Winter 2023/24 - A Post Mortem

[Cheshire Freeze]

 bluearmy Yes. I feel sorry for the cold chasers…wasn’t too bad for me because I mentally checked out in early Jan with the failure of the split SSW.

It was painfully evident to me that we needed that.

[reef]

 North-Easterly Blast Sorry, but the cold September = cold winter theory is just total nonsense. The coldest September of the last 30 years was 2015 with 12.7C on the CET and it was followed by the mildest winter in the series. 2013 was also below average and we all know what followed that.

The idea that a 30 day period we choose to call a month has any reliable bearing on what happens months later is thin to say the least. The fact is, most months are warmer than average now  and getting just one below average is difficult so regardless of what September does it'll probably lead to a mild winter.

Edited February 10 by reef

[Chesil View]

An interesting discussion of ideas and thoughts from Matty H. Tamara and Nick F.  

I think perhaps what those not familiar the Gsdm tools might  be missing and therefore reacting to when things don't come out to give us the emotionally invested result of deep cold or snowfall. Is that like many other forms of science. These tools are also a work in progress in terms of learning and attainment of results.

Tamara to her great credit has often made the point that A plus B doesn't always equal C in this subject. Which can perhaps to the uninitiated seem counter intuitive when describing something as a tool.

It could be argued that if you have a tool like pair of pliers for instance and A is the pushing together of the handles which helps to produce B the bringing together of the grips then surely if the grips don't then grab the object your trying grip (C) then that pair of pliers are a pretty useless tool. And often the answer that comes back as to why the pliers didn't work was because the chisel wasn't on the workbench as well  can often just sound like a get out of jail free card.

But the ocean/ atmosphere is so massively dynamic on both horizontal and vertical levels that the simple analogy of the pliers not working is just too simplistic to cover all the nuances and small alterations than can make a huge difference to our tiny corner of the globe.

Surely both nwp and gsdm tools can as Tamara out points be complimentary. My own feeling as very much an amateur trying to understand the nuances of both is that gsdm is not there to tell us if its going to snow in our back yard or country or region. That's nwp's job

Moreover its main use as I understand it at the moment within its current limitations is to give probabilities around which regime in terms of global placement of ridges and troughs  may  predominate and thus the likelihood of which weather/climate regime may be likely to hold sway over a  an area of the globe  at a given period  even a month or more  hence. (I hope I'm not doing it a disservice.)

In conclusion niether nwp or gsdm are the finished article in terms of perfect results ( and indeed may never be)  of what many winterwatchers seek and are to a greater or lesser extent somewhat emotionally invested in.

On a personal note I'm just extremely grateful to have access to the wealth of knowledge from those of both nwp and gsdm schools available on this forum and have huge respect for both.

 

 

 

 

[North-Easterly Blast]

 reef I never thought that it was clear that a cool September had any bearing on the following winter's weather.  I think, and have only ever thought that the theory only worked one way, that only warm Septembers have an effect on the following winter's weather, whereas I have never thought that there was any trend with a cooler or even near average September and the following winter's weather.  The records show that it is clear that whilst it is not unheard of to get a milder winter after a cooler or even average September, it is very rare if not unheard of to get a cold winter after a warm September.

It is certainly true to say that if you want cold weather in the following winter, then you do not want to see anomalous warmth in September, otherwise you can almost guarantee that it is bad news for cold weather in the winter to come, but if September is cooler or even average then it does make a colder winter to follow more likely, but it does not guarantee it by any means.

Edited February 10 by North-Easterly Blast

[Snowyowl9]

 Don

Winter 1974/75 although february was cooler..

What about 1987/88 winter is my bog standard for poor winter..

[Met4Cast]

2 hours ago, Nick F said:

If the GDSM is such a great tool, how come it's no longer available from NOAA. Or anywhere else. Met Office don't mention it publicly but do with all other drivers including MJO. There's no substantial evidence or papers that the theory is water tight and certainly with confidence can anyone attribute to AAM influencing weather patterns over N Atlantic.

We can't question those who make these predictions using GDSM because we don't have to hand archive charts, verification stats and any access to such data

The lack of data available is something that is irksome, more data is always a good thing but the AAM remains limited both non-public & public. 

I don’t know why NOAA shut down the page but I presume funding was a big part of the decision & a lack of someone to take over and continue the research. EDIT: It seems copyright was a big part of the reason when Ed Berry retired from NOAA, see Tamara’s post below

The Met Office however do use the AAM internally, mostly for the contingency forecasts but do occasionally use it for the extended forecasts that appear on the front page of the Met site, the GSDM is obviously very complicated so i’m not surprised they don’t mention it, they probably prefer to simplify it & discuss the MJO for example instead, something relatively easy to explain vs frictional & mountain torques and even then, it’s only in recent years the Met have begun to talk about drivers such as the MJO, they never used to. 

