. Ridging north or north east it can re-enforce existing HP cells and indeed its presence can help maintain lower heights in the Med which help HP evolution to our NE. The problem to this observer seems to be the amount of energy in the northern arm of the jet - this may be (one hopes) a final convulsion as the downwelling from the SSW goes through the Canadian Lobe. We need to see that lobe migrate ideally west or south west into Canada to allow the amplification downstream but the sheer volume of cold air is energising cyclogenesis so we simply can't catch a break. 06Z Control shows what can happen: The Canadian HP moves NE into Greenland rather than E or SE into the Atlantic which then forces the PV away. This is the break we need.
  5. Afternoon all A degree of concern and despondency among the usual suspects because one OP run doesn't upgrade from the previous. I thought the 00Z output generally was the best of the winter so far - excellent charts for cold and snow for many - and inevitably the 06Z has not looked quite as good and the worriers have come out. As a contrast, I really like this chart: It's barely a week away. Signs we will see the trough drop SE into NW Europe in about 10-12 days after which we have to hop we get the height rises either to the NE or NW. One poor OP doesn't make a poor suite and there will be worse charts than this:
  6. That's very interesting from Todd Crawford. The 10HPA charts show the strat regaining size and some strength but still well above normal temperatures with -72c on offer rather than the -88c or lower you would expect in mid January which is the peak of mid winter. Signs at the very end of GFS of a new warming starting and I wonder what the impact of a renewed phase of Wave 1 warming at the very end of January/beginning of February would be. Possibly not what we want overall if it knocks the PV back over Canada but could it lead to another split in say mid February which might lead to an interesting start to spring.
  7. Afternoon all Again, I'm a little underwhelmed by the output but a couple of points of note across the models today. First, our old friend the Canadian PV lobe - this may surprise some people but if you want prolonged cold you don't want it to disappear. Losing the PV completely sounds like Nirvana and of course a 1070MB Greenland HP is infinitely better than sub-990 MB heights but the problem becomes one of longevity. All too often the negative NAO becomes west-based as the HP ridges SW into Canada - that's what did for the December 2010 cold spell and indeed the rapid movement of the HP from Scandinavia to Canada in March 2018 set up a west-based negative NAO which again did for the initial cold spell. Ideally, we need to see the PV displaced slightly to the west (allowing Scandinavian HP formation) or further to the west over Canada (supporting Greenland HP formation and with WAA continuing up the Davis Strait to maintain). There are signs of the Canadian PV lobe displacing slightly SW and allowing height rises over Scandinavia (supported by the strat charts as Feb1991 mentions above). This is encouraging as the stagnant cold pool forming over Scandinavia will encourage heights to develop. Second, timing. We've had a vortex displacement followed by a split. The standard displacement response, as we are seeing, is to re-enforce the Canadian lobe so we get a fired up Atlantic as cold air is displaced south. I'd hoped we would be seeing clear signs of amplification by the 22nd or 23rd of the month but we are still struggling to get clarity with the GFS output. and we are tantalisingly just beyond the edge of ECM and GEM output. It looks like an increasingly cold and unsettled outlook as the airflow shifts gradually from west to north. The question then becomes whether we can catch enough of a break to allow either a mid-Atlantic ridge or (and this now seems the form horse) heights to develop over Scandinavia in conjunction with lower heights over the Med.
  8. Afternoon all Have to say I was a little disappointed with some of the GFS output this morning. The 06Z OP was unremarkable and maintained a strong PV in place whereas the 06Z Control shifted it south west into Canada and allowed a mid Atlantic ridge to set up creating a very unstable and frigid looking Northerly for NW Europe. GEM was interesting and looked better for cold while ECM wibbles and wobbles a bit but got there in the end. The concern for me from the GFS remains the heights close to Iberia and the Med. They don't stop Northerlies per se but they keep the jet too close for comfort. I was hoping we'd see the Azores HP exiled into mid-Atlantic and again a hint at the very end of FI it might be getting there. 12Z output to come - as ever, more runs are needed.
  9. Evening all Lot of unnecessarily downbeat nonsense on here this evening. The split in the SSW has only occurred today so add two and a half to three weeks to that and you're looking at 24th - 27th of the month. Yes, it's not as quick as people would like and there's still plenty of uncertainty and the tropispheric response isn't going to be as immediate as some thought and many hoped but that doesn't mean it won't happen at all. We also have the situation that all the models except GFS (JMA admittedly does slightly as well) only go to T+240 so that means January 16th as the limit of what ECM for example shows us and at that point it shows nothing of interest (though there's plenty going on for those wanting to look) because it's too early. Yes, there were hints we could have had an earlier burst of cold but other factors haven't worked to our advantage and it's worth repeating SSWs don't guarantee cold for NW Europe. I'm more than happy with the 12Z GEFS out beyond T+300 - plenty of cold or very cold options from the north at first and then perhaps from the NE later. We need to get the cold air into Scandinavia and points east first but the signs of the trough dropping into NW Europe and the Atlantic slowing are starting to come into view in furthest FI. I'll be honest - IF we are next weekend with the eye candy still out at T+300 I'll be surprised and as disappointed as anyone. If, as I suspect, it's coming into view at T+156 and beyond it'll be time to start getting excited.
