Singularity

GFS gave me a 12*C max today and the actual is in the 16s. Go figure, oh wait we already have Anyway - just popped over to bring you a glance into another reality in which the GEM is right and we become even balmier (okay, warmer!) next week: ...but if we look at heights in particular we can see a vast difference with GFS as early as +144: This difference is seeded around a day beforehand when GEM places the main low in our vicinity further north and is also more progressive with the one west of the Azores, so shutting the door on the jet stream taking on a NW-SE orientation into Europe to bring the UK a day of blustery showers on Saturday such as GFS shows and UKMO looks headed toward. It'll be interesting to see which side ECM picks later, as sometimes it shows a surprising affinity with GEM.

Given it's the only model seeing any MJO activity next week, I'm wary of the GFS output too seriously at the moment, especially given how those sliding lows do usually end up adjusted south nearer the time which would result in something more akin to the 12z UKMO - a raw wind with cold rain and maybe some sleet showers, perhaps snow on high ground depending on just how much cold air has been drawn in from the western flank of the Scandi trough. To be honest I'd much rather see the low banished south nice and quick with a ridge building in by the weekend and a much better chance of avoiding having a trough complex sat over or close to southern UK during the following week. Apart from that snow event (or especially because of it, depending on your inclination), the 12z GFS run is pretty awful for the southern half of the UK in general.

Just quoting my post over from the MOD thread

A consistent feature of recent GFS runs is for a region of anomalously warm stratospheric temperatures to move across Greenland by Friday and then drift slowly toward Iceland over the following week, where it facilitates a stratospheric ridge. The tendency for high pressure to build back in after a changeable start next week looks to be at least partially in response to this. It is very uncertain, though, to what extent we might see a bit of MJO activity working with or against a ridge in our vicinity - but ECM is keen on having a quiet MJO for the foreseeable and GEFS have backed off recently so it could well be that the stratospheric forcing gets to dominate proceedings. It's interesting to see how resilient the vortex is this year despite being so persistently displaced toward Siberia. It makes me wonder whether the severely damaged thermal inversion over the Arctic has made it less 'inviting' to the vortex as a mostly weak but unusually persistent vertical transport of energy drives pulse after pulse of stratospheric warming. Meanwhile Siberia is able to retain an inversion setup due to being a solid land area, making it suitable for a lengthy stay of the vortex core. I'd wondered whether Greenland could act as an alternative home once the Arctic inversion was lost, but it seems the typical movement of the weak stratospheric warming works against this.

Behold, our own ring of fire I'm enjoying the tendency for a bit more of a ridge across from the southwest early-mid next week from ECM but GFS remains less enthusiastic - though even it has increased the influence a little, with unsettled conditions a bit slower to return Wed-Thu. Overall it seems that those seeking a protracted fine spell are having to wait patiently for the polar vortex to either move away from Siberia or weaken sufficiently to put an end to the tendency for the jet stream to return toward a path that heads straight into Eurasia on either a W-E or NW-SE trajectory. The unusually persistent displacement of the vortex made a mess of Feb and is now troubling us as we look toward getting some springlike weather. Thankfully it appears that an inflation of the subtropical ridges will be sufficient to produce at least one day next week of appreciably 'warm' temperatures for the time of year (mid-teens) and dry conditions, to accompany those of this week. Given the way ECM disrupts the Atlantic trough and drops a low south - represented loosely by the 'ball' of below-normal temperatures in the above image - there looks to be a chance that the progress of the jet into Eurasia will be impeded, in fact a good chance given that UKMO looks primed to produce a similar outcome as of +144. Height rises toward Scandinavia, often beyond initial model projections, has been a theme of recent years from spring right through to autumn (but of course, not so much in winter, when it would be more interesting to a fair few on here - typical eh?). At this time of year, it may have something to do with early snow cover loss and the polar boundary moving way north of what was once typical. Whatever the exact cause - it's something to keep an eye on.

