Model Output Discussion - Colder spell ending, what's to follow?

[Anthony Burden]

25 minutes ago, swfc said:

Where has it moved??? Its still in Russia unless putin has flited and taken the ussr with him

As I said moved its position, I don’t think I said out of Russia.

[alexisj9]

17 minutes ago, Catacol said:

ECM at 240h maybe beginning to smell the coffee. Not much more to say tonight - the potential prognosis for a switch to colder weather in the last third of the month remains the same.

Lots of posts at the moment questioning the signals and wondering why, on 8th December, we don’t have snow drifts on the horizon already. It is probably worth confirming the narrative so far. All the talk of a front loaded winter was based on historic modelling of previous Niña seasons where a mid Atlantic ridge was favoured and then the season flattens out as time passes. This theory was turned on its head a couple of weeks ago when it became clear that the atmosphere is not responding to Nina as expected (at least not yet) and so plans have been reset. Niña is fading fast, we have had a semi permanent high close to the Urals for what seems like weeks. BFTV’s article today in that regard is timely. Meaning? Don’t moan at the signals - try instead to understand them! They have changed and frankly I think have changed significantly for the better. 
 

So now we are waiting for the MJO to come back around and for the impact of warming events to upset the vortex. The impacts of these don’t happen in a week! The very short term reality of the battleground over the U.K. at the moment is that it is Dec 8. Even in the heady days of pre climate change U.K. when there was more ice and lower global temperatures how often has winter arrived before the second half of December? Is it genuinely a surprise that we haven’t got cold pools yet to tap into? No. Not one bit. 
 

Patience is going to be a real virtue right now. I am very definitely optimistic now about the season which lies ahead. For me winter doesn’t start until Dec 15 unless you live in the Highlands.

I over reacted earlier, re the GFS putting the low in it's usual place, early on, should be expect in that model.

Edited December 8, 2020 by alexisj9

[chris55]

I’m sure the thread is full of wonderful analysis.... haven’t read it yet....

But for me, coming in blind (so to speak) the ECM is one hell of a Christmas present! 
 

The classic westerly December is being usurped by some WTF charts. Loving 192 and onwards, the above chart is as rare as it gets, the potential being loaded for a prolonged cold spell. 

Can’t remember such disruption to the normal type in a good few years...and that disruption is evident in one form or another in a number of operational runs recently.

Definitely something to watch......it seems the building blocks are in place.

 

[Premiere Neige]

2 hours ago, Scott Ingham said:

Yes mate that's right. How far North the ridge from this will get is open to question still but its certainly the lag effects is expected from MJO Phase 5 into 6

Cheers mate! I got something right for a change

[Cleeve Hill]

5 minutes ago, chris55 said:

I’m sure the thread is full of wonderful analysis.... haven’t read it yet....

But for me, coming in blind (so to speak) the ECM is one hell of a Christmas present! 
 

The classic westerly December is being usurped by some WTF charts. Loving 192 and onwards, the above chart is as rare as it gets, the potential being loaded for a prolonged cold spell. 

Can’t remember such disruption to the normal type in a good few years...and that disruption is evident in one form or another in a number of operational runs recently.

Definitely something to watch......it seems the building blocks are in place.

Yep, there is nothing in the whole ECM12z that makes me think this slight warm up is a pre-cursor to the atlantic driven weather of recent winters. 

This Autumn and early winter is old school with Fog and Frost and isn't is great not to have gales force winds we have become so accustomed too. 

It all looks different this year and great to see the polar vortex all over the place.

[MATTWOLVES 3]

I'm that peed off with my earlier post stating Im not seeing significant cold this side of Xmas, I've had to glue myself to the ensembles to find something... Some are peaches... The last one is a real brute... Now if that came off I reckon I'd have me dog working overtime on snow clearing duties... Rrrrrrr.... How he loves it..

[stodge]

Evening all

Before I begin my look at the models, just a comment on those who argue posting T+240 or later charts is pointless because said charts never verify. 

