But it all flattens out again by the end, courtesy of GFS pushing a large chunk of the PV through Greenland and into the North Atlantic.

All somewhat academic as it's deep FI and akin to the output from a random number generator.

Control has better ridging NW 

Might just get there 

Have a feeling the Control will squeeze the high out and topple , but at least signs are there

The GEFS ensemble data are getting more interesting by the run. Here is the 06z set for Aberdeen

a few decent ens members appearing

The snow row percentage here is at 60% at day 11 and the mean t850hPa down to -5°C. That tells me it is more than a few stragglers or eye candy. I would classify the 8 or so ensembles dipping below -10°C at t850hPa in that category.

Indeed 6fgs ens continues momentum towards cold

https://www.meteociel.fr/modeles/gefs_table.php?ext=1&x=&lat=51.5085&lon=-0.12574&ville=Londres

A few ice days now appearing for London

https://www.meteociel.fr/modeles/gefs_table.php?x=0&y=0&lat=51.5085&lon=-0.12574&run=6&ext=fr&mode=7&sort=0

... plus the op was pretty much a mild outlier. I study the 850 hPa London ensembles a lot and the trend is downwards.

Some people do crave weather action rather than what we have now and will have for at least another week. I think Chunky and Irish members on t'other side relish an Atlantic battering.

Snowiest GEFS of the winter upto 41!  Are we finally getting somewhere ?

Let's hope so Ally!

We all definitely deserve a cold and snowy spell this has been the longest  "build up" in the history of TWO. 

That's true, though while saying that the build-up to the Beast at the end of last winter seemed to last for rather a long time too. I can clearly remember the SSW that led to that snowy spell being openly discussed on these threads almost three weeks before it actually took place, bit once it did happen we didn't have to wait long to see it bear fruit.

Well the Met Office outlook says third week of Jan, which is barely in range of the models yet, so be prepared to wait a while longer!

No, we've had build ups that have lasted two winters and never materialised, believe me!

At least they are being consistent. They have been expecting a change around mid-January in their outlooks since just before Christmas and the third week of January begins in the middle of the month.

The GFS 12z has a lot of eye-candy runs this time. So many showing good coldie runs (some really snowy - potentially course), that I was surprised it is just reflected in the controle and not the op'. 

Does anyone know how the op' run is selected? I.e. Is it the opinion of the chief forecaster for the model - based on experience or most likely / common outcome of the raw data?

anyway heartening to see so many colder runs and a definite shifting of the GFS, possibly even might amount to a trend in favour of a higher risk of colder scenarios.

The GFS 12z is running at the moment and the GEFS 12z has not yet started.

The GFS op run is a higher resolution than all of the other GEFS runs. It initiates using unadjusted data, so in theory at t+0 it should be closer to the real world conditions than the GEFS pertubations 1 to 20 which are all tweaked. The GEFS control run also initiates with unadjusted data but is lower resolution than the GFS op.  As far as I am aware the chief forecaster has no input into the model run. 

day 11 may as well be jam tomorrow, when those enter the reliable I will take notice. However the cluster of ENS packing cold 850’s may hint at something of interest. In the meantime all very quiet and on the whole quite useable weather, if somewhat boring. 

Its the deep breath before the storm 😉