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

[Methuselah]

6 minutes ago, Man With Beard said:

GFS 06Z still on a completely different page to the ECM ... or is it? Heights pulling back to the Atlantic, low heights back over Europe, breakthrough of low pressure into the North Sea and beyond ... ok that's as far as it goes!!

  

The parallel continues to promote a massive storm to our north in deep FI (between Dec 20 and 24) - will be interesting to see if that verifies

What's even more remarkable is the difference between the GEFS and ECM means at T240. I usually see this as a sign of high uncertainty.

  

However, over the years I've rarely seen the GEFS mean be wrong when it produces a 1030mb high, so I'm going to side with the ideas that the Euro High at D8 will move towards a UK High by D10.

And just for fun (some of us need it after the past eight tortuous weeks) - P14 has the eye candy this morning!

 

Thanks for that MWB: a much better explanation than my own 'interesting'!

[daz_4]

A Torpedo from the east on pertubation 16, heh.

And still huge scatter on 13th. Same as 24 hours ago.

[chrisbell-nottheweatherman]

1 hour ago, bluearmy said:

Ecm op AO/NAO dive negative day 10 and interestingly the GFS also though much less pronounced

 

 

Doesn't that contradict the evolution of the ECM 00z ensembles Matt was discussing?  Wouldn't a Euro high and mid-Atlantic trough constitue a ++NAO?

[bluearmy]

3 minutes ago, chrisbell-nottheweatherman said:

Doesn't that contradict the evolution of the ECM 00z ensembles Matt was discussing?  Wouldn't a Euro high and mid-Atlantic trough constitue a ++NAO?

Yes but I'm speaking op and he's speaking ens

my point was you wouldn't usually speak op at day 10 against ens trend 

incidentally, the eps AO is fairly neutral Days 10/15 whilst the gefs not surprisingly take it negative -1/-2. The eps NAO also positive 1 to 2 in that period.

[jvenge]

7 minutes ago, chrisbell-nottheweatherman said:

Doesn't that contradict the evolution of the ECM 00z ensembles Matt was discussing?  Wouldn't a Euro high and mid-Atlantic trough constitue a ++NAO?

I believe blue army is going by the Deterministic and others must be looking at the EPS. It is indeed true that the Deterministic puts the AO heavily negative and the AMO negative, although not as deeply as the AO. The EPS are really not agreeing though.

The GFS is more inline with its own GEFS in sending negative. 

 

[Tamara]

Recent days has seen the traditional annual dismissal, from some familiar suspects, of the "global drivers" - which are related to tropical and extra tropical wind-flows (and which serve to framework the hemisphere patterns and determine whether NWP will head in a direction of favouring flatter westerly patterns or more amplified colder solutions) 

These (somewhat parochially) driven dismissals primarily stem from frustrated expectations of weather preferences having not been met - and therefore scapegoats required.

I believe  "soothsayer blame" is also attributed to a failure from relatively small activist posting sections of the audience to take any notice of the repeated downsides of the start of winter.... which have, in truth, been stressed several times. These, pitched next to the more favourable possible solutions which at one time, not so long ago (as stewfox latest amusing instalment reminded us) jived in tune with the long range model ensemble data suggestions. An illustration here of what one wants to hear vs what one doesn't.

Good example of the messenger(s) being hailed for all the good news, but then being shot simply because the bad news was ignored. On a forum thread that is geared towards swerving up and downwards in mood with every (apparent) model suite mood, its probably no surprise that "global drivers" are viewed as mystic meg tea leaf reading - except when they appear to support cold weather.

However, having said all that, its time to run the gauntlet once more...

So, it is the lower angular momentum (milder, flatter and more mobile solutions) that are set to prevail for the shorter tp medium time period.

Away from the NWP rollercoaster, how can we measure this? ( as previously pre-warned was possible)

The Global Wind Oscillation is currently moving through Phase 8 as angular momentum falls and the colder seasonal blocked patterns of the recent past crumble away

Frictional torques falling into -ve territory, and leading mountain torques with them...