It's Model Output Discussion - we're not discussing actual forecasts but looking at directions of travel  - not what WILL happen but what WOULD happen if such and such a synoptic evolution occurred. We're discussing trends and I'm well aware these change and as the output changes (as it does every day) so will the discussion. Those who want to deal in detail are happy to stick to T+96 or earlier but if we all did that it would get very boring. We all want to be the first to spot the trend, see the sign, appreciate the nuance.

That said, and with a definite milder interlude on the way, let's see where tonight's speculation takes us:

12Z GEM - not much obvious change at T+120 as the LP from lower latitudes gives an energy boost to the main LP as kicking the Azores HP into southern Europe - the result is the trough re-aligns positively and it;s seasonal SW'lies for us into the weekend. Note the weak heights to the north. By T+180, the evolution is getting messy and fragmented - the original LP has filled and moved only slowly north and a secondary feature has deepened markedly as it approaches Ireland. Note the more defined heights over Greenland - symptomatic of a weak PV - the Atlantic isn't powering through either. T+240 shows that even with a Scandinavian HP and a Greenland HP it doesn't work out for the British Isles in terms of cold. I mean, there's plenty of cold air nearby - just not where we want it (at least not yet).

12Z GFS - I'm expecting a more progressive Atlantic-driven run from this model. As you might expect, nothing unremarkable at T+120 and by T+192 the LP has more or less filled in situ. A weak LP is over southern Britain with a hint of troughing into Europe and heights remain over Greenland with another Atlantic feature moving slowly out of the Canadian Maritimes. The two LP systems join and oddly enough the pre-existing feature re-invigorates and eases back fractionally to the west by T+240. The SW'ly flow continues over the British Isles but this is a long way from a zonal Atlantic. On to T+312 and the jet has eased south as heights continue to persist over Greenland and the LP are now crossing close to or just to the north of the British Isles bringing a more unsettled spell. Christmas Eve sees an unseasonal N'ly with a secondary feature moving towards the SW.  850s are heading in the right direction as well - could it be? The 10HPA continues to show a distinct warming but it's a long way off a strat-splitter.

12Z ECM - as expected, GFS keeps the Atlantic in charge though it tantalises with a nice bit of eye-candy at the very end. Will ECM be the icing on the cake or the fly in our soup? T+120 brings no real surprises - it looks very similar to GEM. BY T+192 a small secondary feature has crossed southern England into the North Sea and swung north to create a complex trough. Mild enough for the SE but more unsettled elsewhere. Heights have returned to Europe though not strong at this time. Yet by T+240 the evolution has switched stride - the trough has moved south into Iberia creating a new LP which comes north to be over southern Britain with a light E'ly further north. Heights over Greenland and Iceland and the trough over Scandinavia all combine to give us chart a sense unlike many we have seen in recent years.  

Away from the output I've already discussed, the 12Z GFS Control ends very stormy whereas the 00Z Parallel was very anticyclonic.

Conclusion - there are always those who, if they don't see storm force E'lies and -20 850s heading directly for their part of the world proclaim the model output to be "dire" or even "dyer". We may not "get lucky" again this winter - that's life. However, the charts on offer tonight are not what I've seen at this time in recent winters. The Atlantic is more docile, the jet weaker, the PV less intense and all that gives us a chance and it's only that. GFS OP ends with a wonderful chart for fans of snow and cold but it is where it is and the key remains, as it often does, for the dice to fall favourably. Intense HP over the Pole looks helpful as does a disorganised PV but as GEM T+240 tonight shows, the 850s aren't quite playing ball yet. 

[sebastiaan1973]

The plume for De Bilt. No winter till 22th of december.

[Chesil View]

27 minutes ago, Catacol said:

ECM at 240h maybe beginning to smell the coffee. Not much more to say tonight - the potential prognosis for a switch to colder weather in the last third of the month remains the same.

Lots of posts at the moment questioning the signals and wondering why, on 8th December, we don’t have snow drifts on the horizon already. It is probably worth confirming the narrative so far. All the talk of a front loaded winter was based on historic modelling of previous Niña seasons where a mid Atlantic ridge was favoured and then the season flattens out as time passes. This theory was turned on its head a couple of weeks ago when it became clear that the atmosphere is not responding to Nina as expected (at least not yet) and so plans have been reset. Niña is fading fast, we have had a semi permanent high close to the Urals for what seems like weeks. BFTV’s article today in that regard is timely. Meaning? Don’t moan at the signals - try instead to understand them! They have changed and frankly I think have changed significantly for the better. 
 

