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

[SMU]

59 minutes ago, feb1991blizzard said:

Maybe I'm wrong but I class a high over us that sits there as mid latitude block, it would be possible IMO to get heavy snowfall from a mid latt block for your location but not most of the UK, if there was a really thin sausage shaped high (like a Richmond skinless not like your fat stubby Lincolnshire ones with that seasoning in) with a very steep pressure gradient to the south then it could deliver for you.

As mentioned above - amplitude wise I would say that a MLB extends from 45-70N & covers the Scandi high, Atlantic High, SCeuro High - therefor the type of weather could be a huge range from a MLB - its the small window from 60-70N that is peak amplitude from a MLB that usually brings snow from the East where as the atlantic can be softer at 50-70N to sweep in Cold ...

interestingly 'the death of the Easterly' -a topic over on TWO by darren has highlighted that the frequency of these high amplitude waves has decreased since 2000 ( Ian browns large teapot ) & therefor losing this crucial 10 degrees of amplitude has mean the locale of the CAA & core of pressure has adjusted further East & South-

Also with less returning jet energy the cold is further south & east- vis a vee why places like Greece & Athens have seen higher frequencies of deep cold arriving...

bestS

[bluearmy]

The eps London graph has a fair spread late on but plenty of very cold options showing up

[blizzard81]

When you have a full day of operational downgrades of cold potential you know where we are heading. 

[Sky Full]

These charts looked just about perfect to round off a happy day.....

.   .  

Chances of them verifying?  Well, who cares really - they just gave me the chance of some sweet dreams.   Same to all of you.....

[feb1991blizzard]

1 minute ago, Steve Murr said:

As mentioned above - amplitude wise I would say that a MLB extends from 45-70N & covers the Scandi high, Atlantic High, SCeuro High - therefor the type of weather could be a huge range from a MLB - its the small window from 60-70N that is peak amplitude from a MLB that usually brings snow from the East where as the atlantic can be softer at 50-70N to sweep in Cold ...

interestingly 'the death of the Easterly' -a topic over on TWO by darren has highlighted that the frequency of these high amplitude waves has decreased since 2000 ( Ian browns large teapot ) & therefor losing this crucial 10 degrees of amplitude has mean the locale of the CAA & core of pressure has adjusted further East & South-

Also with less returning jet energy the cold is further south & east- vis a vee why places like Greece & Athens have seen higher frequencies of deep cold arriving...

bestS

Btw I was only debating 87 and 91, that first chart you posted from the latest run, is definitely a mid latt block, I have no argument with that, anything with the core on the same latitude as the British isles is MLB IMO.

[bluearmy]

1 minute ago, blizzard81 said:

When you have a full day of operational downgrades of cold potential you know where we are heading. 

that depends when you were expecting any deep cold to arrive. 

imo, today has seen repeated v cold week 2 solutions on the GFS ops and the eps have firmed up on the euro low anomolies after yesterday's blip lessened them. add to that the GEFS are now consistent on these. 

 

[SMU]

13 minutes ago, feb1991blizzard said:

Btw I was only debating 87 and 91, that first chart you posted from the latest run, is definitely a mid latt block, I have no argument with that, anything with the core on the same latitude as the British isles is MLB IMO.

No probs

far reaches of GFS- peak amplitude MLB

 

[blizzard81]

6 minutes ago, bluearmy said:

that depends when you were expecting any deep cold to arrive. 

imo, today has seen repeated v cold week 2 solutions on the GFS ops and the eps have firmed up on the euro low anomolies after yesterday's blip lessened them. add to that the GEFS are now consistent on these. 

 

I will bow to your superior knowledge BA but the ops today seem to have downgraded in the 8 - 10 day range.

[Ali1977]

3 minutes ago, blizzard81 said:

I will bow to your superior knowledge BA but the ops today seem to have downgraded in the 8 - 10 day range.

Looking at the GEFS at day 10 tonight's ENS are looking much better than the 12z, lots more amplification which by day 12 offer some more potent Northerlies.

[bluearmy]

8 minutes ago, blizzard81 said:

I will bow to your superior knowledge BA but the ops today seem to have downgraded in the 8 - 10 day range.

