Catacol

Yeah - damn that fiddled data. The cloak of mendacity that somehow makes us hallucinate that snow levels are falling, summers are getting hotter, winters are getting wetter, rainfall events in general are getting more extreme… and polar ice levels are falling fast. In this context the oceans are, of course, not getting warmer. That is another illusion.

Interesting article today. Even the big wigs are struggling with explaining things right now… Climate models can’t explain 2023’s huge heat anomaly — we could be in uncharted territory WWW.NATURE.COM Taking into account all known factors, the planet warmed 0.2 °C more last year than climate scientists expected. More and better data are urgently needed. Taking into account all known factors, the planet...

For all the correct talk of climate change impact on our weather, this needs picking up. An understanding of windflows - whether impacted or not by CC - is only a "misdirection" when it is not understood. You would do well to look at the two cold snaps we did manage to get out of this year's winter and ask yourself the question as to where they came from. The point is - teleconnections will not always deliver, and perhaps are becoming less likely to deliver for the UK, but without them you have no chance at all of reversing westerly dominance. Ignorance is not an excuse for making an assertion like this that fundamentally undermines the steps forward that have been made in understanding what drives our weather. This winter the stratosphere dealt us a blow and reminded all that momentum and wave action originating from the Pacific is not always destined to put a high lat block in place in the Atlantic sector especially when the strat is not in sympathy. The biggest single factor that shredded the second half of winter was the failed SSW in early January and what transpired afterwards. I am sure the real strat grogs will come up with an analysis as to what reversed that very optimistic position at New Year. And AGW is not a teleconnection. It is a background constant against which everything is operating. There is less cold air, there is more warm ocean. A constant, not a driver. Finally, you have pushed the GFS agenda all winter but the stats do not support this. We are now able to look at EPS alongside GEFS and GEPS and the Euro model continues to be the go to, with UKMO close behind. Check the stats, they do not lie. There may be a case to argue that over Greenland all models substantially struggle and the GFS is no worse than the others at interpreting data in that area, but once we get to lower latitudes GFS is less accurate. Do not be fooled by the fact we see 4 GFS compared to 2 of the others each day and equate occasional identification of a future pattern in the 06z or 18z as being the same as being "better".

Probably says a lot. I think I’m swinging back to the perspective that without a favourable SSW to force a dramatic crash in the AO our cold winters are now at an end bar a very long odds development. Cold snaps of a few days will continue, cold months overall will not. Oceans too warm, +NAO too dominant. Only a major SSW can shake it up. We reached a global tipping point a few years ago. Nino probably a bit too strong this year when aligned with such ocean warmth. Next year probably Nina and wQBO. Need that Nina to be weak to give us a chance of a major SSW. Enjoy Spring and Summer everyone. See you all in the autumn.

100% agree. I felt like a tipping point was reached about 4/5 years ago - sudden and obvious increase in summer heat-related incidents and misery and the rate of acceleration is stark. My Mum claims it is all media inspired...we think things are worse because more people talk about it and more pictures are taken - but while I'd like to think that's true, from a personal (and admittedly anecdotal rather than rigorously evidenced and fact collated) perspective we are heading into difficult times. I think Europe in particular is heading for very tough times, and maybe in 10-20 years we will be mighty glad of our atlantic blanket helping keep away the worst of things (despite its constant destruction of our winters!) It's hard not to be gloomy about it all. Keeping this thread-relevant, a summer heat dome wont be far down the line. Should help May be lovely. But June-August? Too hot for me.

A sound summary and makes a lot of logical, teleconnective sense...but I'm not sure it will come to pass now and I'm ready to hang up my snow boots and depart this forum for another year. The vortex has refused to crack all season whatever the record books will say about a double SSW season, and predictions of a blocked February drained away all too quickly. Unless the vortex splits - which it now looks like it wont - then we are left with a weak and wobbly westerly vortex, not much of a downwell of any supportive reverse flow, and pacific forcings that will need to produce output that has not come to pass through most of this season. I can see the jet whipping up, and in theory with such a strong uptick in the GWO it ought to promote cold blocking....but I have a feeling that transient cold phases and a lot more rain is where we might end up. It has been a fairly sapping experience over the last 6 weeks. I fear that the impact of CC is skewing everything in the wrong direction faster than many expected (just look at Alpine temperatures, Moroccan temperatures and the jaw dropping speed of ocean warming) and UK winter is going to get shorter and more scarce. For mid February our own temperatures have been fairly extreme. Meanwhile summer approaches and I am dreading how much heat may come with it. Perhaps something significant can shift next winter so that the patterns and the accompanying temperatures can give snowball players more of a chance.