So now we are waiting for the MJO to come back around and for the impact of warming events to upset the vortex. The impacts of these don’t happen in a week! The very short term reality of the battleground over the U.K. at the moment is that it is Dec 8. Even in the heady days of pre climate change U.K. when there was more ice and lower global temperatures how often has winter arrived before the second half of December? Is it genuinely a surprise that we haven’t got cold pools yet to tap into? No. Not one bit. 
 

Patience is going to be a real virtue right now. I am very definitely optimistic about the season which lies ahead. Winter doesn’t start until Dec 15 unless you live in the Highlands.

A  very measured and sensible post Catacol. 

10 years ago we were treated to a December to remember for ever, an extraordinary quite possibly once in a lifetime event, Away from the high ground of Scotland and Northern England It is unrealistic to expect anything much in the way of snow pre Christmas, so in that regards we have already done better in some places than we should expect.  While I,m mentioning legendary cold spells like 2010, it is also worth remembering that 62/63 really get going properly snow wise until Christmas week,and 46/47 until thelast week of January. 

As Catacol so rightly states patience  ( in this got to have it now world) is a virtue, but one that could well pay off big time.  We shall see.

[Griff]

What's occurring? 

Busy day so not had a chance to catch up much today, so whilst I wait for the 18z, let's have a look... 

144 (ish) 

 

And JFF at 240 (ish) ..

 

 

I'll have whatever the GFSP  and GEM are drinking  

 

(Took about 10 attempts to get these to show in vaguely the right order as intended... lesson learnt don't use my phone)

 

 

 

 

Edited December 8, 2020 by Griff

[captaincroc]

10 minutes ago, Cleeve Hill said:

Yep, there is nothing in the whole ECM12z that makes me think this slight warm up is a pre-cursor to the atlantic driven weather of recent winters. 

This Autumn and early winter is old school with Fog and Frost and isn't is great not to have gales force winds we have become so accustomed too. 

It all looks different this year and great to see the polar vortex all over the place.

This is my thoughts too.  I have never seen such consistent attempts for the Atlantic to move in to kinda get in...but then disrupt in a few days later....then rinse repeat. Normally they battle to get in, but once in then normal patterns resume. It's just the constant disrupting that is just baffling (in a good way). I still think things might happen sooner than we think...

[Scott Ingham]

8 minutes ago, Premier Neige said:

Cheers mate! I got something right for a change

Don't do yourself an injustice mate! its a waiting game. I'll be taking a back seat for 3 or 4 days while the MJO works its way back round and we feel the effects of this hitting 5/6 possibly 7 and the wave breaking in the strat starts to filter through. Both have a lag but the end of December is still the next push of amp for me. Question is will it be a UK high or something far enough North. High aplitude 6 going into 7 will decide that along with how much the current wave effects effect the strat. Personally the high will be too close to us come the end of December but I wouldn't rule it out and then the mjo being in 5/6/7 (these are ssw precursor numbers) and renewed tropical disturbances in January I think well feel the true effects 3rd week in January and all of February from a ssw late dec early jan

[Daniel*]

Even on milder output I'm definitely noticing a trend to take jet stream more south we get some more significant blocking which we could in late December I'm seeing a lot of blocking in EPS, and well who knows what can happen. People talk about cold potential always out in day 10 when it is colder presently, some output suggested it would be milder by now, today my maximum was 4C and 2.9C yesterday and I live in inner London on Thames floodplain some places have seen ice days. The capital is experiencing the coldest opening to December since 2012, it is likely if this pattern repeated in January there'd have been a lot more going for it, alas it is early and there's not much cold air and seas are warm. The models have never offered potential for significant cold in this period so I really don't understand the talk of models fooling us. The mid term is still open to flexibility remember how often when we turn milder and then see no interest for weeks, every single day there has been something to look at, I think this indicates something if you ask me. The models appear to be struggling with getting a grip of changes to vortex, and well this still isn't clear, so how can you be sure of anything? 

