The 6z squishes the UK high early again, but then evolves into a great set-up with snow for most/all.

So far the 06z ENS shows both Operational and Control being one of the warmest up until the 24th: - Would be ironic for it to then be the coldest ENS run a day later!?

Zzzzz....

Mystic Meg has spoken……..thats that sorted then🙈

Interesting few days in model land

As a few have mentioned quite a noticeable shift in the ens in the mid to longer term with a trend for lower pressure over the UK although the extent of the switch does vary over the GFS/ECM ens set IMBY.

The flip side is of course that the previous HP dominated set up would probably have been cold (at ground level) and dry and if the more unsettled theme strengthens and turns out to be 'correct' there'd be more chances for snow as there's still a lot of very cold air moving in just to our east.

Just looking at the ECM ens IMBY, the mean 850s for around and just after Christmas are actually the lowest I've seen on the 00z sets, the T2M temps though aren't, reflecting the fact that whilst some keep the HP influence a lot now don't (or not to the same extent) so the more mobile pattern means more volatility in terms of surface conditions. 

Overall and again just looking at the ECM, IMBY cooler than average weather is still more likely post Christmas than milder than average but there's less certainty on that and whether it'll be cool and unsettled or cool and dry is very uncertain. Plenty more runs needed as always

Eh? Something that may or may not happen in 10 days time is very disappointing?

Ah.... I think I've identified the source of your disappointment. The weather in any given location for tomorrow is "almost certain". The weather in 10 days time however..... well that's anyone's guess!  (Despite what the forecast models would try to convince us). 

06z from GFS showing another possible mash up of the cold and mild air. It's going to be an entertaining few days watching this chop and change.... now that IS certain 😆

oooof

Still very dry, but with the strength of the wind and those uppers, some showers will happen

Will feel crazy bitter

Not seeing that yet to be honest. HP is hard to shift so I still favour a quiet time.

If the HP does start to sink or collapse then it might lead to some robust zonality but that really is speculative and probably a long time out.

6z op run rather nicely demonstrating that more of an Atlantic influence over the UK might mean more snow, with snow sinking south on Xmas day evening (preceded by rain), reaching the south early boxing day. (Not suggesting that will happen, just that the pattern means it might!).

Probably also worth mentioning that it's still a very blocked picture, just the block isn't always directly over us. The evolution shown is though a pretty classic one for places getting snowfall, with LPs hitting the cold air and fizzling. 

I'd imagine that there's going to be a fair bit of scatter in the ens, as this kind of pattern is one where small changes mean big differences in ground conditions- both in terms of mild air encroachment and whether LP gets over the UK or stalls to the West leaving us cold but dry.

Yep, there's no real evidence of that in the output given how blocked the pattern is. I don't get Taylor yet, sometimes his posts are well reasoned and others, like the one you quoted, are just a troll?

I think the 6z is monstrously exciting 🤯🥶🤔

GFS 06z 850's ENS has come out - Quite a lot of scatter - Some going down to and below the -10c @ 850 hpa and one going up to +10c but it's an outlier. The Op run goes from one of the mildest on 23rd and 24th to one of the coldest run on 26th.

All still very uncertain but precipitation spikes have returned but are fewer in the longer term than in the 00z run - meanwhile last night I saw the EC 30 day which went for cold and blocked or dry weather for the next month and the CFS which also went for a lot of northern blocking and even the MET Office 16-30 day outlook has mention colder in the south with over night frost and fog to persist into the New Year especially in the south.

Sill a lot of uncertainty! All eyes on tonight's ECM and GEM? Will they follow the GFS Op run or will the Op run back track!? - We shall see!?

Having reassessed and looked at the 6z ensembles there does seem to be a good cluster that has perhaps strengthened somewhat for cold sub -5c uppers, however at the same time there is also now a fair number of runs bringing much milder air in.

It's a finely balanced scenario now and is exciting as potentially some places could get buried in snow, but at the same time there is a possibility now of the Atlantic pushing through, when it just looked very blocked and cold and dry before.

We will see how it plays out but yes very exciting but past experiences means I don't get my hopes up too much.

Still too early to say!

However talking of a SSW - the models are still showing a significant warming over Siberia - Usually a precursor to a SSW later down the line (January?) - we saw this around this time last year.

NAO goes negative:

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif 

it goes off a cliff doesnt it

Some VERY cold runs in MOGREPS 06z.

https://www.theweatheroutlook.com/twodata/mogreps.aspx?run=latest&pschartname=1_5m_temp&pscharthour=177

Dec 2010 I'm sure had a big rain to snow event where the high then reasserted itself and kept the snow on the ground for weeks, so a wee shoogle or shift of the high is maybe not all bad.

 LLTNP 105m asl 

It can happen - Reckon it's only once in 15 years on average or less. February 1985 or January 1985. I know it was one of those months.

As others have said, it's way too early to be making any assumptions about the Christmas week yet. The potential is there for a fairly memorable cold spell in line with the recent EC 30 day outlook, but as ever, there's a lot of variables and plenty that could go wrong.

Interesting times ahead though.

Re: Gavin’s post just now - It was perhaps both of those months. I recall well as I was living in Hull at the time which despite its low elevation, was very snowy that winter. Data from Feb 1985 suggests a very cold late winter in the south of the UK, with long periods of snow lying, although the synoptics and raw 850s suggest it’s shouldn’t have been quite so cold.

With the exception of a brief “westerly” phase at the end of January and into early February, the winter months of 1985 were characterised by repeated incursions of cold air from easterly directions combined with quite a mobile set up. Perhaps a difference between that year and those we are more recently familiar with, is how very cold air built up to the east of us earlier in the winter (late December) than has happened over much of the last 20 years (if it happens at all!). I suspect that if we looked into it, sea ice on the Baltic for example, would have been quite extensive and very large areas of the Eastern European and Scandinavian land masses frozen solid. When this happens, simple geographical proximity (even allowing for sea crossings), I contend that our winters are more likely to be characterised by frequent cold snaps or possible longer cold periods, than if the Eurasian land mass, remains (mostly) snow free, particularly early in the winter. I think this also has an influence on snow frequency and longevity in the south of the UK, with close continental influence keeping dew points low, even if southerly and southeasterly winds and upper temps say something otherwise.

Understandably, all eyes are on the upcoming festive period. But irrespective of whatever might be happening over us during this period. keep an eye on the breadth and depth of cold to the east of us. Short days and long nights over the next four weeks combined with deep cold not far to our east may have an interesting effect on our winter to come

Jeff