Model Output Discussion 29th December - Into mid-Winter.

[Day 10]

3 minutes ago, nick sussex said:

Once again today the GFS flat bias is showing up. You'll see upstream the 00hrs had a flat shortwave running east across the USA around T144hrs. The GFS 06hrs now slowly backtracking towards the Euros with that more amplified wave.

 GFS 00hrs run to T144hrs                            GFS 06hrs run to T138hrs

 

 

The stand out model today for those hoping for the easterly is the UKMO with the most amplified upstream shortwave. Looking at its T168hrs output Atlantic view you can see a different shortwave running se'wards this is the trigger for any possible easterly. The UKMO has this the furthest west of any of the outputs.

Its not just what happens to the east with the Russian ridge but the critical area is upstream with the pattern in the eastern USA, the more amplified the pattern is there at that crucial timeframe the higher chances of that easterly. If for arguments sake the UKMO verified at T168hrs it would have the coldest solution past that point and would likely bring in an easterly.

I think at the moment there looks a bit too much energy in the northern arm of the jet with the odds more in favour of you guessed it the coldest air heading towards south/se Europe but theres still uncertainty with how much amplitude there will be over the USA and Canada.

Regardless of that any amplitude upstream will help back the pattern further west.

 

 

 

Maybe that's why the met keep leaving this line in their further outlook, it has been there for about a week now, so the chance must still remain:

There is a small risk of a cold easterly wind developing later in the month, which would bring very cold weather, and an associated chance of snow in places.

 

[chris55]

Flicking through the 6z GEFS it seems Thursdays pattern is far from nailed. A fair few members really ramp up that wave on Thursday turning it into a nasty little low, the intensity and track are very varied. 

There is a chance for some blizzard conditions on its northern edge if and when it lands. 

Therafter we have a slight trend to drop the lows further south east leaving us on the cold boundary once again.

these smaller details for our little patch are outwaying the global means etc in my opinion.

p4 even develops a channel!

the pattern for the end of the week has plenty of chances to come yet! 

[Tamara]

17 hours ago, TEITS said:

. I feel its our lack of understanding them and how they interact with each other that makes me dismissive. However my opinion is based on the teleconnections and not a personal snipe at the members who use them.

Finally the models already take these into account and supercomputers are far more capable than humans in my opinion. As someone on here once said "You cannot solve the unsolvable". that is perfectly apt.

I agree. This is precisely the issue

There is no problem at all with anyone (such as yourself) who is sceptical of the use of the GSDM/teleconnections based on the difficulties involved in deciphering, applying and then, harder still, communicating them.  This is quite understandable.

 I can relate to this scepticism because I used to harbour a very similar approach myself, and whilst I am certainly not trying to suggest everyone else should do so in some holier than kind of way, I decided to challenge my own belief and opinion by trying to read up on the technicalities myself. Like various others have also. So far, I've found the reward for a lot of "headaches" along the way  (as Karlos aptly refers to them) personally rewarding, even if there are, alas, small pockets of individuals who are hell bent on seeking to undermine and rubbish each attempt along the way.

Its not being a "know all" by any means (this is or *should be* a place for equal contribution), but the approach does provide a lot of extra perceptive insight that enables stepping away from the roundabout of each and every NWP output and offers an opportunity to formulate a forward thinking programme that attempts to be pro-active to evolution of weather patterns, and not reactive to them (each and every NWP output)  I know how tiring this can be, and am glad for the small mercies of no longer doing this.

So for the reasons described, I profoundly disagree with any charge that this is purely a hindsight based approach. It provides a means to both test forward thinking and then have the benefit of evaluating progress, or otherwise, moving forward. There is nothing either to prove or defend - the posts are there to read back for themselves, and are deliberately constructed as probabilistic weightings rather than definitive forecasts of "x will happen and y will not"

The net is a place for self learning first and foremost, so if one decides to test a methodology on a "live" platform voluntarily, then there sure is/shouldn't be an exam to sit to satisfy the needs of other members. Answer questions where (and if) possible yes - but somehow have to live up to loftily expectations of others ( a few who offer nada themselves except sniping whether blatant or subtley disguised ) then no way Jose, not at all.

