snowking

Whilst we look further afield the ECMWF Det. this morning actually throws up a marginal snow event on Monday morning: Dew Points and WBFL's supportive of something wintry in roughly a line from London to Aberystwyth Northwards. Not of course that I'm advocating the following of distant marginal snow events.... SK

Hahaha! I apologise for the off topic start to this post but that is absolutely brilliant. I'm starting to think we should collate all the ridiculous media overhype and mis-use of terminology they clearly don't understand and form some sort of weather stand up comedy tour. E-P Flux forecast direction still looking better going forward but with the sharp decrease in overall flux as wave activity starts to wane in 10 days time we now await to see where the next stage of wave activity comes from. Given repeated tropospheric projections of a Scandinavian ridge my guess would be that we won't be too far away from seeing another bout of strong wave 2 activity later in January which could land the killer blow. SK

http://meteocentre.com/models/explorateur.php?lang=en&map=eur&run=12&mod=gemglb&stn=PNM&comp=1&run2=12&mod2=gemglb&stn2=PNM&hh2=000&fixhh=1&hh=240 Always seems to be out earlier on there SK

It perhaps depends upon which perspective (time-wise) you are looking at it CC. In the shorter term you are completely correct, with just enough of a ridge at 100mb to give us the interest around Scandinavia towards the end of this week but nothing too significant currently modelled...that could still change but for now it looks mostly cool and dry (thank goodness) with perhaps Western areas more prone to something less settled. However it has been stressed by numerous posters ever since September that this winter would be one that required patience. Most of the stratospheric posters have not been expecting anything of too much excitement until later in January and towards February, and to that extent there are some very encouraging signs this morning. The first being this: With the E-P Flux forecast finally heading somewhere a little more poleward which helps to deflect wave activity to where we want it to be going. The other encouraging thing though from a tropospheric point of view should be this: A scandinavian high is a classic tropospheric precursor to an increase in wave 2 activity a little way down the line. Remember December 2012, the failed 'beast from the east'? The high really stalled out over Scandinavia...but a few weeks later we started to see the an increase in both wave 1 and wave 2 activity (wave 1 I believe was driven by the pattern over the pacific) and come early January 2013 we saw the results. Admittedly we would probably like to see the Scandi HP a little further North of where it is shown at present (assuming of course it does verify) but that should be an encouraging sign for anyone seeking cold - it forms the basis of Cohen's snow advance index theory, with the rapid increase in snow cover aiding the development of a siberian high which ridges Westwards in to Scandinavia and in turn leads to an increase in wave 2 activity (thanks to all kinds of feedback mechanisms) a few weeks later. So in summary shorter term my punt is for cool and dry and I think that has always been the favoured scenario - along with offering relief from the relentless rainfall and strong winds. But it is longer term prospects that continue to excite and up until now this sits bang in line with the majority of winter forecasts. SK

It might be worth reposting this from yesterday - MJO phase 7 SLP Anomaly for January based upon wQBO and ENSO Neutral conditions: Phase 7 is certainly where UKMO and GEFS were heading as of January 1st but we're still awaiting an update since then... OLR plots certainly suggest things heading in this direction too towards the middle of this month: So actually the UKMO/ECMWF op suggestions from yesterday (and indeed the extended ECM EPS today) should not come as a major surprise and perhaps offers an answer as to whether the ECMWF MJO projections have finally come around to the same thought as the UKMO/GEFS - that answer looks to be yes. We of course have to bear in mind that all of these projections are NWP projections at 10-15 days+ away and so the usual caution should be applied, especially considering at the moment we only have one (perhaps two from Ian F's as ever very useful insight) ensemble suite showing something like this, but this all works hand in hand and so for as long as the MJO phase 7 projection is shown, NWP ensemble suites are likely to move towards a mean Scandinavian ridge solution - a solution which, it should be noted, also has lower stratospheric support to some degree. It's difficult at this stage to tell whether this will become an end game or whether this will prove to be a temporary blip but with the minor damage about to occur to the stratospheric vortex we should at least be able to contemplate a less energetic jet stream and that in itself always leaves things open to meridonality, split jets and all sorts of other solutions in stark contrast to our current 'flat and fast' set up. To use an anecdote to describe what we are seeing in terms of the potential (at long last!) for a pattern change, it's like cooking a chilli con carne. We are just sniffing at the first few hints of this - the mince just starting to cook in the wok (other cooking instruments are available). If we can see the NAEFS suite come on board with this idea in the next few days it will be the onion and tomato being added. We then get in to the nitty gritty of how far east/west the pattern sets up, how far south the jet can dig, how much jet energy goes over/under, and that's when we start adding the spices. Subtle hints for now but NWP can be a very ambivalent mistress 15 days in to the future and it wouldn't be the first time she has made a fool of us all. SK