High pressure is even more influential during Sat-Tue on the 12z GFS run with Sunday much drier overall than had been shown, due to what was a sliding low now being held away by a ridge from the Azores. Its a good trend if you fancy more pleasant spring weather and ECM has been heading in a similar direction. Could be a fair bit of cloud to get rid of this weekend though and there is that risk of the ridge building far enough SE to set up a chilly easterly flow by mid-late next week.

Great find there Knocker, cheers While the MJO is on the brain for a mo - I noticed just now how the propagation lately has been persistently underestimated by the dynamical models such as GEFS and closer to what the basic statistical models have been predicting; Currently the models have the MJO hitting a virtual wall where it is now and decaying. I wonder if this will actually occur or if the MJO will just sail right on... that'd shake up the output at least a little. Beyond that, we have GFS showing a re-emergence in phase 1 in around 9 days time which would promote blocking to the NW in late March - highly undesirable in my view - while ECM seems to keep it very dead indeed when looking at the H-W plots... of course that could be hiding contrasting signals, such as that from the unusually warm areas in the ENSO region which seems to be driving GLAAM a bit higher than might be expected when considering Indian Ocean MJO activity alone; This could explain GFS being keen to slow the Atlantic down a bit next week. ECM has other ideas although it has backed off a bit with today's 12z.

Strange to see GFS so insistent on inflating a Mid-Atlantic ridge, perhaps even with an omega block setting up, yet other models all persistent with cutting of a wedge of higher heights over Greenland with the jet stream just romping across to the south of it. The latter is a dire outcome as low after low is directed our way and March begins to look like a possible contender for one of the wettest on record. So it is that I very unusually find myself hoping for the colder GFS outcome as at least that should not be as wet!

12z versus 00z for midnight on Tuesday. This does not inspire much confidence in the model output. The trough configuration has changed substantially and so has the HP over Scandinavia by way of response. Some kudos to ECM for sniffing at this idea over the last few days, but it's still been very inconsistent so not many marks gained. Longer-term there is uncertainty over how the stratospheric vortex behaves - how displaced it will be and to what location? It is noteworthy how resilient it looks to be in the face of so many waves of warming. These are wave-1 attacks which only manage to push the vortex around - so we're not at all on a par with 2016 or 2013 in terms of an early destruction or severe disruption of the stratospheric polar vortex. While the seasonal relaxation of westerlies should encourage an increasingly extensive blocking response as March progresses, the lack of consistent signals for where the stratospheric ridge and vortex will locate means the UK looks equally likely to find itself on either the warm or cold side of blocking features, or stuck under slow moving lows with variable temperatures. Another factor to consider is the more ocean-like state of the Arctic than usual this year, with the climatological inversion struggling to establish for very long at a time, allow for frequent bouts of rising motion fueling intense storm systems which have been tending to shove blocking features more toward the mid-latitudes than would otherwise be the case. The optimist in me sees this as increasing the chances of scoring a mid-lat block near or over the UK... but you just know that would position such as to bring a cloudy flow off the N. Sea

Model madness and hints of highly anomalous conditions one way or the other. A plain and simple 6.4*C will have to do please. I'd not be surprised to see a 3-4 day run of exceptional warmth trash this, though!

Aye, these rumblings are really messing with my CET thinking this month. Very inconsistent output in terms of the details for our little slice of the hemisphere over the past week. Signs of very extensive blocking, in fact incredibly so by day 10 and it almost seems as if the models aren't sure how to handle such a messed up longwave pattern. Prepare for the weirdest March on record...

