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A further illustration from me to show how the various trends in atmospheric angular momentum impact the tropospheric patterns as modelled by NWP Here is the current year AAM plot which straddles the rolling year starting Jan 2017 to date Jan 2018. I think using a long term trend period of the atmospheric circulation that is representative of how the global wind-flows have ebbed and flowed within that time, focusses particularly well on NWP output and the key synoptic changes and 'weather events' that occurred as a result of those (often) sudden changes in AAM. Some folk may be trying to remember the last attempted cold air advection Scandinavian ridge - though many will remember. It evolved during the opening 10 days of February 2017 - and look how it precisely coincided with the spike in AAM - which corresponded with an (albeit rather transitory) orbit of the GWO through Phase 4. Which has been a constant theme of discussion to look out for during this winter - and thus far elusive due to the strong easterly trades c/o the grip that La Nina has on the atmospheric circulation. As reflection of the brief GWO orbit to Phase 4, note the brief if prominent spike of AAM tendency that produced it. The associated amplification flux in the troposphere that was responsible for its creation, and following a very brief weakening of the polar vortex, was rapidly scrubbed out by the MJO returning to a Nina atmospheric signal and the higher latitude ridge was unable to retrogress as it would have done under more sustained +AAM anomalies Take a look again at the above AAM plot and see how momentum collapsed again properly during the summer - and, again no coincidence, mirrored synoptically by the poor weather seen especially after mid July, lasting through much of September after a reasonable start to the summer (but more so for southern parts) . Finally, see how an October rally in tropical forcing led a recovery of relative angular momentum into the early part of the winter - again coinciding with the repeated amplified patterns seen through that period, leading to the series of cold incursions that at least allowed glimpses of wintriness further south Charts will be more recent and relevant in people's minds so space saved by no need to post them That leads us more or less up to date with the further collapse in AAM heading into January, this time even more pronounced, and the consequent failure of the early winter pattern to re-amplify once more. As the AAM plot above shows, the latest downward tide-mark has just about eclipsed the early autumn minimum. So plenty of intra seasonal evidence just packed into a 12 month period to illustrate why rising AAM tendency propagating from the tropical to extra tropical circulation can build downstream amplified ridges that can assist cold weather in winter, and also, (because of the natural changes of wavelength that tends to migrate the ITCZ further northwards under higher angular momentum states in summer) warm spells at this time of year. For many, the two most popular types of weather to chase between seasons on this MOD thread. A year on from last Jan/Feb another Scandinavian high pressure is being chased. Also, a year on we are look again at a similar scenario in many ways in terms of waiting for tropical forcing to propagate into the Western Pacific and set up another significant rally in angular momentum tendency to usher the GWO (representing tropical and extra tropical wind-flows) away from the Nina dominated Phases 1,2 and 3 into Phase 4. That just happens to lead us towards a focal point of anticipated hope that is similar time-period to 2017 Recent summaries have outlined the odds stacked against. Not insurmountable, but to give full credence to this methodology and how it works, the risk outcomes must be stressed fully to encompass the total range of probability of solutions that NWP might pursue over this last third of January. The commonly referenced GEFS product forecast needs the usual caution caveat applied to it in terms of interpretation. Its often Nina biased, but this is one of those occasions where its focus of tropical bias might lead its modelling trends to actually under emphasise the atmospheric circulation in the extra tropics which will be swamped with easterly inertia c/o the La Nina forcing. This has to be meaningfully overcome before rising AAM tendency can be seen to lift total atmospheric angular momentum to an equilibrium that enables the more amplified Phase 4 pattern taking heights further north and east to become more than phantom suggestions that come and go in some extended NWP ensemble sets. This essentially re-emphasises yet again the main point of the last watching brief earlier this week, and posts prior to that. As others have posted, there are tentative signs of changes to perhaps impact patterns in the extended period that relates to beyond the turn of the month. This can happen - a lot of data sets with new information are going to come and go over the next 10 days to a fortnight. However, with that in mind, subsequent AAM budgets really need to show that tropical signalling c/o the eastward propagating MJO are overcoming the considerable lag of easterly trade winds dumped into the extra tropical circulation. In that sense its not at all just about the MJO - its about the consolidated La Nina feedbacks within the global circulation which have continued to cancel out attempts from the tropics to shift patterns. That annual AAM trend tells us that we approach Feb 2018 with angular momentum required to recover from a lower base than 2017. That is a measure of the la Nina feedback in the extra tropics that has to be overturned in order to amplify the tropospheric pattern. It also puts some perspective on the stratospheric angle in terms of how tropospheric wave flux through frictional torque can propagate from the tropics c/o the MJO into the extra tropics and activate mountain torque induced perturbing of the vortex boundary layers Anyone continuing to debunk the concept of poleward tropical>extra tropical forcing and thinking that a La Nina tropospheric circulation has no bearing on mitigating the process of poleward +AAM disturbance within the polar field really needs to think again and adapt a wider acceptance more open minded perspective in my opinion.