So what is a huge problem, is using "scepticism" as a divisive and personally aimed tool. Echoes in some ways of the climate area with "believers and deniers" or maybe the serious discussion/political arena. This is classically characterised by a ramping up the "us vs them" tribal nature that is omnipresent through winter on this virtual platform through discrediting and seeking to more widely contaminate opinions of posters who use such methodology/ies (usually through an identified principle "spokesperson")

For what little it is worth, there have been summary posts made though this winter which have documented both the possible upsides and downsides of the pattern in terms of the tropospheric extra tropical and tropical jet flows (as the GSDM provides valuable insight into) vs the equal difficulties involved in anticipating stratospheric developments.

For those minority who richly suggest it is for those who provide an attempt to pro-actively contribute to somehow defend themselves, I would suggest that they read this, take as long as it takes to get some understanding, and then come back and "Discuss"....

http://journals.ametsoc.org/doi/full/10.1175/MWR3293.1

There is no obligation to do anything of course, but if that is the case, then desist instead, period, from attempting to flare up the over-machoistic tribal divisions of this thread through cynical attempts to discredit and disrespect one side of the perceived "divide". A divide which palpably doesn't exist in the real world of science and meteorology...

This is a weather forum - not football fan gang warfare....

@Steve Murr   The WDT site hasn't updated since the festive season so the latest AAM plots, which would be highly valuable to offer some update, are not available for follow-up at the minute. That is out of my control - its only possible to comment on the information that is available  - and this is well out of date. I've actually e-mailed WDT yet again about this.

However, the abundance of current (not hindsight) evidence that was/is clearly available as posted the other day suggests that the "pistol" is going to require a fair degree ammunition. Also that post did not promise snow - it simply highlighted (with a view to try and provide some optimism to the snow starved including myself) where an upstream forcing might come from.

I can't speak for any other poster who expected amplified higher latitude height responses in December - I only know that I posted my own reservations. But again, its not necessary for me (or them) to have to keep justifying themselves to you....

But this theme seems to recur year after year unfortunately

Not sure how noaa haven't invested in the GSDM when the two authors of the linked paper represented noaa itself and the organisation published AAM/GWO data until the author)s) left (!!?)

@Interitus It wasn't that long back that the research into the stratosphere and its effects on weather patterns (more especially in winter) were treated as something "mystic meg" even after peer reviewed scientific papers were published on it for quite a few years  Chiono and others had to deal with a lot of sceptical anti- flak in this respect and then it even became mainstream into METO and public domain. The SSW of 2009 played a huge part in this imo.

As an even newer area of research, the GSDM formulated by Berry and Weickman and published in 2007, offers further progressive and ground-breaking approaches to longer range forecasting.  The application of this method received a fair few fast successes within net weather and commissioned GP to his appointment (just by way of example)  It might be worth revisiting this type of discussion in another 5 to 10 years and then appraising its recognition within the world of science.

 

Edited January 7, 2017 by Tamara

[nick sussex]

11 minutes ago, karyo said:

Nick, that's the most promising chart I have seen from the UKMO in a long time.                                                                                                                                    The 12z ECM also has some kind of slider and the 6z gfs flirts with the idea but then flattens quickly.

Yes its a very good chart. That shortwave circled red would run se'wards. You can see if you flip between the T144 and T168hrs the direction of the ridge upstream would build further ne at T192 hrs and we'd see the ridge the furthest north of any of the outputs.

The forward projection of the UKMO is not too difficult to work out because we have very good agreement that the upstream pattern will eventually flatten out and the PV will start to head south to the west of the UK. As that happens if you have the ridge sufficiently north this will be pushed ne towards Scandi with that shortwave heading se and helping to feed lower heights over southern Europe. You can tell just how much more amplified the UKMO is upstream because the shortwave circled black started out from just north of the red arrow and heads se between T144hrs and T168hrs.

 

 

Edited January 7, 2017 by nick sussex

[blizzard81]

8 minutes ago, nick sussex said:

Yes its a very good chart. That shortwave circled red would run se'wards. You can see if you flip between the T144 and T168hrs the direction of the ridge upstream would build further ne at T192 hrs and we'd see the ridge the furthest north of any of the outputs.