Cheers Interitus - so I gather we're looking at a lagged phase 8 MJO response that builds upward and reinstates a displacement of the stratospheric vortex toward Asia? Also I see what you mean about the vortex and warming events - and this is where the sense that displacements aren't good for cold weather in the UK come from; they are mostly as a result of Asian-sourced warming that occurs because the tropospheric/lower stratospheric vortex is over Canada/Greenland, where we don't want it to be. Exceptions may well exist if the vortex is far west enough, so more toward central/western Canada. For the elusive Canadian warming, it seems an unusual configuration of the mid-upper vortex is needed. Late autumn was particularly unusual last year and we came close to a technical CW. I believe we came within a gnat's whisker of a December to Remember, only for unexpected tropical activity in the Indian Ocean to kick off a feedback that trashed the whole configuration for us. It will be many decades before that defeat from the jaws of victory no longer triggers a furrowing of my brow. Same goes for the equally horrific failure of the models to correctly handle the MJO-related signals for mid-Feb this year. 'twas the winter of our greatest discontent! Well, mine anyway Never mind, moving on... - - - - - - - Cross-posting from the MOD thread as permitted; It's been a long time since we last had a jet stream shifted south yet remaining quite strong and sending lows across the UK. With a few tweaks and occurring in the depths of winter it can be a snow-lover's nirvana - but on this occasion, due to the time of year plus quite possibly the overall warmer state of the climate, this will only ring true for up on the mountains in the north, and even there perhaps only intermittently. We have a fairly strong bit of MJO activity in the IO at the moment, in terms of wind signals - convection is lacking. The odd run here and there has toyed with moving the ridge from our N to our NE seemingly by way of response, but it seems to me that with signs of the GWO nosing into phase 4, the models are finding too much of a subtropical ridge + flat westerly signal to let this really take shape. Whether that 'too much' is down to model judgement remains to be seen - I've often seen an MJO signal rise up to seize the day having initially been underestimated... but that was back before the winter of 2016-17 which if anything has displayed the reverse tendency, catching a fair few forecasters/climatologists out - including me of course; the MJO enthusiast. Still - I believe the blocking high to our N should start to be able to exert a more direct influence in the 8-16 day range, though from what location exactly is hard to say. If the models keep trending toward MJO phase 3 to follow phase 2 then a failure of the blocking to move to our E/NE could mean that it sticks around to our N for a long time. Increasingly I worry that with GWO orbiting negative - albeit weakly - the jet might keep on firing across under such blocking to bring about an exceptionally unsettled and wet March. We could really do with the hints of El Nino in the Pacific forcing a bit of a kick in GLAAM to hold up the Atlantic lows. Hopefully a Kelvin wave will turn up to help things along.

It's been a long time since we last had a jet stream shifted south yet remaining quite strong and sending lows across the UK. With a few tweaks and occurring in the depths of winter it can be a snow-lover's nirvana - but on this occasion, due to the time of year plus quite possibly the overall warmer state of the climate, this will only ring true for up on the mountains in the north, and even there perhaps only intermittently. We have a fairly strong bit of MJO activity in the IO at the moment, in terms of wind signals - convection is lacking. The odd run here and there has toyed with moving the ridge from our N to our NE seemingly by way of response, but it seems to me that with signs of the GWO nosing into phase 4, the models are finding too much of a subtropical ridge + flat westerly signal to let this really take shape. Whether that 'too much' is down to model judgement remains to be seen - I've often seen an MJO signal rise up to seize the day having initially been underestimated... but that was back before the winter of 2016-17 which if anything has displayed the reverse tendency, catching a fair few forecasters/climatologists out - including me of course; the MJO enthusiast. Still - I believe the blocking high to our N should start to be able to exert a more direct influence in the 8-16 day range, though from what location exactly is hard to say. If the models keep trending toward MJO phase 3 to follow phase 2 then a failure of the blocking to move to our E/NE could mean that it sticks around to our N for a long time. Increasingly I worry that with GWO orbiting negative - albeit weakly - the jet might keep on firing across under such blocking to bring about an exceptionally unsettled and wet March. We could really do with the hints of El Nino in the Pacific forcing a bit of a kick in GLAAM to hold up the Atlantic lows. Hopefully a Kelvin wave will turn up to help things along.

