Looks like there will be a fair few more mild runs on the 18z ensembles as compared with the 12z. Please let it not be a trend setter. With the previous non-easterly event after Christmas, I noticed that Slovenia was pronged to have -15 uppers almost unanimously across the ensemble set just three days before New Years Eve and yet on the day itself uppers were close to zero. The 0z could be very interesting.

Update - almost a 50/50 split between very cold cold and average on the ensemble set IMBY but the good news is that the very cold members remain consistently cold throughout FI.

Still ok IMO

Ok is the word - maybe a slight downgrade from 12Z, but isn't the 18Z run with less data?

Psychologically, it always feels worse when the Op Run is one of the less inspiring runs in the bunch.

I'd take those tbh. I'd also listen to the ECM long before GFS in my experience, though I accept not all agree. GEFS certainly a downgrade of sorts, with FI split only marginally in favour of prolonged cold of the type shown earlier today. Either way though, tis but one run. I'd wait to see what the pros say, what the over nighters do and where we are by the weekend before having a clearer view. Worth remembering that the ECM was the true holy grail - it could only go one way from there! 

straw clutching to say missing data? Haha I hope so! Looking at JH forecast am keen to see tomorrow's set which hopefully will prove to hold a more sustainable block 

But don't all perturbations have the same data set?  Why is the Op the only one bouncing along the peaks of the rest for the whole of the Hi-Res section?

12z ECM ensembles for London

No scatter of any note until Day 8 and even then only around 10-15%.  The main cluster stays cold throughout although there's a developing cluster returning us briefly to average temperatures for Days 10-13.  The Op sits well within the cold cluster until Day 10 when it's at the lower end.

http://www.weathercast.co.uk/services/ensemble-forecast.html

Something to do with being in a coastal location perhaps?   If you click on other south coast locations you get a similar picture - although not for every one.

On the 2m temperature chart you can spot the outlier...  Not completely without support but out of kilter with most of the output.

now those are outstanding. The op WASNT an outlier and actually goes with the bulk of the pack. The question now will be whether it veers to GFS18Z or GFS swings towards ECM. On balance of probability and experience (hardly scientific) you would expect the former, but you never know. 

The 0z set probably will be a downgrade on the 12z, but these ups and downs should be expected. 

At the end of the day the broad picture implies we are heading for a major pattern change, it may not be next week; it may be the week after or even towards the end of the month; but these signals will become stronger in the long term despite any short term oscillation.

Last night's ECM ensembles were interesting. The cold cluster is still the favoured option, but there's now an increasing chance of milder conditions by day 9. This of course means the mean charts are even more useless than usual!

The interesting bit is that the op and control were in alignment at the colder end of the spectrum. This is the reverse of what we frequently saw in December, when both of them were milder than the other members. In December's case they were correct (by being milder than the pack) more often than not. I wonder if it'll be the same outcome this time?

The actual charts for the control were pretty much a carbon-copy of the op at 240. Beyond that NE'lies kept blowing until 324, then low pressure became slow moving over the UK to 360, with thicknesses around 516dam over us.

GEFS tell a similar story with more scatter in the 7 day+ range, but Op and Control remain in the cold pack.

EDIT: Also of note is that quite a few GEFS delay on the onset of -5c or be;ow 850s (at least IMBY) until Day 5.

Looks to me like its going to get colder next week.  There will be wintry showers in the north, snow on hills.  The models to me suggest much drier weather than of late. 

Beyond about day 7 there appears that there's a small chance of westerlies returning, but a greater chance of a cold scene with a northerly flow with uppers somewhere between -5 and -8 for the bulk of the UK - a marginal snow set up for those with a bad altitude and proximity to windward coasts.

In summary, much more seasonal than the current  sodden mild dross, with areas towards the NE and with altitude favoured to see the white stuff. Heres the 0z GFS ens for London:

A good summary IMO.

I think we can say with some confidence that it will get colder Monday through Wednesday. After that we are talking about +144 hours.  We just don't have model reliability to know whether the cold snap will continue or a return to milder weather will follow.  Each day when we look ahead day 7 -10 will forever more continue to show a range of options, nothing in this range will ever be fully settled. As each day passes we will be able to say with more confidence whether we can add another day to the cold spell.  I hate the word downgrade and find it bizarre when it's used in the day 7-10 range. 

So jury is still out as to whether it will turn milder late next week, some encouraging output to suggest it won't  but as some recent runs and ensemble members have shown it could well get milder and the Met Office seem to see this is a likely outcome. 

It's an equally big spike in the 850s for the south. When I first saw it I thought there was a data problem, but it's correct.

Yes Brian... And if you click on, say, Buxton, you get the ppn spike up to 25mm or so with the 850s staying below -5C. :)

Meanwhile 00Z ECM has an equally messy rain/snow event but 100 hours earlier...

http://www.theweatheroutlook.com/twodata/chart.aspx?chart=/charts/ecm/168_mslp850uk.png?cb=235

Edit: ECM now out fully and not bad at all. A bit slower to get the cold in, with more low pressure around, but by the end of the run there's still a nice solid block in place with plenty of cold waiting across the North Sea. http://www.wetterzentrale.de/pics/Recm2402.gif

I'm going to keep my feet firmly on the ground with this one. It looks, at best, like a marginal event down here. 850s never get below -5C and, going on past experience (2010 in particular), GHs rarely deliver for us for prolonged periods. There are always milder sectors in the mix and the cold is always 'waiting across the North Sea'.

That isn't to say areas further north won't get clobbered. I'm sure they will. Just - if you live in the south - don't expect much out of next week and you won't be disappointed.

Most amusing when you look at the projected snowfall totals on the ludicrous Metcheck forecast.

Yes, with a Greenland high you always have the risk of mild air coming up from the south (as shown on the latest ECM). However on the flip side that is also how some of the biggest blizzards in UK history have occurred. 

Unfortunately on this occasion I don't think anything of that sort is very likely as we don't look like getting deep enough cold in place. 

Meanwhile ECM has nothing over most of England and Wales at 168, followed by 4 inches widely across central southern England at 174 - over an inch across areas from the Midlands south. At 180 there's 5 inches of snowfall over the Midlands, Wales and northern England. Beyond that, out to 240, there's not much else for England and Wales, but by then Scotland is buried - it's showing around 3 feet of snow over the Highlands, for example!

The only place in this run which misses out (aside from Cornwall, which only gets a dusting) is Northern Ireland, which again only gets a dusting.

Far too far out to pay any real attention to, but fun to look at anyway!