18z GFS - we're flirting with some seriously cold air just across the North Sea.

This isn't getting resolved any time soon. 

Yes, very similar to the 12z Parallel too! If you retrogressive that 100 miles things could get very interesting! 

Indeed. The differences between the 12z and 18z, even at the end of high res, constitute a perfect illustration of why it's best to use at least half the run for entertainment value at best.

This whole thing feels like slipping away like the beauty in black in the the nightclub you thought was yours for a mere 30 seconds...

A few comments along the lines of "not great at 240..." and yet there's so much uncertainty about what happens long before then.  Models haven't sorted t144 yet, so no point fretting over FI.

Looks to me as though the jet over the US is changing from run to run and will take a while yet to resolve.

This is a ridiculous post. As several posters have pointed out, there is considerable uncertainty and shifting around from run to run post-144-ish. 

Posts like this are not helpful at all and are completely misleading.

144 is generous.  Mid-term developments have huge implications around 96-120, a slight intensification of a low to the west of GL and we get a boost in WAA.... whole different ball game for the next 4 weeks' weather.  

Also its track is absolutely key to how it plays out for us.

Fax chart for T+120 (midday on Sunday) looks promising.

http://www.meteociel.fr/ukmo/fax/fax120s.gif

I think most people would have grabbed this with both arms only a week ago: wriggling cold front moving slowly south with sub-528dam air following with a trough slipping south behind.

Meanwhile, the ECM 12z ensemble for London confirms the picture painted earlier

Reasonable agreement out 5-6 days of the transition from the current cold continental drift via a brief incursion of milder air into Arctic maritime for a while.

As Tom observes, relatively minor upstream changes are going to dictate what happens a week from now.

Exactly so. Predicting either winter nirvana or mild apocalypse post 144 would be equally tendentious.

Wait a sec.. what was set to be cold wintry blasts 1st/2nd Sat 7th/8th and so on, now looks more zonal westerly? Have the models over cooked those amazing northerly blasts and north easterlies that were showing in the GFS charts we saw during Christmas Eve and Christmas Day etc?


http://old.wetterzentrale.de/pics/Rtavn26417.gif

Looks like the only cold weather will be NYD and this is only set to last a day. It was only a few runs ago they showed a potential for some very cold weather and now this has gone from dry cold to zonal after 3rd Jan? Why always the flip for the worst for cold weather fans!? For all we know this could default to back to zonal by the 00z runs. 😬

A quick look through the ensembles for the 18z GFS... they don't look too bad at all 

Quite a few maintain a northerly flow to T240 although most have a mid Atlantic block rather then one ridging up to Greenland. Very few ensemble members go back to the anticyclonic mild gunk we saw in December thankfully (upto T240).

I think the chances of anything really cold are quite low at the moment but I think we could well get more attempts to get things right.

And as an above post states little changes can have a big effect. AO is forecast to go negative so I'm hoping this northerly may well be sustained like this:

http://www.wetterzentrale.de/maps/GFSP04EU18_216_1.png

Also of note, a fair few members go for greater heights over Scandi later on:

http://www.wetterzentrale.de/maps/GFSP05EU18_342_1.png

http://www.wetterzentrale.de/maps/GFSP18EU18_342_1.png

http://www.wetterzentrale.de/maps/GFSP17EU18_342_1.png

http://www.wetterzentrale.de/maps/GFSP06EU18_342_1.png

In summary a northerly flow develops at the New Year, temperatures may recover to average before more potential northerlies. After that who knows?

It's one run in one set of ENS.

Tally - did you not bother reading the last page before posting?

Please refrain from such ridiculous posting based on one run.

Lack of data 

Even on assumptions that all is normal in terms of output, the situation post T120 is always more tenuous and the ensembles for London are not exactly frigid, just rather cold. As for talking about events on 7th/8th Jan well you might as well pxss out of a moving truck ;)

EDIT - I agree with Nick 

LOL.  Certainly a lack of something....

Lol really

Have you gone through the ENS individually

try

P1 , 2 , 3 , 4 , 5 , 6 , 9(ISH) , 10 , 17 (ISH) , 14

some of the others have a HP in a decent position that could end up favourable, who knows .

http://modeles.meteociel.fr/modeles/gem/runs/2016122800/gem-0-132.png?00 

Thereafter, high pressure retrogresses as low pressure over Scandanavia takes hold along with to associated north north westerly winds. Things are beginning to shape up nicely on the 0z.

http://modeles.meteociel.fr/modeles/gem/runs/2016122800/gem-0-210.png?00 

GFS looks better than the 18z and the ensembles are trending colder!

http://modeles7.meteociel.fr/modeles/gens/graphe_ens3.php?x=311&ext=1&y=130&run=0&runpara=0 

Yes Karl. Things are looking decent this morning. Yesterday's 0z CMA had that area of low pressure over the channel at 156 as GEM has today at 132...

I detect a slight northwestward shiftt of the hP cell on some models. It's going to be wintry in the new year. Once the cold is in, then get some moisture in and the capacity for snowfall, particularly with altitude, (places like NY Moors and Snowdonia could do well) can pop up unexpectedly. We need to get to t72 and lower to get confidence on detail of transitions between weather types.

Steady as she gets on the good ship 'Cold Snap'.

Very good output this morning. Things are poised nicely with masses of deep cold air just to the north and east. 

 I agree generally good output this morning but ecm keeps pressure annoyingly high to our south which scuppers what could have been a stunning effort. 

http://old.wetterzentrale.de/pics/Recm2161.html

Great post 

Looks like some people just pick up the main GFS run and then base their whole opinion based on that one run (!) without even going through each member to see how the main run is made up in regards to the number of cold vs mild members. I would say after new years day this is still far from resolved and anything after that is subject to change - more eye candy is certainly possible as is a milder option. Looking at today's runs from ECM / GFS plenty of potential and even the main GFS run seems to turn chilly in the late FI stages so potential is still there certainly. Far more encouraging at this stage than it has been for the last 3 Januaries. 

Low to moderate chance of a colloquial Siberian blast in the next 2 weeks IMO. Looks like the most "promising" set-up for cold weather we've had since 2012/13.