Met4Cast

Because they go hand in hand with the models, they provide context to modelling which can help to understand why modelling is doing what it’s doing, I don’t see how a bit of knowledge on that is a bad thing? The rest of your post is a little bizarre if i’m honest, nobody has suggested synoptic modelling can’t be discussed?

TillyS The only real "teleconnection" fail this winter was in January when we saw a reflective SSW event, something that's rather rare and cannot be forecasted beyond the short term, the stratosphere is a very important factor & can overrule tropospheric forcing, which is what happened (See my post in the Winter post mortem thread where I explained all of this) Otherwise, they've been a good indicator throughout this winter in terms of broadscale patterns. What you can't do though is take the MJO in isolation like many in this thread do. Many see the MJO phase, look at the composite and expect that to be the pattern that verifies but unfortunately it's not that simple. The MJO is just one variable in the broader windflow budget and you need to look at both tropical & subtropical forcing, looking at just 1 variable will not give accurate results. I hope the thread becomes more filled with teleconnection talk rather than less, these teleconnections drive the models, not the other way around and the more we understand them, the more accurate future forecasts will become. In terms of the shorter term though, yes NWP rules the roost. Teleconnections can only give broadscale indications of potential pattern changes, they cannot tell you it will snow in X location on X day.

AM tendency is rising once again thanks to another strong (albeit likely brief) +EAMT event. In terms of the broader patterns going forward though I'm struggling to see much in the way of a trop response to the SSW next week, MJO forecasts have been all over the place and I suspect we're seeing influence from the SSW there skewing modelling somewhat but general consensus appears to be out of the COD into phase 4/5. In early March this correlates to stronger S European heights and a flatter zonal Atlantic jet (there's a surprise). With the recent sharp fall and rise in AAM tendency it does seem plausible that we'll see the jet stream encountering some road blocks in the form of high pressure, probably to the NE of the UK (though as mentioned previously, the high probably too far NE to influence the UK much) before the pattern flattens out again by the end of week 1 into week 2 of March. Broadly +ve and -ve anomalies are propagating poleward now so a brief relaxation of Iberian heights and a more amplified jet does seem plausible next week but again, not sure it'll be in the right place to influence the UK in terms of colder weather. For the UK at least, a continuation of mild & at times unsettled weather seems the favourite going forward, just to make a change. Quite a tricky period to try and "diagnose" but I've given it a go anyway! This is fairly low confidence. Interestingly the Met Office extended forecast suggests the opposite of this & currently favours blocking/colder temperatures to take hold post March 11th so will be fun to watch that evolve!

My focus is primarily on the stratosphere at the moment & potential impacts from a major SSW during early March. Still not much urgency to downwell the -ve anomalies quickly, modelling now goes out to the 10th March. Strongly -NAM state despite this though but with little blocking to speak of in the troposphere. We've seen quite an abrupt change in MJO forecasts in recent days too, initially looking like a return to phase 5 has now switched to returning to phase 3/4 in the Indian Ocean following the previous decayed signal. Phase 3/4 composites for March are very unsettled for the UK, phase 3 perhaps a little chillier. In essence though - For those still chasing cold/snowier outcomes, I think it might almost be time to give up the ghost.

The lack of posts in here in recent days tells the story I think. No sign of anything remotely cold or snowy in the forecast with modelling overwhelmingly favouring a return to milder conditions right out into the extended. No real urgency in the downwelling of -ve anomalies from the strat.

Thanks for the correction, appreciate that!

I don't think you'll find a single climate scientist that's made this claim. Cold records however are much less frequent and pale in comparison to heat records by a ratio of about 10:1.

Rain All Night Wind reversal. Westerly winds are inherently more stable than easterly winds. Descending easterlies disrupts the usual westerly flow in the troposphere which can lead to blocking.

No real sign of that currently & SSW’s do not always = cold weather of course. Given the timeframes there’s a lot of uncertainty but current modelling doesn’t indicate a quick downwelling & tropospheric response to the early March SSW & the MJO won’t be particularly favourable for blocking (it may become so later). I wouldn’t expect much impact until mid March at the earliest.

