stodge

Afternoon all Before the 12z toy-throwing starts elsewhere, a thought or two on the medium to longer term evolution. The picture for next week and beyond is still being resolved at this time (naturally) but the signal for a shift to a more anticyclonic pattern seems to be strengthening. The 6Z Parallel brings in some very cold air next week as the Azores HP ridges cleanly into Scandinavia. The OP doesn't make the transfer cleanly while the Control looks promising until a spoiler LP drops down the British Isles and the ridge is broken. Interestingly, the 00Z GEM brings back my little mid-Atlantic LP from last week which pushes NE and brings heights to the east of the British Isles. I'm also noting a hint of another Wave 1 warming from the Eurasian side which we emphatically don't want or need. The 06Z GEFS look very anticyclonic in far FI but where the core and orientation of the HP will be is still to be resolved.

Morning all Sky Fall makes a valid point about model volatility and accurately which is always worth noting but there is a game changer emerging in the medium to long term and those looking beyond whether it will snow on Tuesday might have first seen it on some of yesterday's runs but ECM picks it up this morning: ECM 00Z OP at T+240: It's not the big LP south of Iceland or the small area of heights to the west of Norway nor even the Azores HP but the small LP forming to the west of the Azores HP. This is a critical feature going forward as it initiates a change in the pattern, For the last few weeks, our LP have been spinning off the Canadian PV lobe and deepening past the tip of southern Greenland but this LP is sourced from the tropical Atlantic. Here it is on the GFS 00Z outputs: OP: Parallel: Control: The LP does what all the other LP have failed to do - first, it breaks the flow of LP from the PV - it's a sign the PV is weakening and pulling away west into Canada but second as it comes NE heights are raised to the east and north-east so all three of OP, Parallel and Control end on an anticyclonic note. The Parallel ends with a 1050MB HP over the North Sea and more than a hint of retrogression. with the PV having transferred across towards Eurasia. GEM shows the small LP as well. It's one to watch and could be the pattern for a cold anticyclonic February dominated by HP to the east. Whether it develops as a true HLB or it's MLB based to the east remains to be seen but it's the direction of travel that IDO hinted at a couple of days ago as well.

Morning all I've not been in the Banter thread This is an excellent analysis, my friend, and I've noticed some sign in furthest FI of the PV starting to shift but we need to see that come forward. One or two of the models starting to sniff the slowing of the Atlantic juggernaut and seeing where we can get some heights. Control at T+300: Parallel at T+360: I said last night the current pattern lent itself to snow rather than cold - the irony might be that come February we might be looking at cold and not snow if we can get HP setting up in the right places.

Evening all After days (it seems) of conflicting and widely shifting model output, perhaps some signs of stability if not certainty this evening. As always, it will be the ECM 12Z which will set the tone for the conversation for the 8 year olds in the banter thread but here in the civilised world, some more objective thinking may be required: Let's look at some 12Z output with some progression: First, ECM T+144: T+240: GFS Parallel in the same timeframe: 144: 240: GFS OP: 144: 240: As a contrast, GEM 12Z: 144: 240: It's encouraging to see strong cross-model agreement and the ECM 12Z at T+144 is very close to the UKMO at the same time so that's helpful. GFS Parallel isn't far away but makes much more of LP to the NE of Scotland and up to the Norwegian Sea. Under a slack flow, stagnant cold air will get very cold so plenty of frost and perhaps freezing fog. I've also noticed how quick GFS does everything - it's an extraordinarily mobile model and that may work well on occasions but not all the time. The Parallel seems to be taking a more leisurely approach than the OP which is by T+240 already gearing up for the next slider from the NW. The GFS OP goes its own way and rushes everything through as you'd expect while GEM sort of gets there in the end. The problem for me remains the lack of heights to the north and north-east and the NH profiles don't fill me with unabashed glee at this time. The Parallel is the most "hopeful" in terms of washing out the Canadian lobe but it still looks to have plenty of fight on the ECM and GFS OP. I was musing on this today and trying to get my head round it. It occurred to me that we had less of a split than a strong displacement and that left a lobe on the Canadian side (always likely given the warming came from the Eurasian side). I just wonder if the downwelling actually re-enforces the PV at lower levels as it works down and does so until it reaches right down into the troposphere. The downwelling struggles to make headway and it's like trying to run up an increasingly steep hill. My conclusion is we will have a window of opportunity between the time the downwelling reaches the troposphere and the re-enforced zonal winds arrive (mid February maybe). We take the tanking AO which is fine but the NAO (thanks to the PV) continues at best neutral. We really need to see that NAO turn negative (though not too much in my experience) but that will be dependent on signals showing the PV is shifting off base. With the PV, if you can't weaken it, move it. Any displacement west or south west gives us a chance to get the Arctic HP more favourably placed toward the European side rather than over Siberia. As I mused last night, the westward shift of the Siberian HP into Scandinavia is something we see after mid winter as the Atlantic slows and amplifies and if Scandinavia has some seriously cold air (and you're looking at something like P19 on the 12Z GEFS) you can get some cold heights. Oddly enough, the current scenario may play well for fans of snow rather than fans of cold. Most snow events are marginal especially in the south as others have pointed out so I worry less about -4 to -8 uppers at this time of year if we can get the thicknesses and DPs right. I simply don't see (and never have this winter in all honesty) a 10-14 day period of severe weather with ice days and frequent snow. Even if we get the pattern right (as we didn't this week but may next week) I don't see how the cold is sustained but in a scenario with a negatively-aligned trough and getting enough cold or very cold PM air it may not matter too much. A northerly is still a northerly even if it isn't being supported by a 1070MB Greenland HP. A NE still works even if it is reliant on an active LP over Europe. Getting the trough down into Europe gives some of us a sniff and I'd be quite optimistic if I lived on high ground in the north of England and Scotland - the prospects for occasional snowfall look very good. As for southern areas, well, the ECM offers -3 to -4 uppers at T+240 and interestingly while the current milder sector gets to +3 or +4 850s, the mild sectors next week are progressively shorter, weaker and smaller while both the GFS OP and Parallel have plenty of cold air about next week with 850s widely down to -8 which is all good stuff. So, where are we? Utopia eludes but doesn't it always? In truth, we could use the precipitation be it rain or snow and there seems to be plenty of that on offer. It may be a "miss" for south western areas but high ground to the north and east looks favoured if you are after snow but as the air gets colder next week more areas come into the game,

