Calm heads needed today. 

We have been here many many times before (it normally ends in tears). We should draw no conclusions just yet though. 

Spot on Steve. I suspect the 12z runs will be different to this morning’s (possibly even the 06z). Why? Simply because of the large shift/jump in the last 12 hours. Whether it is to something more or less wintry is a different issue. 

Incidentally all GFS ensemble members show snow here later this evening, that’s scuppered it. 

Some good posts this morning from Brian in particular highlighting some of the misconceptions in here by one or two re GFS and ECM. 

Its natural that some will have their favourites, and its also natural that thier favourites usually tie in with it being the outcome they want to see. Take yesterday’s 12z GFS. All of a sudden the GFS was being lauded.

Most of the time it’s just frustration, but it becomes more than that when certain other people are dirided for their views if they don’t match theirs. Constant use of smileys such as  this one for example. 

Golden rule about the train and the station etc. That’s just as relevant now. Could all flip back later. 

Have a good day all. 

Interesting but not surprising, perhaps winter is not over until February after all?

More runs needed. 

Best taken with a bit of caution: the op fits in well with the ensembles around 120 miles east of MBY, for example:

https://www.weerplaza.nl/15daagse/?type=eps_pluim&r=zuidwest

ECM Means still look decent for a snowy slider scenario in the day 6 to 8 period . In fact much better than the Op all the way.

Key thing on ECMENS SD is the spread that opens at the end. 

https://www.theweatheroutlook.com/twodata/ecmwfens.aspx?run=00&lg=850&lglocation=london

That’s an extraordinary level of uncertainty.

Overnight ECM is a reminder that ensembles can flip as well as the op.  Something changed in the data between yesterday’s 12z and this morning’s 00z, seemingly affecting the projected jet stream pattern.

When the professionals say a week ahead is a challenge to predict why do we expect otherwise, I wonder?

As you said earlier, it still looks rather cold or cold next week but clarity of the synoptics we will have remains elusive.

Sorry, you made a couple of points in recent days I didn't reply to.

1) I currently get some, but not all, of the GFS temperature data for different levels. Downloading more is a simply a case of making a change to a regex. However, integrating into the site is more time consuming, so for the moment is on the nice to have list

2) Thread lengths. You are right about the software being able to go well beyond 50 pages. In the UIA threads often go to 100 pages. However, I ran tests on the paging a number of years ago and its performance falls away as threads grow. Therefore, on Google indexed parts of the forum I prefer to restrict thread length.

De Bilt is not the closest representation available but for consistency and perspective based on the previous runs its useful.

A continued cool down to the 24th but a distinct milder cluster after 240 hours.

Basically we've maintained the northerly cool down next week but lost the easterly signal.

Its far from disastrous though. 

http://www.weersite.net/?actueel&ensemble&ecmwfpluim

A grim start to the day with the the much lauded ECM quietly being sent to stand in the corner all by itself ( the naughty boy ) whilst the derided GFS once again highlights why you should never write off any model no matter what.

I very much agree with this.

Until such times as all the models fall into line and settle upon a particular outcome which they stick with consistently over successive runs, then we can't be sure of anything IMO. FWIW I wouldn't be at all surprised if the effects of the recent SSW are still causing the models issues.

This is the million dollar question when will the downwelling start affecting the troposphere if at all.  No one or model seems to have any idea .

ECM ENS are all over the place at +240 Easterlies, Northerlies, More mobile Westerly types, some high pressure dominated ones. Further out the spread only widens.

Brian - what does the shared blue area represent on that chart?   It can't be the ensemble extremes, as the Op falls outside of the range.

What this indicates to me is that the medium range models are now finally getting to grips with the down welling (or lack of it). The signal has propogated low enough for its influences to start showing its hand. 

Something related to the strat warming signal has happened between last nights 12z and the 0z that has been spotted by all the NWP.

The encouraging thing is that very soon we shall all know where this is going.

Next week's cold northerly outbreak would have happened irrespective. Strat influences circa 25th January are still very much in the balance.

The will it or won't it game should soon be over.

We should be very mindul though of the background signals anomolies pointing to significant height rises towards our north. To ignore that based on a potentially eroneous 0z would be a little foolish.

Decent EC ENS mean, more of a trough disruption next Tue with a ridge building and cold weather, overall, until next Tue. Divergence after that, still plenty of blocked solutions within the EC Clusters, but can't get away from the fact that the Canadian vortex remains an issue...

— Matt Hugo (@MattHugo81) January 16, 2019

Yes, it's the standard deviation from the mean rather than the full spread of ENS.