Model Output Discussion - Into the new year

[The Enigma]

Just now, kold weather said:

By the way, just to note that if we see an extreme burst of cold coming through the Greenland/Iceland area, it runs a very high risk of developing an area of LP in a place that may very rapidly help us to switch back into a SW pattern, especially should the upper high migrate westwards.

For example:

You can very easily end up on the wrong side of that sort of pattern and default back into an Atlantic set-up even if the AO remains negative.

Just a word of cuation for those that see deep cold coming out of that area and think we are in the money, its REALLY rare for that cold to make it down to our neck of the woods, I've seen it literally a handful of times looking back at the last 100 years of charts on the archives. 

This is largely more to do with the development of high pressure over Iberia though, no? Too far out to worry about now anyway.

[matty40s]

1 hour ago, Tim Bland said:

Look again...it’s the 12z run from GFS Not fir the time period 12pm.  Both are for Weds eve. I was showing the most northerly point each one goes and ECM is much further north ..

My bad, on mobile screen, apologies.

[Nick F]

2 minutes ago, bluearmy said:

Ec op is further south with Wednesday - along the m4 and n Home Counties ..... a long way to go on pinning this one down ! 
 

tomorrows less intense snowfall is more consistent across the models  

Perhaps the usual one model to far north, e.g. 00z EC and one too far south, e.g. 00z GFS ... with a meeting in the middle. 

 At 48 hrs out a difference a 100 miles makes all the difference to where parts of southern UK see snow or not Wednesday. Met Office warnings may well have to be tweaked south or even abondoned. 

[clark3r]

1 minute ago, Steve Murr said:

EC 96 -

Low still stuck in the SE in -5c air

Deep snow if settles? Similar to dec 10? 

[Catacol]

43 minutes ago, Gael_Force said:

Is there such a thing as a displacement split?

The cold is coming. Snow chances on and off now for the foreseeable, and this is everything we could have hoped for 10 days ago. This strat chart represents the key to the history books - whether we end up with a spell that will be remembered as a good one, or whether we translate good conditions into great ones. There have been the usual scattering of gloomy comments over the last few days asking why uppers of -4 have been attracting such interest, and boldly proclaiming that nothing remarkable is happening. Knowledge is power.

The strat holds the key to sustained cold. Be under no illusion - once the MJO passes back into the Indian Ocean and if the vortex regains shape and coherence then these synoptics could fade once we pass mid month. We would have a 2-3 week period of cold, of snow and positive memories....BUT there is a rare opportunity the way things stand now for cold to dig in for the long term - as has happened in a very few past winters that I refuse to name.

If the strat chart above, indicative of a vortex splitting across a Greenland axis, was to occur mid month on top of a substantive displacement forecast somewhere between 4 and 10 January then I don’t think the vortex would recover any real influence for the rest of winter. A split producing a Russian/Siberian daughter operating in a reversal/stagnant/weak wind speed context would aid in feeding the brutal cold we are seeing bottle up over Siberia back towards NW Europe. This could turn a 2-3 week of cold into a 5-6 week of cold/very cold conditions... and a chapter in the weather history books all of its own.

I’m ramping a bit here (obviously - to say the least) but I see no point coming onto this forum to talk down snow chances at this time of year and look for holes in the analysis. There will always be potential holes. Little in this world is ever certain...but I would encourage those with a cautious tendency to understand the teleconnective thinking that is underpinning the excitement, to enjoy charts that are cold and getting colder, and cross fingers, toes and anything else moveable that we get that precious strat vortex split with a shard dropping into Russia. Dream hemispheric conditions.

Edited December 28, 2020 by Catacol

[kold weather]

6 minutes ago, bluearmy said:

Ec op is further south with Wednesday - along the m4 and n Home Counties ..... a long way to go on pinning this one down ! 
 

tomorrows less intense snowfall is more consistent across the models  

I do think the models are starting to come a little closer mind you BA. The models are probably now within about 100 miles of each other, though with a ESE moving system, even 30-40 miles further north/south means the difference between several million seeing snow, and several million seeing cloud to the south!