Just over a week on & indeed transient Atlantic ridging seems the most likely weather pattern through this month, certainly a departure away from the recent anomalous warmth across the UK (and indeed Europe) but nothing overly sustained or notable as largely expected. Any snowfall in the coming week or two will be mostly restricted to higher ground in the north. Going forward I'd not be surprised to see this pattern repeat a few times, i.e Atlantic ridging before collapsing. The MJO signal has now decayed into the Circle of Death (COD) and is not currently driving global weather patterns, a result of this is an abrupt loss in westerly inertia triggered by a strong -MT event, led particularly by very strong -EAMT. There is now evidence of poleward propagating +AAM anomalies which should help to generate Atlantic ridging and amplify it away from Iberia (the opposite to the recent equatorward fluxing helping to strengthen the Iberian high). The forecast going forward is quite uncertain, the MJO seems likely to emerge into phase 4/5/6 but the direction of travel & amplitude is very hard to ascertain at the moment. A major and sustained (perhaps final warming) SSW looks to take place during early March helping to destabalise the polar field but there's currently little sign of these -ve anomalies downwelling to impact tropospheric patterns before the middle of March, again though this is a large uncertainty within the forecast period. I'm still of the opinion that early-mid March will feature an increasingly -NAO regime albeit probably not notably cold across the UK with the high never really gaining much in the way of amplitude due to the lack of tropical (MJO) forcing. Looking beyond the early March period is difficult, much will depend on the outcome of the major SSW (and any downwelling impacts) & the trajectory of the MJO, again currently uncertain.

Yes, I think too much emphasis is being placed on this likely SSW in early March. Firstly because the timings involved here are worth mentioning, we've seen how poor modelling has been with SSW's this winter, why should we assume this one will be any differently? Secondly, an SSW in early March, assuming the usual 2 week lag we're looking at the 2nd half of March for tropospheric impact. Too little, too late imo. That said - As stated a day or two ago, I do think a -NAO regime is more likely than not going into March regardless of a potential SSW or not. AAM tendency has fallen through the floor as the MJO now sits inside the COD, this removal of tropical forcing has caused the previously sustained +MT to collapse into strongly negative territory, as a result westerly inertia is now being scrubbed from the atmosphere. Another way of visualising this is with the 850hPa anomaly hovmoller, a rather sharp increase in easterlies just west of the dateline following the collapse of the MJO. There are signs the MJO will return into phase 5/6 but the forecast on this is rather uncertain. The important part though is the sharp fall in momentum which is driving the pattern change currently advertised within NWP outputs. Atlantic ridging/Scandi trough scenario currently the favoured option but huge uncertainty over Scandinavia with regards to possible height rises around the Urals, the precursor to the early May SSW. I suspect any high pressure that does build to the NE will likely end up too far NE to provide much hope to those still chasing colder outcomes. In terms of the UK - Chillier than of late but little currently to suggest widespread cold/snowfall, as we go through March we require more spectacular synoptics to produce the goods. So to summarise, -NAO regimes are likely, UK will be colder than of late as a result but in terms of UK specific cold/snow likelihoods I'd still rate these as being rather low.

Agreed re: Cold/snow likelihoods, I think we will see a -NAO return but I’m not confident on that translating to a winter wonderland, like you it will probably be more chilly rain. On the quoted part though - I agree re: Summer, this perpetuating Iberian high pattern going into summer wouldn’t be good, Spain is already drought stricken & soil moisture is rapidly drying up now, I can definitely see scope for yet more record breaking temperatures across southern Europe this summer, especially when you factor in the declining El Niño & associated lag with the AAM as we transition into La Niña (probably sometime around mid summer). Early indications of summer patterns don’t bode well.