I do wonder if the unusually stormy winter has seen the usual freshwater layer disrupted to such an extent that a lot of the ice that has formed is tainted with salty deposits. Someone needs to get over there and tuck in to see what it tastes like

Great chart there Interitus, thanks for sharing Just taking a moment now to think about whether the MJO is going to produce interesting events for early March 2017 or not. Looking at this MJO-filtered product, we see that the wind signal left phase 8 on 20th at 850 hPa but back on 16th or 17th at 200 hPa. Since then the 200 has become weak but 850 is holding on better and looks to retain some degree of signal through phase 2. It's the phase 8 timing that's of most interest for the mid-range though, as a 10 day lag for encouraging height rises to the NW of the UK is not uncommon, and we have been seeing hints from recent model runs of such events around the turn of the month. In fact more than that; a clear 'bubble' of higher heights across Greenland by 1st which may have some support from the stratosphere as a ridge is also evident up at 30 hPa for example. Or perhaps the ridge works up from the troposphere? Either way it has scope for being very persistent in early March. Trouble for us, though, has been a lack of much indication that the Atlantic jet will take a breather in the mid-Atlantic and allow the subtropical high to link up with the Greenland High and at the very least pull us out of the unsettled regime. Without that happening, lows just keep on rolling in further south than usual and producing excessive amounts of rain and perhaps some strong wind events. The 00z (day 10 shown below) was in line with this and most recent operational runs from it and ECM. There have, however, been some attempts among the ensembles to hold up the Atlantic troughs long enough to allow the connecting ridge scenario to unfold, and the GFS 06z is the first operational in a while to at least give it a go, as shown below using the day 10 and 12 charts. Interestingly, this run then moves the ridge into Scandinavia for a time before retrogressing it to become a stronger feature to our N/NW (see day 16 chart below-left). This may be tied in with the stratospheric vortex being kept more displaced toward Siberia (see below-middle) than was the case in the 00z run for example. Either that or the model has started taking the MJO to phase 3 in the mid-range as per the notably enthusiastic UKMO (see yesterday's update, below-right), which corresponds to height rises to our NW and would probably shake things up a bit. Coming back to that displacement again though and believe it or not, pre-winter one of the strongest matching years for 2016-17 in terms of a wide array of teleconnections/drivers, including the state of the stratospheric vortex in late autumn, was 1952, and that winter saw the vortex displaced to Siberia more persistently than any other that I've seen. In light of which, frequent displacements that way have not been surprising to see this winter - but I had hoped they would be further toward East Asia with a stronger warming and positive GPH situation around Canada and Greenland. as opposed to the current situation which just seems to encourage a (somehow?) still dominant tropospheric Canada/Greenland vortex to keep handing off lows to a weaker one across Siberia, on a path that brings the UK either predominantly mild and quite benign or - based on next week's output - very changeable conditions in terms of temps, with a fair bit of rain around.

Hello - which measures have you considered for the starting point? Something I would very much like to look into if I can find the time some day is what correlation exists when considering sea ice area and volume as opposed to extent, or even the quality in terms of core temperatures but I expect data for that is hard to come by or doesn't exist in any consistent form going back far enough in time. In fact, it's possible that this year's sea ice area, volume and quality combination is so far below historical cases that we're in uncharted territory anyway... what a fun (!) time to be involved in climate science

