LomondSnowstorm

Hmm, it's going to be in the top 10 certainly but not sure it's quite record breaking - Phillip Eden currently has the anomaly at around +2.1 to the 25th for Scotland (+1.6C for North, +2.3C for West and +2.5C for East), the 81-10 mean is 2.8C for the whole month which means we're probably running around the 5C mark to the 25th. The next few days aren't going to see anything massively mild to push that upwards so I reckon we'll be stuck somewhere between 5.1C and 4.7C for the month as a whole. Anything above 4.9C would put us at 5th highest in the rankings but I think we're probably safe from ending up in the top 4, which are: 1988: 5.8C 1971: 5.7C 1934: 5.6C 1924: 5.6C The next ones down are '31 and '21 (both 4.9C), '74 and '42 (4.8C) and then '56 and '53 (4.7C). The lack of very mild Decembers since 1988 has been very noticeable given almost all other months have seen either record or near record highs in the 100 year series since then - 2006 at 4.4C was the mildest since then and we're almost bound to come in higher than that, so this will be the mildest December in 25 years and will bring to end the longest run of consecutive sub 4.5C Decembers in the last 100 years. http://www.metoffice.gov.uk/climate/uk/datasets/Tmean/ranked/Scotland.txt Seems odd to say when talking about mild months in the context of AGW/the general increase in Scottish and UK temperatures in the last 100-200 years but we were overdue a mild December

I've done a wee blogpost on how the winter (and my winter forecast) is shaping up so far and on the medium-long term outlook for the rest of the winter. http://forum.netweather.tv/blog/237/entry-4709-winter-forecast-recapupdate/