It keeps a little hope alive I suppose but as you know,  the ext ukmo only seems to verify when going mild.  Let's hope it bucks the trend this time. 

[bluearmy]

I assume that the meto 30 dayers retention of the snowy easterly possibility is predicated on a cluster of members showing an SSW on glosea later in the month. 

that was the case either last winter or the previous one

 

[johnholmes]

An interesting post from Steve a page back. We have our differences at times and we each have our own method of trying to predict what might happen. It is good that folk with different views on how to produce a viable forecast express their views on here. It allows everyone to read them and make their own minds up, not which is right or wrong, but I hope to see just how complex meteorology is. As an ex senior forecaster with UK Met I continue to be amazed at the depth of knowledge and understanding from a number of folk on here. Over the years on this web site like everyone I have learned a lot, especially forecasting ideas beyond days 1-5. One has to remember that prior to computer models forecasting from basic physics, essentially fluid dynamics, was limited to 24 hours with the odd occasion when a reasonable outlook could be given for 48 possibly 72 hours. So without the computer 24 maybe 72 hours is where we would still be in all probability. Some empirical rules can allow, on occasion, this to be extended to 72-96 hours but not often. The creation of sites like this has generated huge interest and enthusiasm amongst those who have an interest in the weather anyway. Long may it continue.

Now to giving my ideas on the next 6-14 days ahead, and guess what I will use?

The latest anomaly charts for 500 mb have differences

ECMEF-GFS this morning

These changes in how   any Atlantic ridging and European troughing are of course the key to what the UK weather will be. EC again, but less so than the last day or two, show some ridging to the west with a flow from north of west into the UK and down into the European trough. GFS goes with the idea of the European trough being linked back to the main trough/vortex, north of Canada, and with the flow north of west into the UK. Thus the heights it shows are a fair bit lower than that from EC.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

NOAA last evening

It shows +ve heights again in the Atlantic and a somewhat flatter flow than either EC or GFS. There have been quite a number of changes on NOAA 6-10 since the end of last year. One of the biggest is the decline of the very large amplitude ridge just west of Alaska which almost disappeared completely and is now shown over the far east of Russia.

The differences between the 3 models  is, to a large extent, what we are seeing in the two main models (ECMWF and GFS) as each run comes out. Just how do the models deal with the ridge-trough set up? Pretty obvious that this is the key really you could say but others have commented on the further out ‘drivers’, teleconnections that can and do affect the 6-14 day time period. Whilst the anomaly charts are fine when used with CAUTION after a lot of experience, the cannot give the detail, and were never originated in the first place to do this, that the synoptic models show. Their purpose is to give a broad overall assessment of the most likely upper air pattern at 500 mb. In the old days we used to call this the level of ‘non divergence’ (see link below for a pretty good explanation of this). At this level it is, believe it or not, much easier to predict large scale changes in weather patterns and is a very good guide for the air mass(s) one can expect to be present through the forecast period. With lots of experience it is also possible at times to predict if certain fairly small scale weather systems are likely.

So to predict

The idea of a Polar Maritime air mass being more prevalent is a fairly sure bet (something the anomaly charts have suggested for 7-10 days). This looks more likely than an upper ridge with its attendant low level high close by the UK which would give mainly settled conditions. How deep any cold will be what most are looking for and can only be given by the synoptic models. It will be below normal temperatures for the greater part of the period and a 60-70% probability of short deep cold penetrations. The probability of much milder air at times is probably for the most southern areas ahead of lows developing the fairly strong upper flow across the Atlantic with the cold penetrations occurring behind the low. It might, note the word, even give a short spell of Northerlies. Beyond about 10 days then more probably still a coldish/near normal Polar Maritime westerly flow as the average.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

Level of non divergence link

http://glossary.ametsoc.org/wiki/Level_of_nondivergence

 

John

ps now I have seen the post from Tamara, I add her name to that of Steve, gawd knows how long it will take to read that Ref T but I will 'try', and even longer to start to understand what it is all about - but thank you for that link

Edited January 7, 2017 by johnholmes

[Bobd29]

16 minutes ago, Tamara said:

I agree. This is precisely the issue

There is no problem at all with anyone (such as yourself) who is sceptical of the use of the GSDM/teleconnections based on the difficulties involved in deciphering, applying and then, harder still, communicating them.  This is quite understandable.