Yes and it's something I'll be looking out for tomorrow and beyond. IF we see heights emerging and most likely as an extension westward of the Eurasian HP, the question will be what will happen to the Atlantic in response. The 12Z ECM OP tonight showed the Atlantic LP slowing and stopping in situ to the west and filling which would then allow the HP to push westward. if we were really lucky, the HP pushing westward might encourage the Atlantic to slide SE but with pressure rising over Europe I'm doubtful about that. The battleground scenario wouldn't be atypical for February.

Just to add to my previous, having skimmed the ECM members, there's a strong and perhaps growing signal for a substantial block to the NE out the Day 10-12 range. This is picked up by the 12Z OP and suggests to this observer the Atlantic could face a growing block to the east. What that might mean is a milder interlude followed by a battleground as the east block pushes the Atlantic back west. One to watch for fans of cold and not to get too upset by the odd milder chart.

We had some very good ECM ENS last night - the Control run being a very good example. I don't share Kold Weather's extraordinarily downbeat analysis at this time - we need far more evidence over the next two or three days. My take on the ECM 12Z OP, which is nowhere near as bad as is being portrayed, is it's a positive sign of a slowing Atlantic and it's worth noting the rise in heights to the NE over Finland indicative perhaps of the continental block pushing back against an amplified Atlantic which is a typical February situation when the Atlantic slows.

Evening all Snow here in lowland East Ham as well. Covering on cars and some other surfaces in the past hour or so. Winter 2018-19 officially NOT snowless.

Superb 12Z output tonight. GEM the pick of the bunch but the others all heading in the right direction. Can't understand all the moaning and whining on here tonight !!

I think one of the myths or fallacies we need to tackle is this notion of the PV preventing cold. If it really worked that way, we'd hardly ever have cold weather so it's perfectly possible to have cold weather with the PV. The SSW reduced the strength of the PV significantly - you'd expect the PV in mid January to have a core temperature of -88c and zonal winds of (I forget exactly - 80 to 90 m/s). We now have a PV with a core of -72 and winds are only now returning back to positive values after a spell of negative or near negative values. So we have a very weak and disorganised PV which has been split into various lobes but it's still there. As the PV gets slower, amplification becomes possible in the Atlantic as the zonal wind speed falls and (I believe) that impacts the jet. Displacing the PV helps - move it a little further west and heights can rise over Scandinavia - move it a lot further west and you can get some Greenland blocking.

Without wanting to get into a dispute over semantics, my point is that anyone looking solely at GFS OP could have had little confidence in the Easterly happening. Yes, it was a possibility but it never became a probability let alone a certainty. All the factors that needed to happen for the E'ly to occur (primarily the trough dripping cleanly through the British Isles and then heights building behind it and extending SW to the British Isles) were never there in enough confidence for it to be a reality. For me, the lesson learned is not to look too far beyond T+120 if you want a sense of what WILL happen as distinct from what you might want to happen. I will continue the comparative analysis of GFS and ECM down to T+0 to see if where we are now id where we end up.

Evening all Just as a variation on the usual (and hopefully okay with the mods), just a little analysis of how the models have moved in the past few days. I've picked January 25th at 1pm as my point of reference and used the GFS 12Z OP as my starting point: T+288 on 13/1: T+264 on 14/1: T+240 on 15/1: T+216 on 16/1: T+192 on 17/1: T+168 on 18/1: T+144 on 19/1: T+120 today: If there's enormous variation here, magnify that four times each day plus the ENS and the Parallel and you can see why seeing the wood for the trees becomes so difficult. As a comparison, here's ECM 12Z output for the same point: T+240 on 15/1: T+216 on 16/1: T+192 on 17/1: T+168 on 18/1: T+144 on 19/1: T+120 today: It might seem ECM "flipped" yesterday evening but if you look at the previous days there was no consiste3ncy in the modelling either. We finished up cold across the UK and everyone was happy but look at the enormous variation of the North Atlantic profile. I would argue therefore for all the "Easterly" was nailed on, it never was. Modelling was hugely inconsistent and although the outcome for the British Isles looked good that was a coincidental outcome of a number of inconsistent variables. Shifting the variables or resolving them changed the outcome and the inevitable whining of "downgrade". It also seems to this observer GFS called this well - the day to day volatility betrayed the uncertainty. Today, GFS has clearly moved to the ECM solution and we can see if that verifies. Lessons - FI is T+120 and occasionally less. The key timeframe for ECM seems to be T+144 for setting the general pattern and we'll see if that proves a good adage especially if the GFS shift this evening is confirmed in the next few days.Further out than that you're better off with other tools such as the Ensembles to provide broad guidance but that's all. I'll run the comparative analysis down to T+0 to see whether what we are seeing now turns out to be the truth or whether further variation is likely.

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.

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".

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.

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.

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:

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.

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.

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.

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.

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).

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.

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.

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.