snowking

"Data issues" you say.....a clear sign that @nick sussex is running dangerously short of netweather branded prozac and has had to bust his way into the control room at Reading to deploy his last resort - some custom data. He even did a great job of trying to make it look realistic by drawing the -6c 850mb line right across the M4 at T+240: For those saying they can't remember the last time the models were this volatile at such a short lead time, I can sadly - December 2012. Though in fairness then, the models did, one by one, drop the idea completely rather than flip-flopping from run to run. By the way that op run, whilst looking impressive, at face value isn't all that snowy until that potential undercut right out at 240...but let's get some sort of agreement on pattern first before we look at anything like that

You need to be careful in recognising that the meteociel strat. charts only show temperature, not geopotential heights. The vortex is not simply a very cold blob of upper air, it is an area of intensely low geopotential heights. So if we look at the geopotential heights for the same period on the GFS: We still see our old foe the vortex spinning away over Canada - though surely after continuous warming thrust its way throughout the period, significantly weaker than you might expect. The good news from the above is the fact that it is displaced away from Greenland, and with a big positive geopotential wave visible across most of the eastern hemisphere it looks favourable for blocking to our North/North East (and, just potentially, our North West too) However, there are two things to bear in mind: 1. This assumes that the stratospheric synoptic setup imprints itself exactly upon the troposphere (which is far from a given) 2. I'm doing that thing I encourage everyone never to do in dissecting a single operational run out at +384 Complicated all this stratosphere stuff!

I'm normally jealous of the snow reports coming in on this thread but this morning I'm more jealous of the number of new puppy reports coming in

Should I bite....should I...ohh, go on then. That thick red line on the graph above shows you where 'average' sits. Not only is every single peturbation until at least Thursday but indeed the entire mean remains below average throughout the next 16 days. There is, as always, some very dramatic posts in here again this morning and I'm still scratching my head as to why - I've said it before and I'll say it again, people were spoiled by the 2009-2013 period and tend to forget just what "standard" winter fare really was/is for the UK. But each to their own.

The ECM run over in Weather.us is well worth a look for those of you of a cold persuasion Plenty of showers feeding in to Kent on Sunday night into Monday, big stalling snow event out West on Tuesday followed by and area of snow moving NW out of the continent (just like the good old days) into Wednesday across much of England. Then another area of snow moving North across us Thursday into Friday, before a snowy breakdown for most away from this region on Saturday - which will almost certainly not be the case come T+0 with things likely to be backed even further west going from past experience. The first bet to watch is whether Tuesday's front even makes it across the Irish sea - probably 50/50 right now looking at this morning's ECM, whilst the ever progressive GFS has it all the way across to us. I said it last night over in the model thread but once you get that depth of cold in across anomalously warm seas, big snowy surprises start to occur the closer you get to T+0 A fascinating period incoming

Well it's probably fair to say that I've been rather quiet on these forums for the last few years really, especially since 2013. After 15 years of internet weather watching, and more importantly, having witnessed the incredible run of winters we had from 2009-2013 (vs the more Ian Brown style winter in the preceding 10 years), it really takes something now to get me to show more than a fleeting interest in what's on offer. Now it's safe to say, regardless of geographical bias (bearing in mind I now work in Central London and live on the SE'ern edges of our ever-warmer capital, so I am pretty neutral when I say this) this winter has, thus far, been the most productive for watchers of a colder persuasion since March 2013, with many parts of the country seeing at least a covering and some lucky folks through Central England seeing 3 pretty decent, if temporary, snow events (of course those further North and more vertical than the rest of us have seen far in excess of this, but those lucky b******s get to see this most years). But what we stand on the cusp of, what is being modelled within a pretty reliable timeframe, is reminiscent of those days back at the beginning of this decade where the sun went to sleep and cold chaos ensued. It is far to say that, beyond just the pure pornographic synoptics, the likes of which we had not seen for many years previous, 2010 ruined the laws of model watching in so many ways. Forecast models are not supposed to pick out the correct pattern at +360 and run with them pretty much right through to +0. They're supposed to tease us with big greeny highs, fallible dreams of the biggest snowstorms of the last 100 years (circa December 2012) and then leave us distraught, crying in the corner of the shower, attacking the 'mildies' on here with our not-quite-waterproof smartphones (what a long way we have come...) at even the merest hint of an 'I told you so'. And I genuinely think the 2010 episode of near flawless modelling has left a lot of people on here far too expectant of the capabilities of predicting the friggin future with a lot of electronic circuitry and fans. This is why, more so than at any time in the past 5 or so years, this current phase of modelling really has my interest. We are on the cusp of something which, pre the 2009-2013 phase, would have had me online from 8am-10pm (which, if memory serves, is when the old BBC slowwatch forums used to shut for the night) in a far too nerdy way (nobody ever understands our snow obsession right?). Some members on here can be accused of being just that little bit too optimistic when it comes to cold and snow chances, but those same people are very much correct in these sort of short-range cold shock scenarios - whilst the models might not yet show anything significant snowfall wise, they never do until much closer to the time. In fact, if we think of events such as Jan 2003, Jan 2004, Feb 2005, Feb 2009, Jan 2010 and even in to Feb 2012, Jan & March 2013, all of them had modelling which at face value painted a cold and dry scenario....which continued until a few days before unexpected features popped up in an increasingly unstable flow given a significantly lower than usual upper temperature profile. When you combine that with the anomalously warm seas surrounding the UK right now, there is an inevitability about unexpected short range snow events. Beyond just next week, we also have a pretty consistently modelled significant warming into the stratosphere, which should yield an interesting second half of February, combined (or perhaps even coupled?) with one of the most significant MJO episodes we have seen to leave us on the cusp of a pretty memorable February overall...now when have we seen that before, with a declining solar profile...memories of 2009. Enjoy the next few weeks everyone, I will certainly be more active on here as we stand on the edge of what, from 15 years of experience, feels like a pretty significant period of wintry weather for our humble little island.

