No, it means that there is data loss at Christmas. Even the best algorithms in the world can't completely compensate for the loss of tens of thousands of input data, thus there will be knock-on effects on the model. It's the extent of these effects which is unquantifiable.

(FWIW, the main sources of non-satellite data are buoys, ships, synop (ie weather stations) and aircraft data. Without half the aircraft data it means you're not getting some valuable info that isn't available anywhere else - namely conditions at 35,000 feet, in the lower stratosphere)

look at the information Retron has provided in his informative post. You will find there are data issues, as most people accept. This may only have small knock on consequences for model output, but as Doc posted earlier only very small differences can have huge ramifications in a climate like ours. 

Am I the only person who took a quick glance at that diagram posted by Stormchaser and thought that Mount Etna had just suffered a catastrophic eruption? (But then I saw the key at the top of the diagram and sighed with relief.)

each to their own Jacko. I tend to agree with Doc and doubt a few minor auto replacement tweaks make a significant or notable difference to an overall data set.

A familiar story in the 8-14 day range today - a strong ridge from the Pacific attempting to reach the pole via Alaska, the potential for low heights over Canada to be separated from low heights over Siberia, GFS and GFSP struggling to produce such a result due to over-vigorous low pressure development across the eastern U.S. and western North Atlantic, GEM and  ECM (on the 00z at least) more willing to allow the split to manifest.

Last time around, the Canadian lobe of the polar vortex trended further south to the U.S. and allowed room for a ridge to reach Greenland, which the models then ran away with for a few days before it all imploded.

This time around, we have better support from the lower stratosphere for a split in the polar vortex, and perhaps this is evident in the fact that GFS is at least having a go at splitting it in the lower-res output. The usual overcooked Atlantic jet causes its downfall.

Not sure what's the deal with GFSP though - it sure does like going mental with the Atlantic jet and continues to make GFS look tame by comparison!

Keeping the faith is proving harder with each new case of bad luck but going by history that just seems to be how it is in the UK.

IMBY there are now about 9 more weeks to during which prolonged lying snow is achievable without requiring a truly exceptional setup. With roughly 5 weeks of such potential now behind us, that places us about a third of the way through... as you might expect really!

So it's far from over and to be honest I think it was unfortunate that the initial strat. based projections (due largely to unusual warming events later on in November) indicated a faster progression to a shattered vortex than now looks probable (back in mid-November, early January was the signal, but now it seems to be late January), with better disruption in the second half of December, as it raised the expectations of quite a lot of people - mostly on other sites  - well above what could be considered realistic when considering how it tends to unfold in the vast majority of years.

Fair enough, we'll agree to disagree on this one. As far as I'm concerned, the stuff you learn in basic stats says the fewer data inputs you have into a system the worse the performance will be. It's not "a few" either, it's tens of thousands of missing observations. You simply cannot make up missing data that well.

Incidentally we're still down on data today, including for the 12z runs. Tomorrow it should be back to nearer normal:

Time  Aircraft  Ship/Synop obs
23/06 113141 73720
23/12 112318 65868
23/18 192319 73024
24/00 193542 63402
24/06 115009 73299
24/12 101293 65816
24/18 177831 72963
25/00 155527 63069
25/06   62505 72938
25/12   49240 65391
25/18 151856 72553
26/00 154841 62917
26/06   63829 72803
26/12   88755 65206

Looks like a very wet spell  to start the New Year now (assuming the missing data has no significance)

At least it looks like cold zonality

Bit of frost/snow then back to normality

http://www.meteociel.fr/modeles/ecmwf/runs/2014122612/ECH1-144.GIF?26-0 

LOL I suppose we will never know if it makes a difference or not. Each to their own, as you say

:-)

If it did make a practical difference to the model output then it should be possible to see a statistically significant (measured over a number of years) dip in the model verification stats at this time of year.

http://www.meteociel.fr/modeles/ecmwf/runs/2014122612/ECH1-240.GIF?26-0

Now the search for the next cold spell begins. At least we have high pressure over the pole and a split vortex, and cold zonality

That in itself looks more promising that anything we saw at anytime last winter. It also looks as though the belt of high pressure to our south may be starting to weaken a bit by T+240 on the ECM compared to earlier in the run.

Here is the Strat chart - shows warming taking place now, but not of the big event variety, so remains to be seen if it has any effect - the effects need to propagate down to the troposphere to be noticeable - should have an idea by weekend of 3/4 January.

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng

Hang on, wasn't there supposed to be a SSW event that would be starting to show itself at the surface early Jan? I know the answers to all this. Just seems chasing the SSW Dream is like watching a dog chase its tail most of the time. 

When a Strat warming is shown on these charts, it is actually happening (or about to) - they are 100% more reliable than forecasts which are weeks ahead. But like I wrote, it is not one of the biggest, but it is real nonetheless and is possibly the reason why ECM shows a split vortex at +240 - just a shame that so much of the energy is shown going into Canada, with the HP cell building over the Pole from the Pacific, instead of from the Atlantic.

SSW somewhere in Northern Hemisphere  =cold and snow for UK = trendy bollox.  All IMHO of course.

I seem to recall reading on a previous model thread that a strat warming event was due to commence about a week or so ago, with something possibly a bit more substantial coming along in January. I could be wrong there of course- I imagine that James (Stormchaser) will be able to shed some light on it.

The general feeling as I understand it has been for a while now that the back end of this winter may well be colder than the early part, perhaps a bit like 2012-13. Time will tell of course.

Not "trendy bollox" at all - what a significant SSW does is to create potential, just as it did in December 2012. Whether the UK ends up in winter wonderland, depends on how all the pieces fall of course - nothing is ever guaranteed.

any efforts greatly appreciated 

Indeed Maunder. I think it's worth remembering as well that at this time in December 2012, the model output in general terms looked little if at all better for cold chances than what we are seeing right now. Some at that time were sceptical that we'd see any major change to the pattern as we went further into January 2013, but change it did, and noticeably so.

DAM you guys have good memories, especially you MR PORTER I think 2012 -2013 we had snow not sure, ?  anyway im very sorry way off topic,  fingers crossed to the new year, but like MR BRIAN say more chance of snow at easter than xmas - winter and any other time, BTW storm-chaser your da man, love your posts,

My guess would be, it could have an effect locally on model accuracy (I blame it for the tonight's low tracking slightly more to the north )

But on a global scale it will have little if any effect in accuracy.

Positive NAO denotes milder and wet winter right!? Was there any snow over VBLACKDOWN's today!?

Just saw BBC weather for week ahead - looks like it will be cold and dry and a mild and wet start to 2015.