 I can relate to this scepticism because I used to harbour a very similar approach myself, and whilst I am certainly not trying to suggest everyone else should do so in some holier than kind of way, I decided to challenge my own belief and opinion by trying to read up on the technicalities myself. Like various others have also. So far, I've found the reward for a lot of "headaches" along the way  (as Karlos aptly refers to them) personally rewarding, even if there are, alas, small pockets of individuals who are hell bent on seeking to undermine and rubbish each attempt along the way.

Its not being a "know all" by any means (this is or *should be* a place for equal contribution), but the approach does provide a lot of extra perceptive insight that enables stepping away from the roundabout of each and every NWP output and offers an opportunity to formulate a forward thinking programme that attempts to be pro-active to evolution of weather patterns, and not reactive to them (each and every NWP output)  I know how tiring this can be, and am glad for the small mercies of no longer doing this.

So for the reasons described, I profoundly disagree with any charge that this is purely a hindsight based approach. It provides a means to both test forward thinking and then have the benefit of evaluating progress, or otherwise, moving forward. There is nothing either to prove or defend - the posts are there to read back for themselves, and are deliberately constructed as probabilistic weightings rather than definitive forecasts of "x will happen and y will not"

The net is a place for self learning first and foremost, so if one decides to test a methodology on a "live" platform voluntarily, then there sure is/shouldn't be an exam to sit to satisfy the needs of other members. Answer questions where (and if) possible yes - but somehow have to live up to loftily expectations of others ( a few who offer nada themselves except sniping whether blatant or subtley disguised ) then no way Jose, not at all.

So what is a huge problem, is using "scepticism" as a divisive and personally aimed tool. Echoes in some ways of the climate area with "believers and deniers" or maybe the serious discussion/political arena. This is classically characterised by a ramping up the "us vs them" tribal nature that is omnipresent through winter on this virtual platform through discrediting and seeking to more widely contaminate opinions of posters who use such methodology/ies (usually through an identified principle "spokesperson")

For what little it is worth, there have been summary posts made though this winter which have documented both the possible upsides and downsides of the pattern in terms of the tropospheric extra tropical and tropical jet flows (as the GSDM provides valuable insight into) vs the equal difficulties involved in anticipating stratospheric developments.

For those minority who richly suggest it is for those who provide an attempt to pro-actively contribute to somehow defend themselves, I would suggest that they read this, take as long as it takes to get some understanding, and then come back and "Discuss"....

http://journals.ametsoc.org/doi/full/10.1175/MWR3293.1

There is no obligation to do anything of course, but if that is the case, then desist instead, period, from attempting to flare up the over-machoistic tribal divisions of this thread through cynical attempts to discredit and disrespect one side of the perceived "divide". A divide which palpably doesn't exist in the real world of science and meteorology...

This is a weather forum - not football fan gang warfare....

 

 

Applaud you for this Tamara. I am yet far from convinced that we have the technical ability to understand the absolute chaotic nature of our weather and the global ramifications for our little Isle, but the knowledge and dedication of yourself and others to pursue these links in an effort to close the gab must be recognised. This is a forum for enthusiasts of all beliefs, and it should not be used for personal attacks on those with contrary views. Keep posting, one day you may win me over, but I do not doubt your integrity....just for now I'm not convinced by the argument.

[Iceaxecrampon]

1 hour ago, Polar Maritime said:

Purely an observation for the up-coming cold spell as there will be many more macro differences over the coming days of interest... But the 6z shows a much better chance of snow further South.

00z was good - but the 06z really  has delivered -  what a run.

Can we draw any comparisons to Dec 2010 on this basis or was it indeed a once in a generation event?

Keep calm - iceaxe not being sharpened yet.

[mcweather]

Superb post Tamara. It should be remembered that any synoptic output that we can view is governed by the interplay of the various global and regional parameters and drivers (MJO QBO Tropical convection and many others)  Longer range forecasting is necessarily based on trying to work out what weighting to give these various players in any given situation or as shown last year will one be so dominant as to negate any kind of weighting given to others.