If the snow will not come to Hawesy then Hawesy will seek out the snow. Beautiful day in Glen Tilt and very quiet.

I was working in Peebles today, and took the road east out of Moffat, past St Mary's and over to Innerleithen via the Gordon Arms in the morning. On the way past the Grey Mare's Tail, I stopped for a couple of photos. On the way home tonight, I went via Stobo and Broughton and put the camera on a tripod for a long exposure of the lonely and abandoned Crook Inn at Tweedsmuir. Thought I'd give them all a b/w rendering as none of the light was particularly colourful. Anyhoo, there's a lot of snow out there http://rossofmoffat.com/albums/midwinter-snow/

Stole this amazing photo of cars queuing over Rannoch Moor from Facebook

Few photos from my mates at Harthill. The car was just bottoming out due to the snow being so deep: And a couple of the view across from my bedroom window, love seeing the wind driven ripples across the fields: and sunrise this morning:

Thanks for the in depth post @Tamara but could you please explain in simple terms what it means?

Looking at day 10 ensemble means, 00z EPS appears further south into mainland Europe with the Azores ridge extension in the means vs GEFS. Though the EC op more progressive with lower heights over UK than the ens mean. EPS GEFS EPS and GEFS mean/anomaly seem to retract the Atlantic trough days 11-15, EPS with a ridge in the means across N and W Europe up toward Scandi by day 15, GEFS making more of a trough in the means over Scandi and E Europe with the ridge retrogressing. Think the models may have a few wobbles / differences in medium-longer range ahead as they deal with anticyclonic wave-breaking over the Bering Sea and into the arctic ahead of Siberian trough, so we could see some changes afoot as we ahead toward the end of the Jan.

Great pics on here today. So good to see the good weather coinciding with a weekend again so that folk can make the most of it. That Glencoe jam was to be expected I suppose, given the forecast was amazing and tomorrow.......isn't. I thought the roads up north would all be a nightmare so opted for a short drive to St Fillans instead. Didn't see a soul all day!

Much of Scotland has a nice white coat I suspect it’s been a few years since anything alike.

Well what a memorable week this has been. The kids have been out every day/evening this week sledging, building snowmen and having snowball fights. Tomorrow we may see some snow before turning to rain as the milder weather finally breaks through. If I don’t see any more snow the rest of this winter I will not be bothered as this week alone has been great! Amazing photos from everyone also!

Some days are just too perfect! Road up to East Lomond Hill, Fife, January 20th. 2018

Had plenty on today but managed a wee walk along the coast. Beautiful winter's day!

Arctic tundra or Central Scotland?

GFS 18z for Friday! back in winters deep cold air !

worth noting that back in 1991, we were in a similar situation. (not that i remember the preceding weather but i suppose i wasn't taking much notice at the time) we went through a period of cold westerlies earlier in jan- then high pressure took over and we were haunted by the azores high for a couple of weeks, which drifted about across europe- that would have given us some benign weather at the time. as i said, its quite similar to what we're seeing (moaning about...) in the current output. then, (and this is the bit i do remember!) this happened- i was working on the construction of a shopping mall at the time and they shut down operations for a week!