With December nearly over (and with me having some spare time on my hands for once) I thought it would be a good time to assess my winter forecast so far and give my thoughts on where we're likely to head weatherwise in the New Year. This was my NH composite forecast for the general height pattern for both the troposphere and stratosphere for December, along with my own adjustments to the composite maps:[quote] [size=5][b]December[/b][/size] [url="http://f1.nwstatic.co.uk/forum/uploads/monthly_11_2013/blogentry-9298-0-31045200-1383526045.jpg"][img]http://f1.nwstatic.co.uk/forum/uploads/monthly_11_2013/blogentry-9298-0-31045200-1383526045_thumb.jpg[/img][/url] For December, the Aleutian Ridge and negative height anomalies over the Western side of the Arctic are the most notable features, but otherwise the anomalies are fairly muted, with a positive anomaly out in the mid Atlantic and actually a slight mean trough over Europe.Half of these winters featured either a Canadian Warming or SSW in the first half of winter, with 8/10 featuring a notably cold stratosphere initially, so this may well be the key to our winter once again. The Stratosphere composite looks like this for December: with a very strong West Greenland centred vortex, but already there are signs of weakness creeping in from the Eurasian side. [url="http://f1.nwstatic.co.uk/forum/uploads/monthly_11_2013/blogentry-9298-0-21243900-1383526044.jpg"][img]http://f1.nwstatic.co.uk/forum/uploads/monthly_11_2013/blogentry-9298-0-21243900-1383526044_thumb.jpg[/img][/url] [b]Adjustments[/b] Given the SST pattern I’d suggest that the mean height anomaly for February is centred somewhat further west over Greenland, while low heights south of 60 degrees north are likely to be confined to southeast Europe through December.[/quote] Although the month isn't yet over, the anomaly to the 23rd is likely to be broadly indicative of the final anomaly, albeit with a less emphatically strong negative anomaly for north of the GIN corridor, a less strongly positive anomaly across continental Europe (perhaps neutral to negative for the British Isles into Northern France) and a more neutral anomaly for western and central Russia: [attachment=200213:compday.jopyVF2xYl.gif] Bearing in mind the likely movements listed above and also the correction suggested in the original forecast, the December anomaly was actually quite a decent match, picking up on the mean ridge across the mid Atlantic to the southeastern US, a strong Aleutian Ridge, low heights into the central portion of the US and generally low heights directly to our north. As for the stratosphere, bearing in mind positive height anomalies around SIberia over the next few days, the vortex positioning anomaly was also pretty reasonable all things considered: [attachment=200259:strat anomaly Dec.gif] So how about the actual text forecast?[quote] A very zonal period to start the month following a short, sharp Arctic blast at the end of November, with west-northwesterly winds and very limited blocking. Near constant low pressure systems will bring wind and rain throughout, with only brief drier interludes. Temperatures above average in England and Wales but near or even slightly below average for Scotland, where colder upper air temperatures will bring the odd smattering of snow even to lower levels in spite of a lack of frost, with precipitation above average initially everywhere. From around the 12[sup]th[/sup] onwards things will quieten down, with high pressure building in from the south, bringing a brief spell of very mild southerlies followed by a dry and eventually frosty spell in the run up to Christmas. Temperatures above average everywhere up to the 20[sup]th[/sup] but cooling down towards average from the south as heights transfer northwards, precipitation generally below average away from the far northwest Highlands where they’ll be around average. By Christmas, heights will transfer westwards with an initial spell of rain followed by a genuinely cold northerly blast as low heights dive temporary southeastwards, bringing more widespread snowfall and low temperatures, although with accumulation generally confined to the usual spots (which of course vary depending on the exact wind direction) before the dam breaks and the heights sink once more by month’s end. Temperatures will be generally above average for most of England and Wales, with an initial CET punt of 5.6C, the Scottish mean will sit around average at 3.4C. Precipitation will be marginally above average for all of Scotland and much of northwest England but for southern England and Ireland it will be around or below average. In other words, a fairly typical December.[/quote] I think, all in all, a decent enough forecast, somewhat underestimating the storminess around the 13th-27th and maybe overestimating the cold potential for Scotland but generally a reasonable account of the month. The CET and Scottish mean temperature punts both look a bit on the low side but moreso for the Scottish Mean, which looks like it'll come in around 5C, while the CET is currently sitting around 6.7C. So how's the forecast looking for the rest of winter? Well, after having had a positive Arctic Oscillation for the entire month of December we may be looking at the first hints of a more blocked NH profile with the AO forecast to go negative for the first time this winter: [img]http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif[/img] We can see how this materialises from the 8-14 day height anomaly forecast chart - positive anomalies across the pole centred most strongly over Alaska with a mean UK trough flanked by positive anomalies over Western Russia and the Azores: [img]http://www.cpc.ncep.noaa.gov/products/predictions/814day/814day.03.gif[/img] What does this mean for us? Well, it's a slightly messy setup but ultimately one where a broadly westerly pattern will prevail into the first week of January. However, that doesn't quite tell the whole story, as, if the height rises over the Arctic verify, we will be looking at a generally cool regime with transient blocking both in the Mid Atlantic and over Russia providing temporary cold snaps and battleground snowfalls as the month progresses (albeit the details of this is very sketchy and it's fine line between these, cold zonality and regular zonality). Looking even further out, the ECM 32 dayer along with MOGREPS appear to back up this generally unsettled but with a hint of something more seasonal at times into mid month, and (apparently) even as far as the end of January. In addition, both the MJO and AAM look to be giving a slight helping hand to more amplified solutions and this will also give some encouragement to those looking for snow (the favourable phases at this time of year are the 7-8-1 wheel). [img]http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/UKME_phase_23m_small.gif[/img] My original LRF for January broadly backs this outlook up for the first 20 days but indicates the possibility of major stratospheric disruption occuring around mid January which could potentially usher in a much colder pattern.At the moment, however, while there is some reasonable warming in the 'surf zone' forecast, it doesn't look nearly enough to actually force an SSW - for the first half of January at least. I still feel that we are looking at a winter of two halves (although if the OPI wave forecast is anything to go by we may have to wait a while before we see anything meaningful) and there have been some increasingly encouraging teleconnection forecasts as we head into the New Year, so I'm broadly sticking to the original for now, with the caveat that an SSW, if it occurs at all, is unlikely until the very end of January into February at the earliest.