Given the extraordinarily poor integrity of the ice (not captured by sea ice extent measures), I expect it would take a cool, cloudy/foggy sort of spring like I believe 2013 had in order to bring 2017 on a par with 2008-2011 for example. A 'regular' spring of weather would keep 2017 close to or a little below the currently record-low values of 2016, while a spring similar to that of last year would leave the ice in a state of degradation some way beyond anything ever witnessed on approach to the summer solstice. I am concerned that given the poor structure to a lot of the ice, even a relatively short spell of exceptional warmth in the early-mid spring could open up enough leads to greatly increase the proportion of solar input being taken up by the oceans during the following peak solar months during clearer periods. Given the scale of the difference in energy transfer between ice and water surfaces, it would take a lot of cloud to prevent a net increase in heat uptake... but I daresay last year came close, with the spring uptake perhaps proving the more significant for how the autumn panned out in terms of ice extent and quality. So it's possible that the increased moisture flux provides a negative feedback that buys the Arctic a bit more time... but I wonder if tropical forcing could still override that and produce a sunny summer month at some point akin to July 2015? I sense that we are one such summer month (perhaps May at a long stretch) away from sea ice being sent into freefall. Even if that doesn't happen we have the impact of strong storms, benefiting from the increased heat and moisture availability, to worry about - another reason why the integrity of the ice is so important. The current colder weather across a large part of the Arctic is looking unfortunately short-lived, but welcome nonetheless. The 7-16 day period is looking uncertain with signs that the jet will trend south but with low heights tending to remain in the Canada-Greenland area which threatens to set up a long-fetch southwest flow from the Atlantic side should high pressure develop over Scandinavia as per some recent model runs. On the other hand, the mild air might just sail right on through Europe, underneath a wedge of higher heights, while on the Pacific side there seems not to be much of a poleward heat flux threat on the cards, and there are signs that a block over East Asia could lift some deep cold out of Central Asia and send it across the Arctic, which would be a nice booster for the sea ice. So as yet I can't see any reason to anticipate things leaning one way or the other with respect to the scenarios I outlined at the start of this post. There remains reasons to be hopeful and that'll do me for now

It's really saying something when you have a cut-off upper high over Greenland and GFS still manages to move most of the UK back onto the milder side of the polar front. Need to keep an eye on Greenland in case the surface pressure response trends stronger. At the moment it's only enough to shift the jet south to run across the UK rather than down into Europe. In this way it turns from friend to foe; were it not cut-off, it would likely drift into Scandinavia and support a blocking high there which could at least have fended off the Atlantic wind and rain. As it is, GFS fancies a go at Doris II: Storming the South, or what the Met Office would less entertainingly name 'Ewan'. One of these days a storm like this will actually take such a path. I've seen quite a few red herrings of this nature from GFS over the past few years.

Classic model-troubling setup mid-next week with a wedge of higher heights trying to establish near N. UK and a negatively tilted trough in the mid-Atlantic. That trough should disrupt and feed a low across to the Scandi trough - but currently we have ECM going crazy with extra disturbances and GFS really powering up a low as it moves through the Azores - both ways to trash what would otherwise be a setup of some interest for those up north in terms of snow potential. Typical stance in these situations is to expect the progress of Atlantic troughs to be well overdone at this range - but to also acknowledge that a change in the background forcing could remove the wedge of higher heights and render this expectation invalid anyway! Such is the nature of trying to get a handle on the chaotic system that is the Earth's atmosphere.

With an MJO signal in the Indian Ocean and a stratospheric vortex persistently displaced toward Asia it seems the ingredients for blocking to our NE are there, but the road that the model runs which follow this script are keen to take on the way there leaves not a lot of cold air to be brought our way, resulting in a nuisance chill and little more. Then we have the sporadic signal for the Atlantic jet to remain strong and keep things mobile for us instead. Possibly the tropospheric polar vortex just doing its own thing rather than aligning with the stratospheric one. I wonder if we might see a halfway house of sorts which sees strong westerlies over a mid-latitude block. Sounds all too familiar doesn't it? Not hard to figure out why I've been silent for quite a while; ever since the massive modelling fail with respect to mid-Feb there's been a distinct lack of particularly appealing charts to discuss (or at least, within the 10 day range). Tomorrow was briefly an exception but it has since gone too far with the wind and not far enough with the cold air component. Best case scenario - but not a particularly likely one - that I can see on the cards for pleasant weather is ending up with a mid-lat block but either positioned far south enough that we avoid a nagging easterly or (best of all but also the least likely) aligned in conjunction with a low over Europe in such a way as to send relatively warm air in our direction from the eastern Med. For cold weather sufficient for widespread lying snow we'd need to see a proper annihilation of the stratospheric vortex and then get very lucky with the orientation of the major building blocks. Not sure I'd want to play that game after such a diabolical winter season in terms of defying our attempts to anticipate it's behaviour (worst I've known since I started paying proper attention a decade ago). Okay, time I ditched the morose hat and moved on. Here's to an entertaining spring season 2017