Jules - you are way off. Pattern matching is a mugs game because no 2 patterns are identical, and analogues have become near useless. And the SSW didn’t reshufffle anything because it scarcely occurred in the first place. Go read Amy Butler’s blog. Far from reshuffling as a result of a SSW, the reflective nature of the failed SSW contributed to the collapse of the cold pattern because we didn’t get that SSW in any real sense. Didn’t reverse early January, climbed above climatological average within a few days. CC is our greatest enemy in terms of landing cold. Claiming seer-like qualities in spotting a warmer than average winter based upon pattern matching is the equivalent of grabbing glory for betting on Bayern to win the Bundesliga because it happens most of the time. No skill whatsoever.

On that we can agree! I'd happily bin aspects of internet comms - I think for all the benefits in communication it has made the quality of our lives much worse overall. When I retire, whenever that will be, I swear I will check my inbox no more than once a week. Face to face always best. Never ever manage by email, message, text or platform. I was advised that way many years ago by a wise sage, and they were spot on.

I'm not sure that's accurate Nick. Most of us look at the broad spectrum of drivers, as much as it is possible to make sense of the unique combinations that arrive every year and try and untangle them. GDSM is a representation of more than just one element - I still count myself a novice in its use, but it certainly includes the progression of the MJO, spikes or crashes in mountain torque (especially the impact of EAMT on the pacific jet and how that affects us downstream), frictional torque and its impact on the overall budget and the gradient of progression itself. You have been around long enough to remember GP using some of this in his forecasting methodology before he disappeared. And then, more recently, many of us talk about the stratosphere....still a riddle all of its own to be sorted out, and we discuss ocean temperatures and the role of the QBO, ozone transport via the B-D circulation (though we havent mentioned ozone much this year) and often solar stimulation of the jet, especially at maximum and the reverse at minimum. I think your suggestion that those using GSDM factors in their prognosis are ignoring all the others is a stretch. Model guidance is an interesting one. We follow it. We watch it change frequently. We watch Glosea be correct and then incorrect. We watch the EC weeklies lead us up and down the garden path. I dont think anyone would argue we should ignore it - but I think old hands know it can often be wrong, and it is in itself a physics calculation that is taking on board all (?? - I often wonder if it is "all") the factors that get discussed by us. Does NWP factor in solar impacts? Hmmm. Many of us remember Dec 2012 with horror. I believe in the end it was decided that NWP went completely upside down at very short range back then because of a sudden increase in solar activity. So....if that is the case then are we wrong to argue that NWP does not have the perfect crystal ball? I dont think so. Surely a huge part of the fun is to try and out-interpret the physics based modelling, not least because we know it is often wrong!! And how far in advance did NWP spot the strat split and BFTE in 2018? I think many of us were a step ahead of the modelling back then and we watched it fall gradually into line. I have no problem stating that NWP is not the be all and end all - precisely because it isnt. Do we admit failures? I guess it depends who you are pointing the finger at here, and probably best not to get into that. I think there are more figures on the mod thread that make unreasoned assertions as to what is going to happen who - when they are off target - just disappear...than there are those who set out a reasoned analysis who then do tend to come back and account for what has turned turtle. There's a lot of frustration right now - hardly surprising. Let's not bin any of the science though - and let's not get into a witch hunt. We like to think that CC might not be the biggest teleconnective driver of all and that we can hark back with optimism to 1947 and 1963 and 1979 and 1985 etc etc - but in truth we probably cant....and the pattern matchers will fall foul of this more than any others and we just have to accept that it is going to get harder and harder for the UK to get a properly frigid cold spell than it ever was 40 years ago. But let's not believe that we lack the tools to predict the next great cold spell. We are sharpening them nicely I think, and someone in the future using a particular predictive combination (including GSDM analysis) is set for cult status at some point!