The only thing I'd add to the reply about uppers needed for snow is that the highest uppers you could 'get away with' are during rare occasions when there's a cold trough (or a slack flow with very cold surface air) sitting directly over the UK as occured at points in both December 2009 and December 2010. In the former we had falling and lying snow with temperatures of 0C with uppers just below 0C because the air embedded at the surface was so cold and still that relatively less cold air higher up in the atmosphere was unable to mix the cold surface air out. Upper air temperatures above 0C in these instances are what give freezing rain events. Anyway, the +240 ECM is a decent chart, although with a very slightly positively tilted trough it would be a case of 'will it won't it ridge northwards' before the next low pushes in. The PV lobe to our northeast is critical too in dragging in that all important cold pool to the Eurasian continent and, eventually (if we're lucky), towards us. Early days but the models are looking a lot more promising for proper HLB than they have done since the start of the month.

The synoptics are what matter at this stage anyway - of course it's not helpful that continental Europe is relatively mild at the moment and ideally we'd probably rather have a trough dropping south into Scandi from the Arctic to establish a better cold pool, but the important point is that we're starting to see positive anomalies over the Arctic and a slow but steady southwards movement of the jet and, subsequently, of troughing features:

I'm going to go a touch lower than my LRF punt to 2.7C as the cold *may* start a little earlier than I initially anticipated - a cool zonal type start but with an increasingly chilly feel even into the CET zone, with eventually a more January 2013-like pattern of not all that deep cold but lots of potential battleground snowfall events into mid month, with a proper blocking setup and deep cold establishing by month's end (I hope).

Had a technical White Christmas here with sleety flakes mixed in with rain showers at around 12.30pm

Such big fluctuations seem a bit unlikely, especially moving 4mb in the one direction and then 5mb back in the other, and if it doesn't revise down I'd be tempted to say that the 00Z revision was erroneous.

I must say this second deepening is both concerning and surprising - it was meant to have weakened by now and certainly I didn't think it'd get back down to 930mb. It should still weaken but I doubt it'll get up to 940mb by 6am as the NAE has it:

Oh I see what you mean now, that's a trough embedded in the flow, the kink with the event in December 2010 was a bit different but in essense it's a similar idea - around this area convection tends to become organised and also associated with increased winds. This analysis showed a few of them lurking to our southwest and they're bound to crop up given the extent of this low (bringing with them associated squall lines) so this could swing round to bring further wind and rain/high ground snow tomorrow morning (although overall wind speeds will have reduced by this stage).

The 'shortwave' west of Ireland? It was sort of picked up by the mesoscale models but at 976mb instead of the 968mb shown: You're right enough though, it may well act to delay the eventual slackening (for us at least) and tighten the pressure gradient for the next few hours, although I doubt it'll have a huge impact either way. Were it sat over us it would conversely bring a slackening of the flow but with some really intense precipitation associated with it, but of course we have the latter at the moment anyway!

Have a great Christmas everyone, could well be a technical white one for a few of us (in spite of a distinct lack of any lying snow away from high ground) particularly for the morning and late evening. Glasgow White Christmas odds are at 21/5 apparently which is just about a value bet IMO since they're likely to see a fair amount of precipitation through the day but Bishopton doesn't exactly endear itself to wintriness generally so I'd say 3/1 would be about as low as I'd go as far as value odds are concerned. Gusts at 11pm were widely over 50mph with sustained winds up to 39mph at Leuchars (about the highest they've been). Blackford Hill had a 75mph gust earlier and I wouldn't be surprised to see it topped now since the winds do appear to be aligned more (un)favourably for most of us than they were when we had the initially predicted worst phase this afternoon.

