Model output discussion - 5th December 2016 - Into Winter we go

[Frosty.]

Well, according to the Ecm 12z high pressure will be returning sooner than expected, that is, if it ever completely leaves in the first place because it seems to have influence on the whole run!

Edited December 6, 2016 by Frosty.

[Methuselah]

1 minute ago, Frosty. said:

Well, according to the Ecm 12z high pressure will be returning sooner than expected, that is, if it ever completely leaves in the first place because it seems to have influence on the whole run!

Well, Frosty, it's still 0C with freezing fog here, just now. So, I sincerely hope that the HP buggers off for at least a little while...Judging from whatever inter-model consensus there is, it'll be back soon enough?

[Geordiesnow]

7 minutes ago, nick sussex said:

After showing some initial promise the ECM looks similar to the other outputs. At the surface it looks on the cold side after day 5 right to the end but looking at the PV and upstream pattern theres no way to anything which includes the S word after day ten.

A small area of low heights develop near Iberia which help to prop the high up later on.

In terms of upto the more reliable timeframe T144hrs it does have scope for a bit more improvement, we do need to squeeze as much amplification as possible upto then. You can see that the ECM has the sharpest upstream trough at T96hrs , if this was post T144hrs we'd have more time to play with in terms of some favourable changes to that.

Later on the ECM develops that digging trough, sadly we can't get a negative tilt and get that even further s/se and then the deep low exiting the ne USA  blows up as its fed by the PV and then too much energy spills ne.

If you like dry weather the ECM is okay and there should be some frost but overall its still not showing us a way forward to the Promised Land.

Think its how you want too see it though Nick, we all know none of the models after 96-120 hours will be shown as it is, the details are bound to change so for me I find the ECM and even the GFS a bit more encouraging. If we get more in the way of ridging in the earlier part of the run, we go from there where it leads upto.

As I said a little further back, cold weather might not be as far away as some people think. Even if the ECM followed up the promise of the early part of the run and shows a colder blocked pattern then its hardly means we will head that way. Just think its best to take it a step at a time instead of having statements where people are writing the rest of December off when we are only 6 days into the month!

[bobbydog]

Apparently the GFS Para is not immune to going 'off on one'

the monster PV approaches....

We're all gonna die!!!

[Captain Shortwave]

Day 6 charts

UKMO/ECM/GFS
      

Pretty decent agreement there with heights building over most of Europe with the chance of pulling some cooler and drier air in from the south or south east.

Once in this ridge could very well stick for a prolonged period, the GEFs certainly show this.

      

So after a brief spell of breezier and wetter weather, it does look like we will see another anticyclonic spell develop. No real sign of a route to a proper snowy solution at the moment. That said the GEFs are trending downwards in temperatures, low to mid single figures by the middle of the month and beyond.

Edited December 6, 2016 by Captain Shortwave

[mountain shadow]

10 minutes ago, blizzard81 said:

Surprised it took so long for anyone to mention the possible start of retrogression between 216 and 240hrs. A very positive sign from ecm tonight and something GP mentioned to look out for.

Retrogression to where? All i see is the bulk of the PV at Day 10 in the worst place possible, namely the Greenland local.

[legritter]

Yes 192 hrs looking good ,and at 8 days away of course it may not come off but there again it could ,wish I could be more positive ,it's going to be interesting watching this blocking take hold ,if we could get a clean high I think that would generate some interest , nothing past 10 days set in stone  That's the way I like it ,are we all a little meryer tonight ,hope so cheers gang .

[Frosty.]

10 minutes ago, Ed Stone said:

Judging from whatever inter-model consensus there is, it'll be back soon enough?

Yes Ed I think it will be..growing support for a crisp settled run up to christmas instead of blowtorch southwesterlies / southerlies with severe flooding & saharan sand like last december..it looks promising.

Edited December 6, 2016 by Frosty.

[feb1991blizzard]

4 minutes ago, bobbydog said:

Apparently the GFS Para is not immune to going 'off on one'

the monster PV approaches....

We're all gonna die!!!

Scotland could get a snow hurricane out of that, drifts metres deep, horizontal, 0m visability snow at 30mm ph anyway.

[northwestsnow]

Well as a natural pessimist i can see a lot of positives in that ecm, its mainly dry and increasingly colder as we drag in some continental air into the mix.The day 10 is full of potential imo, its worth noting a strong pv to the north west does not always mean the death knell for cold in the uk,all imo of course..

[karyo]

5 minutes ago, mountain shadow said:

Retrogression to where? All i see is the bulk of the PV at Day 10 in the worst place possible, namely the Greenland local.

Agreed! The high pressure cell appears to get repositioned somewhat in the later stages perhaps giving the impression of a retrogression but let's face it, it can't move to Greenland so we have to make do with quiet weather with a bit of frost. This is all well and good for now but I get the feeling that soon people will be hungry for some proper wintry weather.

