In summary only the old GFS of the big three keeps the block patent to the east. UKM and ECM along with GFSP both collapse the high SE and allow westerlies in, although at +144 on the UKM a colder S drift still exists in the South.

If there are data issues, the bulk of the NWP is doing a very good job of coming up with the same result this morning. Even at this late stage though, there is still just enough time to save the Scandy block scenario as it's demise depends largely on the behaviour of this weekend's low and any subsequent shortwave developments which have yet to be resolved.

The data issue thing is banded around every Xmas when the models don't show snowmageddon. Someone, and I cannot remember who, disproved it as nonsense on here a couple of years back. 

Wasn't me, and it's clearly not nonsense! A big loss in observation data will have some effect and no matter how small it'll still have an impact on the model output. It won't be until later today that things finally get back to normal. Over on the other channel they're saying that the models will compensate for lost data (true to a limited extent, but you can't "magic up" lost data) and that data loss happens every day (also true, but you don't lose half the aircraft obs each day!).

In short - data loss happens at Christmas. Whether it has much effect is open to debate.

FWIW, here are the data figures for aircraft, ship and SYNOP observations so far.

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

No it wasn't you. IIRC it was either Brian or that wanabee weather god that used to come on here preaching about SSW and scorning anyone who didn't kneel before him. In which case, that makes sense now. 

To coin a phrase you often use, I wonder if people read these threads first before posting

Darren posted a link yesterday to show the reduction in aircraft data input , but these obs may only effect the first day or so of the higher-resolution output and later stages may be smoothed or else interpolated data used.

the irony of your opening sentence is above 

TBH, it's one of those things I wish I'd checked years ago - for whatever reason I just didn't think to see if ECM data acquisition stats were available. Still, the actual effects are unquantifiable so although the question of whether data loss occurs is solved, the question of what effect it has will probably never be answered fully.

(I seem to remember it first coming to prominence back in the bad old days of the late 90s, not even on this board - for a few years in a row the models, especially MRF*, switched from zonal to more blocked and back to zonal over Christmas Day/Boxing Day. Once TWO came along, people posted who'd been on the BBC boards, usw etc and thus the question of data loss was brought over. And as people then filtered over to UKWW and NW, so it followed to there as well. It's the stuff of (a not very exciting) legend!)

* MRF was nicknamed Misleading Rubbishy Forecast as a result of these swings that happened over Christmasses past. In time it turned into AVN and these days it's the GFS.

NAVGEM holds the block as well. The only model that had done this consistently

http://modeles.meteociel.fr/modeles/gens/run/gens-19-1-150.png?0

Quite a few GEFS members hold the block. This isnt dead yet

AVN! Bloody hell there's a blast from the past. I'd forgotten that.

LOL. I typed my post then had to get some emergency hangover relief before posting

Morning Steve. So are sausages still on the menu?

You have my complete sympathy 

Still, can start all over again today 

Back on topic - sausage meat. 

Ian Brown has eaten them all

Yes both GFS and UKMO look more interesting today. A shortage of deep cold to the east but still could lead to a chilly spell. It's certainly bloody freezing here in my in-laws' house already!

Is that more because of the atmosphere after some less than appreciated presents were given, though?