Aberdeen ensemble set looking pretty good for some proper cold. Hardly surprising! 

https://www.theweatheroutlook.com/charts/gefs/gefsens850aberdeen0.png?cb=5

London using Brian’s charts. https://www.theweatheroutlook.com/charts/gefs/gefsens850london0.png?cb=6 A couple of -10C runs.

Definitely the snowiest I've seen for London.  Interesting times what could possibly go wrong!

The precipitation amounts look wrong to me on the London plot but other locations seem ok. I'm checking it out.

GEM wants things mild in the longer term: with near-Bartlett in place.

The Chinese also go for a" miss" with the cold skimming through NE Scotland and residing in Scandi:

Will the ECM follow suit or "blend" or holdfast?

The precipitation figures were filling me with hope for Thurs-Fri this week, but they do look dubious.

Agree that GFS tends to be flattening in FI.  Looking at GFS nervous that the up coming weekend could have the mild spell running longer followed by a less virulent northerly around 7th December.hoping that the 240h ECM holds onto a strong northerly pattern.

ECM coming out and now it appears to be the model which does not want to join the party.

Why is it so hard for all the main models to sing from the same hymn sheet?

As soon as UKMO falls into line, ECM goes off on one.

Sorry about that. The problem only affected the London plot on today's 12z run. It was caused by changes I made to the script earlier today to incorporate the 30 year reanalysis data. Updated version is this:

I really like the 30 year mean line (black) added to the GFS ensemble chart; not only does it give us that instant visual comparison, but the quirks are interesting- upping a bit mid December etc.

 The ECM is very similar to the hem previous couple of runs and the GFSand will no doubt show a northerly by the end of the run. I’m sure we have had this same conversation in the last day or so.

At T+168 it does not look too promising. We shall see.

Looks as though I was right - at 192 ECM gives us the Euro slug

Anything past 144 is still hope-fuelled. that has not altered in 15 years.  Meanwhile the ECM at 192 hrs is looking dubious: All going Pete Tong at 216, thankfully, its FI

Fair to say GFS and ECM are taking a different route this evening

Hopefully, I'm wrong but at T+192 it looks as if that low will squeeze up to the NW of us. Not good at all.

LOL, low disappears entirely by T+216. Looks to be game on, again.

Why do the models do this? We get two in alignment and then the others go off on one. Demonstrates that even with the multiple inputs and super fast processors and most developed algorithms, the NWP models are still all pretty damn useless beyond t+144.  About as much use as a chocolate teapot. Why do we waste so much valuable time on them?

A bizarre run. Looks as though the HP is undercut from the east instead of from west.

There is pretty decent agreement between the GFS and ECM (again) given the timescale. A cold northerly then a milder anticyclonic period then a second cold northerly. That has been the cross model picture between the GFS and ECM for the last few runs.

Quite a down-grade and the cold looks bottled to the north on day 9.  perhaps day 10 can redeem the run?

T+240.

I'd call that a northerly.

http://www.meteociel.fr/modeles/ecmwf.php?ech=240&mode=1&map=0&type=0&archive=0

Yip a very strange run indeed. Doesn't look credible. One for the bin I think.

Day 10. Ok. Given that it won't verify it's not worth worrying too much. However for those of us in the south I think we need to see rock solid cross model agreement before get too excited by a northerly. It's different for the Scottish contingent but in this part of the world ALL of the boxes need ticking.

Day 10 on the ECM - we have the northerly, but it is not a patch on the GFS 12z at the same timeframe - the HP cell is much further south and whether it moves up to form a proper Greenland HP later, or sinks instead, we don't know. Only plus point is the LP over Spain - getting heights to drop to our south has been one of the issues if we want a decently prolonged cold spell.