I see your point, certainly I've had some great times on there, with the best one for me being the high stakes drama of December 2009 when we had the 'mildie' collossus of Ian Brown (and his hypothesis of an era so controversial it can't be named on the forum) taking on the plucky coldies and, for the first time in internet history, losing, and then the 'WTF' moment from the same poster after a similar standoff with Steve Murr and GP in January. This thread is brilliant when it comes down to the nowcasting stage though, during 2009/10 and December 2010 it was the first thing I would read when I got up to check how things were developing on the ground, where the travel disruption was, even stuff like impending school closures tend to get picked up on here pretty early. We also got to have a good rant at the Beeb for the occasional utterly shambolic forecast, like in December 2009 when a 'dry morning' was forecast on the pre-recorded regional forecast even as the news itself was reporting on 5 inches of snow for central Edinburgh

When I joined in 2009 this thread was very helpful in the sense that I could post my thoughts here without feeling 'stupid' or having my post get lost among hundreds of others during busy times. The learners area helps immensely, as does reading the MT (particularly either the in depth thread or going in during quiet times when the coldie/mildie arguments aren't blighting the thread). Of course I still mostly stick to posting here anyway because it's far more enjoyable but I've learned a huge amount in my 4 years on the forum so far.

Reminds me a lot of Christmas Eve 2004 when we had a similar wintry mix with the snow line visibly lowering down the hill until it was just above us. Currently a wintry mix here but with cloud cover starting to break up again, would need some proper intensity for it to turn properly and start to lie but still good to see flakes nonetheless. Should be similar wintry opportunities in the coming days if the models are correct, uppers mostly suppressed below 0C with sub 528dam thicknesses at points with a mean that steadily declines into FI - with generally low heights and winds from the west or northwest any slackening in the flow or increased amplification would give us a good chance for snow, with high ground snow being an almost constant feature for the foreseeable: No run has temperature getting above 8C for Fife, with the mean maxing out at 5C during Friday's storm and after that the mean tracks generally downwards to around 1C by the end of the run. Nothing mild on the cards certainly with the general direction of travel pretty clearly downwards as we move into 2014.

Indeed, with all the Gluhwein and Czech beer I've drunk in the last few days I'm not sure I would've survived two hours of spiralling over London