  10. Evening all Coming into range of my birthday which is the true start of winter as we all know. GFS 12Z OP at T+240: GFS Parallel 12Z at the same time: Here's the 12Z GFS Control at the same time: ECM 12Z OP at the same time: To be honest, all variations on a theme. Oddly enough, we need the first attempt at building the ridge to fail - why? The ridge fails and this allows LP to move down through Scandinavia into central Europe and the Med finally lowering heights in this key area. This enables the HP to withdraw westward opening the gate for the trough to move SE into NW Europe and as the trough tilts negatively the possibility of a mid Atlantic ridge is increased so all the negative nonsense misses the point. The Scandinavian HP ship hasn't sailed but it will be a by-product of the cold zonality as the jet meanders south and increasingly frigid air moves into Scandinavia which will allow cold HP to become established in situ but that's a fair way off at this time (hinted at in GFS 12Z OP in far FI).
  11. Morning all Another day, another set of interesting and varied output to digest (though trying to take it all in at once might not be good for any part of you). There may be three steps to heaven according to the song but there are two routes to cold as I see it and both are covered this morning. Route 1 - from the East: This isn't difficult - we simply need to catch a break in the flow of LP allowing a nice push of WAA up the EAST coast of Greenland and a slight displacement of the PV further west into Canada and we get either a small Scandinavian HP or ridging from the main Siberian HP WNW into Finland and southern Scandinavia. Lower heights over eastern Europe and you get a very cold E'ly flow which then engages with the milder Atlantic flow and we get the fun and games many on here want. Route 2 - from the North This has been touted by GFS for a while and is still around. The Azores HP retreats west out of Europe into the Atlantic and this allows the trough to sink SE into NW Europe and set up over or just to the east of the British Isles as a lobe of the split PV sets up over Scandinavia. This initiates an unstable Polar flow with spells of N and NW winds with plenty of embedded troughs and features which gets the fun and games many on here want. My money (and very nice money it is too) would be on Route 2 at this time but Route 1 has come back into favour this time as the weakened PV becomes more prone to further slight displacement especially with another warming about to start. The PV may or may not fully split - it fragments but obviously won't be destroyed as it was earlier this year but whatever emerges by mid month is smaller, weaker, warmer and less organised than in most midwinter periods I can remember (10 HPA PV core temperatures at -68 rather than the -84 or lower normally experienced in mid January) Timing - I've always said 2 1/2 - 3 weeks after the PV split is the time so assuming the split is happening about now-ish that puts us at January 20-24, later than many would have liked or wanted but still gives us plenty of winter to enjoy or endure as appropriate. Some of the output brings changes a little closer this morning which might be accurate - we'll see.
  12. Afternoon all Hyperbolic and inaccurate over-reaction to one run from one model notwithstanding, we have come a long way in a few days. I've always reckoned on 2 1/2-3 weeks from stratospheric split to significant tropospheric response so we remain on track for a shift soon after mid month. Some concerns about downwelling in the stratospheric thread and we may need some help from other factors - the problem is it's not March and we won't destroy the PV with a displacement/split in one go. It's not midwinter and the PV can reform but it will remain weak compared to other years and vulnerable to later warmings. The two main routes to a colder incursion are explored in both the 06Z OP and Parallel output - the OP pulls the HP far enough west to allow the trough to drop down from the NW (this is an option we've seen from GFS OP quite a lot) while Parallel raises heights from the NW - both end up with a cold unstable and snowy regime from between NNW and NE. I don't rule out the possibility the stronger Canadian vortex lobe will prevent the height rises to the NW but the PV will be warmer and weaker so the chance of height rises to the NE IF the lobe can be shunted back west (the OP goes down that road at the very end of FI) but the 06Z Parallel solution would be the most suitable for cold with the PV split apart., To be honest, I don't know - we're in the game and have a decent hand. Whether it's a winning hand who knows - one thing's for certain we'll know more in a week.
  13. Thanks as always my friend for the cogent comment. As I recall, back in March, the MJO was at record-breaking levels of amplitude and we saw the HP move west across the northern hemisphere from Scandinavia to Canada. That did for our initial cold spell and I've never seen anything like that. I suppose we can never catch a break of getting a reasonable level of amplification to prevent the west-based negative NAO setting up quickly - that also killed the December 2010 spell.