ECMWF not on board but GFS and UKMO continue to suggest a phase 7 progression of the MJO: 500mb height anomaly composites for which (taking in to account ENSO Neutral conditions and a West QBO) suggest this: And gives an SLP anomaly of: (Key composite years for such conditions are 1979 and 1981) I would still be cautious until we see the three big guns all pointing in the same direction but putting aside for just a moment the warm vs cold debate in view of current conditions I think we could all do with something like this - certainly the potential for some cold from that but above all else something far drier and more settled. SK

I think it's certainly fair to say that the GFS 0z never reaches the dizzying height of yesterdays 6z, however what we do see is a sustained phase of warming at 10mb. It starts at day 10 (+240): (Also note the slight warming on the Asian side once again - every little helps!) It then peaks around day 12: But it carries on going right through to day 16: Now whilst of course in an ideal world we would see as high a temperature attack as possible it is just as important to keep a sustained attack going on what is a very strong and (thus far) resilient vortex - the ultimate result remains this: Still all a long way out but all still encouraging as we head through the month. With the ECMWF also still indicating continuing wave 1 and wave 2 activity it is just a case of waiting and seeing (hoping) when the wave activity can work its way down to the troposphere too - perhaps some more poleward facing flux would assist here, and days 9 & 10 on the ECMWF look at least a little more encouraging on this front though still not there yet: Finally on a slightly different note I see there is still some uncertainty over on the model discussion thread about the potential for something more settled out towards days 9/10 which would of course be a welcome relief from the relentless rain. Certainly strong suggestions from the lower stratosphere from both GFS and ECMWF of ridging around the vicinity of the UK during this period, ECMWF shown below: And also fits in to some extent with a continued MJO phase 7 projection from UKMO and GEFS: SK

GFS plays mr. consistency - not often you could say that about it's tropospheric output at T+300 onwards ECMWF backs off a little from yesterdays projections but still very aggressive with continuing Wave 1 and Wave 2 Activity out to day 10, though the day 10 projections from yesterday of splits within the upper vortex did look a little too rushed vs the GFS prognosis. Nevertheless when you see this much warm air entering the core of the vortex: With some subtle hints of some downwelling too: It begins to look rather in line by day 10 today with the GFS outputs: Which of course later goes on to develop the warming shown above down to 10mb. Some patience will still be required but things are still looking positive from a stratospheric standpoint through the second half of this month. SK

As ever a terrific post from Recretos showing us even more data pointing in a similar direction. Just to show those who are perhaps new to stratospheric monitoring why we are excited about what is forecast (worth bearing in mind this is still quite a long range forecast) to be happening 30 miles above our heads. At the moment we can see from the Northern Hemisphere 500mb plot that we have two main segments to the polar vortex (the larger purple blobs), one over Siberia and the one I have circled that's proving crucial to our current setup over E Canada/W Greenland: If we look even out to T+384 at the lowest level of the stratosphere, 100mb, it becomes apparent why this current pattern is with us. Whilst we have a split in the energy of the vortex, one of the core areas of energy is still over that E Canada/W Greenland area, as shown below: But if we look higher up the stratosphere, at say 10mb these areas of the vortex are in slightly different positions, moving away from Greenland: And then looking right up to the top of the stratosphere, it moves even further away: So that's all well and good but why does it look exciting? Well what's actually (hopefully!) happening is the pattern from the top of the stratosphere is downwelling (moving down the atmosphere). If it were to continue to downwell in to the troposphere then we would see the remaining vortex energy to our North-West retreating Westwards away from Greenland and potentially opening that area up to some higher heights and ridging. This is still all a long way away but that's what we are now looking for as a minimum. A more optimistic view would be that we see the total disintegration of the vortex from the top downwards. We are already seeing this downwelling occur in the latter stages of model runs as the split occurs at 1mb and translates down to 10mb further down the line, along with the position of each of the segments of the vortex. If that can carry all the way down to the surface, then things are looking much better as we head in to the second half of January and more especially February. SK

Very encouraging output from the GFS and ECMWF this morning. Just as Wave 1 is forecast to tone down a little: Wave 2 strengthens once again: For those asking the other day what the difference between a wave 1 and wave 2 attack actually looked like, well here's a pretty clear wave 2 forecast from day 10 at 10mb: You can see pressure being placed on the vortex from two different areas (hence wave 2) and squeezing the vortex in the middle in to that sort of monkey-nut type shape: (for those unsure of what a monkey nut is) This is why wave 2 activity is more likely to lead to a split in the vortex as the two waves attempt to slice through the middle of the vortex, where as wave 1 often leads to a displaced vortex because pressure is being placed on it from just 1 side - like pushing a box across the floor. The most encouraging thing, whilst timing may differ somewhat, is that both the GFS and ECMWF are showing similar setups towards days 10-15. Taking 30mb as an example: Very encouraging overall, though as BA says above we now need to see this become a consistent forecast. SK