Hey everyone, I've returned from sunny (well reasonably so for December) Prague and the flight wasn't actually too bad, if a little windy on the descent into Edinburgh. I see there was a slight tiff on the other thread regarding the ongoing 'southern bias' argument, which can be quite good fun if kept light hearted but we do need to remember that we're a' jock tamson's bairns and these storms do have a particularly strong impact on areas which don't experience them as often, and also many of us have relatives in or indeed hail from Fluffybottomshire (as it's endearingly known) who are perhaps suffering storm damage. I certainly wouldn't want English born members like BMW and even our frequent Sassenach visitors who like to get away from the rough and tumble of the MT to be put off visiting our lovely thread so we should all remember to keep the banter as respectful as possible. Anyway, down to the weather and I'm going to discuss the two main aspects of this system separately - the wind and the precipitation (with an obvious emphasis on the snaw). First off, the wind: the EURO4 has sustained winds over 50 knots for the Western Isles by 6am, with more modest but still substantial speeds of around 15-20knots for most and 30-40 knots at the coast: ramping up to what will likely be the peak of the winds for most by mid afternoon, with sustained winds of 30 knots and hurricane force gusts widely, with 40-50 knots again sustained winds near the coast, with the potential for a worsening by maybe 10-15 or so knots across the board depending on how sting jets are picked up on at the last minute: However, for the Uists in particular the worst may still be to come, with late evening holding potential for sustained Hurricane force winds: Similar story from the NMM, although what's more notable is the longevity of the high wind setup, with 40+mph gusts from morning to evening for a large swathe of the country, concentrated around the East Neuk, the Firth of Clyde, Inner Hebrides, the Galloway Coast and, moreso by night again, from North Uist to Barra. This is the sustained wind map, as I reckon Tony (Lorenzo)'s already posted most of the gust maps up and I've described them too in great detail. This is around the peak of it for most and shows the potential for near hurricane force sustained winds around coasts exposed to southwesterlies: Onto precipitation - the latest Euro4 (the above is based on the 12Zs as only accumulations are out yet) give some impressive totals on the Cairngorms in particularly, with a maximum around 55mm up to midnight tomorrow, more like 20-30mm across the NW highlands and generally 10-15mm elsewhere: So what will it fall as? Currently, pretty much everything is falling as rain: However, by morning the lower thicknesses will have pushed in and, although patchy, the morning will give perhaps our best opportunity for more widespread falling snow: Temperatures across the north of the country are worryingly chilly given the wind speeds, so blizzards for the high ground and inland northwest of the boundary fault looks a near certainty, but with temperatures more like 2-3C for the central belt it will be more likely a wintry mix which turns snowy with much forcing from intensity and moreso where sheltered from the high wind speeds: On the NAE, 950hpas aren't brilliant but we're in a funny old paradigm where 950hpa represents temperatures pretty close to the surface: In fact, at this point most of Scotland has sea level pressure below 950hpa anyway, which makes a theoretical 950hpa temperature of 3C with 930hpa pressure seem rather 'good' for snow: A better measure for those marginal areas is the Wet Bulb Freezing levels, which, according to the GFS at least (since we don't have free access to that metric on either the NAE or EURO4 models) are likely to be sub 0C for most east of Glasgow and away from the unremitting coastal mixing up in Aberdeen City and shire, where it will feel bitter but likely won't see much in the way of snow away from Deeside: However, precipitation is likely to be a bit sparse and more in the form of showers in the morning, which makes the best chance for widespread snow the front edge of the occlusion which is likely to hit around lunchtime: Behind that, warmer uppers push in and turn snow to rain up to relatively high levels: although still with low enough WBFLs to keep a fair number of us interested through the rest of the day: By evening we again have a shot at some snow, with sub 528 thicknesses pushing in along with generally slacker air However, a feature at the surface level through into Christmas will be the slightly 'warmer' air extending up to 900hpa, so any low ground snow will struggle (although I certainly wouldn't rule out a wintry mix given such low heights for the big day). Once again, intensity will be key below 200m and with some of that we can drag down the freezing levels and turn the rain to snow: Just a word on the severity of the storm - the NAE drags the core pressure down to 924hpa, which is exceptionally low. particularly given how close its centre is to us (the Butt of Lewis could well see pressure readings below 930hpa: It's unlikely to beat the record low of 925hpa from Ochtertyre, Crieff from 1884 ( http://forum.netweather.tv/topic/48934-the-lowest-pressure-reading-recorded-in-the-uk/ ) but it will come closer than any storm since Braer.

Jeez, crazy reading through the last 24 hours of this, weather absolutely on steroids - who said zonality was dull? Here in Prague we've had a really rather tranquil few days in comparison, some sleet at 1C on Friday night, 1/-3C yesterday with some nice sunshine and some nice hoar frost on the train to Dresden today but milder with light- rain by the time we got back. Slightly dreading the flight back tomorrow evening but very glad we aren't flying into what looks to be the worst of it on Christmas Eve - even then gusts around 30-35 mph won't be that fun to be in a plane in. I can proxy report sleet via my grandparents in Freuchie but not settling and I'm looking forward to experiencing the wintry stormy smorgasbord first hand from the comfort of our log fire from tomorrow evening onwards.

Yeah, the skew-t shows a slight warm layer up to 900 hpa. Up to 950hpa would've been fine but this is just slightly too much for snowfall unfortunately: Still potential inland and with elevation though this evening: Some decent accumulations possible too: However, we do appear to have the same problem with the Euro4 in the sense that the DPs are either vastly underestimated or at such a poor resolution on the website that it distorts the picture (I think the latter to be honest since the locations under the values happen to be rather elevated so probably do have comfortably sub 0C dewpoints): The next band coming in appears to have a bit more intensity and combined with the time of day this might kick temperatures down enough for some decent snowfall. In fact, the temperature has dropped from 2.9/0.9 to 2.4/0.5C since I got back to Fife. There's been snow on the Lomonds (although you'll already know that from Scotster) and it did snow here earlier but it didn't lie unfortunately.

The EURO4 did seem to stall the arrival of the cold air somewhat by placing the low that bit further south, however behind that squall line it does appear that DPs will lower somewhat and with intensity any rain will turn to snow away from the immediate coast as the day goes on.