To visualise a string jet... They dont always form even with intense storms, but when they do, they occur near the centre of a low that has rapidly deepened, usually as it reaches peak intensity, and can be seen as hooked streaks of cloud and clear slots wrapping in close to the 'eye' of the storm. In this region the winds from the upper troposphere - near jet stream level - are descending down toward the surface. Occasionally they can retain most of their momentum on the way down and deliver gusts to 100 mph or so inland. More often the peak is 80-90 mph. Sometimes convection occurs in between the descending streaks of air, in a very tilted form with height - known as slantwise convection. These narrow bands of tall clouds can be another marker of a jet streak.

I know low Barents-Kara sea ice has been linked to cold N. Eurasian winter weather so I expect a negative NAO response? The Arctic amplification link to increased meridional jet stream motion is something I became aware of about half a decade back and has seemed increasingly convincing ever since, from observing global tendencies. Should a net poleward movement of climatological weather 'bands' join the foray then extremes will become even more frequent and severe. A few years back I ever thought I would soon be considering the possibility of such a climatic shift occurring within he next decade as opposed to between 2040 and 2100... oh how times have changed. Or seemingly, bar a miracle in the Arctic which I for one am desperately hoping for. I realise this discussion has dragged things off topic for this model discussion thread - sorry mods! Hopefully it can stay as something to reflect upon when considering what the models show us in the year of 2017? Thanks if so

That's one of the other parts you've identified there, and a reason why I'm so interested in any scope for even a half-hearted MJO phase 8 response building a ridge toward Greenland. As yet the fog refuses to clear on how exactly the MJO is and will be behaving.

Good point there, and I don't see the changing Arctic as an absolute controlling factor - just something nudging the balance of probability in perhaps concerning directions. @Catacol I actually have the inverse concern regarding storminess in the UK; as this tends to occur with the milder air on the SE flank during times when maritime/continental contrasts come into play, it's the Eastern Seaboard of the U.S. for example that may be in trouble there. We could if anything see a reduced tendency for storms to come our way, as the polar boundary migrates increasingly far north by way of adjustment to the new climate regime in which the Arctic cold pool is increasingly small and weak. A predominance of mid-lat blocking such as we've seen this winter ties in well with this theory. A notable side effect is that the most major cold pools in the N. Hemisphere tend to exist either over Greenland or across the mid-high latitudes of Asia. The former may encourage storms to track SW-NE past the mid-lat highs across or near the UK - another behaviour seen again and again this winter. The latter, in combination with the mid-lat highs tending to build across the UK, places southern parts of Europe at great risk of well below normal temperatures and snow in unusual places. Also a feature of this winter. I have been hesitant to consider this winter as a preview of what may become the norm once the Arctic changes are complete (I know I should say if but given the state of affairs it seems like only a matter of time now), given that after all, there was some MJO activity in Dec and to some extent in Jan that is known to increase mid-lat blocking in our vicinity, and perhaps the unusual storm tracks have some connection with the very positive AMO state of late (not yet researched)... but gradually I have found this to be a more compelling idea, as other explanations have been placed in the 'unlikely' drawer following investigation. I expect the next few years may tend to favour HLB more through low solar forcing so this may distort the picture and mean it's near a decade before meaningful conclusions can actually start to be drawn regarding whether the climate shift I have outlined is indeed coming together already. Now, who's betting on a Mediterranean summer? Oh if only the wintertime pattern rules were all that applicable to the summers!

Phone's not letting me link to it but Fergie has tweeted that the models may be lagging in response to phase 8 MJO. With that in mind I still see next weekend as a good opportunity for at least a cold snap. Failing that, the following week should offer interesting opportunities - or increasingly frustrating if you live in the far south for example where lying snow is as rare as hens teeth by late Feb/early March.