[Man With Beard]

Looking through the 51 ECM ensembles for 23rd December ... there's a lot of noise as you would expect, but there's also a lot of HLB around. The cold depends on where the blocks are - some are favourable for the UK, some other parts. The polar vortex, though, looks all over the shop. Looking at these charts, I'm thinking just 30% or less chance of zonal conditions by the start of the Christmas period, and probably an equal chance of a cold spell.

Edited December 8, 2020 by Man With Beard

[bluearmy]

Still waiting for decent extended eps guidance as ‘single’ cluster remains in place 

the e euro upper ridge remains solid looking through week 2 but I’m still unconvinced that we will see this maintained and blocking across to our north .... if both don’t verify, which one is more likely ??

cross model ens persist with neg nao and AO sig pretty well out to Xmas 

Edited December 8, 2020 by bluearmy

[blizzard81]

7 minutes ago, bluearmy said:

Still waiting for decent extended eps guidance as ‘single’ cluster remains in place 

the e euro upper ridge remains solid looking through week 2 but I’m still unconvinced that we will see this maintained and blocking across to our north .... if both don’t verify, which one is more likely ??

I think it is definitely possible to have both. The models were forecasting this for last week when they sent the diving atlantic low to our south and we were forecast to have south easterly's. Block to the east and also to our north. In the end the trough stalled over the UK instead. They got that wrong last week but not because its impossible. The situation we face this time round is different as the trough next week shows no sign of diving south east like last week. We are more reliant on pressure rising to our north. Ecm op tonight sort of went for that in the end. 

[Mike Poole]

It seems quieter in here today.  I don’t think that is because there is a downturn in prospects, (there isn’t), more because most has now been said and it is a waiting game for the next piece of the jigsaw to fit into place.  

ECM mean T240:

Vortex still marmalized, block to NE, hints to  the N, trough into Spain but heights in E Europe, this needs to change but could only be temporary.  

AAM forecast from CFS seems to be holding firm about neutral, the point being that a few days ago it was tending more negative, so still no sign of connection of atmosphere with La Niña, which itself seems to be weakening now.  

Suggests to me any Atlantic spell will be weak and short lived, the next focus on where the blocking sets up next in our vicinity.  And of course, eyes on the strat.  It is a long game once again, but so much more going on of interest than last year, for example.  I started watching the models in 2011 (so I missed Dec 2010) and since then all bar one of the few decent snow events here in Oxfordshire have been in response to a SSW, the exception being 10/12/17.  There seems increasing likelihood of an SSW this winter, so buckle up and enjoy the ride...I’m not suggesting everyone in here enjoys model watching more than the snow if it comes, but we sure as hell do a lot more of it!!  I hope we may be rewarded at some point over the next three months.

Edited December 8, 2020 by Mike Poole

[SqueakheartLW]

After picking my way through the GFS 12z options there are yet again a number of colder options for Christmas Eve which could very likely or most certainly with a number of them lead onto a cold Christmas Day. As before least cold option first through to what looks to be the coldest option

GFS 12z Member 4

The least cold option. Most likely surface cold at best but there are colder uppers waiting to our east. This one looks like more of a patience game waiting for more substantial cold to arrive if the pattern can hold

GFS 12z Member 25

This scenario looks poised to deliver a snow event somewhere in the UK. As the first low clears east it will likely pull the colder air down from the north which should then interact with the next low coming in from the west to produce a snow event. The exact location depends on the track of the low but timings on this run could be the perfect makings of a white Christmas where the air masses collide.