OK - seeing the weather as pure chaos is fine as a position to take....but you can't have it both ways and pull discussion of a strong Nino, ENSO and even Hadley Cell expansion into the conversation. Either analyse drivers such as the ENSO, consider factors such as sea surface temperature that might promote a resilient ridge over Iberia - or perhaps do the same for what has caused a near permanent cold trough over Scandinavia this season - or don't. There is no middle ground in the debate between chaos and understanding. While fighting the lurgi I have been as disappointed as any with the developments of the last 4 weeks or so. It is a bit early to say goodbye to winter yet because we have seen cold spells in March deliver twice in 2013 and 2018 and another late season flourish may come again, but for the heart of winter it has indeed been underwhelming. You correctly identify that the MetO have not had a good season either - the seasonal and longer range models have thrown out some persuasive anomaly charts suggesting a continental flow, but it hasn't arrived. Why? That is the crux, and I would hope still a fun part of what we are on here to do. As I reflect a bit I think the strong rather than moderate Nino may be part of the answer and there is no doubt in my mind that CC is altering the base state over mainland Europe, putting together a context where pressure is higher almost all the time. There are datasets that bear this out and it hardly takes a genius to notice the extreme temperatures Europe is experiencing in most summers now. This context pushes on into winter too - higher pressure, higher temperatures, less continental cold. There is nothing we can do about this now and we need to know that the 60s-80s are a thing of the past. The bar for winter "success" needs to be lower....hard though that is to swallow. 4 to 5 cold days in January as we experienced this time around may need to be the future definition of a cold winter. I note that the MetO themselves have advertised most of January as cold. I challenged Marco P a bit on that - he came back with a graph to evidence it, and clearly anything even a touch below average now attracts "cold" as a descriptor. I dont like it - but again it is probably where we are these days now. To stick to teleconnections a bit, which DO explain our patterns (no matter how much mud gets slung) - we have seen a season where the MJO has failed to maintain active phases once through the Maritimes, and the vortex has not been knocked out of shape enough. Add strong Nino on top and we get a near but not quite near enough scenario. And lets not forget solar maximum either. Why has convection died in the western pacific? Early doors the IOD was unfavourable...and perhaps it did not fade fast enough. And I really think the failed SSW in early January was a key factor, and not something that is yet understood. There was a lot of positive precursor stuff in early winter and the models fell in line. Indeed - modelling of SSWs tends to be under rather than over modelled, so when it went upside down in early January it was a surprise. Reflective reaction to wave attack was what we got instead, and the science of strat analysis will move forward and benefit as a result, case study on case study. Finally - dont rule out luck. Forecasting is probabilistic. 95% isnt a guarantee. This season we probably had a better than average chance of a proper cold spell in winter's heart - shall we say 60%? - but 60% isnt a guarantee either. The dice didnt roll. C'est la vie. We know we will be back for more. It's the nature of snow obsession. Don't abandon the attempts to make sense of the drivers that create our weather. To do so would make this forum pretty much redundant.

Been suffering from Covid the last week and it drove me away from screens and brain activity. Sheesh - talk about brain fog. Nightmare. Feeling a bit better, and better again for what may lie ahead. No need to go over the crash from 22nd Jan, the disappointment of the final stages of January and the prognosis at one stage that suggested February could flatten out. But but but - we always knew a crescendo of drivers supporting a more blocked/cold pattern for our part of the world were on their way as we left January and that - with a degree of uncertainty on lag - there was a good chance February could deliver. A few core pointers. AAM tendency has been positive for a good while now, and this leads to: = a good high level of GLAAM, ready once again to support the right kind of blocking. This leads to a positive picture of the current GWO orbit: We are in the Nino 5-8 range which represents wind flows conducive to the North Atlantic blocking snow hunters crave. All this is good. What about the issues around the strat, which about a week ago looked like it might spoil the party? What a change that is in the space of a week. We have a significant slowdown imminent - maybe even a second bite at a significant SSW - and a context from top down that has swung back in dramatic style to provide a blocking opportunity once again. Where does the EPS see this heading? We are on track for substantial height rises to the north, and likely north west, as we head into school half term week. Whether we can get some more late season joy out of this remains to be seen - if the strat continues to be modelled as under ongoing stress then who knows. I hesitate to mention 2018 because I dont think we got the precursors to cause that kind of SSW this time around, but I certainly wouldnt be surprised to see a cold and blocked March given how things sit right now. Given the declining nature of the vortex by then, a GH embedded in late February in a high GWO orbit background looks likely to me to stick around. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5030427

Meanwhile - will it snow later this week? GFS says no but the MetO seem pretty bullish (a snow warning 3 days out??) and the ECM says yes. The macro provides no answer here - will the trough elongate and slide through? Marginal, potential high reward.

