LomondSnowstorm

Those areas, with the addition of anyone on the east coast where the pressure gradient will be tightest, looks set to hear the brunt of the winds. I'd expect to see 100+mph gusts on Cairngorm and maybe 70-75mph elsewhere, with Glasgow, Dundee and Edinburgh all having gusts upwards of 50mph. Certainly could be a close call as to whether a sting jet develops (if so gusts could be comparable to the January 2012 storm) but I haven't had an in depth look at the charts yet today so I'll reserve judgement on that until later on.

With a wee dram and a wistful look about how the current charts are nothing like that Joking aside, BUS put this together a week or so ago - saves the bother of having to go to meteociel for the actual charts : 60+mph gusts on Thursday morning with rain turning to snow from the northwest: Going to be an interesting one to watch and hopefully we can get some slight last minute upgrades to extend the cold that few hours longer.

Excellent points, what you were saying about how the models are improved through tweaking towards 'what works' rather than strictly looking at the additional physical factors which affect the weather and modifying the equations towards that is one that was brought up at the MJO talk at the uni that I believe Lorenzo was also at. All models do seem to have different inherent biases - the ECM towards overdoing northerly blocking, the GFS towards low heights to the north particularly in FI (there's a graph somewhere showing the biases that Lorenzo posted up which does show this up quite well, particularly post D4) and during northerlies a frequent occurence is the entire pattern getting shifted eastwards. I did worry about this occuring but as the models were broadly in agreement on the east-west thing until yesterday it seemed as though we might avoid it this time. However, one positive is that the upper air profile for Wednesday seems to be a bit more conducive to snowfall, so Wednesday might stil be quite interesting: 950s are marginal but given that the precipitation is coming in the form of showers and in the middle of the day we can probably get them pushed down fairly readily during precipitation: e Another interesting one is the signal for snowfall on Thursday morning from the extended NMM. Not sure how good it is for picking up on accumulations but very interesting chart nonetheless: http://www.meteocenter.eu/fajli/index.php?domain=euNMM12km&region=NW&forecast=Snow&time=84

Some impressive interrun consistency from the GFS: UKMO will be interesting, GFS 12Z is keen to shunt the cold eastwards more quickly than the other models (although still very cold for most):

Hmm, very interesting, almost as interesting as the fact that they're now able to model these features so far out rather than just the possibility of them. In that kind of airstream I'd say a polar low is quite likely and moreso for the east side rather than the west side of Britain. Interesting that he mentions dry inland 'south of the Scottish border'. The implication of what that means inland north of the border is particularly interesting, especially when considering maxima on Friday are progged at no more than 0-1C currently.

Hmm, I think that, while the wishbone effect will be in operation, it really depends how close we can keep the low. If it drifts eastwards too quickly after the cold front the convective potential will be reduced. However, if we can keep the instability with those deep cold uppers (particularly with sub -40C 500hpa temperatures) then I'd be surprised if we didn't all see at least some of the white stuff with such a massive temperature gradient. We've all seen our fair share of disappointing northerlies but there's a big difference between -8C and -13C uppers so it will certainly be an interesting one to watch.

First time I've seen this within such short range - there's a run which brings sub -15C uppers to Shetland: Most runs (as many as 15 I'd say at some point in the run) give sub -10C uppers to central Scotland:

December 2010 was the closest, but even it wasn't quite as potent as many of the current runs , particularly UKMO which has -14C uppers north of the Grampians.