Those who try as you gp and others do to understand these and give some kind of guidance as to the POSSIBLE  broadbrush synoptic outcomes should not be derided or put into some kind of us and them situation because that lowers the level of the debate in this often brilliant thread to a level unworthy of us all.

It is all about learning  and hopefully learning together so that our understanding can help us recognise which synoptic developments to take seriously and which not to, thus eliminating a lot of stress each winter.

 

 

Edited January 7, 2017 by mcweather

[karyo]

24 minutes ago, bluearmy said:

I assume that the meto 30 dayers retention of the snowy easterly possibility is predicated on a cluster of members showing an SSW on glosea later in the month. 

that was the case either last winter or the previous one

 

That was up to yesterday's update. Today they have dropped the mention of an easterly.

[damianslaw]

Strong consistency continues in today's models for the reliable timeframe, all showing a potent PM airstream come Thursday (edge of reliable at this stage). Differences thereafter between ECM and GFS, as there has been for a few days now, ECM doing what it tends to do - maintaining a more amplified flow, GFS a flatter flow, more often than not, something inbetween tends to occur. However, notably UKMO is the most amplified.

My own thinking is we will maintain a flow predominantly from between west and north in the 6-12 day timeframe, trending from NWN to WNW in time, temperatures below average in the main,but returning to nearer normal especially in the south, with Scotland always exposed to further wintry episodes. 

There are major changes taking place over the N Pacific, the ridge is about to be replaced by a trough, and consequently we see major ridge/height rises over E Asia - this could have an impact on the strat/trop profile, perhaps some warming on the Asian side which would lock the PV in place on the canadian side but also weaken it as we enter Feb, any further amplification could help promote the chances of mid atlantic heights eventually building NE thanks to warm air advection through Greenland.

Edited January 7, 2017 by damianslaw

[SMU]

Just to add in from the earlier post- theres no derision of people inc @Tamara or @GP or anyone - more persuit of something more reliable...

From what I have personally seen over the last 10 years the discussion is great all high level - but the bottom line remains is that underpinning the probable impossible task of deciphering the weighting to throw towards any 1 set metric there is also the very real issue of changing climate paradigms - where due to the speed of our climatic change the weighting of cause & effect you give one year may well hold less weight The following year- ( or more ) add to that the 'unknown' factor

to quote

"As we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know. "

The reality of the climate is there are to many unknown uknowns...

If we was working towards one solution where we finally worked out all the answers out then yep that would be worth chasing however not only do we have a multilayered problem to solve - that multi layed problem is now revolving in an ever increasing ripple of change- in terms of the forecasts I have seen based alone on T/Cs ( & note this isnt an attack on anyone as what I have forecast before hasnt worked out ) but the reality is they have been poor & less reliable than some of the climo models -

- The front loaded winter- burned in 4 days- why due to ' unforeseen change'

- Look how many differing conflicting teleconnective  tweets we have seen this winter via twitter- that never landed due to 'change'

- GP's posts all through Dec - expect high lever ridging NW to greenland soon due to fast changes in the indian ocean- that all burnt due to 'change'

- Glosea dec strat forecast & High lattitude forecasts - never landed once due to 'change'

-@Tamara you said last week 'quite positive' your were waiting for the GLAAM pistol to be fired - well were still waiting for that -yet we are looking at the coldest spell of the winter with a possible reload from the NE - yet the pistol hasnt even fired...

like I said above im not hear to discredit people - this is about how reliable a method is & from the perspective I see it is very low - & its unsurprisingly TBH. if there was more accuracy involved, or indeed more accuracy expected down the line then there would be more investment from the Met / NOAA / NCEP etc.

At very best broadbrush scenarios for the globe can be painted which for us with *potential* for a scandi ridge is totally meaningless in terms of the ability to forecast it...

 

have a good one

S

PS

Edited January 7, 2017 by Paul

[Severe Siberian icy blast]

24 minutes ago, Steve Murr said:

Just to add in from the earlier post.