Been suffering from Covid the last week and it drove me away from screens and brain activity. Sheesh - talk about brain fog. Nightmare. Feeling a bit better, and better again for what may lie ahead. No need to go over the crash from 22nd Jan, the disappointment of the final stages of January and the prognosis at one stage that suggested February could flatten out. But but but - we always knew a crescendo of drivers supporting a more blocked/cold pattern for our part of the world were on their way as we left January and that - with a degree of uncertainty on lag - there was a good chance February could deliver. A few core pointers. AAM tendency has been positive for a good while now, and this leads to: = a good high level of GLAAM, ready once again to support the right kind of blocking. This leads to a positive picture of the current GWO orbit: We are in the Nino 5-8 range which represents wind flows conducive to the North Atlantic blocking snow hunters crave. All this is good. What about the issues around the strat, which about a week ago looked like it might spoil the party? What a change that is in the space of a week. We have a significant slowdown imminent - maybe even a second bite at a significant SSW - and a context from top down that has swung back in dramatic style to provide a blocking opportunity once again. Where does the EPS see this heading? We are on track for substantial height rises to the north, and likely north west, as we head into school half term week. Whether we can get some more late season joy out of this remains to be seen - if the strat continues to be modelled as under ongoing stress then who knows. I hesitate to mention 2018 because I dont think we got the precursors to cause that kind of SSW this time around, but I certainly wouldnt be surprised to see a cold and blocked March given how things sit right now. Given the declining nature of the vortex by then, a GH embedded in late February in a high GWO orbit background looks likely to me to stick around.

Well - here we go. ECM 192 shows the bulk of trough energy moving to the east, in line with strat forecasts, and ridging arriving out to our west. This fits with the drivers that have been described on multiple occasions, so I wont describe them again. Won't be long before excitement builds in here once again.

Agree - spot on. I've been keeping my head down as we live through this westerly, mild mush that darkens my day so much - not because I dislike getting up into a warmer house or dislike opening the windows when the sun pops out and it is 13 degrees outside....because I enjoy that very much in Spring!! But the seasons define the ebb and flow of the yearly calendar, and when winter is routinely so mild and damp and windy and dross-like it does not improve my personal mood. I grew up with snow in the 70s and 80s and would love those days to return. CC likely means not for a generation or 3 at least. Back on topic - I agree with you - this is what it will be all about. Can these substantial tropospheric drivers seize control of a pattern that could yet be held tight by the SPV? Showing another representation of peaking momentum, here is the relative tendency from earlier this week Here is the sharply rising total AAM budget and here now is the fast rising GWO orbit, a representation of windflows that demonstrate how predisposed to a blocking pattern these windflows are This is all good news - as good as the last rising phase at an earlier stage I would say, and likely therefore to exceed the totals we got that set up the mid January cold snap. Meanwhile....the vortex stays strong but according to GFS a growing signal that the lower layers are going to be firmly displaced over to the Siberian side as they were in December by early season warming from Canada The door for a NW centred block is very definitely being opened here. Can we push it wide and let the wintry floodgates open? The latest CPC text on the MJO, a key feature of the overall wave driving operation, is rather tasty: "Good agreement exists in the dynamical models looking ahead, which initially favor a high amplitude MJO signal over the Western Pacific that weakens and slows after the week-1 period." - because, weakening or not, a high amplitude west pacific signal that stalls is exactly what we would want to sustain this wave driving, with the potential to render the strong SPV less relevant than it might be. MJO plots, as ever a bit unreliable, are illustrated here and are lining up favourably: January has done a lot to knock the stuffing out of cold winter forecasts and forecasters, whether that be because of failed late month progression that indicated cold longevity or the comments of those quick to jump on the fail as evidence of the pointlessness of trying to forecast the unforecastable. We move on from all that. February starts next week, there is a distinct chance of a cold spell through mid month and beyond and that without a SSW or even a weakened vortex. The cold light of post season analysis is going to provide some very useful bits of guidance and information for seasons ahead, whether or not we land a proper cold snowy surge this winter or not. And there is still March to come, arguably the month that has delivered the most over the last 10 years or so. So.... here we go again on another chase. Winter would be dull without them even if, like the a tiger, we fail more than we succeed in our hunt. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5024700

