Yeti

Fairly heavy snow here in Cambridge. Settling everywhere...

Yes, ironically as some have said, it looks like the East may actually be in a better position for Monday/Tuesday's snow event than the West, because the low looks like tracking too far west for anywhere, in England/Wales at least, to pick up a northerly flow but at the same time this could draw a SE'ly flow off the continent up the eastern flank: http://www.wetterzentrale.de/pics/Rtavn1202.png http://www.wetterzentrale.de/pics/Rtavn12010.png So the North and East currently look most likely to see snow from this event although this is obviously still subject to change. A small shift W may actually help keep DPs lower further W, but it requires a pretty big shift E now to get the full effects of the N'ly and this looks unlikely.

If the whole of the UK is sitting under the high on Thursday/Friday as Lewis seems to be suggesting then I will eat my hat. Sorry but this is really getting quite annoying, what "point" is actually being made here? That we're all in for a big disappointment if we don't listen to what he says? The only reason that anybody should be disappointed is if they took those tasty FI charts at face value a few days back. In fact I remember certain individuals were already talking about snow for most of the week in Yorkshire. FI is, and always will be, UNRELIABLE, especially wrt details such as where snow will fall! Honestly, if anyone is disappointed at that 12z they have themselves to blame! The UKMO and ECM still have the high slightly further N anyway (and the 12z is marginally better than the 6z, so quite what this new "trend" is I've no idea). There's no reason to think that this is all going to be a flop - http://www.wetterzentrale.de/pics/Rtavn961.png http://www.wetterzentrale.de/pics/Rukm961.gif http://www.wetterzentrale.de/pics/Recm961.gif All in all an excellent selection of charts, with cold for all and snow for most places S of the Wash and even N of it at times.

Really I don't see what the big issue is at the moment - this was always going to be more of an event for SE/E Anglia as soon as it appeared within the more reliable timeframe and I don't see much output to change that? Easterlies rarely affect the whole of the UK - in fact they are usually severest in the SE - and people were warned of this a few days ago but as usual, many seemed intent on ramping it up: blizzard this, Feb 86 that. There has been a SLIGHT shunt Swards but this is almost always the case with the models, and often they readjust (upgrade) later on to reach a halfway house. Besides, the difference this will actually make at the surface, as TEITS says, is really very small indeed. Snow showers could still crop up in most areas with more and more the further S and E you go. It still looks an exciting week for many, and even if it doesn't snow, at least it will be relatively settled, cold and sunny. http://www.wetterzentrale.de/pics/Rtavn961.png Doesn't seem a bad chart to me considering we were looking at raging SW'lies just a week ago!

Yes, I seem to remember that during previous cold spells this winter the models were already showing breakdowns which kept being put back over and over again. However this time the ops just keep it cold all the way through, even to T384. This can only be a good sign - and we should bear in mind also that although good synoptics are difficult to get, they are also very difficult to get rid of, rather like mild patterns. With the SSW kicking in later, we could be in for a very cold February overall.

Eh? If the sun enhances land convection then it must also enhance sea convection... both involve exactly the same mechanism, except that the sea has a lot more water so it produces a lot more activity. Similarly, if the sun is strong enough, as some people are suggesting, to make a difference to daytime temps by heating the ground more, then it cannot NOT have effects in other areas... that just doesn't make sense. It's certainly true, though, that cold uppers are vital to decent convection which is why I suspect there won't be that much around before midweek. In fact, the upper profile doesn't look brilliant, all things taken into account - the core of the cold pool is now trending further S into Germany with more S and E areas still seeing some really decent 850 temps - still subject to upgrades/downgrades.

There is lots of talk about longer days and a stronger sun which is certainly true, but we ought to remember that this also increases convection potential. A stronger sun than in Jan, shining over a comparatively cold N Sea should result in a lot of beefy snow showers - the question is will these make it far inland. The flow isn't great if we're honest, but it's better than a lot we've had where snow showers have formed in many areas, so I think it would be fair to say that some places could see a good amount of snow even this week - particularly parts of East Anglia and the SE from Wednesday onwards - the risk zone being a bit further N prior to this.

Nice to see you back Steve, your input is always v. popular - I see you are as excited as many other members are!! Now that is a nice NE'ly from the ECM at 120!

