snowking

WeatherBell snow accumulation out to +240 from the 0z ECMWF Det. Bear in mind not to take the actual depths shown too seriously as this is based upon a 10:1 snow to liquid equivalent ratio - something that is unlikely to be true under marginal conditions, nevertheless it shows that the 0z ECMWF det. was indeed a snowy run and suggesting otherwise is a little misleading. Of course that is taking this at true face value, this does not mean this is what will necessarily occur. SK

It doesnt get much better than this at 192 from an ensemble mean if it's snow-hunting you're in to: Very positive trends this morning which could set us up for a very interesting start to February. Anyone concerned by the GFS det. should note it is much further North with the pattern than it's ensemble suite: Still a way to go with this one yet - we saw just a short while ago how quickly things can fall apart in complex situations like this, but we are now seeing just how quickly fortunes can change for the better too. SK

I've only got access to them in Fahrenheit in increments of 5F i'm afraid, but generally at +144 it's sub 35F (so sub 1c-ish) for all but the far South-West. Most of Scotland is sub 30F, so it would be touch and go I would suggest. Far more interesting (though merely stated for the purposes of interest as this is 9 days away) is the low sliding South-Eastwards between 192 & 216 - an almost all snow event suggested for the UK from that. SK

Yes a well reasoned post by Matt and perhaps we run the risk of a February 2005 type scenario (by all rights should have been a significant cold spell with 17 consecutive days of snow recorded in my location, but much of it was daytime showers with little in the way of significant accumulation). The optimist in me though says this the below at day 9: Could be the beginning of the final curtain call for any meaningful vortex for the remainder of the season. Still plenty of wave activity bombarding the stratospheric vortex but as has been said plenty of times it is a big beast to bring down. SK

Only taken from one run but this is encouraging for me stratospherically: The stratospheric vortex whilst reformed (slightly - still rather bent out of shape but back to a single core system) is aligned SW-NE from our perspective and is being 'pushed' towards Siberia with forcing from the Pacific. So we have a potentially weaker vortex from the warming episodes and hopefully (as long as we can see this pattern downwell in to the troposphere) a vortex that is being displaced to our East/North-East - the usual key ingredients behind getting some more favourable towards Greenland. Taking the current tropospheric and stratospheric projections in to account (and assuming these hold true) my suggestion would be cool and unsettled followed by cold as the general outlook through until mid February. SK

Seems relatively consistent with one another for now for the timing of the GFS warming we have been watching for some days now, centred around January 28th: Nuances in exact temperature but the warming occurs at a pretty similar location on both suites. Of course there are likely to be differences with the effects of the warmings, but that is to be expected. I think the warming BA is referring to is this one (from 6z): Which centres itself around 2nd February, and has (much as the Jan 28th warming) been pretty consistently modelled by the GFS in recent runs: That's the last 4 runs showing the same idea - again we can expect nuances in terms of exact temperature but that's pretty consistent modelling at such a range. We can even go further back than that, 24 hours previous: And 24 hours previously again: Certainly wise words to offer in terms of awaiting the ECMWF's approval too but I think we have seen that the 28th January warming has been pretty well modelled and is now coming in to the range of the ECMWF output, so I think it's hats off to the GFS thus far for me, which proves encouraging given the second warming now showing. SK

For informational purposes (as I've seen a couple of comments about this) the Feb 45 day that I've read suggests a very mild February - think the mentioning of December 2010 is just a sales ploy and bares no relation to the forecast for Feb '14But if you would like some more comforting news his forecast this winter so far has been (as ever) very hit and miss, with two previously forecast snow events across England and Wales having failed to materialise, so I wouldn't hang too much upon his words.SK

VERY encouraging ensemble mean from the ECM: GEFS not too far behind either but with less agreement on heights over the pole: A lot then becomes reliant on the remaining Atlantic energy clearing to a favourable position but ensembles certainly keen to build heights to the North (be that Directly North or North-West) of the UK in 10 days time. We should always remain vigilant when outputs start to develop and Arctic high as with little operational data input from those regions NWP can struggle to deal with such a feature, but cautious optimism should be the flavour of the day. SK