I won't argue with that timescale though they have upgraded in the period thereafter which is when the ens have always indicated the potential to be re the lowering of euro heights. 

[blizzard81]

2 minutes ago, Ali1977 said:

Looking at the GEFS at day 10 tonight's ENS are looking much better than the 12z, lots more amplification which by day 12 offer some more potent Northerlies.

But this always happens. When the ops downgrade, the 18z is the last to smell the coffee. I do hope I am wrong but we have been here so many times now.

[Man With Beard]

GEFS 18Z looking game set and match for some sort of New Years Day northerly - overwhelming signal now.

[Geordiesnow]

For me personally I think the models are painting the same picture as yesterday in terms of the broader term signal of high pressure over the Atlantic with some sort of ridge and a Northerly blast of air heading down from the Arctic into Scandi and to a lesser extent the UK. Its all down to how much ridging we get depends how much of a Northerly flow we get, most indications suggest the Northerly flow to be fairly weak and may not last all that long but the models suggest we may get another attempt later on but that is definately subject to change.

So the trend for it to turn colder from the North is still there, question will be, just how strong this flow will be and how long will it last for and just how much ridging will we see in the Atlantic. Past experiences tell me we won't see a full ridge into Greenland and we will get a messy half hearted northerly flow in the end but there is a small chance we won't even get that and things remain flat as hinted by the UKMO output and the odd GFS run. Only the ECM has maintain consistency of a more amplified outlook. 

Still not too much to get excited about as of yet but there is some hints the outlook may get better for snow lovers but unfortunately its another one of those periods of model watching.

[snowray]

Well certainly looks like its going to turn a lot colder in the New Year, the trend is our friend.

[snowray]

Ensembles for London and Manchester just in case your wondering about the second one.

[Catacol]

2 hours ago, Steve Murr said:

Using the Merra data @ 10HPA V the AO which is the best barometer for any disconnect between the 2 shows a pretty cohesive upward response from the AO as the vortex recovered- so whilst the propergation could have been quicker the 'actual' observed pattern was-

The zonal wind increased significantly from 10M/S on the 4th to 55M/S on the 23rd-

 

Steve - Agreed that the AO profile has not been what we wanted, but not convinced this is down to propagation from the stratosphere. If you look at the arctic profile it doesnt appear at all that the increasing strength in the SPV has caused any great response. (Apologies for these links - I dont know how to convert a pdf graphic into something that will work any better.)

https://acd-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/zmplots/U___lat_p_70N-90N_zm.pdf

There is a growing response down to about 70hpa - but above that really little in the last few weeks to show a connect.

Add to this the vertical profile for closer to our own latitude - and again the response is hardly dramatic. There is a degree of correlation here now as zonal speeds in the troposphere have picked up now - but go back over the time series you quote and I dont see it.

https://acd-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/zmplots/U___lat_p_50N-70N_zm.pdf

The question I guess is - how have we ended up with a +AO when semi pros and experts from Cohen to GP to even the extended models such as GLOSEA didnt see it? I dont have an answer here... and GP's post implies that perhaps he is currently unsure too.... but I dont think it is as simple as a troposphereic vortex whipped up by the SPV. Is there something in the loss of sea ice we dont understand yet? Or has the QBO profile - which everyone admits is different to any predicted profile we have seen before - had a greater than expected impact?

Therefore I dont think you can draw a straight line comparison between AO and SPV.

The teleconnections have all gone muted and hard to predict. GWO and MJO are both pretty neutral at present. SPV is strong - but actually TPV (as argued above) is not dominant. As IanF has posted recently - even the Met are scratching their heads a bit at the list of neutral signals and the lack of any clear forcing for the second third of winter. Given all this I suppose the chances for an unexpected turn of events through January are greater than normal. Could we see an unexpected HLB form as a result of a small tip in the teleconnective package? Perhaps. Its frustrating at the moment trying to glean where the forcings are heading in the medium term... but perhaps we ought to try and be a bit optimistic and enthusiastic at the same time, given that the envelope of uncertainty feels so great.