Fantastic post Steve. I personally really appreciate everyone's efforts on here and Tamara always does very well reasoned posts based on genuine meteorology and makes opinions based on science behind it but the weather makes mugs out of all of us and it really makes us all realise that we are only stil in infancy stages of truly knowing what the weather does and why. It's great trying though but the winter has so far been a complete wild card and continues to be so. 

Edited January 7, 2017 by Polar Maritime
To snip long quote.

[jonboy]

1 hour ago, Tamara said:

I agree. This is precisely the issue.

Excellent post Tamara

People forget computers etc only work on the information given to them and then decipher that information given a set of what if's and why for's so they are only as good as the programs themselves.

It is therefore vitally important that we then are able to interpret what outputs are achieved if we don't we can't improve the said programs. In my own mind I believe we are in a new era especially inregard to our atmosphere in that we are may have modelled certain aspects and thought we knew consequences but we have never been in such a rapid slow down of a solar cycle and as such we don't fully understand how therefore our atmosphere will react. I liken it to slowly turning down the heat on a pan of water over say five or ten minutes until the heat is off the water takes time to cool this cycle is like taking that pan of boiling water taking of the heat and putting it in a fridge

For me we are in a transition phase to a time when we will see greater and greater High Latitude Blocking

 

Keep up the excellent posts Tamara

Edited January 7, 2017 by Polar Maritime
To snip long quote.

[Methuselah]

1 minute ago, jonboy said:

Excellent post Tamara

People forget computers etc only work on the information given to them and then decipher that information given a set of what if's and why for's so they are only as good as the programs themselves.

It is therefore vitally important that we then are able to interpret what outputs are achieved if we don't we can't improve the said programs. In my own mind I believe we are in a new era especially inregard to our atmosphere in that we are may have modelled certain aspects and thought we knew consequences but we have never been in such a rapid slow down of a solar cycle and as such we don't fully understand how therefore our atmosphere will react. I liken it to slowly turning down the heat on a pan of water over say five or ten minutes until the heat is off the water takes time to cool this cycle is like taking that pan of boiling water taking of the heat and putting it in a fridge

For me we are in a transition phase to a time when we will see greater and greater High Latitude Blocking

 

Keep up the excellent posts Tamara

Which, in turn, are only as 'accurate' as the inherent chaos in the equations will ever permit?

[Guest]

2 hours ago, Tamara said:

I removed to save repetition

 

@Tamara100% spot on as usual and extremely well put. As several others have already said, if one criticises the use of teleconnections, one is criticising the models themselves, rendering this model thread completely pointless and those people may as well go back to using 24 hour forecasts. As @johnholmes puts across so well, he has lived and worked through a period of huge advances in this fascinating science such as the use of computers, satellites, advanced modelling as well as understanding the teleconnections. These are now all built into the various forms of modern forecasting..Like the vast majority on the MOD, I only have a limited understanding of part of the teleconnection science but it is enough to see how they play an increasingly vital role in the model's output. As Tamara says, it should not be an us vs them on this thread and I have attempted to address some of these issues in each of my last few weekly reports. So, please do not let your emotions cloud your judgement and opinion. I will certainly find the time to read through the paper that Tamara links us to and anyone who feels the need to comment on the relative benefits (or lack of) of teleconnections should only really do so from a better informed knowledge base. Finally, let's all make an effort to respect each other and their opinion. Any constructive comments are to be encouraged.   

Edited January 7, 2017 by Guest
A vital should "NOT" has been added!

[Polar Maritime]

OK back to discussing what the Models Outputs are showing please before the thread really goes off the rails..

Thanks..

[Interitus]

1 hour ago, Tamara said:

For what little it is worth, there have been summary posts made though this winter which have documented both the possible upsides and downsides of the pattern in terms of the tropospheric extra tropical and tropical jet flows (as the GSDM provides valuable insight into) vs the equal difficulties involved in anticipating stratospheric developments.

For those minority who richly suggest it is for those who provide an attempt to pro-actively contribute to somehow defend themselves, I would suggest that they read this, take as long as it takes to get some understanding, and then come back and "Discuss"....

http://journals.ametsoc.org/doi/full/10.1175/MWR3293.1

There is no obligation to do anything of course, but if that is the case, then desist instead, period, from attempting to flare up the over-machoistic tribal divisions of this thread through cynical attempts to discredit and disrespect one side of the perceived "divide". A divide which palpably doesn't exist in the real world of science and meteorology...