I'll have to have a full read through when I get a chance but that's both interesting and encouraging to hear! SK

So the warming we have been tracking for some time now centred around January 28th maintains its consistency and continues to move slowly forward in the output, the 'epicentre' as it were down to +288: The next signal that then appears to be emerging is for a warming close to or over the Atlantic sector - still an emerging trend for now but if we take a look at the end of the last few runs: We could do with some more consistency within this but nevertheless a bit of a (dare I say it) trend developing to create another minor warming in to early February. Ordinarily such a warming on it's own would not be enough to have an impact but following on from the potential sucker-punch of the January 28th warming (we should bear in mind at this stage it is still an FI forecast) it could prove enough to give the vortex the final kick out of the way/weakening that we need to set up interest in February. The only words of caution I will throw in at this stage (something I commented on last week too) is that with Wave 1 displacements it can be a bit of a lottery. What we are hoping for is that the vortex becomes displaced towards the Siberian/Scandinavian sector as the Wave 1 takes effect. But it would be foolish not to point out the risk of any potential Wave 1 displacement simply pushing the cyclogenesis associated with the upper vortex in to the Atlantic and leaving us in need of a minor miracle (secondary minor warmings could potentially provide such a service). At this stage that all remains conjecture as nobody can tell the exact longwave setup across the Northern Hemisphere for early February this far in advance, but it is a risk that we should be prepared for. Of course the dream scenario in such an event is true cold zonality, but thats a scenario best left alone for now. So positive signs still as we head for February and should current mid-range projections prove true our patience could be rewarded. SK

Not quite, there has certainly been a warming but we are yet to see the reversal of the zonal winds up in the stratosphere from the more recent warming (to this extent the term 'warming' within SSW can almost be misleading in terms of the definition as it is generally the increase of temperature which causes the winds to reverse direction but it needs the winds to reverse to achieve a technical SSW) Although anyone following this subject on Twitter could understandably get confused. The trouble is this is an extremely complicated and relatively new area of meteorology. We are blessed here in that Ed, and of course previously Stewart had a heck of a lot of time and a wealth of knowledge to offer us to show us the ropes. But over on twitter you will find that even some of the meteorologically trained are still yet to get to grips with the stratosphere. Fortunately we do have some of the more knowledgeable amongst us, notably Lorenzo and Chio posting occasionally on there, and Matt Hugo has been quick to step in and correct any mistakes made there too. It perhaps also doesn't help that Piers Corbyn has decided to create his own definition of what an SSW is to suit his forecasting technique. However, for anyone new to this subject or indeed anyone who has been looking at it for a while now and is still scratching their heads about it all, you should find some comfort in the fact that people who forecast weather for a living (in some cases even teach it to others) are still struggling to get their heads around this vast new empire of knowledge and this brings home just how complex the science involved here is. I think it's fair to say that even the more expertised in this subject continue to learn something new every season and will continue to do so for very many more seasons to come. Regards SK

Just a quick one from me. All models seem keen once again on MJO phase 7: We have to be slightly wary of this once again because we saw this signal before the previous Easterly debacle before the signal slowly waned, but the initial amplitude looks higher this time. This is probably why we are suddenly seeing a projected resurgence in some runs from those Scandinavian heights. A quick reminder below of the MJO phase 7 SLP composite under wQBO and ENSO Neutral conditions: We see perhaps why the GEM is reluctant to give us anything interesting right now: JMA offering some support though: So we now have to wait and see whether this amplified MJO phase 7 signal is overplayed or not. If it ends up being close to reality then expect to see some more interesting runs in the near future. SK

The most notable thing for me is that as an overall trend, the more we reel this warming in to the closer timeframes the more impressive it is beginning to look. Taking a starting point of T+384 from Saturday, rolling forward to T+312 today: Still some variation of course over time but overall it's beginning to look more and more impressive at least temperature wise. SK