[nick sussex]

3 minutes ago, Geordiesnow said:

Think its how you want too see it though Nick, we all know none of the models after 96-120 hours will be shown as it is, the details are bound to change so for me I find the ECM and even the GFS a bit more encouraging. If we get more in the way of ridging in the earlier part of the run, we go from there where it leads upto.

As I said a little further back, cold weather might not be as far away as some people think. Even if the ECM followed up the promise of the early part of the run and shows a colder blocked pattern then its hardly means we will head that way. Just think its best to take it a step at a time instead of having statements where people are writing the rest of December off when we are only 6 days into the month!

Where did I write the rest of December off? Sorry but I was just reporting what the ECM showed I didn't say its later output would verify. Its pattern at day ten over the USA is too flat. Do you really think I like reporting underwhelming output. And I did say within T144hrs it had a chance to improve. The problem isn't that we don't get a ridge to the ne its the upstream pattern which means currently we can't take advantage of it.

You need a much sharper elongated low to the west at the crucial timeframe and not the football shaped one. Can I be blunt the GFS and ECM at T240hrs are not upto much. The GFS is dire at that point going forward.  Looking for signs of life in the GEFS at T300+ hours is going to lead to disappointment instead look for those earlier changes to build on. The ECM has some scope earlier  but we need to find more amplification.

[booferking]

9 minutes ago, feb1991blizzard said:

Scotland could get a snow hurricane out of that, drifts metres deep, horizontal, 0m visability snow at 30mm ph anyway.

Yep and jet digging further South more could join in on the fun leading to snow before Christmas maybe even a White Christmas for some,  beats anticyclone weather with grey skies.

Edited December 6, 2016 by booferking

[Frosty.]

The GEFS 12z mean becomes colder and increasingly anticyclonic from mid dec, there is very strong ensemble support for this now.

Edited December 6, 2016 by Frosty.

[Matthew.]

36 minutes ago, Frosty. said:

Well, according to the Ecm 12z high pressure will be returning sooner than expected, that is, if it ever completely leaves in the first place because it seems to have influence on the whole run!

Quite remarkable Frosty! The jet isn't the same this year is it. That Low just keeps spinning away in the same spot. Benign it is then!

[nick sussex]

This is the ECM at T168hrs. The only way to get the high further north at T192hrs is for the trough set up to be negatively tilted. For newbies we talk of negative, orientated nw/se, neutral, n/s, positive ne/sw.

The tilt of the troughing is crucial when you're trying to pull the high further north, you'll see that deep low circled in black this will phase with the troughing circled red. As this happens you'll get a shove of energy eastwards, now the ECM takes more of that ne rather than se.

So you want to see the troughing set up like this circled red:

 

[Singularity]

As and when the tropical forcing in the Pacific becomes more dominant, the pattern will become more able to attack the vortex and keep the Canadian and Siberian lobes apart. This being something the models are continuing to see only intermittently in the longer range.

Until then, the standoff between N.America-Atlantic sector amplification and the Canada-Siberian exchanges of low heights is why mid-lat blocking is favoured, and why I've not once mentioned snow chances yet - it'll likely be week 3 at the very, very earliest before we see much scope for that. Not entirely ruling out a miraculous degree of undercut next week, of course 

Edit: Given that it goes even further than the GFS 00z with the continental feed even on Monday, I expect the ECM 12z is seriously chilly under that high. As GFS brought the warmer upper air in over the established cold air, daytime highs were only 1-3 degrees above zero, and nights at least than many below. I know - that sounds a lot like what the models once showed for this week... but the tropical forcing trend should be in the opposite direction. Hopefully.

Edited December 6, 2016 by Singularity
I just can't stop myself.

[karlos1983]

As we are in a bit of a lull, can anyone just give me a bit of a heads up, (not too technical if possible) as to why tropical forcing in the Pacific would disrupt the PV? 

TIA Karlos 

Edited December 6, 2016 by karlos1983

[Summer Sun]

 

[karlos1983]

2 minutes ago, Summer Sun said:

 

I'm bimodal at the moment. Don't know whether I'm coming or going. 

I do like and underdog though 

[northwestsnow]

That split will be all about that critical 96-144 timeframe imo, gotta get that azores high  north of the UK!

[Matthew.]

Day 10 ECM would be a joy in summer, something to hope for when the cold dark days are over

[Frank Trough]

To be honest, just catching up with the ecm op this evening, I would gladly bank that run for now let alone summer. 

I should have added that I mean in the context of what we could get....in fact, what was showing on the ops just a couple of days ago. 

Edited December 6, 2016 by Certain kind of fool

[mulzy]

Short ECM ensembles for De Bilt illustrate the high level of uncertainty past 120 hours

 

[WeatherGuru2012]

Ive never known a winter month to be so dry but be cold for a week, then rather mild for a week, then back to cold! But theres no real unsettled weather taking hold as you would expect in between the dry periods pressure over and theres a lack of snow, particularly with recent blocking and potential.Not that the ecm is set in stone.