Only have time for a very brief post off of my phone but the ensembles (primarily ECM EPS) continue with the theme that had been hinted at by the Fi range of recent det. runs, that is weak HP across the pole and the low heights draining away from Greenland....the trick to the pattern for little old us in the UK now is to what extent those heights drain away from Greenland, and that is where it would be wise to remain VERY cautious until we get things in to a more reliable timeframe. The tendency over the last couple of years (especially from the ECMWF last winter and so far this winter) is for it to drain those Greenland heights far too much (vs the eventual outcome) in the day 6-10 range. Should this prove to be the case again then it's going to take us a while longer yet to develop something colder. The overall N Hemisphere pattern continues to look encouraging as a whole but obviously it's a big step from there to getting the right pattern to advect any colder air to our little corner of the NE Atlantic. Merry (belated) Xmas to all! SK

Might be best to take a hemispheric view of things at +144 The pattern across the Arctic is fairly encouraging. Nothing spectacular but for the mean of 51 separate runs to create such ridging in to Greenland at day 6 provides more interest than of late. It is fairly fruitless taking mean charts at face value out to 10 days away, especially when the 'lack of detail' on our side of the hemisphere due to the noise from conflicting signals is pretty apparent: If I were to look at that from an optimists point of view I would say there is a tendency shown there for low pressure to be reluctant to move too far past the Western top of Greenland, evident by the comma shape of the progged mean low with some weak ridging in to Greenland once again. Though I would agree you could also look from a pessimists point of view of a mean trough stuck to the North-West of the UK. But as the spreads by that stage show: There is a lot of uncertainty still for our locale and just to the North-West of us. Overall as BA initially stated the renewed mean trough solution over us by day 10 looks a good call, but it is the wider pattern that still holds more promise. Of course we need to reel that in to the nearer timeframe still but plenty of be optimistic about in towards the middle of January. Nothing especially wintry within the 10 day timeframe but I think that has been a given for some time now. It's now a case of trying to set up a better profile to our North and North-West to give us something of more interest next month. SK

Interesting end to the latest ECMWF stratosphere forecast: Concurrent wave 1 and wave 2 attacks at the top of the stratosphere. As Chio has already said nothing yet breaking the surf zone, with the E-P Flux facing away from the pole at the moment: We ideally could do with some poleward flux in to January, but should the wave 1 attack continue to ramp up following the wave 2 attack then with more and more pressure being piled on to the vortex eventually something has to give. We saw something similar last year (though in reverse if I recall correctly - wave 1 followed by wave 2). Most forecasts for the winter as a whole currently look right on track. SK

Indeed!

And the FI warmings just keep on ramping up: By this stage the tropospheric vortex is pretty shredded too. All still a bit too far away to be excited about just yet (To help answer Karyo too)...the time I generally start to get a little more excited is when this falls in to the range of the ECMWF, and we see some consistency in the picture between the GFS and ECMWF stratospheric outputs for a few days. So if all this comes in to the range of T+168 and both the ECMWF and the GFS still show a consistent picture, thats when I tend to allow myself to feel like a kid again! SK

Certainly in the short term but the longer-term Arctic profile over the last few GFS det. runs has looked better than we have seen for some weeks now: Of course mere speculation given the timeframe but the last few GFS runs have been keen to develop some weak pressure rises across the Arctic, which can only be a good thing moving forward..assuming of course it were to verify. It will be some days yet before we can start to look at the nitty-gritty of the details IF it comes to within T+200 hours and other models start to suggest similar themes within that timeframe, but taking the last few FI outputs at face value there is just enough optimism there for coldies to sit up and take interest. It could be another doomed FI chase, but at least we have something interesting in terms of cold potential to look at than of late. In the the shorter term though cool and unsettled rules the roost - I would much prefer the GFS scenario for christmas itself with the worst of any winds clearing away through xmas eve and not returning until after boxing day. SK

Bears a striking resemblance to a certain Mr O'Toole's January composite: And then of course we still have this setup this morning: With the ECMWF picking up on something similar by day 10: GFS: ECMWF: I wonder when we might see the first 'BOOM' in the stratosphere thread this year... SK

Still a lot of uncertainty regarding the proceedings over the next few days with significant model differences for our locale from as early as t+72, so looking further afield at individual deterministic runs at present may prove fruitless. As such, the latest NAEFS warning system output from MeteoCentre now stretches out to christmas day itself: Currently a 50% chance of >2cms of snow across the highlands, so the risk of snow here looks fairly good at this stage. Elsewhere it most likely wont be clear until the other side of the weekend. I should imagine there's a few bookies entering squeaky bum time... SK