I do think the chances are there though for a snow event in the south, though again with the caveat that these systems have a nasty habit of adjusting south at short notice so we will need some luck here.

[kold weather]

2 minutes ago, The Enigma said:

This is largely more to do with the development of high pressure over Iberia though, no? Too far out to worry about now anyway.

Yes but that only forms because the deeper vortex comes down and forces pressure to rise further south as a consequence of it, if you run P4 on the ensembles between 240-300hrs you'll see that action in progress.

 

[Harsh Climate]

5 minutes ago, I remember Atlantic 252 said:

been following this last few runs, as a guess south of M4 event, that 'dreaded' M4 some may say

Ye looks that way, could get as far north as oxford but no where near us. Plenty of opportunities to come though!

[kold weather]

2 minutes ago, Catacol said:

The strat holds the key to sustained cold. Be under no illusion - once the MJO passes back into the Indian Ocean and if the vortex trains shape and coherence then these synoptics could fade once we pass mid month. We would have a 2-3 week period of cold, of snow and positive memories....BUT there is a rare opportunity the way things stand now for cold to dig in for the long term - as has happened in a very few past winters that I refuse to name.

 

Yes, I posted a little earlier this eveing that there is a legitimate chance at a very special set-up evolving out of this, especially if we do get any slight relaxation of the upper high somewhere between the 5-10th which could allow an attack from the SW. If it digs in we could get a straddling front stuck over our shores with a wave of cold air coming down - something very similar happened back in Dec 62...should we get another burst of upper highs forming we are going to be stuck then with a very cold set-up that won't even need decent temps aloft, the surface will do the job itself to a greater extent even under less than optimal set-up.

Anyway before that as you rightly say, there is some good winter set-up here, it is borderline and I suspect time of day, etc is going to make a world of difference as to where gets settling snow or not.

[Mike Poole]

ECM T120, compared to GFS, think this one will be a better run, could link up with scandi (GFS didn’t)

[Guest]

22 minutes ago, bobbydog said:

I haven't woken up to a magical winter wonderland for nearly 8 years....

Extended cold, snowy weather or not. The 12z has something for everyone.

 

Just once... this time... please.... 

Lol just the depths of FI - models struggle

with snow 24hrs out....

[chionomaniac]

3 minutes ago, Catacol said:

The cold is coming. Snow chances on and off now for the foreseeable, and this is everything we could have hoped for 10 days ago. This strat chart represents the key to the history books - whether we end up with a spell that will be remembered as a good one, or whether we translate good conditions into great ones. There have been the usual scattering of gloomy comments over the last few days asking why uppers of -4 have been attracting such interest, and boldly proclaiming that nothing remarkable is happening. Knowledge is power.

The strat holds the key to sustained cold. Be under no illusion - once the MJO passes back into the Indian Ocean and if the vortex regains shape and coherence then these synoptics could fade once we pass mid month. We would have a 2-3 week period of cold, of snow and positive memories....BUT there is a rare opportunity the way things stand now for cold to dig in for the long term - as has happened in a very few past winters that I refuse to name.

If the strat chart above, indicative of a vortex splitting across a Greenland axis, was to occur mid month on top of a substantive displacement forecast somewhere between 4 and 10 January then I don’t think the vortex would recover any real influence for the rest of winter. A split producing a Russian/Siberian daughter operating in a reversal/stagnant/weak wind speed context would aid in feeding the brutal cold we are seeing bottle up over Siberia back towards NW Europe. This could turn a 2-3 week of cold into a 5-6 week of cold/very cold conditions... and a chapter in the weather history books all of its own.