Coming back on this one. The probability of the unexpected. A genuinely relevant and interesting question in itself. Some will groan and grind their teeth at the tendency for anything that can derail a cold pattern from coming to pass almost routinely. How many times do we read curses around "short waves" messing up the pattern, for example?! I dunno. Some of this is micro stuff, and when we get to the micro analysis of tiny shifts of 50 miles or low pressure waves popping up - I begin to glaze over. We don't have the computing power yet to be able to forecast these with any accuracy and I think they are beyond the wit of the human brain to be able to interpret from an analytical perspective. So the unexpected micro development will be a thorn in our side, and a thorn that arrives on the scene frequently, until resolution and computer modelling gets better. In terms of large scale "unexpected" features I do sense that these are less frequent than might appear to be the case. Having watched with a mixture of hope and horror a long run of winter seasons since the internet came into existence, I think the macro driver interpretations are not often derailed by the unexpected. Sometimes the unexpected comes to our aid. The BFTE 2018 pattern was a split SSW impact that was not seen at all until late in the day, and it didnt really feature in the long term analysis as something that was likely. Hindsight analysis has since picked up on hemispheric patterns in mid January that set up what happened....all part of the learning. But these were not screamed about at the time. Our current fail, the impact of a reflective strat response to wave driving, is another unexpected event. But this one, and the 2018 one - how frequent are they? Each season seems to me to run fairly accurately to script for most of the time. So...take the current winter. We got early cold as forecast by drivers. We got the relaxation as expected. We then didnt get an MJO enhanced Xmas spell - but this was likely down to some over enthusiastic interpretation of that phase rather than the drivers themselves misaligning. We then got the mid month cold as expected. And if we get the mid Feb cold as expected then, across the season, we have around 5 phases of weather with a single unexpected feature that derails things. In probabilistic terms, we cannot hit 100% accuracy. In general pattern terms I think we should be extremely happy if a season gets to roughly 75% accuracy. 50% for me would be minimum satisfaction rating. And in all this the "unexpected" factor is perhaps not that common.

A good question as I butt in here....but EAMT establishes the strength and direction of the Pacific Jet, and the Pacific Jet is all important when looking at wave patterns across the NA continent, far more than any impact off the Rockies. I would say that NAMT is significant when looking at warming of the stratosphere from the Canadian side. We have seen a lot of this through the current winter, and it is no coincidence the Aleutian Low has dominated as a feature, driving this torque. But I dont see that as impacting as much on the jet and jet angle across the atlantic as the much more significant Pacific Jet which gathers so much energy when Tibetan torque is engaged. EAMT therefore the most important....?

Agree - spot on. I've been keeping my head down as we live through this westerly, mild mush that darkens my day so much - not because I dislike getting up into a warmer house or dislike opening the windows when the sun pops out and it is 13 degrees outside....because I enjoy that very much in Spring!! But the seasons define the ebb and flow of the yearly calendar, and when winter is routinely so mild and damp and windy and dross-like it does not improve my personal mood. I grew up with snow in the 70s and 80s and would love those days to return. CC likely means not for a generation or 3 at least. Back on topic - I agree with you - this is what it will be all about. Can these substantial tropospheric drivers seize control of a pattern that could yet be held tight by the SPV? Showing another representation of peaking momentum, here is the relative tendency from earlier this week Here is the sharply rising total AAM budget and here now is the fast rising GWO orbit, a representation of windflows that demonstrate how predisposed to a blocking pattern these windflows are This is all good news - as good as the last rising phase at an earlier stage I would say, and likely therefore to exceed the totals we got that set up the mid January cold snap. Meanwhile....the vortex stays strong but according to GFS a growing signal that the lower layers are going to be firmly displaced over to the Siberian side as they were in December by early season warming from Canada The door for a NW centred block is very definitely being opened here. Can we push it wide and let the wintry floodgates open? The latest CPC text on the MJO, a key feature of the overall wave driving operation, is rather tasty: "Good agreement exists in the dynamical models looking ahead, which initially favor a high amplitude MJO signal over the Western Pacific that weakens and slows after the week-1 period." - because, weakening or not, a high amplitude west pacific signal that stalls is exactly what we would want to sustain this wave driving, with the potential to render the strong SPV less relevant than it might be. MJO plots, as ever a bit unreliable, are illustrated here and are lining up favourably: January has done a lot to knock the stuffing out of cold winter forecasts and forecasters, whether that be because of failed late month progression that indicated cold longevity or the comments of those quick to jump on the fail as evidence of the pointlessness of trying to forecast the unforecastable. We move on from all that. February starts next week, there is a distinct chance of a cold spell through mid month and beyond and that without a SSW or even a weakened vortex. The cold light of post season analysis is going to provide some very useful bits of guidance and information for seasons ahead, whether or not we land a proper cold snowy surge this winter or not. And there is still March to come, arguably the month that has delivered the most over the last 10 years or so. So.... here we go again on another chase. Winter would be dull without them even if, like the a tiger, we fail more than we succeed in our hunt.