The idea of blocking during March certainly isn't without merit and for those chasing some early spring warmth (like me) the direction of travel is rather poor. The MJO looks likely to return to phase 5/6 before the end of the month if we look at the VP200 anomalies (RMM plots are all over the place currently, some support this idea, some don't). I wonder if this is SSW related? An uptick in +EAMT is expected thanks to a strengthening East Asia jet stream and we're currently seeing the highest amount of +ve westerly momentum since early December, this shown by the GWO plot being the highest of the season so far. With the current SSW helping to destabalise the polar field combined with another likely weakening/possible reversal (maybe final warming?) early-mid March the idea of an increasingly -NAO regime seems to be the best bet currently.

I think a good way to see how thing are progressing is to check previous posts so I've quoted this over from the teleconnections thread. Broadly this is how things are heading. Certainly turning colder as next week progresses but for most not cold enough to produce snowfall to lower levels. Further ahead into March is rather complicated, the RMM MJO plots are proving rather useless currently but viewing the VP200 anomalies seems to suggest a decaying MJO signal into the COD through phase 8 before a resurgence into phase 5/6. Broader westerly momentum continues to rise as yet another +EAMT begins to take hold which perhaps gives some confidence to the current modelling re: another stratosphere u-wind reversal early - mid March, an early final warming perhaps? Too early to say. Given this, I'd not be surprised to see a -AO and perhaps trending -NAO towards the middle of March. Blocking patterns potentially finally taking hold, once again, too late?

Thank you for the mention and I 100000% agree with this. Teleconnections cannot be used to forecast for the UK specifically but can be used for the broadscale direction of travel, i.e blocking regimes might be more likely or even develop but what that translates to UK specific weather is impossible to say! That includes the MJO & use of it’s composites etc.

In fairness that’s not too unusual, will likely be the final warming.

Blessed Weather Great post! I had actually been planning to create a post on this at some point in the coming days so good timing too. I think your conclusion on it being a strong reflection is probably correct, there were several things going on which likely led to the results we saw. It's quite difficult to "untangle" it all with limited vertical direction of travel on the charts, but I'll try & explain what I think happened using this strat observe chart. 1: Minor warming occurred in early January and as highlighted in your post, Amy Butler & Simon Lee both talking about this leading to the -NAM state & Greenland high, I think this is probably right but we also saw AAM anomalies propagating poleward with support from the MJO meandering in phase 3, this minor warming likely added some extra juice to what was already becoming a favourable tropospheric led pattern for Greenland blocking/HLB. 2: This -NAM then worked upwards into the stratosphere at a time we saw yet another SSW (whether this caused it or merely helped it? I'm not sure), I suspect this -NAM is the reason for the technical reversal we saw with this secondary strat event, the upwards propagation of -NAM however probably served to "cancel out" any downwelling from the major SSW in mid-Jan which then ultimately led to a breakdown in blocking and return to +ve zonal winds in the troposphere, as shown on the strat chart above due to the Canadian vortex shifting eastwards into the Atlantic sector. Quite a complicated entanglement of different forces/drivers coming together, one that would absolutely not have been possible to predict at longer ranges and something that seemingly caught even the experts out, let alone us mere mortals! From what I've read since, these reflection events are rather rare. So.. typical UK winter luck at play?

In a word, no, as my post 1 page back attempted to diagnose & show. Perhaps if you took the time to read my post 1 page back on this thread you’d see that i’ve done exactly that. You’d also see that broadly teleconnections have gone largely as anticipated throughout this winter but shorter term changes within the stratosphere (that cannot be predicted) have caused a lot of issues.

Very likely the opposite based on a few different studies. The Stratosphere is actually cooling with climate change rather than warming, increasing amounts of CO2 trapped in the atmosphere means less heat radiating out & as such heat gets trapped primarily in the troposphere allowing the stratosphere to cool, a cooler stratosphere = larger temperature gradient between the Arctic and Equator which would lead to a stronger polar vortex rather than a weaker one. You’re right though, more energy in the troposphere would suggest an increased likelihood of stronger “attacks” up into the strat so it’s quite a difficult one.

They’re available here; http://www.bom.gov.au/climate/enso/#tabs=Tropics&tropics=History-to-now

Just 2 runs ago 100% of EPS members had a technical reversal (Major SSW) The GFS was less keen but still had a significant number of members reversing u-winds. So in fairness expectations of a major SSW were high.