Ohh no, not the 'P' word again! You are certainly right though and if we take a look at the wind directions for The Netherlands: Certainly a cluster of solutions following the deterministic run (the det. actually providing quite a good mean for those solutions) taking us back towards hints of an E/SE'ly flow. We of course though have to bear in mind recent events and whether the ECMWF just has a tendency to over-amplify post day 5. We have often commented in the past that the GFS throws out the same zonal solution over and over again post 192 and thats why occasionally it deals with a breakdown better than the other models - it's a case of a stopped clock is correct twice a day. It could be that we are now witnessing a similar weakness with the ECMWF in that up until now it has always seemed to deal with northern blocking and trough disruption better than the other suites because it has a tendency to over-amplify a pattern and therefore during previous cold spells that have indeed verified it comes out looking the best (it must be stressed that I have no statistical evidence to back this up - just an observation from the last two winters in particular - even during the colder spells of January and March last year heights were constantly over-estimated towards Greenland). So certainly a significant minority clustering of Easterly solutions but as stressed last week it's best in situations like this to wait until a much closer timeframe before heightening any personal expectation. SK

Just to illustrate what I was mentioned earlier (and indeed last night over on the model thread) the continual theme from GFS det. runs to move the vortex mostly to the East of the Meridian towards the end of this month: It's not happening on every single run and it should also be noted that at present there is not strong ensemble support for it, but just an observation and backed loosely by today's Berlin ECM 100mb charts: The core of the vortex moves towards Asia/Siberia but at this stage at least still some left trailing across towards Greenland and Canada. The hope is though with the potential warming and possible consequent wave 1 activity looking likely to be towards the Pacific side that we start to move away from the situation where by the majority of the vortex gets displaced towards the Atlantic, instead the hope would be (dependant upon the angle of any potential attack - something which at this stage is still pure speculation I should hasten to add) that any 'leftovers' as it were in terms of pieces of vortex close to Greenland would be pushed away from there and that the majority of the vortex ends up to our East/North-East. That of course still is far from a guarantee of the longwave pattern being conducive to UK cold, but it makes things a heck of a lot easier. I'm probably getting a little ahead of myself here but based upon current observations/forecasts (both tropospheric and stratospheric) thats my take on things potentially later this month. SK

Indeed there was brief discussion about this last night over in the model thread. Wave 1 is certainly less favourable when you look at statistics. However of course it all depends on where the vortex is when the displacement hits and from which direction the wave pushes. Recent GFS det. runs have been rather keen to start moving the vortex towards the Eastern hemisphere towards the end of this month. It could be that this is trop/strat linked in terms of where successive GFS runs have been suggesting the stratospheric wave 1 activity will "push from" - which looks to have a central point somewhere over towards Alaska. This would be the ideal sort of situation of course - worst case wave 1 tropospherically would be the vortex situated over Greenland and a push from the Central Pacific. Of course it should be noted this is all making the assumption that the wave 1 would not completely dissipate the vortex, that is at least my assumption given how strong it has been. SK

It may well end up all being linked but that would be my suspicion - certainly something within the realms of the GIN corridor and if we can get the tropospheric vortex somewhere towards the East of the meridian before the next suspected wave 1 hits later in the month then it certainly gives us the best chance of something like Greenland height rises going forwardSK

Only time for a quick post but that ^^^Very noticeable trend over the last few runs (will have to check ensembles in the morning) - could co-incide with next wave 1 attack and if it does then it would be the best result possible for the UK. Last thing we want is a wave 1 displacement that displaces vorticity in to the AtlanticSK

As per the previous couple of posts, the ensembles show exactly why nobody should assume anything is 'nailed' until at least this weekend. The GEFS Panel at +150 sums it up: So that would be err... - Scandi High - Slider w/ SEly flow - Easterly - Greenland High - Massive Positive NAO and a westerly - Low slap bang across the UK Thats quite a lot of solutions for just 6 days away. And where does the biggest uncertainty lie... Oh OK then that would be in the three most crucial areas for our evolution. Thanks for another clear solution GEFS... SK Another triumph!