  14. This was, as I recall, one of the possibilities from the SSW and something mentioned by Judah Cohen as a possible outcome. If you get a strong anticyclone over the Pole the possibilities for cold at lower latitudes increase considerably because, as you rightly say, the cold gets chased south. One evolution touted last week on a number of GFS OP and Parallel runs was dropping the trough into NW Europe or Scandinavia with a mid Atlantic ridge behind it - the 12Z Parallel ends with a sharp N'ly. Other evolutions today have returned to the possibility of the mid-latitude block creeping into southern Scandinavia. - you can see the kick of WAA between T+288 and T+300 over eastern Greenland on the 12Z GFS OP that allows an HP to build over Scandinavia and re-enforce the mid-latitude block. Developments in the stratosphere continue to intrigue and perplex in equal measure and as others have said may constitute to make the model output even less unreliable than usual. We seem to have stepped back from an Atlantic breakdown in the New Year to a continuation of the quiet anticyclonic theme but it's by no means assured and a number of the GEFS keep the signal of a revived stronger jet. Oddly enough, as the cold does draw out of the Polar region I could see a brief return of a more active regime before more amplification takes hold. The onset of much colder conditions took two and a half weeks in February from the initial PV split so if the split is due Jan 1 that takes us to Jan 18-19 or thereabouts and as I recall there was plenty of wailing and gnashing of teeth earlier tin the year when some output seemed to suggest the SSW having no real effect in our area.
  15. From this night 12 months ago, this was the projected state of the PV on 11th January 2018: Tonight's 12Z Parallel offers us this: Quite a difference.
  16. We have seen a shift in emphasis in the past 48 hours. The Scandinavian HP has been off the table for some time and we are now looking to the north and north west. OP. Control and Parallel (I think) are surprisingly similar - all flatten the second HP but shift it west in the week after New Year before bringing the trough SE into NW Europe with mid-Atlantic pressure rises behind so quite a potent shot of PM air followed by (hopefully) a mid Atlantic block. As to the strat, certainly plenty of signs of the PV coming under serious strain and fragmenting rather than splitting and is there another minor warming coming in the New Year?
  17. Afternoon all Sometimes the new day makes things clearer but more often it only makes it all murkier. Those who were hoping for an early New Year present from the stratosphere look to be out of luck - whether we get a split or a displacement the initial impact of the ongoing warming seems to be, as we often see, to re-group the focus on the Canadian side so the second burst of HP which sits over the British Isles as a mid latitude around New Year is flattened as the jet powers up at the end of the first week of January. There is then the usual 7-10 day period of renewed Atlantic conditions as the PV sits over Canada/Greenland before the amplification or the downwelling takes over and it shifts either westward or over to Siberia with the latter looking the favoured option which opens the door to the trough dropping down into NW Europe (suggested by both 06Z OP and Parallel). Whether we can see mid Atlantic height rises behind that is the next question. The option of a Scandinavian HP seems off the table. Plenty of the 06Z GEFS favour an anticyclonic FI but where the HP ends up still seems open to question. P11 would be ideal for the cold fans (PV over the Pole and heading for Siberia). A lot will depend on how quickly residual PV energy can be washed out of the Canada/Greenland region - it may be we will have to wait until mid January for the process to complete and the way to be clear for high latitude blocking in our part of the world.
  18. Morning all First, Christmas greetings to all fans of cold and snow (and presumably frost as well). It looks very anticyclonic to end 2018 and start 2019 - the first push of HP will retreat slightly but the second push from Iberia looks much stronger and will create an MLB centred over or perhaps just to the west of the UK at New Year and just after. We could hopefully see some nice inversion under the anticyclone so some cold for many. It does look as though (and the MetO forecast suggests this) we'll get another short-lived Atlantic push after that before (hopefully) we start seeing something more interesting. so yes, we might have to wait three weeks before we get the wintry nirvana for which we are all hoping (in this thread at any rate). One route might be for the HP to pull far enough west to allow the Arctic trough to drop down over north west Europe - shades of December 2010. The GFS continues to frustrate with its strat forecast but we are seeing a significant warming event now and what comes out the other side will be a much warmer and weakened PV which can only bode well.
  19. As an aside I'm also struck by the difference in 10HPA temperatures between the stratosphere this time last year and now. By early 2018 it was still showing values of -84c and below at its core - the early 2019 value is scheduled to be -68c which is quite a difference, much warmer and much weaker.
