Who says Northerlies are always mild and tame these days

Nice to see a bit of interest in the GFS - shows what can happen if the HP sits around until conditions are more favourable to suck it North.

Before then drying out with temps TBA depending on how clear the HP is, where it sits, any initial shot of cooler air etc.

Longer term it'd be nice to see a few more of the ens going with some colder solutions, rather than the odd one or two.

Edit: Hmmm, not without support in the ens too. There's quite a lot of members going with HP relocating North.

New Year’s Day onwards is when the interest starts. IMHO, this is getting quite exciting now.

The ECM 00z ensemble for London has a little more of interest for cold weather seekers.

In the short term we finally have some clarity on events on Xmas Eve and Xmas Day, with the high pressure bringing a brief but sharp drop in temperature; not especially cold but pleasantly seasonal, I think.

Beyond Day 10 the dominant cluster delivers daytime maxima around 4-5c and overnight frosts. There's a clear trend away from mild outcomes as we enter 2019.

As for the 06z, classic retrogression and a decent northerly. 

Interesting!

Maybe yesterday's 06Z P20 was on the money.

Except in this morning's 06z Op the high doesn't waste time going via Scandi, it goes straight for Greenland - but stumbles a bit on the way.

Anyway, MO watching isn't dull at the moment, even if the weather over the next few days might be.

Yup David 

Neil I'll be blocked to ...but  if 1987 could be on the table. Snowed during the morning in Porto.

After the 26th the models will begin to pick up the trend. 

I hope

Think it's the first time I've seen the London snowrow reach 7 at day 16. 

Ah, one day you'll realise that yes, models do lose data over Christmas and no, it's not really worth making sarky comments about.

(The loss of aircraft data will, as usual, start later on Christmas Eve and continue through to Boxing Day. It will lead to lower accuracy in the models, but with an SSW on the way accuracy isn't going to be high to start with!)

We have this debate every year - and there can’t be a debate about data depletion (roughly 20K datapoints compared to 35K on normal days). The depreciation on accuracy however is debatable - I’m not convinced it has much effect on the 5-7day range given it’s only around 80% on the verification stats anyway.

What’s your feeling about the SSW and the speed of downwelling Darren?

We do indeed. It usually leads to a visible dip in the accuracy stats here, has done for years. Anyone wishing to claim it doesn't is, of course, entitled to do their own research and post it. Having already done that in previous years, I won't be doing it again this year (although I will be keeping an eye on the stats anyway!)

Any effects look to be pretty slow to work their way down this time, compared with the one we had in February. You can see it gradually downwelling on the ECM charts here:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

As such, I'd agree with those who aren't expecting much before the middle third of January, although I reckon there will be more in the way of noteworthy blocking runs showing up by this time next week (I'll be ignoring blocking that shows up on Christmas and Boxing Day, as the lack of data seems to have odd effects with regards to blocking on the outputs - again, something I've noted over the past 20 years or so!)

as ever a voice of reason though I’m afraid some posters just won’t listen. I suppose everyone has their own opinions, even if they are clearly wrong. 

Not quite on the 12z Op although we still manage to drag some -10 850s over a fair bit of the country for a short while, with snow for some.

The High then topples/retreats on this run and a lobe of PV sits somewhat further south than normal over Iceland. The jet's a fair way south at that point, which leaves it open for colder air to make its way back (although the air over Scotland is already cool enough for some hill snow).

Again, be interesting to see what the ens make of things.

did we see a SSW last winter when we had 3 beast from east at the back end of winter Scotland/north copping the worse of it now talk of another where The SSW has begun over Russia and will not strengthen before moving into the North Pole over Christmas... then ????

hopefully we will see a nice prolonged beast in the new year.

Martin

Thank you Santa - that's just the ticket: 1987 eye candy under the tree, and deserved, as I've been very good this year...

Here goes the roller coaster ride of model watching as we get nearer to mid Jan... But I love the ride.

great timing too...like 1987 it was the perfect time for a real coldie memory - just need double the length and double the snow depth...not sure Cantebury dwellers would agree with that, but 2 ft will do me!!! Listening still Santa - and I have been very good !! LOL

Ops at the bottom in FI....Control and mean stay above average....few cold ens in far far away land...nothing trending yet.....give it a couple of days see where this looks like heading....

depends on your definition of trending, more members going colder is a trend compared to previous runs. Whether it comes to fruition is a different question

[quote=ballamar;1064455]

depends on your definition of trending, more members going colder is a trend compared to previous runs. Whether it comes to fruition is a different question

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agreed 50% showing a colder trend....but need to see it sustained ....hopefully it's the start....

This has always been my point; the effect on accuracy, not denial of reduced data input. Even the stats historically available on those links show barely enough difference to poo-poo or as some posters do, discount the output altogether.

I think the reduction in data is significant: over 40% less actual data means the opening approximation of the state of the atmosphere is going to be more suspect than usual. Now bearing in mind that the ensemble suites are designed to test the sensitivity of the model output to small errors in the starting position, and given how we see quite substantial changes in the evolution across those ensemble sets, it seems obvious to me that we are adding a significant layer of uncertainty to an already uncertain position.

GEFS fast improving , some decent charts starting to show their hand 

When you see so many of the purtabations showing similar patterns, I start to get a tad more interested. The latest GFS is snowing several similar mid Atlantic blocking scenarios, with screaming northerlies, with embedded polar lows. Remember that one that dumped a shed load all down the west side from Birmingham to Bristol, must have been the nineties or naughties? I was expecting the scenario shown on the 12z op to have gone for a day or two, but it seems to have multiplied from the control to many more versions. Whether this is data mehem or an emerging trend, the eye candy is most welcome.