These certainly don't look too disappointing and leave us pretty much where we were yesterday: It suggests that at least 50% of the EPS members want to continue sliding enough energy South-Eastwards under the block to give us something of interest, and in all likelihood for that to be a mean chart (accounting for offset from less keen members) possibly a little more than 50%. So, really as we were then from the ECMWF Ensembles - on the colder side of the fence but not convincingly so just yet. SK EDIT: Dutch graphs tell the story well too: Encouragingly dew points too (considering we are looking at a shallow Easterly flow) - 80% are sub zero from Thursday to Saturday And still strong convergence on an Easterly wind:

Well i've lost track in recent winters of the number of times i've checked the forum first thing in the morning thinking ohh dear there must have been some pretty serious downgrades only to take a look at the models for myself and realise that in fact there has been very little change since yesterday and all the deterministic runs are displaying this morning are the variations within the ensembles that we have been seeing for the last 36 hours. Deterministic modelling is not as good as it was at say 0z yesterday but I think some people need to try and get their head around what NWP is trying to model here. Attempting to model the physics of two streams of jet energy travelling in two different directions running in to a blocking high is a ridiculously complex equation. There were various members yesterday trying to impart wisdom from years past to tell everyone that whilst face value model output was looking exceptionally good it would be some days yet before we would be able to determine the final outcome. We see models struggling enough to calculate fairly straightforward situations a week in advance, never mind something like this. When Ian F said yesterday that in terms of ensembles it was essentially a 50/50 split (with just a tad more on to the cooler side of the fence) he wasn't saying that for the sake of it, that really is what you get with situations like this, particularly against the background of how strong the jet stream has been. All I can say is it's a good job I am not a newer member attempting to decipher what on earth is going on because the conflicting messages this morning have been something else. What I would say to any newer members for now is this - wait until the weekend before drawing any major conclusions. The only certainty for now is that temperatures at the surface are going to drop in comparison to recent weeks. On the subject of the actual outputs yes the GEFS ensembles are certainly not as good as yesterday but two crucial points to make here. First of all once again both of the higher resolution outputs (det. and control) are still firmly in the colder camp - when you're dealing with splits in jet energy those are going to be the more likely to resolve things correctly, though even within these as we have seen with the ECMWF this morning, expect some variation through the next few days on how much energy travels north/south. And finally, whilst we're on the subject of resolution, please correct me if I'm wrong but last time I checked the GEFS were running at a resolution of 55km out to 192? Well when you consider that, for example, the NAVGEM has an operational resolution of 35km, and how very little we take it's output seriously, you start to see the potential issues (in the interest of balance it should be noted that the NAVGEM issues could also be model physics related). But overall the point here is not to take any output you see as gospel until towards the weekend when we should hopefully start to see some consistency between outputs. SK

Most encouraging chart of the night for me is this: Let's worry about surface temp/850 temp/precipitation when it comes in to closer timeframes. For now let's focus on the trends...and the trend there is pretty solidly behind winds from an Easterly direction across the near continent. Small steps. SK

And finally we have the London ensembles: Sub 5c Mean all the way from next week onwards and with the strongest clustering below the mean. We can also see that the end of the 0z GFS was an outlier compared to the ECMWF ensembles, most notably from the wind: Reading through the running commentary of the 6z was actually quite entertaining. One might hope that the events of the past 48-72 hours would show once and for all not to draw meaningful conclusions from a single deterministic run for 5+ days in to the future, especially before the run has even completed. But there we go, you live and learn...hopefully the latter part of that more especially! SK

0z ensembles from Holland: Control and Op in harmony but on the colder side SK

Glasgow Ensembles: Taking an educated guess based upon the slowly increasing Max. temperature trend but rather steady Min. temperature I would say generally high pressure sinking from the ensembles which we can also see in action here: SK