...The cue taken for falling relative angular momentum tendency to mirror the falling torques, as net easterlies are added to the global atmospheric circulation

 This favours Pacific amplification in tandem with the -ve PNA pattern which in turn favours cold air heading out of Canada, "hello winter" to the US, and an ignited polar jet as gradients are steepened across the western Atlantic

Which also is a personal reminder. I remember posting about a month back that an EPO poleward ridge could be either friend or foe downstream - according to whether the NH profile was inclined towards an amplified downstream pattern (higher AAM)  - which is the one that would take advantage of stratospheric weakness and in turn translate that to meaningful cross polar ridging to raise heights this side of the pole. Or, under falling AAM - the frustrating scenario which is presently unravelling where stateside steal the cold and amplification stays upstream.   Again.

A good example of where it proves to be highly cautious of two week extended NWP ensemble data that can be both too bullish for stratospheric instability estimates, and also cannot foresee accurately how tropical and extra tropical drivers are going to evolve. Yes "those" once again. There has been another lesson here in that department as well, with delays and overriding of downstream amplification potential due to a greater coupling of the ocean signal with the atmosphere occurring at the time it was least wanted (in terms of taking advantage of weakness across the polar field)

A lot of stewards enquiries into abandonment of a "front loaded winter"  All who have pointed to this have had sound reasoning to base their initial expectations - and it is still very early winter anyway to draw conclusions and tear up scripts completely. The "drivers" lead the models (not the other way around as perception persists with a few) but making such predictions is made ever tougher year on year against the alarming global warming trends, not just in the arctic, but also the tropical oceans where homogenous and anomalous warmth is playing mayhem with the intra seasonal and cyclical phenomenon with ENSO etc.

We should expect tropical "noise" to become more and more of a feature as this warmth translates to higher and higher instability and cyclone activity "destructively interfering" with the more predictable low frequency signals that have been discussed of late within the context of downstream weather patterns (will it get cold and snow or not)

For what little it is worth, I've had doubts since at least October, or, to put it more positively, an open mind as to how this winter might play out - and without taking up any further boring band-with in explanations within this post, there remains enough to suggest that a more traditionally timed SSW might well be the path towards greatest chances of cold this winter. I agree with the few recent suggestions from some others emerging in that regard, However, too much is clouded by the short term developments and how soon the atmosphere might bounce back and favour amplification - therefore backing any extension of milder westerlies is as risky as any overriding suggestion of being in a cold place by year end.

To be honest, while some will make predictions, no-one really knows.

However, answers appear around natural corners, so I will keep watching the GSDM data and basing interpretations of the lead provided by that data to then try and evaluate how NWP might evolve. Not the other way around. Good enough reasons to help keep safe open water distance from the 10, 32 and 46 dayer "will they/won't they saga that threatens to undermine health and sanity with 12 weeks of official winter still remaining. Much as seems to happen each year within parts of the net weather model watching audience

In this respect I'm glad I'm old fashioned enough to not use twitter! Though keeping up with others thinking is always useful, even if nothing should ever be taken at face value.

But have fun, whatever is your favourite tipple

@mountain shadow  pm message sent to you

 

Edited December 8, 2016 by Tamara

[Faronstream]

Looks pretty good in 06Z GFS for coldies, if just the center of the high pressure would be like 600km more up to the north around iceland then it would bring down even colder 850hpa temperatures

[Seasonality]

@Tamara I could kiss you for that post ^^^^^  Not only written in your usual elegant style with all kinds of erudite meteorological tidbits but a razor sharp critique of the forum 'madness' so typical of this time of year. 

[karlos1983]

You can only sit back and respects those that invest so much time and effort into the global drivers to be able to come up with such a detailed informative post such as Tamara's. That's not taking anything away from those that perhaps put more faith and equally as much effort into nwp operational models. 

At  the end of the day, the weather can and will make fools of us all, pros included. (not saying it has btw*)

 

 

Edited December 8, 2016 by karlos1983

[BLAST FROM THE PAST]

11 minutes ago, Seasonality said:

@Tamara I could kiss you for that post ^^^^^  Not only written in your usual elegant style with all kinds of erudite meteorological tidbits but a razor sharp critique of the forum 'madness' so typical of this time of year. 

Forum madness driven by teleconnections and forecasts leading folk up the garden path as their 'cold blocked signal' got quickly stamped on?  Indeed composites of early signs did look good.....but only as good as how much of a driver a certain tele is.  