Indeed - and with the sun that bit stronger, and the North Sea that bit colder than the last cold spell, these charts would produce some very impressive convection. On the GFS and UKMO 12z the high is also in such a position that the whole of the eastern side would be affected. I remember last cold spell people were complaining about the precip charts being too dry and that it was going to be a cold dry spell. When it came to it that was far from the case - but look at this already: http://www.wetterzentrale.de/pics/Rtavn1504.png For the GFS to pick up on that convection so far out, it's difficult to imagine how awesome the activity would be if that 144 chart actually verified! Still a long way to go though yet, but things trending in the right direction. And obviously, those precip charts are only useful as an indication of the sort of pattern we're looking at atm, i.e. sunshine and snow showers.

Well there's reasonable model agreement tonight on the future synoptic evolution which is obvious because people are starting to argue about where the snow is going to fall!! The truth is that the SE and EA will nearly always be the favoured spots for snow showers in these easterly setups, but as we know, snow would crop up in most places IF the charts were to verify, as fine detail is a long way from being modelled atm. Let's hope things firm up in the right direction more and more, otherwise I think any backtracks to mild tomorrow will be too much for some members to cope with emotionally! If this does turn out to be a notable easterly spell, this winter really will go down as one where luck has been very much on the side of the cold ramper, after years of misfortunes.

Tbh CC I think things are looking pretty clear now; it doesn't look like there is going to be a cold spell in the near future. The fabled easterly has once again disappeared from all the models. This time I fear it is too late for it to reappear. There was hope this morning from the UKMO but this, too, has now turned into mild SW'lies and I believe the first truly mild spell of winter is nearly upon us. The problem is that the west based NAO is almost more than a help rather than a hindrance as we just end up trapped on the wrong side of the trough with the block holding the unfavourable pattern in position, and whilst it wouldn't take much to bring us a colder flow, these small changes would actually be quite stubborn to occur. I have refrained from posting until things firmed up somewhat but tonight it seems things have done exactly that. The writing was on the wall a couple of days ago when the easterly appeared only on certain models, and each time that particular model was "the favourite" for some reason or other; for example until this morning the UKMO was written off by most but when it showed the desired undercut this morning it was clearly a "trend setter". For the newbies on here, this is a good indication that a cold spell isn't on the cards. Hopefully things will be more favourable mid-month as the SSW pumps up the height rises over the Arctic - this may be a more promising period for a cold spell to occur. Until then, the background signals were looking pretty mixed, with conflicting cold/mild signs that in the end look like giving us a frustrating near miss!

As far as I can see the main problem is the new trend for a ridge to develop over Europe; GP hinted at this a while back but unfortunately, rather than low heights over Europe sucking in undercutting LPs we end up with the ridge deflecting them N at the worst moment. Of course the west based NAO actually helps to lock in the mild for a time as lows struggle to make much eastward progress but then on the other hand, as others have said, it only takes relatively small changes to move the pattern eastwards into a more favourable position for the UK. Certainly though nobody can honestly deny that there is a trend for milder weather now on all of the major models, and the ECM ensembles have taken a dramatic turn for the worse. So this has to be the most favoured outcome IMO, however annoying that is!

We have a covering here in Cambridge atm after a little fall last night... a nice surprise, as I wasn't expecting anything. Looks like that's it for showers in the E though now except the extreme E of E Anglia.

Yes the NAO is forecast to go slightly negative but perhaps we shouldn't worry too much about just how negative it actually goes: http://www.wetterzentrale.de/pics/Recm1441.gif If you look at the ECM - so far the best of the models today - the NAO is only slightly negative, with the Azores high not displaced very much and the block more E based than GL based. A strongly -ve NAO will be recorded when there is a large GL block forcing low pressure over the Azores. But this setup, as we know, isn't necessary to produce long, deep cold...

With the greatest of respect CC, if my memory serves me correctly you have been calling a return to cold ever since the end of the last cold spell - so, inevitably if/when it does return you will obviously be the first to have called it! As Tamara has already pointed out, the signs for a cold spell have not been (and still aren't) concrete, and February could quite easily have gone either way even though now a cold month is certainly favoured. IMO it is far too early to be celebrating forecasting victories, so let's just sit tight and see how things pan out. Even the northerly hasn't arrived yet, never mind any potential reloads from the East. This thread has, IMO, become quite polarised recently with two clear camps, which is a shame because judging by the comparative lack of posting with December, it is not just me who's decided to "lurk" instead of post. As for the 12z, the HP doesn't get as far N as the 6z although I suspect that - as usual - the GFS is overdoing cyclogenesis and deepening those Atlantic depressions. http://www.wetterzentrale.de/pics/Rtavn2041.png Still, this is such a long way out that tiny changes in the short term will give rise to enormous long term changes, so it's almost useless looking at the 850 profiles as in the scheme of things these are small details that will become firmer later. Best keep an eye on the short to mid-term, particularly how the models are handling the troughing in Europe and upstream as this will be crucial to correct HP placement...