A real sense of deja vu from the MT because, once again, the duration of a cold spell is dependent on how an Atlantic trough is tilted. I would do a paint chart with the various outcomes based on yesterday's runs but, in true Blue Peter style, here's one I did earlier, much earlier, this time last year: In this case, +120 ECM is tilted vertically or very slightly negatively (good): UKMO is tilted positively but only slight which prolongs the cold a bit compared to the earlier GFS (which has NOT but rock solid on a shorter or less intense cold spell no matter what they say on the MT, it's chopped and changed more than the others and continues to be unsure of whether it's coming or going) GFS has a pretty flabby low but it is moving closer to the Euros at 18Z: No matter how you skin this cat, Thursday into Friday is going to be cold and snowy for a great number of us: That trough, which is a particularly interesting and worrying feature in terms of snow and wind, is going to be interesting, but the cold will affect more of us more severely and for longer if we get the trough tilted neutrally or (even better) negatively and will be shunted eastwards more quickly if the trough is positively tilted. The GFS can't be right because it's incoherent and because its own makers, the NOAA, consistently disregard its solutions in favour of the euros, but its more recent ideas on the tilting of the trough could be closer to the truth than the ECM. More likely is an ECM/UKMOey blend whereby the trough is very close to being neutrally tilted but on the positive side and we still get some deep cold. Incidentally, the uppers STILL haven't downgraded: -12C uppers from the north is utterly brutal cold and would be very likely to lead to an ice day for almost everyone on Friday, regardless of the positive/negative trough outcome. Interesting potential for Wednesday too, with uppers around -5C and winds westerly we could see some snowfall inland from any showers: Anyway, in summary, still cold, still potential for snow, still irrelevant to us when someone on the south coast suggests it's not going to be cold. Hint: it's Scotland in winter - it's almost never not cold, but from Tuesday night on we're looking at uppers cold enough for snow and from Thursday to at least Saturday for some deep Arctic cold, no matter which model is closest. LS

1 fatality, STV reported 3 last night which are most likely the helicopter, 32 in hospital but there are still people trapped in the pub. Anyway, yeah, ECM snowiest, although the uppers are *only* -9/10C for most of the cold spell, but on the plus side it lasts 3+ days: GFS is a bit shorter lived and perhaps drier, but with the potential for shortwave or polar low development due to the exceptionally cold uppers: UKMO is only out up to +144 but it looks a bit more shortlived on it given the poor orientation of the trough, still very cold though with snow potential:

Maybe it's worth setting up a separate thread for this on the serious discussion thread, although the mods will be absolutely fine about us discussing this on here.

twitter, although allegedly police confirmed. BBC are very slow and in fairness they also need to be totally sure before they issue a statement to make sure they don't have to retract at a later date. STV I believe tweeted the story but I'm waiting to see. Another eyewitness claimed to have seen 2 bodybags but latest statement is that Police Scotland are unable to comment on any injuries still.

Yeah, I think the fatalities were the helicopter crew, still a horrendous incident and hopefully there aren't any more fatalities reported

10 sub -10C runs overall (11 counting the op), another solid set of ensembles and crucially the uppers don't appear to be downgrading in strength as so often happens(yet).

I had a post ready but I held off because of the helicopter crash, latest reports are that the three in the helicopter that crashed are dead. I've got a lot of friends and family in Glasgow so I've mostly been trying to find out if they're all ok, I'm pretty sure it's not a pub most of them regularly frequent but with reports of fatalities it's best to check in with friends and family to make sure they're ok. Models look pretty good, pub run a bit weird but par for the course with the GFS, ECM has major snowfall potential particularly from that secondary shortwave but this is a very complex setup so I wouldn't count any chickens yet.

I thought the topic was the mate controversy - pure racism/banning of syntax not used since 2005 Anyway, I honestly haven't seen the 12Zs yet (shocking, I know) and haven't read through the other or MT thread but I'm assuming the ECM is good judging by Nick's post and the fact that it's been excellent for five out of the last six runs for here. I'll get back to you with a summary and maybe even a look at the Fax chart if we're into interesting territory with it(I suspect we aren't quite yet but getting closer to it).

The 6Z comes up with yet another solution, phasing a deep Atlantic low with the main trough early doors to delay but also prolong the onset of the cold and adds in a bonus shortwave for good luck: Even manages to bring in an easterly in low res: Possibly the wintriest run to date with some deep and quite prolonged cold.

Mine's the same, very sheltered on three sides which means that even in the worst storms gusts rarely exceed 25mph so it's only any use in a northerly. I think the highest gust it recorded was around 80mph during the late March 2010 winter storm.