@RainAllNight - Tamara has answered your question and I'll add a bit to it. Recent discussion around failed blocking at the end of this month has not centred on a "failed" process. Indeed, as expected, the pendulum nature of momentum swings started back in favour of blocking at about the expected time (ended up 16 Jan, could have been a day or 3 earlier but this fits within the noise) but what changed was the overriding strength of a reflective stratospheric event that was not forecast. I'll go a bit further than that - unless you are Simon Lee who has written on this subject I'm not sure that the way the stratosphere responds to vertical wave assaults is well understood at all. Simon himself, a pretty modest and helpful X poster, would probably quickly agree that there is a lot we still need to learn. So - this reflective event has overridden the tropospheric signal that started as expected. The week we are in now was always flagged as vulnerable to a flattening pattern, and the strat response has flattened it hard and fast. The impacts of that flattening will now endure through next week it appears....but all the while the forcings pushing us towards renewed northern blocking are gathering in strength as many of us thought they would through this period and out into February. The question will be - can the bottled up effects of a momentum surge overcome the strat quick enough to make an impact before we get too far through February? Earlier this week I felt quite glum about that - chances in my mind reducing. I look at strat forecasts for the month and am still not confident that these tropospheric forcings can seize control from the strat once again....but I feel a bit more optimistic about that today. Why? Well - not as a result of this chart which looks horrendous... but more maybe as a result of this - already posted by Tamara and linked to that the high spiking nature of the calculated tendency which is, without doubt, going to drive us back towards a tropospheric disposition towards higher lat blocking. That MT spike is very significant. It has arrived as expected but looks bigger to me than I expected and that is good for winter fans. I cannot help but curse our luck this month. First a failed SSW, and noone expected it to fail - indeed the strat big guns all came out and started to celebrate in the run up - and then a really positive tropospheric setup that has been undermined and stalled by an unexpected and not fully understood impact of strat developments. It could all have been so very very different! Watching battle commence between this momentum-led forcing and the strength of the SPV will be an interesting watch if nothing else. We can but try and learn. Perhaps, after 2 bouts of poor fortune and a truncated cold snap sandwiched between them, we can strike it lucky in February. I remember some epic snowy February weeks - 1991 and 1996 at the top of the pile and it would only take a week like that to save this winter from mediocrity. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023764

@RainAllNight - Tamara has answered your question and I'll add a bit to it. Recent discussion around failed blocking at the end of this month has not centred on a "failed" process. Indeed, as expected, the pendulum nature of momentum swings started back in favour of blocking at about the expected time (ended up 16 Jan, could have been a day or 3 earlier but this fits within the noise) but what changed was the overriding strength of a reflective stratospheric event that was not forecast. I'll go a bit further than that - unless you are Simon Lee who has written on this subject I'm not sure that the way the stratosphere responds to vertical wave assaults is well understood at all. Simon himself, a pretty modest and helpful X poster, would probably quickly agree that there is a lot we still need to learn. So - this reflective event has overridden the tropospheric signal that started as expected. The week we are in now was always flagged as vulnerable to a flattening pattern, and the strat response has flattened it hard and fast. The impacts of that flattening will now endure through next week it appears....but all the while the forcings pushing us towards renewed northern blocking are gathering in strength as many of us thought they would through this period and out into February. The question will be - can the bottled up effects of a momentum surge overcome the strat quick enough to make an impact before we get too far through February? Earlier this week I felt quite glum about that - chances in my mind reducing. I look at strat forecasts for the month and am still not confident that these tropospheric forcings can seize control from the strat once again....but I feel a bit more optimistic about that today. Why? Well - not as a result of this chart which looks horrendous... but more maybe as a result of this - already posted by Tamara and linked to that the high spiking nature of the calculated tendency which is, without doubt, going to drive us back towards a tropospheric disposition towards higher lat blocking. That MT spike is very significant. It has arrived as expected but looks bigger to me than I expected and that is good for winter fans. I cannot help but curse our luck this month. First a failed SSW, and noone expected it to fail - indeed the strat big guns all came out and started to celebrate in the run up - and then a really positive tropospheric setup that has been undermined and stalled by an unexpected and not fully understood impact of strat developments. It could all have been so very very different! Watching battle commence between this momentum-led forcing and the strength of the SPV will be an interesting watch if nothing else. We can but try and learn. Perhaps, after 2 bouts of poor fortune and a truncated cold snap sandwiched between them, we can strike it lucky in February. I remember some epic snowy February weeks - 1991 and 1996 at the top of the pile and it would only take a week like that to save this winter from mediocrity.