We have so much snow here in the western isles. Its hard to believe we can have a winchill of -7c on a Swly@!!!!! We have anout 4inches on the ground. Not bad going at all making it a total of 11 days if snow falling this winter season and 21days of snow lying on the ground... no bad for a wee island on the atlantic.

Few photos from Inverness today during a walk with the dogs. Currently -6'C but with a wind chill in the order of -11'C / -12'C

I’m here.... liking the swathe of nothingness to the north on the ECM - Still 7-8 weeks of snow potential for the UK remember !

Some tentative pointers going forward emerging over last few days that we could have an increased chance of a cold wintry pattern as we head into February. Recent low GLAAM is forecast to increase back into the null phase and both EC monthly and recent EPS pointing to MJO moving at decent amplitude towards 7/8 into Feb. There are no signs of a SSW yet, though the stratospheric PV likely to take some knocks from wave no 1/2 activity - so could see displacement over coming weeks. So GLAAM improving, MJO looking good in Feb but will have to wait for it’s lagged effects, may get some help from stratosphere too through displacement. Stumbling block will be the strong feedback from La Niña on the troposphere pattern, which may interfere with MJO, let’s hope it doesn’t rely on a SSW, which is not looking likely atm, to over come La Niña and the troposphere can do all the work in the meantime!

Shower still on here. Nice feathery flakes gently falling. Hope it makes it across the few miles to Hawesy! Some weird cylindrical space ships have appeared above the house across the road or I have drunk too much wine.

I will take this please!!!!! If ever there was a run you could label 'The Murr run' - then this is it - never seen a monthly mean as cold as that before.

Noo that's whit ah call a proper winters day! Blue sky, sunshine, Max temp here -2 Deg C and powder snaw getting on for a foot deep in the park. Took the Grandsons oot oan the wee quad bike and had to dig it oot umpteen times till ah got a track pummelt through it. Then drove one of the Daughters tae Stirling, through Coalsnaughton and Fishcross along the stunningly majestic Ochils and saw temps of -4 Deg C at half one in the efty and still some snaw cover oan the roads. Noo, if Carlsberg done days!!! ? Big Innes

We just CANNOT get sustained northern blocking in the model output, during the winter months any more,thats why only really Scotland are having a cold winter ,because their location is far enough north to benefit from colder maritime polar air than further south. Further south you need maritime Arctic air or continental polar/artic air to bring cold and snow further snow,because of the shorter sea track thats the simple explanation,of the differences and still NO sign of blocking setting up in the correct location from ANY model to bring a decent cold spell for all the country.

Went for a walk from Clarkston to the World War Two Anti Aircraft Battery on Netherton Braes via Linn Park. Graffiti in the third photo includes ‘nostalgia used to be better’.

Well thats another sunny ice day with a maximum of -0.5c.I think this about the fifth ice day this winter so far. Some marvellous cloudscapes today again to the north and east. The ones to the east I have heard descibed as "Buchan Boaters" as they come on to the Buchan coast off the Firth . It seems that it will become less cold next week but on our local forecast but there will still be a risk of a ground frost most nights except Tuesday/Wednesday night and snow showers and an air frost return on Friday. Winter is not over yet and it seems this winter the milder spells get shortened every time they try to take hold.

A few pictures

Been around freezing all day and the car currently says -2. Had a walk around the village earlier. Dry, crunchy snow rather than the usual West of Scotland wet mush. Been to the shops this afternoon and I can confirm there is snow in Kilmarnock!! Albeit not that much. Looking a bit meh after tomorrow. Hopefully February brings some more fun.

Whiteout! Terrible conditions in Birmingham.... Got to love the Daily Mail

Cold day , walking in the ice that was snow fields ! Fingers crossed for one last snowfall tomorrow morning

Some cracking pictures being shared on Facebook!

At the football in Alloa today, stunning back drop.

Sorry all - was trying to express how inaccurate models can be rather than tell everyone who lives in the Midlands that the snow they're watching out of their windows is in fact fairy dust. I know better than to accuse every single Netweather member in the Midlands of being a teller of porky pies!