Indeed! Very nasty conditions shown from that with peak gusts of 90-100kts (100 knots is 115mph) up the Bristol Channel - certainly hope this is a one off run for anyone in those areas with the flow aligned perfectly (not sure thats an appropriate word in the circumstances) to allow a funnelling effect. But so far no support from elsewhere so lets hope it does one come the 12z. ECM this morning bringing the low closer to the NW of Scotland too for the weekend: Disturbed just about sums it up, with indicated gusts once again up to the 90-100kts category on the 0z for a short time Sunday evening in the far North-West. The best hope for cold lovers is to go up to the scottish mountains with some PM and rPM shots increasingly modelled...just maybe leave it until after the weekend. SK

Only have time for a brief post, but the overnight ECM32 generally sticks with the Westerly flow through December - signs of something a little more amplified in the Atlantic, and consequently cooler at 850mb for the UK as we head in to January. SK

And straw clutch of the day comes from the ECMWF projected EP-Flux: Look at that at day 10 - pointing very slightly polewards! Let's take a closer look at that in action: A very benign but not hugely unexpected outlook both tropospherically and stratospherically at the moment - and I'm not personally expecting too much to change from that this side of January. I know Ed's own thoughts on the stratosphere differ slightly from this in terms of years, but the composite years from my own winter forecast for December give this at 30mb: Which bears reality when we take a look at the observed 30mb heights for the first 7 days of December so far: Similar to Ed my own composites (unsurprisingly as many of the years are the same) produce this for January and February: Though when I break it down week by week the initial disturbance to the placement of the vortex looks likely to start during the second half of January. So it's a case of repeating the message from all the way back at the start of autumn when we all began to look for signals for the upcoming winter - patience will be key. SK

No I completely agree, I am being a little pedantic in all honesty but I am growing tired of seeing constant calls for 'a return to zonality' with no evidence to back things up. I am always open to any idea if somebody can provide a reasoned and evidence-based argument, but without it becomes nothing more than a Madden style guess-cast. It may well be that he has some evidence to back these ideas but the only evidence I have seen from Ian in the past is some vague references to the 'American guys'. Anyway - the GEM is the light green line, the CMC. The best way to calculate the performance from these is to use the figures at the bottom left - these provide averaged verification stats over a period of 30-31 days. Kind Regards SK

Not according to the stats at present Ian: Level pegging with the UKMO at day 5, still comfortably ahead of the GFS at day 6: That's its best verification statistics for some time and I believe we are now officially in winter. When you look at the 12z stats the beloved GFS sits even behind the JMA in 5th place. In terms of the suggestion of 'conventional zonality', there is very little to suggest this from either the GEFS or the ECMWF EPS this morning. GEFS even by the 18th: Still with a very strong signal for MLB. Awaiting the extended ECMWF ensembles but out to day 10: Still a very strong signal for MLB. So I am not entirely sure how any of your post is accurate? Perhaps in future it may help to provide a little evidence to back up your claims. This will also help any newer members who are trying to learn rather than misleading them. Of course at 10 days away we cannot take anything for granted and indeed the final result may well be something closer to zonality, but off current face value evidence there is nothing to suggest such an outcome. SK

Obviously I cant speak on behalf of Ian there but in terms of raw stats: It's currently verifying second best of all the models overall, ahead of the UKMO even. When you consider how much emphasis is placed on the GFS on this forum (mostly down to the wealth of data freely available plus the fact it is run 4 times a day) in reality right now the GEM is outperforming it. In fact when you look at those 12z stats you start to wonder why anyone is placing any faith in the GFS det. at day 6 - in fifth place! Shocking. GEM Ensembles outperforming GEFS too. SK

Indeed. 12 day mean 500mb anomaly: However with the split in the ensembles the mean flow remains a Westerly for now: But with a virtually 50/50 split in the ensembles at present I wouldn't read too much in to those means at present. Just briefly the obvious trend for the 10-15 day period from last week was for the main thrust tropospheric vortex switch from Siberia/Scandinavia towards the Canadian/Greenland sector. We can still see these changes in motion (this time in the 5-10 day period) from the ensemble means: Day 3: Day 9: Now whilst I mentioned in a previous post that this was the reason for the certainty that the upcoming Northerly would be a short-lived one with little prospect for height rises towards Greenland for the 10-15 day period (from last week), this of course does not rule out the possibility of height rises towards Scandinavia. The difficulty now comes in the modelling of how much of any influence from the vortex gets left across the Scandinavian sector. The theme from forecast models over the past 18 months or so has been generally for early runs to under-estimate how much of the 'vortex energy' remains, and that would be my biggest note of caution. Admittedly that observation was generally true last winter of the Greenland sector as opposed to Scandinavia, but the same caution should be applied. For this reason I would expect to see some further 50/50 splits and some flip-flopping of both deterministic and ensemble modelling for the next few days on this situation. Anyone making a call at this stage for where the high pressure will end up beyond day 10, from the model data available to us, is rather brave. SK