  20. Evening all Onwards with the roller coaster it seems. The main model output still not yet factoring the stratospheric events but it's not surprising with the warming barely underway and still a couple of days off its peak. I get the sense however there is some movement - the option of building a Scandinavian HP seems to be receding in favour of keeping the HP to the west or north west and allowing Arctic incursions as the main trough (and a lobe of the weakened vortex) to drop into Scandinavia. I imagine heights to the North West and a raging northerly in January will probably be cold enough for most. If the HP is kept well out to the west we might see the trough drop down right over us (shades of December 2010) and I imagine most people on here would be happy with that. Watching the stratospheric modelling is fascinating - GFS seems to go less for a split than a shearing of the PV and what comes out at T+384 is a smaller, warmer and weakened PV (no -90c raging PV to start 2019). Looking at the 12Z Parallel and OP (which look very similar) the forecast sees this shredding of the PV rather than a full split so instead of two distinct intact PV segments you get a single weaker vortex - I don't know how that will play out and clearly the EC isn't seeing that. For now, the immediate outlook looks benign for most with the weather not seemingly getting in the way of Christmas and New Year events.
  21. First, it isn't flat but yes, the first build of HP is declining SE and the second, more substantial build is coming NE from the Azores and Iberia. There's also a good sign the Atlantic is slowing and weakening on the UKMO as well which we also need to see.
  22. Afternoon all As usual, those wanting snow, ice and -20 uppers are complaining because there's nothing showing in the next 7-10 days. True and it looks a remarkably benign Christmas and New Year period for most which is no bad thing for those having to travel and visit their families and/or loved ones. The signals for something of more interest in the early to middle part of January remain there - the 06Z Parallel was a thing of beauty in far FI and interesting to see both Control and OP toying with slowing the Atlantic to a crawl and rising pressure over to the NE of the British Isles. GEM 00Z looks more like an inflated ridge from the UK and that's ten days out. The first HP for Christmas won't be strong enough to ridge NE combined with too much residual energy in the jet so it slides ESE but a second burst of HP at New Year looks more promising but nothing is settled. The 06Z GEFS does indicate more members taking the core of the HP to the north which may be good for cold fans but there's no snow in many of the members at this time. It's a three phase process I think - the HP moves up from the south, transfers north or north east and later retrogresses. Ideally, we'd need a nice cool down before we get the easterly and then the northerly and then back to an ESE as the Atlantic tries to come back in from the SW. That's a 7-14 day severe cold spell for mid January (or maybe later). The split PV continues to be modelled on the Parallel if not the OP with the split coming on January 2nd and indeed the 06Z Parallel initiates another burst of warming on the shattered PV which would pretty much finish it off. Even the OP weakens the PV significantly from what we would expect in January but it is a displacement not a full split. That said, even a displaced vortex offers opportunities for cold.
  23. Afternoon all Well, the ship has sailed for Christmas cold but the New Year, well, we'll see. The Parallel has been consistent in splitting the PV on or about 3rd Jan and the GFS 12Z OP looks like ushering s second warming to split the PV soon after 6th Jan. We'll also see if Amy Butler's tweet is a sign of a backtrack or just some modelling inconsistencies over the next few days. The substantial pressure rise from the south and the subsequent transfer to Scandinavia followed by retrogression to the NW provides a typical 10-14 day severe spell as we have seen before. The risks remain substantial - in splitting or displacing the PV may have enough energy to sink the initial HP into Europe before it goes wandering and the amount of energy in the northern arm of the split jet remains troubling. I'm still of the view we are looking at more severe conditions from mid January (halfway through winter for those who are worried or counting) rather than earlier.
  24. Afternoon all I suspected this morning's output would restore some colour to people's cheeks and get the curtains a-twitchin'. For those of us who love cold without the snow, GFS FI is delightful with both OP and Parallel showing substantial mid-latitude blocking and as I constantly have to remind people, it's perfectly possible to get an ice day in London without a flake of snow on the ground if you get a serious inversion and both OP and Parallel - I know the 2m temperatures aren't suggesting that at the moment but I'm absolutely convinced IF we got a set up like: We would have fog and frost as long as (and it's a big proviso) we can avoid embedding cloud in the circulation. This is why I quite like an HP forming from the south over land as they have less cloud in the embedded circulation than an HP coming in from the east or west. Anyway, all a long way off and of course the big positive is the split PV now showing on both OP and Parallel which is significant IF it plays out. All this will be too late for Christmas and New Year celebrations I suspect but promises a lot for January if the cards drop right.
  25. Morning all :) 10c here in lowland East London but no rain as yet. Breezy with a SSE wind and cloudy but with variable cloud levels. Looking at the wonderful NW radar, the main pulse of rain for SE England is still over North West France so we may get a few dry hours yet this afternoon but I think we will have a wet night. Looking elsewhere, the rain band looks particularly heavy and slow moving over western areas and especially the Lake District - I hope we won't get a repetition of past flooding spells around Christmas in these areas.