I would actually argue that on a hemispheric scale, for two operational charts 10 days out they are remarkably consistent - if we take the main features in: Atlantic ridging Asian ridge Big Alaskan ridge Core of the PV west of Greenland and into N Canada These features are pretty similar on both charts, with really just the Asian ridge that bit further west on the ECM v GFS Of course on the more micro scale our tiny little island has two very different looking outcomes across the suites but I would say in general, for a single set of deterministic runs, they're pretty similar Of course I know you were referring more to conditions on the ground back home which is what we're all here to see, but probably not something we should be paying too close attention to at the Day 10 range. At least we know the major players in our hemisphere, let's see where we end up in the winter lottery draw

Indeed! Getting up to a very toasty 10c at 1mb by the end of the run Of course we know from history that the GFS Op has a tendency to post phantom warnings towards the end of its runs but will be good to monitor this and hopefully reel it in like we did back in Dec 2012/Jan 2013 Interesting times and not unexpected given the advertised tropospheric pattern (despite the nuances around the exact surface conditions for our tiny little island) as highlighted by Ed some days ago nowadays. @ArHu3 - of course, March 2013 springs to mind...

I have to second this at present. We are at risk of overanalysing things at such a range which is Cold Spell 101 in terms of mistakes (and the sort of thing many of us would be cautioning others about) - but if we want to take things at absolute face value right now, minus the GEM, things look chilly and dry to me right now. Fortunately there is still plenty of water (or ice) to flow under the bridge before we get to the secondary phase of the upcoming evolution (hopefully - as long as the GFS isn't going to play late scrooge on us) and if we start to get some undercutting of energy then things could get interesting further down the line. But in the realistic timeframe, things look a little more seasonal, and certainly synoptically things looks spectacular in comparison to recent winters, but there's nothing in the shorter term which especially excites me just yet. But as alluded to a few days ago by Chio, and re-iterated again a few posts up by Catacol, the tropospheric pattern certainly conducive of something more exciting stratospherically in terms of Wave 2: Which will hopefully serve us well as the season goes on

Current verification for the Northern Hemisphere 12z runs. Over the 30 day average - Day 5: 1. ECMWF 2. UKMO 3. GFS 4. GEM 5. JMA Day 6: 1. ECMWF 2. UKMO 3. GFS 4. GEM 5. JMA Day 10: 1. ECMWF 2. GFS 3. GEM That's for 500mb heights. If we look a bit closer to the surface: Day 5: 1. ECMWF 2. UKMO 3. GEM 4. GFS 5. JMA Rather than clogging up the thread any further, this is the exact same at Day 6 and Day 10, with the GEM marginally ahead of the GFS over the 30 day average. Incidentally, I know I switched from heights to pressure for the surface charts (for reasons which are hopefully obvious in terms of what we are interested in at the surface level), however we see the exact same results for heights at 1000mb. A few things for everyone to take away: 1) Given the above, you would probably say that GFS and GEM are generally on a par over the last 30 days, the GFS perhaps just about edging it in terms of average score across disciplines 2) GEM is worse than GFS for 850mb temperature skill (not shown above) 3) You can probably throw all of the above away when dealing with the current situation because the dynamics of the atmosphere are vastly different to anything we have seen these models try to handle over the past 30/31 days, and so this is probably not the best measure of which model has the best handle on our unfolding situation (which I'm sure anyone who has read through all of this post to this point will be really pleased to hear). So that's the 12z stats, a few things to note for the 0z's: 1) GFS generally remains ahead of the GEM over the last 30/31 days 2) ECMWF 0z has performed really rather significantly better than the ECMWF 12z in recent weeks (by a correlation score different of around 0.4-0.5 - which at the day 10 range is probably quite noteworthy) 3) And the final nail in the coffin for anyone wanting to blindly follow the GEM believing it to be better than the other models out there....at 0z, it has performed worse on SLP than the NAVGEM. So, all hail the NAVGEM. (admittedly, the NAVGEM only has 29 days of data available for some reason vs 31 for the rest).