Unfortunately as highlighted by myself & others in recent days, “background drivers” have been against the idea of a significant high latitude blocking episode. It seems a major SSW is now unlikely too with a relatively quick sPV recovery compared to recent forecasts. Very odd winter in terms of the stratosphere.

Yuck.. Absolutely no sign of anything of interest on the ECM det (or the GFS, really)

Given the recent discussions around teleconnections/AAM & the broader GSDM framework I thought I would begin posting in this thread, hopefully we can build up something of a more technical discussion here & separate from the usual chaos and ups and downs of the model output thread. Winter is coming to an end now so I suspect the forum will be quietening down so it's perhaps a good idea to start and see where we go through summer. I've been delving into the GSDM and broader teleconnections for just over a year now after DMing Tamara & asking for some guidance. I'd still consider myself a novice but I do think this is the way forward in terms of mid-extended range forecasting despite recent comments from some. I wonder if @Paulor another mod could move this thread to the model output section? It seems a better fit vs here. My main goal is to try and get broader teleconnections discussed more by those who have an interest in the science & in forecasting vs just wanting a particular weather type. Late February I've posted elsewhere re: late February prospects but figured I would discuss the current situation here too. The MJO is currently dwindling through phase 7 and into phase 8 which if taken into isolation correlates to a mid Atlantic ridge/amplified Azores high. The up-coming stratospheric warming can be linked back to the MJO passing through the Maritimes and into the Pacific Ocean (Phases 4 > 5 > 6) through mid-late January, this created +ve Frictional Torque which in turn creates Rossby waves that amplify northwards, the impact of this was a very strong +ve mountain torque event in late January leading to a Pacific jet extension, this created further Rossby wave packets that have led to anti-cylonic wave breaking into southern Europe helping to strengthen the Iberian/S European high over the past couple of weeks. You can see these Rossby wave packets on the ECM time longitude plots. Back to the SSW (technical or not), the strong +ve East Asian Mountain Torque (EAMT) essentially deflects waves from the troposphere up into the stratosphere, this has been sustained more or less since late January with wave activity impacting the stratospheric vortex & now resulting in it's collapse. You can see this heatflux on the stratosphere plot from stratobserve, it's no coincidence that this is showing strongly downstream of the Himalayas (this is the EAMT at work) North American mountain ranges have also helped to generate heatflux (namely the Rocky mountain range) albeit to a lesser extent and now we're in a position where we're expecting significant deceleration of u-wind speeds in the stratosphere. AAM anomalies and indeed flux direction plays a part in the Iberian high mentioned above & subsequent anticylonic breaking. I wont go into too much detail on this in this post as there's always a lot of information here, but in summary; +ve anomalies have been broadly equatorward since late January (between 30S and 0) with little momentum propagating poleward, this (from my understanding, happy to be corrected) tends to drive energy into sub tropical ridges (Hadley cell inc. the Azores high) and this broadly has been the dominating pattern through February so far. There's no real sign in this fluxing switching to poleward fluxing and as a result there isn't much forcing to amplify Atlantic ridging into high latitude blocking later this month, hence the forecasts (and this is well represented within NWP modelling) generally favouring an amplified Atlantic ridge sending energy SEwards, for the UK this will likely bring colder weather than the anomalous warmth we've been seeing/will see in the coming days but probably wont be enough for a notable cold spell or widespread snow risks. Any questions please feel free to ask, the idea of re-igniting this thread is to get more people interest in the science & forecasting aspect this can provide, the more people joining in and being open to background teleconnective forcing the better in my opinion. It is a shame the GSDM data is locked away and it does somewhat limit potential learning on the topic but I think we can get around that via discussions/sharing of data where possible on this forum.

I think the point being made is that Tamara doesn't live in the UK and therefore the weather the UK sees has absolutely no impact on her personally regardless of personal desires for particular weather types, given she's not in the country, that alone removes any bias and allows her to be completely objective & scientific when it comes to UK specific weather.