Interestingly the control is also extremely cold so the op and the control (the highest resolutions?) both go for extensive and prolonged northern blocking. Incredible charts tonight especially considering the doom and gloom that has been almost non-stop on here since the last flake of snow fell; we even had "winter's over" posts a few days back. We're still a long way from the real deal but things are looking more and more positive every day, and what we are seeing is a trend for an initial northerly (the synoptics of which are remarkable in themselves considering recent winters) followed by the high toppling N and E above the trough over Europe, not only sustaining the cold spell but potentially delivering some really deep cold associated with the offshoot of the PV being advected west. ...Which I believe is what BFTP pointed out quite a while ago now!

Tbh I think BFTP may end up deserving a lot of credit; he went against even GP wrt a cold February and the Atlantic high eventually toppling into Scandi well before the models even hinted at this. Of course, we're still a long way from this happening but the signs are increasing that this may occur and if it does, then hats off to him

And indeed some showers will penetrate further inland, especially in places like northern Scotland and here for us in EA (hopefully!). There is a period (Friday) where winds may swing more NNE as well, which would only help matters.

Snowing here in Cambridge now - not expecting much but maybe a nice covering? Nearly everything has melted here from the last cold spell.

The ECM 12z has a better tilt to the trough than the GFS - this is crucial because it helps to keep us in a continental flow, obviously helping ground temps but also the upper temps to a lesser degree. http://www.meteociel...CM1-96.GIF?09-0 . EDIT: 120 chart is not very good with the high ridging into France and Spain - more like the UKMO?

Those SE'lies are not bitterly cold at all. If that chart is to be believed we can expect 4c minima in the S by Thursday: http://www.wetterzentrale.de/pics/Rtavn15017.png Not saying it will happen at all, but people seem to assume that just because the flow is SE'ly it will be cold. Yes, parts of Europe are now bitterly cold and a surface flow from these areas would bring correspondingly cold temps. However the flow is now predicted to have a more southerly element bringing it off France rather than Germany, which is nowhere near as cold (see above chart). We need as much of an E'ly element as possible helped by undercutting low.

Well there we are, our hope of extended cold seems almost to have vanished this morning. The GFS has stuck to its guns re the low slipping E rather than SE gradually giving rise to southerlies as the block is pushed E, but far more worryingly the UKMO and ECM are now all suggesting something similar. Ever since the GFS lost confidence in the undercutting scenario all the models have slowly downgraded the cold IMO but nothing compared to today! If it hadn't been for the previously cold-looking outlook a breakdown would be looking totally inevitable this morning. However there is still a chance that this is a wobble. That said, the GFS, ECM and UKMO all roughly agree on a similar evolution. But that isn't everything; I've dug out our only hope this morning which is the GEM! http://91.121.94.83/modeles/gem/run/gem-0-156.png - THAT is what we want to see back on the UKMO and ECM. One thing is for sure; if this turns out to be correct and the LP doesn't undercut, the GFS will have been the first to pick up on this. I wouldn't trust its post-180z output though as its switch to the euro high is far too quick to be trusted.Worrying trends this morning.

If upper temps are too high at the time of any SW attack though, freezing rain rather than snow may result?

Thanks for these fantastic assessments - I have a question though! You mention upper temps returning to milder (though still below average) values - this presumably being down to the cold air simply running out of steam underneath the Scandinavian ridge. If we were to see blocking retrogress to GL/Iceland, would this potentially allow another stream of cold air to leak out of the Arctic down the eastern side of the block once again and (perhaps) drive this towards the UK, hence creating another cold reload later on in January? Thanks

Thanks One thing you could do and probably the easiest is just to set your camera to a smaller photo size, then they won't come out big! Or you could upload them to facebook or something which downsizes them automatically and then just link them in from there. Amazing just the amount of snow falling over the UK at the moment. Shame it's so dry here but at least it's very white.