GFS 12z Member 18

This one looks to be a bit of a knife edge situation with the Atlantic trying to break through and the block trying to stay in place. All the while colder uppers are coming around the block and if the block wins here this will result in a colder Christmas Day

GFS 12z Operational Run

At last the operational run decides to come out to play here with this run that looks like we are headed into an Arctic northerly just in time for Christmas. There is the small matter of that developing low out to the west and that could push east and interact with the Arctic northerly to produce a snow event, especially in the SW of the UK

GFS 12z Member 6

A classic -NAO chart here on Christmas Eve. Looks a lot like the Christmas period in 2000 this chart. Could be a snow maker in southern UK where the air masses collide

GFS 12z Member 5

A nice end to this run with an easterly that is just getting started. Uppers are cold but not exceptionally so. More likely a seasonable Christmas Day to follow here with a snow shower risk in the E

GFS 12z Member 19

This chart is looking like a total snow fest as milder air pushes into the quite cold air in the east. That is some big block to the NE and could very likely hold which could mean the cold floods back west again after the low fails to push the mild air through

GFS 12z Member 28

An already established cold setup here. Most likely dry and cold. Even if less cold uppers look like they are heading in there should still be plenty of surface cold on this run at least

GFS 12z Member 17

The coldest option of all in terms of the uppers at least. Very anticyclonic too. Very cold nights with this run. Even colder uppers look to also be waiting to the east too and if these move in then a very cold end to the year is set

Summary

As with the 06z update we have once again got 9 colder options showing up of the possible 32. Still a good fraction of the total considering the usual default zonal signal we usually get

[damianslaw]

Sticking to the reliable, still have a very sluggish atlantic, frontal systems and low pressure running out of steam and power as they make inroads into the UK, not normal December standard fare, on average this is when the atlantic goes full on turbo charge.. until the weekend we remain just on the colder side of the jet, so temps at or a little below average.

Through the weekend and the new week, we see more energy in the jet and consequently low pressure powering through to bring strong winds - I can't remember the last time I felt the wind, its been notable by its absence, unusually so.. however, I am not seeing a change to an active atlantic, far from it. There are indications of a sharpening in the long wave trough what this will do is aid ridge development to the rear and crucially north of the deeper low, and with the PV in disarray, this could be the pattern shift required to more northerly blocking. Russian high is moved and replaced by a scandi trough. GFS and ECM suggesting such a pattern change in the run up to christmas.

We've been looking to the Russian high in recent weeks, this has been the dominant force, now our attention should be turning to events over the Pole and the state of the PV. if we maintain a ragged shape with lobes locked in place as they are now, the key forcing will come from height rises direct over the Pole and where they decide to orientate themselves, hints towards Greenland and to our north, if so, jet will be switched to the south again.

It will be a few days yet before we can begin to call how second half of the month may pan out, with any certainty. I will not be surprised at all to see the current low pressure being forecast for early next week, to be a more stretched affair, the idea of a secondary low to the SW as shown by ECM very plausible then watch those height rises to the north and west. 

[BLAST FROM THE PAST]

I’ve seen mention of the solar flare incoming (it will perturb the jetstream but where it hits Earth will determine how it affects NH profile), yet generally the solar state is quiet....big ejections don’t mean active solar state.   I’ve seen mention of my BFTE for Xmas week (Beast or Blast for Xmas week whiich is 24-31) get ridiculed....but we see the not outlandish evolution still very much in model’s evolution.  The sun is still Q as a rule, a strong ejection doesn’t mean a very active solar state.

I’m ‘hopeful’ for a BFTE which has been with me for sometime....a.big blast or beast from East...models aren’t disappointing currently  and still on the table imo.

 

BFTP

Edited December 8, 2020 by BLAST FROM THE PAST
Additional

[Matt H]

Decent heights rising to our north on the 18z, similar to the 06z earlier. I think the pub could be open tonight lads.

[Mike Poole]

Pub run rolling, here T 156 compared to T162 on the 12z:

Better position of the wedge to the north here, improvement so far...

[chionomaniac]

Pub run very close to being great no matter what happens next on it. It is up to day 6 that we need to take notice of

[Griff]

Fair to say the synoptics are more pleasing than the actual weather we'll endure IF they start to pan out like that (I've have had enough pain in 2020 with very little gain so far thank you), but yes 1040 hiding amongst the blue near Greenland  

[Mike Poole]

Pub run T180:

Pick the bones out of that!  Going to be a classic!  I’m not even going to try to draw the invisible block on this one, I’m still trying to wrap my head around it!!!   Suffice to say, I think it might have moved since yesterday’s 18z!!

Edited December 8, 2020 by Mike Poole