Encouraging output today but it appears to me that the models are having trouble in removing higher heights to the south. Height rises towards Greenland courtesy of the mid atlantic ridge will bring a cold northerly UK wide but it will only if we see lower heights developing over continental Europe.

Caution needed for a  few days yet.

I would imagine that will be dependant upon whether the Op run is the best option available. 

Question...

Is there any reason why the Op and Parallel seem to differ how they treat the post Xmas development, with the Op going for the toppler, whereas the Parallel seems to invariably favour the ridge and extended cold?  Or is it just chance?

GFSP has a slightly longer cold outbreak but mobility isn't stopped and the high pressure collapses over the UK. The GEFS will be key, but given the ECM and latest GFS/GFSP runs I'd say most of the interest is focused in the north. 

GFSP has just shown us how we could have a chilly Christmas Day, a (relatively) milder Boxing Day and then a cold, briefly snowy spell starting on the 27th.

Actually a good reminder that while getting significant cold is one thing, getting widespread snow is quite another.

Room for the Scandi High scenario again from day 10 but of course it's hitting lower-res at that time so don't hold out any hope!

That's why I keep banging on about how even a cold winter can usually be boiled down to 2 or 3 snow events for the majority of the UK population. This is how it was in the 80s when I lived in York. 

Even the GFSP is still showing the blues over northern Greenland, so although this chart isn't bad in isolation it is not really what we want to see for any kind of sustained cold into the New Year.

http://www.wetterzentrale.de/pics/Rpgfs2401.gif

That low on the other side of the Atlantic ridge remains the real troublemaker, further east on this run even as early as day 5. A relatively small change at that point but it escalates into something far more marked by +180 as can be seen above, this not allowing the Atlantic ridge to pull NW as effectively as we'd like to see.

The low is actually in a less favourable position than it was on the ECM 00z op run. With this in mind, the fact that it doesn't race over to the UK on the GFSP run suggests that the ECM solution is still very much 'out there'.

I see the Scandi High nearly made it on the GFSP 06z in the end... the Atlantic push is just a little too vigorous for it to unfold days 10-14. The Atlantic trough then falls apart and things are headed in the right direction by the end of the run.

GFS also gets very close, perhaps even a little closer.

Further signs that we will get more than one bite of the Apple and from different angles as well.

For me the 6Z looks much like the 0Z, with the only difference being the Parallel run wan't one of the coldies. The ensemble looks pretty much the same.

GEFS 6z look quite messy and slightly less favourable if you're hoping for a nationwide cold spell rather than snap.

Lots of little features being picked up by the parallel in particular. Could bring some significant snowfall to some places particularly after xmas.

This one showing rain for boxing day night, but it probably wouldn't take much to turn it into snow. Rain=green, Snow=blue. 

The GEFS do tend to wobble in these situations, the trouble here is that when the jet tracks well south of normal, conditions on the warmer side tend to feature a lot of unusually warm air masses, which is in stark contrast to what happens if we end up on the colder side.

This explains the huge scatter in 850hPa temps on the GEFS line plots.

Still, it's good to see 5 or 6 runs (about a quarter of the whole pack) touching -10*C over London at some point or other.

Reading around on other sites, some suggestion from the Americans that the extent to which blocking establishes in 8-12 days time and manages to resist collapse thereafter could be being underestimated by the majority of model output, this also supported by another highly technical post from Tamara which to be honest starts to enter 'cold ramp' territory when talking about the prospects for January.

You see it just so happens that a vast number of different variables appear likely to come together in the right way to deliver something special next month based on the results from current forecasting tools. I have to really stress that underlined part because when it comes down to it, the tools (models, meteorological theory, analogues etc.) are all we have to work with. There's no crystal ball technique.

My end point for now being that there's currently a lot of reason not to get too hung-up on how much in the way of cold and snow we manage to achieve in the final week of this month 

The pattern is virtually the same, people need to stop looking at the finer detail , that will come nearer the time .

Agreed and wise words

Think it was your good self who said yesterday about picking what suits folks at any given time and theres a bit of that here just now I think.

Just becuase the runs this morning havent shown exactly what pepole want them too it's all doom & gloom from some....

Things are still far more encouraging than they were just a few days ago so give it time.... Good things come to he who waits (sometimes)

OK lets compare the 6Z and 0Z objectively :)

The 0Z is on the left and the 6Z is on the right (I added some more colours so now the range goes up to +50 rather than +40 I hope they arn't too sixties for you matty ).

Which one is superior? Well clearly the 0Z was superior in terms of bringing us snowfall quicker, but looking at the overall pattern I think its harder to tell. The one one the left has more impressive WAA at the 500 level indicated by the browns, however it is further east. The Azors high seems weaker at the surface level on the 6Z but stronger at the 500mb level while the Greenland high is the other way round. 

Its very hard to plump for one, but I guess I would say the 0Z is superior because it has more organised WAA despite it being further SE, and the surface high does look more impressive; but it was a very hard call, so if this is a downgrade it is only a very minor one.

Afternoon all.

Have to agree Marcus, general overall patterns look the same, though we must take a step back and let the detail become apparent in the next few days. I for one wasn't expecting anything other than a cold "snap" and I think for many lowland areas of England and Wales that still looks the best bet. And I don't think it will be a snowfest either- though some parts up north may do pretty well.

So chill out and relax- have fun watching the models deal with the detail.

Anyway, 12z's awaited with usual interest, albeit there's really no particular alarm bells being expressed here re next week's developments. Just a watching brief, but anything noteworthy continues to look a low PROB solution, as others here have rightly stressed.

From Ian Ferg  on NW

The medium range models is a bit like throwing a rugby ball inside a hall, provided I have a good aim, I would know roughly where it'll land on the floor (equivalent of between now and seven days time) but then becomes very difficult to tell where that rugby ball is going to go upon hitting the floor (beyond seven days).
  I could throw that rugby ball roughly towards the same spot every time, but then once hitting the floor, it may fly towards a wall on some occasions or the ceiling on other occasions or onto the face of a passing person or through a window if I am really unlucky - but it doesn't mean I'm going to be that unlucky (or lucky if I have never liked that passing person) with every throw.

Back to about the models themselves, one thing for certain is that there is going to be little in the way of proper wintry weather for all of us living on lowland Britain (save for the usual suspects over the Scottish Highlands, of course) in the run-up-to Christmas, in fact, it's even going to stay very mild over the southern half of the UK.
  Then the *potential* is there in that "no man's land" bit between Christmas and the New Year - even if that cold snap does end up as being a blink-and-you-miss it affair.
 
But one thing for certain is that it is already turning out to be completely different to last Christmas and we all can remember what a nightmare that was (unless you love stormy windy weather). Yes, there is that deepening depression system cutting through the sea area between Scotland and Iceland on the 24th - but it should be absolutely nowhere to the same scale as last Christmas Eve with a 927 mb just off to the north of Scotland!
  At least I haven't got to be talking about risk of flooding and structural damage here at Kent in my own Cloud Master forecast for the next few days, something we can appreciate what with everyone travelling around before the Big Day.

12z looking quite different

Different in a good or bad way?