@Stravaiger Spot on. Your analysis of CC impacts I would say nails it. To the Mods - taking out the Quote option completely is a mistake. Anyone who wants to know what it is I am agreeing with here now needs to backtrack through the thread. For any who choose to follow key posters only, rather than read every single post, that is hard work. Can we have quote as well as reply??! Minor edit - this is Stravaiger's good analysis, copy and pasted: "My simplistic understanding is that GHGs stop heat escaping from the troposphere into the strat, cooling the strat, which in turn gives us a tighter sPV and tPV, with the polar jet pulled poleward, which allows HP to ridge north into southern Europe."

This is a really good explanation of the real context behind the latitude of high pressures in winter. For those who believe that an Iberian High drives the pattern it would be worth scanning your eyes over general north atlantic patterns in summer when there is no vortex. This gives you a sense of the "true" tropospheric inclination towards pattern evolution and you will note that, in general, we see a lot more high pressure cells floating around at a more northern latitude than in winter. The impacts of the winter polar vortex are the reason why these high pressure tendencies are squashed down, and the latitude of the jet, impacted itself by the polar vortex, is key in this too. The Hadley Cell exists, and there is evidence it is getting stronger. But the idea that a specific Iberian ridge is acting as a driver of the pattern in our sector is a stretch. It is a symptom of other goings on. If we go back to the origins of generally more dominant westerly patterns I think we start with the temperature of the stratosphere, being driven down by the impacts of rising CO2. And to keep this post relevant, this is not a chart that fills my wintry heart with icy joy. Strat vortex now spinning faster than average and forecast to remain so Doesn't tell the whole story because, lower down, we have temperatures continuing to run a fair bit above average and this will be aiding in preventing a full on downwards coupling of westerly forcing. We need the fates to jump onto our side a bit here and prevent this kind of solid looking 10hpa forecast on GFS today downwelling through February. Looking at pressure anomalies at present I'm not seeing anything digging in to suggest significant disruption of the vortex as we move through February. Snow lovers like me are going to need place a lot of faith in a very active pacific pattern and (hopefully) a jump in momentum. The MetO text continues to keep the door open to a cold outbreak, though I'm starting to wonder if the constant mention of low probability cold air from the east with snow impacts is anything more than a media marker against a low probability outcome to keep all bases covered. It did feel that the text in late December was seeing something develop in January. My fear would be that the failed SSW and now up gunned vortex at 10hpa has spoiled that potential. I'd love to know what Glosea based the strong February -NAO outlook on. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5023036