 

BFTP

[Seasonality]

Just now, BLAST FROM THE PAST said:

Forum madness driven by teleconnections and forecasts leading folk up the garden path as their 'cold blocked signal' got quickly stamped on?  Indeed composites of early signs did look good.....but only as good as how much of a driver a certain tele is.  

 

BFTP

The only way you can get led up the garden path is if you see a forecast as a certainty.

[swfc]

2 minutes ago, karlos1983 said:

You can only sit back and respects those that invest so much time and effort into the global drivers to be able to come up with such a detailed informative post such as Tamara's. That's not taking anything away from those that perhaps put more faith and equally as much effort into nwp operational models. 

At  the end of the day, the weather can and will make fools of us all, pros included.

 

 

Indeed altho i cant say that i have a great understanding of tamaras,gp and sm etes posts.Ive looked and watched forecasts for 40 yrs and take what i can from watching models and looking at charts from way back and sometimes matching.I guess any forecast esp the way oct-nov have panned out with the blocking nao ete was always a tough call.Always on to a hiding to nothing it would seem esp with the longer range forecasts.Todays output still looks a minefield tbh and a brave call beyond 7-10 days is not what i would be doing altho if pushed would go dry-cool/cold  mlb set up into xmas

[BLAST FROM THE PAST]

Just now, Seasonality said:

The only way you can get led up the garden path is if you see a forecast as a certainty.

Indeed and well presented....but one can understand a following when presentations of forecasts are done in such depth and of what 'should' result.  Long may the attempts continue.....and the madness

 

BFTP

[fergieweather]

Given that today's EC Seasonal update remains steadfast on broadscale lack of zonality J-F-M, retaining it's eagerness for marked northern +ve GPH/MSLP and drier than avg anomalies, I'm not expecting any sudden change of tact from UKMO Seasonal Team based on current op modelling mash-up. What is now very striking is the growing evidence of apparent disconnect between impending and strongly-signalled upshift in stratospheric zonal winds, versus zero evidence in EC Seasonal for it to manifest in a marked change of mean tropospheric anomalies (towards zonality). I'm trying to discover via UKMO Seasonal boffins exactly *what* forcing mechanism could be overridingly at play here, because (despite the snipers/doubters on here) it is quite irrefutable that *something* is driving these two key high-end coupled models (EC & GLOSEA) to reach similar prognoses. Fascinating enigma; fascinating times...

[Seasonality]

3 minutes ago, BLAST FROM THE PAST said:

Indeed and well presented....but one can understand a following when presentations of forecasts are done in such depth and of what 'should' result.  Long may the attempts continue.....and the madness

 

BFTP

Will leave this as my last reply to avoid the thread straying too off topic. I raise a glass to the attempts continuing and to the continued fun on the forum, but I do think Tamara was right to criticise the attacks which became quite vicious, petty and ill informed. On to the 12z output and what madness may ensue!

[karlos1983]

8 minutes ago, swfc said:

Indeed altho i cant say that i have a great understanding of tamaras,gp and sm etes posts.Ive looked and watched forecasts for 40 yrs and take what i can from watching models and looking at charts from way back and sometimes matching.I guess any forecast esp the way oct-nov have panned out with the blocking nao ete was always a tough call.Always on to a hiding to nothing it would seem esp with the longer range forecasts.Todays output still looks a minefield tbh and a brave call beyond 7-10 days is not what i would be doing altho if pushed would go dry-cool/cold  mlb set up into xmas

Agreed. But if you have the capacity to be able to see the wood through the Trees then why not share that, even with caveat or two? Which I think I remember Tamara providing a few weeks back when things were looking rosy as far as December Northern Blocking was concerned. 

I think, no matter what type of long range prediction is made and by whom, if you can make the call and it doesn't quite work out, as long as you can identify what went wrong and why, then that's fantastic. That is a good platform to learn from. I once drilled a hole in my kitchen to hang a cupboard up, I can assure you, next time I will use pipe detector to save me getting wet.

Edited December 8, 2016 by karlos1983

[Ali1977]

Great post from Ian F again, a little blip but the workings in the atmosphere sound as messed up (and exiting) as they did a few weeks ago. All ALL to play for and it also sounds like the whole of winter could see something interesting.

[mountain shadow]

43 minutes ago, Tamara said:

Recent days.....

 

Great post Tamara.

I wonder if I might trouble you to give us a clue as to what you expect the GWO and GLAAM positions to be in Christmas week?