I’m ramping a bit here (obviously - to say the least) but I see no point coming onto this forum to talk down snow chances at this time of year and look for holes in the analysis. There will always be potential holes. Little in this world is ever certain...but I would encourage those with a cautious tendency to understand the teleconnective thinking that is underpinning the excitement, to enjoy charts that are cold and getting colder, and cross fingers, toes and anything else moveable that we get that precious strat vortex split with a shard dropping into Russia. Dream hemispheric conditions.

I agree and disagree, Alistair. The strat is already such a wounded dog, and with the trop in control, I think the damage has already been done. The strat Pv is unlikely to recover for quite a while, so to me the pattern is set, with the extent of split following the displacement is not just the icing on the cake, but more like how is the icing being shaped and set.

agree with the excitement- when all paths are leading to the same conclusion then it is more of a case of being patient enough to get there rather than which route is taken. Hopefully. 

[Scott Ingham]

7 hours ago, Catacol said:

Perhaps we really are seeing downward impacts of the weak strat already. ECM for Jan 3 on the trop/strat boundary is extremely supportive of an Iceland ridge and Euro cold backing west. 

Living the dream at the moment! 

When you consider the extremeley sensitive tpv i believe the same. Ive been busy today but i had the same thoughts this afternoon as i didnt expect these charts to kick in till the 6th or 7th of January

[MJB]

Nice 144 from ECM

[Mike Poole]

ECM T144:

Seems more similar to runs from yesterday compared to 12z today, but it is going to be really decent run here...

[bobbydog]

2 minutes ago, Alderc said:

Lol just the depths of FI - models struggle

with snow 24hrs out....

After 10 years on this forum, I'm well aware of that... doesn't stop us hoping though.... 

[MJB]

13 minutes ago, clark3r said:

Deep snow if settles? Similar to dec 10? 

Some area's will see several cm's and some a light covering . Hopefully going forward we can talk about feet rather than cm's lol

Edited December 28, 2020 by MJB

[AWD]

2 minutes ago, MJB said:

Nice 144 from ECM

Eastern Mediterranean air getting into the mix in Europe there.  

Edited December 28, 2020 by AWD

[Howie]

2 minutes ago, AWD said:

Eastern Mediterranean air getting into the mix in Europe there.  

Irritating 

[Tim Bland]

Here’s the full run of precip for Weds- Thurs. ECM has all of Wales across to East Anglia and all points south in with a chance of up to 10cm in 24hrs. If I was a betting man I’d say this will adjust south a bit over the next few runs. That would mean more areas in the south seeing snow rather than rain. It lalso means norther extent mid Wales to south midlands across to southern East Anglia 

[Day 10]

GFS, UKMO & ECM

144

Not a bad choice really is it.

[Eskimo]

ECM absolutely plasters the SE corner. 10-20cm. 

[SMU]

ECM 96 wrap around

[Mike Poole]

8 minutes ago, mountsbaysnow said:

Oh well it was good whilst it lasted...LOL 

UK long-range forecast: 21 inches of snow to blitz Britain as bitter -9C Arctic blast hits | Weather | News | Express.co.uk

WWW.EXPRESS.CO.UK

---

BRITAIN is bracing for 21 inches of snow to strike as a bitter -9C Arctic blast could hit, according to the latest forecasts.

 

I’m amazed we have been able to keep it to ourselves for so long! The express have had their hands full with covid nightmare stories to be fair!  

Anyway it has to happen yet, and this cold spell starts gently, first bite at the cherry today, may take one more before anything significant happens, but it is coming!

ECM T168:

Take that, any day!  Great run!

Edited December 28, 2020 by Mike Poole

[Skullzrulerz]

1 minute ago, Mike Poole said:

I’m amazed we have been able to keep it to ourselves for so long! The express have had their hands full with covid nightmare stories to be fair!  

Anyway it has to happen yet, and this cold spell starts gently, will take a few bites at the cherry as it cools gradually and then freezes!

ECM T168:

Take that!

That "high pressure" though trying to get in Norway