00z EC op much less enthused to build the MLB over UK, but will have to see where it sits with the ensemble guidance. After a few days of double figures early-mid week, models appear to be agreeing on turning colder towards the end of the week, as we get a little amplification over the Atlantic to allow a brief polar N to NWly flow next Friday. After that, models diverge on position and shape of the jet, GFS amplifies a trough over the NW Atlantic - which forces MLB into western Europe, whilst EC doesn't amplify near as much and keeps the upper flow flatter over the Atlantic.

A new netweather trend to turn the output thread into a gossip site during the night? I feel for the mod who needs to clean up each morning. Anyway. The GFS leads to quite strong high pressure situated over the UK and influences much of Europe. This will divide opinion. On the one hand, settled. On the other, i'd think daytime high single digits. No snow chances. Probably also a struggle for frosts. Later on, it could ridge towards Greenland, but since I'm already talking FI at T240, I'll leave it there. On the edit, it really did take another route and one that would make most cold lovers sigh.

you pesky midlanders, bragging about your snow....pah!......nothing compared to whats happening here.....snow's so heavy here, it's a total whiteout, and here's the piccy to prove it! see what I mean?

It’s transitory on all models and that doesn’t show the High winning out as there is strong westerly flow, so the high Fails to build in. What is interesting to note is that UKMO and more so ECM as it goes further, is that there is a shift south of the LP coming in and after the High is squeezed south. I think we could see some more deep depression activity come in and the further south the more wintry for some. For me tentative signs for the end of month turnaround to coldest spell of winter. I think GFS is headed the wrong way BFTP

Just been outside for an admittedly beer-fuelled run around in 37cm of snow. Absolutely knackered now and with a chafed ankle from ma wellies. Brilliant!!

Oh for a repeat of that blizzard. the retaining wall in the first picture is over 10 feet high and there was still the last remains of snow behind walls on the tops in early May.

Aye, whit a crackin day. Sun splitting the heavens and snaw glistening fae dawn till dusk. No a drip heard near fort SS. Still a guid 17 cm oan the picnic bench and Meto has us gaun oot wi a bang the morn. Great snaps folks.

GFS now showing signs of the HP control being the potential wrong direction. UKMO showing further squeeze south. So what I look for is deep depression / displaced PV coming in from Atlantic on fair south trajectory crossing the UK as we go through last week of the month and into Feb. I am encouraged by what may be developing on the models. I was interested yesterday on the Beeb forecast when they said Sat had gone backwards due to the failure of the front to push through NE. Made think...is this the start of the adjustments BFTP

That means a record warm Feb then. Don't take any notice of him he always says cold without fail every winter which generally ends up being a huge fail of a forecast.

Always a fun read when there's lots of pages to catch-up on in here?? Cairngorm was well worth the -25c windchill. Decidedly Scottish winter sport conditions, don't pull any funny faces or it'll be frozen that way until tea time Occasional showers in these parts today but the windchill was the main feature. Currently -6c

It’s worse than that I’m afraid.... that’s at +384... D16 I've been probably a bit pessimistic over the last couple of days. But we’ve seen before things can change quickly. At the end of December we were staring down the barrel of an Atlantic onslaught, which within a couple of days changed to much better looking cold chances.

Best chart for potential I've seen all winter. Pity it's at 384hours!

Have to laugh

WRF/NMM view of tomorrow.. Arpege still rolling out the 06z and Euro 4 to follow. Arpege

Another fine frosty start to the day at -3c Snow showers to the north again. A bit of spring light starting to show giving these amazing colours. Slight change of wind sending showers in the North Sea onto the Abedeenshire Coast.Seeing these showers off on the horizon always reminds me of spring as this is usually our last view of a cold spell as it moves east before milder weather moves in. Another point to consider with regards to liking snow or hating it is that a lot of farmers especially with livestock spend the summer securing feed for when it arrives so it has an economic impact too.

Yep that's what I was thinking, it's the day before my dad's 5th anniversary and I know I have said it before on here it's the same way the snow fell the moment he passed away at the same time of the morning!

The north seems to have had constant snow showers on and off for days and days this winter If I see more Northerners moaning how they dont get snow ill get angry I will Angry