Recent GFS Ops appear keen to raise an amplified ridge to the West towards Greenland which might give a chosen lucky few the chance of seeing the white stuff around the big day.

Do you expect angular momentum to be on the increase by then?

Thanks

[Paul_1978]

7 minutes ago, fergieweather said:

Given that today's EC Seasonal update remains steadfast on broadscale lack of zonality J-F-M, retaining it's eagerness for marked northern +ve GPH/MSLP and drier than avg anomalies, I'm not expecting any sudden change of tact from UKMO Seasonal Team based on current op modelling mash-up. What is now very striking is the growing evidence of apparent disconnect between impending and strongly-signalled upshift in stratospheric zonal winds, versus zero evidence in EC Seasonal for it to manifest in a marked change of mean tropospheric anomalies (towards zonality). I'm trying to discover via UKMO Seasonal boffins exactly *what* forcing mechanism could be overridingly at play here, because (despite the snipers/doubters on here) it is quite irrefutable that *something* is driving these two key high-end coupled models (EC & GLOSEA) to reach similar prognoses. Fascinating enigma; fascinating times...

Interesting stuff. So is this to say that if there is a disconnect between the strat and the trop, that if a SSW does occur, that this will have a negligible effect (due to the aforementioned disconnect)?

[karlos1983]

9 minutes ago, Paul_1978 said:

Interesting stuff. So is this to say that if there is a disconnect between the strat and the trop, that if a SSW does occur, that this will have a negligible effect (due to the aforementioned disconnect)?

I guess it can't hurt though? I'm not sure how long the disconnect would last? However, can the the right setup have an effect on the Strat from the Trop up if there is a disconnect?

SO MANY QUESTIONS!!!!!! 

PS I love the "Met Office Boffins" comment by Ian, made me chuckle.

[Sky Full]

Thanks for your extremely well written post, Tamara, to the point where I believe I could understand quite a bit of your reasoning!  

"but making such predictions is made ever tougher year on year against the alarming global warming trends" .....  and I am beginning to believe that global warming has already changed our weather for ever.   What I cannot get my head round is why the UK seems always to be in a 'protected' zone of warmer air than almost any other landmass at the same latitude.  Look at this short animation and see how the UK is currently modelled to avoid all the cooler upper air which seemingly is kept away by some invisible 'force field'.  Is this the Gulf Stream?

As long as we remain protected from the coldest upper air we are not likely to enjoy many Arctic interludes.  

[Summer Sun]

 

[karlos1983]

3 minutes ago, Summer Sun said:

 

Hmm, although good news, I think I'll take that with a pinch of salt for the sake of my sanity.

 

Edited December 8, 2016 by karlos1983

[fergieweather]

13 minutes ago, Paul_1978 said:

Interesting stuff. So is this to say that if there is a disconnect between the strat and the trop, that if a SSW does occur, that this will have a negligible effect (due to the aforementioned disconnect)?

I'm unconvinced re SSW. What looks more possible from EC climagrams is a reversal of original expectations re this winter (going to back-loaded for colder risks Jan-Feb?) but it's impossible to fathom exact journey of travel from 3-month combined fields, that will mask month-by-month trends/extremes and also cancel out each other in eg resultant temp anomalies.

[blizzard81]

27 minutes ago, fergieweather said:

Given that today's EC Seasonal update remains steadfast on broadscale lack of zonality J-F-M, retaining it's eagerness for marked northern +ve GPH/MSLP and drier than avg anomalies, I'm not expecting any sudden change of tact from UKMO Seasonal Team based on current op modelling mash-up. What is now very striking is the growing evidence of apparent disconnect between impending and strongly-signalled upshift in stratospheric zonal winds, versus zero evidence in EC Seasonal for it to manifest in a marked change of mean tropospheric anomalies (towards zonality). I'm trying to discover via UKMO Seasonal boffins exactly *what* forcing mechanism could be overridingly at play here, because (despite the snipers/doubters on here) it is quite irrefutable that *something* is driving these two key high-end coupled models (EC & GLOSEA) to reach similar prognoses. Fascinating enigma; fascinating times...

There is one possible explanation for this - both the EC and glosea seasonal models are wrong. Time will tell of course but quite telling that the EC 46 dayer has shifted away from the overwhelming northern blocking signal during the last 2 updates.