If it comes off I'd say it's likely to be pretty much a direct hit, particularly if it lasts more than 24 hours like the ECM does. We'd be talking about an early March 2006 type event with the ECM, although still a long way to go it must be said

Both the ECM and the GFS are agreed on sub -10C uppers (actually -13C uppers for the northern Highlands where the convection will have to develop) at Day 7. For a northerly that's about as good as it gets frankly and, while it might get watered down, usually one of the models would have started to water down the cold pool by this stage whereas both seem determined at the moment to beef it up. Still 7 days to go but if the ECM in particular verified we'd be looking at widespread lowland snowfall, widespread ice days and some proper 6 inches + snowfalls north of the Grampians, not to mention Shetland which would take an absolute pasting. I'll dig out some examples of northerlies with -12C in the mix (I think the last one was maybe December 18th 2010) but they are usually accompanied by very significant snow for Scotland so it's worth keeping an eye on, especially this early in winter with still relatively high SSTs

What's really quite striking to me is the depth of cold both the ECM and GFS want to bring southwards. Now of course it might end up significantly watered down but even for this location a sub -10C 850hpa temperature from a northerly is impressively low and yet both 00Z ops manage it at D7. Not only that but both dig it quite a long way south, although it must be said that it is fairly brief. The potential on this has always been greater the further north you go so with the latter parts of FI very much up for grabs still depending on how the energy separation is resolved I'm personally quite looking forward to seeing if this notable cold plunge actually verifies and if so how long the 'toppled' can last. Just under a week ago many were calling for a 'zonal reset' but I'm sure now we can all see the benefits of keeping what amplification we do have upstream in order to try and squeeze out as much cold from a hemispherically unfavourable period as we possibly can.

I've revised mine down from my initial winter forecast to bang on the average at 4.4C, although I'm tempted to go lower. I reckon it'll be a generally anticyclonic month, with most of the 'genuine' cold and snowfalls generally staying north of the CET zone, but with enough mid latitude blocking and well enough placed to stop zonality ruling the roost completely.

To be honest Catch I like our chances on this one. Even more runs go sub -10C with the uppers on the 18Z than on the previous run, with 11 sub -10C runs for Midlothian now whereas it was more like 8 on the 6Z: The 12Z GFS op showed how it could all go staggeringly wrong if we didn't get energy separation (particularly when 95% of the UK's oil is in Scottish waters {sorry Lorenzo}) over Greenland, but given it was perhaps the only run of the last 3 days to put high pressure over northern Scotland by the 6th/7th December I'm not all that worried about it. Ultimately I'm happy enough just to be in with a shout at this early stage, a mix of cool/cold anticyclonic and cold wintry north/northwesterlies is an excellent way to start winter.

We're six days away from a potential (albeit a bit speculative given the models differ on this) snowy spell, as cold uppers push in from the west: With the 6Z we'd then have a secondary low forming which introduces a warm sector but on the plus side tees us up for a proper Arctic blast: ECM does similar: Some seriously cold air in that, and if it came off the potential for Polar low formation would be greater than it's been in a long time: Once that kind of cold becomes embedded it becomes difficult to shift, certainly at the surface level, and given that the coming relatively mild week isn't exactly warm: we're likely to continue a run of cold starts to December which goes back to 2009, when of course by late December no one remembered the first bit anyway. SM was mentioning counting the number of sub 10C runs on the ensemble suite, and I make it eight for Midlothian (nine if we include the op): More like 10 or 11 for Aberdeenshire (i.e. half the runs) And more like 14 for Shetland: The other thing to look out for is the possible sting in the tail east/northeasterly which could follow as mid latitude heights ridge northwards behind the trough. The Pressure ensembles for Oslo are instructive and show very clearly the Scandi trough setup followed by possible Scandi height rises: A 60mb pressure rise in 48 hours with the op!

Bit of both Westerlies are better for snow than northerlies for most of us, but also it would've stopped any TOORPing on the MT because most people wouldn't have known there was anything more than a slight frost coming up (other than Frosty, Frosty would've known). Anyway, either way I'm happy, and of course the beauty is that we'd get back to where we were basically through slight downgrades, so it's really win-win