 

Edited December 26, 2016 by Catacol

[nick sussex]

Happy Christmas to everyone at NW. Been very busy with friends over so not had much time to spend here. Having caught up with tonight's outputs I think this first cold shot is looking a bit brief . I think of more interest is what happens after that, the trend is to have some shortwave energy running over the top of the high and it's whether we can get the high to retrogress back nw allowing the troughing over Scandi to back a bit further west.

For any deeper longer lasting  cold I think it's going to have to come from the ne or east as it's hard to see any HLB setting up near Greenland.

Overall the outputs show some potential but not really shouting from the roof tops in terms of cold.

[Scandinavian High.]

By this we are turning much colder as we go in to January can't seeing it being short lived by looking at this .

[snowray]

Could be a big turnaround in January after the very mild December, I am expecting a much more seasonal month, the potential (don't we just hate that word) is certainly there and there are a fair few runs now turning up with more that a little interest. Light at the end of the tunnel for cold and snow fans maybe?

Merry Christmas!

Edited December 26, 2016 by snowray

[knocker]

today

Huge contrast between the north and south today. For the Midlands south a much brighter day than yesterday with temps nearer normal. For N.Ireland and northern England windier with showers. For Scotland becoming very windy with storm force wind in the very north (gusts 90mph) and for a time hurricane force in the Shetlands. Accompanied by violent showers of snow, rain, hail, you name it. In all, take care and stay safe. Especially anyone at sea where huge seas are running.

The GEFS anomalies this morning show little change in the ten day range so previous comments still apply and it is essentially a case, yet again, of assessing the consistency of the daily evolution of the det run. The later time frame is continuing to show pattern changes but that's for another  time.

After today high pressure once again builds from the SW and slowly slides SE during the week whilst an upper trough in the Atlantic track east and arrives over the UK, with surface fronts, on Saturday. So a dry week with temps around average and quite pleasant.

So over the weekend some rain in most places as fronts traverse the UK tracking south east whilst the upper feature does similar and phases in with the trough to the south west. Simultaneously the high pressure again builds fro the south west but is quickly flattened by the energy rushing east from upstream on the jet.

The HP manages to hang on until forced to give way to an upper trough driven in from the NW and swing SE over the UK

So there we have it. Generally mainly dry with temps around average but trending a little below towards the back end of the ten days.

Edited December 26, 2016 by knocker

[booferking]

Yep not bad at all from the 00z..

It gets better.

Edited December 26, 2016 by booferking

[Ali1977]

Oh yes, what a chart.  There will be some happy campers on here this morning!!

 The GEFS are better this morning too. 

Split PV right there, expect a METO wording change if this is to be believed!! 

Edited December 26, 2016 by Ali1977

[Polar Maritime]

The GFS certainly advertises a cold outlook into wK2 once again this morning, With the Jet way South. Much more seasonal charts on offer than of late, And not without interest. Winters certainly showing his hand at last.

Edited December 26, 2016 by Polar Maritime

[knocker]

The ecm is full of excitement this morning. It's similar to the GFS until towards the end of the run when the energy shooting out upstream via the jet running around the high pressure cell is too much for the high cell and pushes it south west allowing an upper trough and surface low to swoop south east over the UK bringing some quite torrid weather by the beginning and middle of next week with blizzards on high ground and even snow lower down.

 

Edited December 26, 2016 by knocker

[That ECM]

On 23/12/2016 at 06:36, That ECM said:

All three at t144 have the ridge starting to build out west. Let's hope we can see this at t72 then it may well be game on. At last output excitement. Personally wouldn't worry about what is shown after this time. 

T72 above T144 ECM has been more consistent in the modelling of the ridge imo.  Getting interesting.  Can't post  ukmo northern profile. First part of getting pressure rise to our west is looking good. 48 hours ago ukmo dropped the idea but I assume it is back on looking at the t96. Now, where will it go? Soooo hope ecm is correct but gfs is not a bad second. ECM is less problematic imo in cold coming to us and prolonging potential fun. 

Edit just seen fergies update. A slightly watered down ecm version? It's a good morning for coldies!

 

Edited December 26, 2016 by That ECM