Quite a morning here overall, somewhere around 7-8cms fell, it eased off about 45 mins ago. Turning really quite slushy very quickly on the pavement and road and sliding off cars but sticking pretty well on the grass and roofs, with the sun now making a late afternoon appearance. It is going to be treacherous out there come the morning

The intensity has eased off now but still coming down Somewhere between 2-3 inches has fallen here - once again it looks like on the whole, the ECMWF has called this one the best over the last 72 hours, with a consistent theme on the most part to bring in some slightly more noticeable totals through the home counties

The heaviest of it has arrived here now, flakes almost 5cm across falling at times here. Somewhere around 4cm on the ground

Somewhere close to an inch here and still coming down. Looking at the radar it looks as though the heaviest of it will head in over the next hour or so

Amazingly it is now settling on all surfaces here...other than directly on the puddles

Moderate to heavy snow in NW Essex @ 100m asl - settling on cars, roofs and grass but it will take something rather substantial to settle on the pavement and roads

Update from 23rd:

Well the 0z ECM suite has shifted things that bit further N and W of our region with the sweet spot very much The Midlands - for the majority of our region on both the det. and the control (along with the majority of ensemble members) perhaps a covering, but nothing too significant showing just yet. So for hope more than anything, it's worth keeping an eye on things as the day progresses. I think the region will see snow falling tomorrow morning, but it's looking less likely that we will see anything too significant at this stage, with modelling overnight generally showing a slight shift away from this region. Worth keeping an eye on this: https://en.sat24.com/en/eu/infraPolair We want to see the low slide as far to the South of Ireland as possible. Right now, things look pretty much as per modelling, if perhaps just a tad further North. That said, it's another incredibly complicated situation, with those mesoscale lows visible behind the main centre of low - our best hope looks to be that as the system swings NE'wards tomorrow morning, the wrap around of the precipitation around the centre of the low is more intense than forecast as it interacts with the North Sea. Sadly, as far as modelling is concerned, the moistest (a word which I'm sure will divide many) of the air will have moved away. We shall see. Any transition to snow into tomorrow morning will be marked I suspect by the winds swinging around to just North of 270 (ie - as soon as they get to the North of West) which should herald the dig in of the colder air from the North as the low passes Eastwards. @Mark N - going purely by modelling this morning not only will you probably be one of the first in this region to start reporting the transition, it looks as though you'll probably report some of the higher totals too especially with any elevation. Further East, we are hoping for something a little unexpected to pop up.

Herts/Beds/Bucks are the median counties shown under the sightly more intense precipitation to the N and NW of London, but the N of Oxfordshire looks to do okay too, especially with a bit of elevation Still more twists to come one would suspect

There's some good news and some bad news from the 12z EPS in terms of snowfall for Wednesday The bad news is that the majority of members look more like the 0z run with a more northerly trajectory and gives little in the way of meaningful snowfall as per the 12z deterministic run for much of the region (a cm or two shown, for some, but to be honest we have already seen from the ECM snow charts on Weather.us from last time that they tend to be a little overblown) The better news for some in the thread is that a lot of members develop some slightly heavier precipitation through the Home Counties, which gives something slightly more noticeable for these areas. Once again though, probably just worth a look out the window really on Wednesday morning - it's even more complicated this time than it was a few weeks ago

Yep I thought of that, but 6am view: Very odd! @shaky unfortunately given that 1 inch ~ 2.5cms, those charts still look at odds with one another!

Not quite sure where that's come from Steve but looks very overplayed The 12z that I can see over on Weather.us is shown below: Still similar zones but a more realistic look in terms of totals potentially (probably still a tad overdone)

Yep latest run looks reminiscent of some of the runs a few days before our last slider episode and more in line with the rest of the 12z suites so far Plenty more twists and turns which will no doubt result in some angry gravy throwing at the dinner table tomorrow

Snowfall for Tuesday night into Wednesday still a strong possibility with the overnight runs. ECMWF has been fairly consistent with the track of this over the last 24 hours, though it remains further south than some - the control also gives a fairly similar track (with a little more intensity) and whilst as ever there is huge variance within the ensembles, the track shown below is about the biggest "cluster". Still a lot of runs to go before we can make a best guess though

Snowing at work in Victoria now too...shame about all the horrible sleet before that