 

Interesting that Google Scholar only lists 7 references for "Global Synoptic Dynamic Model", 5 of those from Berry+/Weickmann, which suggests that with regards to the GSDM framework, the real world of science and meteorology hasn't exactly picked up the ball and ran with it, just saying.

[Gustywind]

From what I've seen over the years, if key parameters point to a mild winter, e.g. Last years super El Niño, a strong La Niña or it's clear by November the polar vortex is stronger than average, then the winter forecast is fairly simple. Almost certainly temps above average and rainfall above average. Last winters forecast for example was pretty easy - super El Niño, supercharged polar vortex = wet, stormy and mild.

The tricky bit is when the above factors are mixed or unclear, making potentially colder conditions more likely. A forecast for an area as small as the UK becomes very difficult in these circumstances. I admire people who give it a go, but the majority end up wrong as it's just too difficult for the reasons Steve stated.

The best forecast on here I've ever seen (in over 10 years of lurking) was GP's 2010-11 forecast, when he correctly called the Dec 10 cold spell and then accurately in terms of dates, called the end of it and switch to mild. It was an incredibly accurate forecast given the strong El Niño conditions, which led most other long term forecasts to predict mild. 

[Cheshire Freeze]

5 minutes ago, Gustywind said:

The best forecast on here I've ever seen (in over 10 years of lurking) was GP's 2010-11 forecast, when he correctly called the Dec 10 cold spell and then accurately in terms of dates, called the end of it and switch to mild. It was an incredibly accurate forecast given the strong El Niño conditions, which led most other long term forecasts to predict mild. 

2010/11 was a La Nina winter was it not?

[nick sussex]

I'm wondering whether the outputs are reading the MJO signal slightly differently. As it is the MJO is weak at the moment. Matt H mentioned this is going to be in phase 5 however the MJO forecast  which tries to remove interference has this about to enter phase 6 and stay there for around a week.

It's of course questionable just how much impact this might have on us in western Europe given its low amplitude however phase 6 normally adds some amplification to the Atlantic.

The actual composites can be rather rigid tools because what ENSO is doing at the time needs to be taken into account, currently we're in a weak La Nina with this declining towards neutral values.

If we take it that the MJO is in phase 5 and could go into phase 6 depending on which forecast you use the research suggests this:

Phase 5 is associated with enhanced trough anomalies over the North Atlantic extending across north-central Europe, and across parts of eastern Asia, with substantial significant ridge anomalies over western Russia. Phase 6 is associated with enhanced trough anomalies over far northwestern North America and parts of East Asia, with significant ridge anomalies over the North Atlantic and parts of interior Europe.

Interestingly if you follow the ECM on the NH view you'll see a pretty good correlation with the above although it makes less of that ridge anomaly in the North Atlantic.

Again though we are dealing with a low amplitude MJO signal so this is likely to mute out some of the trop response and of course there are other factors to take into account.

PS If you were just using the standard MJO composite this doesn't show that strong ridge anomaly in western Russia,  you might conclude that the NH pattern is more closely following that research which  looked at not just whether you were in say El Nino or La Nina but more importantly were they declining or advancing and the different impacts that could have on the NH pattern.

Edited January 7, 2017 by nick sussex

[Gustywind]

39 minutes ago, CreweCold said:

2010/11 was a La Nina winter was it not?

Sorry Crewe yes your right, 2009-10 was the El Niño year.

Edited January 7, 2017 by Gustywind

[Summer Sun]

Friday into Saturday London hits 16/23 on the snow row

So around a 70% chance of snow in London based on the 06z

At the same time, Aberdeen peaks at 13

 

[Methuselah]

I've been wondering again:

Are the teleconnection forecasts separate from the 'ordinary' models or, are they constructed using the very same starting data? If they are related thus, won't they be subject to exactly the same degree of uncertainty? Why would, for instance, a GFS-based MJO forecast be any more (or less) useful than other GFS products?

These are genuine questions, and are not a nit-pick.