Well this is where things get interesting: Not a huge amount showing on the accumulations charts as of 9am but much of central Scotland does have at least the lightest shade of pink i.e. 2cm of snow: Could be a fun wee walk to my exam tomorrow morning and then train back to Fife in the afternoon...

Possibly, although the advantage for you is that anything that falls is quite likely to lie. For example the Euro4 on both runs has (slightly worryingly for me as I've got a flight at 7am Friday from EDI) push snowfall eastwards across the central belt, either reaching Edinbrgh around evening or just after midnight: Temperatures above 0C for most so probably not causing massive disruption to transport away from high level routes (at least nothing that can't be cleared if Councils and MO are on the ball) but enough to give a dusting or even a covering in the garden:

Well tomorrow certainly looks to be below average temperature wise for most of the country, and for Ireland in particular I'd go as far as to say cold and even rather wintry - the Euro progs maxima at no higher than 4C for Scotland and as far south as the Midlands, with Wales also struggling (away from the coast where obviously coastal modification and increased mixing will keep temperatures a degree or two higher). An ice day for the Grampians and Northwest Highlands down to even about 400m or so and even at low levels in northern Scotland and Ireland temperatures will be no higher than about 2C: The snow accumulation charts also paint a very interesting picture, with significant accumulations right down to low levels by 6am Friday everywhere northwest of the Highland Boundary Fault and also for a large chunk of Northern Ireland and the Republic. Accumulations also signalled (albeit maybe 2-5cm at most at this stage) for the central belt, the Eastern Borders, the Pennines, elevated parts of the Midlands and in particular the Cambrian Mountains: Obviously these will probably change around a bit, and as this is the first day we've had access to the Euro4 it will be interesting to see how well it fares, but it is illustrative of the fact that we don't *necessarily* need blocking to deliver at least a modicum of wintriness to the British Isles, particularly the northern and western parts.

Certainly not much to be concerned about away from the immediate west coast as far as marginality goes from 6am tomorrow, according to our newest model friend the EURO4: Rain turning to snow by the early hours of tomorrow, heading northwards and then stalling along the Southern Highlands: Slight adjustments in the movement of this feature could make things even more interesting for rush hour tomorrow though - a very slight southwards correction in the scheme of things and it becomes a Glasgow-Dundee blizzard. Temperatures are pretty close to being spot on as well, just 2-3C tomorrow through the day and struggling to get above freezing further north, maybe 1C in Inverness maximum: On the 0Z it picked up on the potential for accumulations into the central belt by evening (and also looking quite snowy for Northern Ireland and much of the Republic) 40+ knots sustained winds for the Western Isles tomorrow morning, only around 15-20 knots for the most part on the mainland with the surface direction almost southerly:

Aye, I had the mother of all beasterlies for late January. Thus far the forecast is panning out relatively well, aside from a somewhat more cyclonic dominated pattern than expected, and there's nothing in there for the next 70+ days of winter that I'd alter at this stage, so I'm still saying late January into February is the main area of interest for those in the east. The charts Lorenzo posted up just there from Ian F though are very promising for central Scotland, with WBFL sub 400m and precipitation pushing well inland. I wouldn't be surprised to see some snow cropping up further east as well given the strength of the flow, albeit with somewhat reduced intensity, and the prognosis for this remains the same as it was when I did my last big post. I'll maybe have a go at a paint job if my revision tomorrow goes well but if not I'll hopefully at least be able to post from the 4km UKMO model (correct me if I'm wrong but I believe that's the UKV?) which goes public tomorrow. Added to that a somewhat enhanced chance of a white Christmas and a reasonable signal for some kind of short lived westerly with an Arctic source to follow along with the continued risk of gales and we certainly aren't lacking interesting weather over the festive season. Just to add to this the average temperature ensembles for Midlothian show an average to cool picture becoming steadily colder over time. A lack of night frosts perhaps but maxima above 5C are likely to become increasingly scarce as we move towards New Year...