This is a really good explanation of the real context behind the latitude of high pressures in winter. For those who believe that an Iberian High drives the pattern it would be worth scanning your eyes over general north atlantic patterns in summer when there is no vortex. This gives you a sense of the "true" tropospheric inclination towards pattern evolution and you will note that, in general, we see a lot more high pressure cells floating around at a more northern latitude than in winter. The impacts of the winter polar vortex are the reason why these high pressure tendencies are squashed down, and the latitude of the jet, impacted itself by the polar vortex, is key in this too. The Hadley Cell exists, and there is evidence it is getting stronger. But the idea that a specific Iberian ridge is acting as a driver of the pattern in our sector is a stretch. It is a symptom of other goings on. If we go back to the origins of generally more dominant westerly patterns I think we start with the temperature of the stratosphere, being driven down by the impacts of rising CO2. And to keep this post relevant, this is not a chart that fills my wintry heart with icy joy. Strat vortex now spinning faster than average and forecast to remain so Doesn't tell the whole story because, lower down, we have temperatures continuing to run a fair bit above average and this will be aiding in preventing a full on downwards coupling of westerly forcing. We need the fates to jump onto our side a bit here and prevent this kind of solid looking 10hpa forecast on GFS today downwelling through February. Looking at pressure anomalies at present I'm not seeing anything digging in to suggest significant disruption of the vortex as we move through February. Snow lovers like me are going to need place a lot of faith in a very active pacific pattern and (hopefully) a jump in momentum. The MetO text continues to keep the door open to a cold outbreak, though I'm starting to wonder if the constant mention of low probability cold air from the east with snow impacts is anything more than a media marker against a low probability outcome to keep all bases covered. It did feel that the text in late December was seeing something develop in January. My fear would be that the failed SSW and now up gunned vortex at 10hpa has spoiled that potential. I'd love to know what Glosea based the strong February -NAO outlook on.

Thanks John - appreciate that and very much appreciate your 6-10 and 8-14 day outlook interpretations. They are as accurate as anything out there....

"Background Zealots"? Hmm. Is this where we are at now, where those trying to unravel the complex task of forecasting get labelled as zealots? Either you know what that word means and are therefore genuinely trying to put the boot in, or you don't know what it means and perhaps shouldn't be using it. I see in general the knives are out today. Disappointing. Let's have a go at a broad response: 1. There are 2 areas of ongoing research that interest those with a passion for this kind of stuff. First is the GSDM theory first put together about 15 years ago by Ed Berry. The second is a greater understanding of stratospheric impacts on our weather, another fledgling science that has also been around for 15-20 years approx. 2. One of the challenges of both approaches is to try and understand the inter relationship between the two. GSDM is largely anchored on developments in the Pacific alongside momentum impacts created by the big mountain ranges - Tibet and Rockies probably most importantly, Urals also. Strat modelling tries to interpret the impact of vertical wave propagation and how the column of air above the arctic is shaped/squeezed/stretched/split (or not) by these waves. Tropospheric patterns feed into the strat and vice versa - so they are definitely linked - but an understanding of the links is still in its infancy. When Amy Butler tweets that the reasons for the failed SSW in early January are not understood (given models tend to under rather than over model the likelihood of an SSW) then you know you are walking in a world of grey. And that failed SSW and what has transpired instead has had a huge hand to play in how January has developed. 3. From this, we have 2 options. Label these areas of research as a waste of time, as likely to produce accuracy as the advice of a cat (!!), or we engage with what is going on and try and unpick it. CC is not making this any easier because CC is making a mess of analogues - the atmosphere and the overall climate just isn't what it was in the 1960-90 period and adapting to the pace of change and how it impacts forecasting is a challenge. 4. Some of today's posters would clearly favour the former. Don't bother trying to unlock the door to understanding because it cannot be done. Fair enough - but not for me. I'm not a nihilist and wish to continue to try and learn. Perhaps those who see chaos theory as the only answer to our weather should have a thread all of their own, though the thread would probably make for pointless reading. 5. Finally - you might want to read posts more carefully. Only the other day I acknowledged in a post that the Xmas forecast was a bust, and that the recent cold was shorter lived than expected. Reasons for both were set out, bust was advertised. Two successes at the same time, early Dec and the snap just gone. And it looks as though next week will bust too. There you go - is that clear enough? If you want the reason laid out again, reflective strat event. Not forecast, not spotted even by those with proper qualifications in relevant climate science. But this winter is not done yet, and I still see distinct opportunity for further cold in February and again into March. As a concluding comment, we are dealing in probability forecasting. No one will ever get to the stage where we say "in 10 days' time it will snow in London and 6 inches will fall and stick." Nonsense. We look at probabilities. And when dealing in probability a 95% chance does not always land. I see some criticism of the MetO today as well. Really? Those of you happy to criticise forecasting methodology and happy also to criticise (possibly) the most advanced national Met Office in the world and its choice of language are seeking a level of absolute clarity that is unattainable. If you have something to say that adds to the debate, say away. If your words are designed to tear, rip and demolish - silence is a better alternative. Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5022417