In terms of evidence, there is plenty of scientific papers on the subject if you google it, including papers from Met Office scientists. 

https://www.psl.noaa.gov/map/clim/wb2007_ams.pdf

And this from Met Office scientist Adam Scaife 

Long-range predictability of extratropical climate and the length of day

IDP.NATURE.COM

---

Ensemble forecasts from a dynamical model suggest that fluctuations in atmospheric angular momentum and the length of day can be predicted over a year in advance, thereby...

Mountain Torques and Northern Hemisphere Low-Frequency Variability. Part I: Hemispheric Aspects

JOURNALS.AMETSOC.ORG

---

Abstract The NCEP–NCAR reanalysis dataset for 1958–97 is used to analyze intraseasonal variations in mountain torques and the large-scale atmospheric circulation patterns...

There are many, many papers written about the topic & as I mentioned previously a huge extensive list of them was on the 33andrain forum but that was sadly lost. There was a thread on this forum dedicated to AAM/GSDM but it wasn’t particularly popular unfortunately, but here are a couple of threads that might be useful for those wanting to try and gain a better understanding. Indeed, Glacier Point relied heavily on the GSDM for the often very accurate Netweather seasonal forecasts, it’s a shame he no longer does them. 

 

Edited February 10 by Met4Cast

[Tamara]

 Nick F

The availability of the data has been already answered in most part with the references to Ed Berry etc & his rights to his work. He retired and took those rights with him. Hence NOAA no longer published them at his request. NOAA did not stop publishing the data due to some lack of credibility as you appear to want to imply.

Many have been on this site, or referenced it long enough, to know that the GSDM has been sourced for analysis since at least 2007/08.  Glacier Point pioneered it for Net Wx with much success in its use. So much so that it led to his further employment opportunities with Centurea weather, where he was appointed a head forecaster using the GSDM as the forefront of forecasting.

The names (implied) under criticism in this thread are just some who have aspired to try and get their heads around the complexities of the science. Difficulty in understanding does not equate to lack of credibility or simply tossing under File 101 as gobbledy-gook.. Quite modest, very ordinary amateur enthusiasts have taken the challenge, very much including me. so not really any excuse for anyone thinking somehow they are treated as also rans by being left out from the GSDM data sets. If the will and enthusiasm is there, then it is open to be studied. 

The fact there is now a mix of both pro-Mets and amateurs across UK, mainland Europe and US who engage the GSDM methodology is testament to its credibility. I can see, therefore, why a pro-Met like Matt H might feel a little peeved as he made the effort to engage the GSDM diagnostic and include it in his professional analysis.

As for the METO, they have actually made enquiries about the GSDM on a private basis to some Net Wx and also US based forum members and there has been a background inspection of the diagnostic which includes recognition of angular momentum processes in the role of inducing jet stream pattern changes. I know this for a fact - but cannot be expected to answer to their actual decisions on whether or not they would be inclined to engage the methodology formally & officially but then again, it is the copyright of a late NOAA official and have no idea of the protocols etc involved in this.

Whichever way, its a bit disappointing to say the least to be trying all these rather confected avenues as means to discredit GSDM analysis as some kind of over hyped mystic meg thesis.

Especially bearing in mind what seems to have triggered this particular pique and GSDM bashing is some unbridled dissatisfaction with a UK winter! You yourself have employed some of the related teleconnection aspects in your (well laid out) forum seasonal forecasts. So with respect, it seems to be rather a contradictory position to take to your own efforts. 

As for papers on GSDM there is a wealth of them. Including references to them on this site.  There has been at least one dedicated thread in recent years to compiling a library of information on this very site. It took me a few years from about 2014 when I decided to take a big interest in this diagnostic to get my head around quite a bit of it. But just reading the in depth discussions between 2008/9 and about the time I started to try to get involved with learning about it, it was surprising how rewarding it was when some understanding started to click into place. Like chionomaniac and the strat threads also in the late 2000's, other have got inspired in this way.

Edited February 10 by Tamara
Edit : @Met4Cast has added related information

[Addicks Fan 1981]

 Cheshire Freeze there must be other variables that have got in the way with the SSW and I'm thinking sunspot activity has some bearing.   We are veering towards solar maximum and the forecasters are pointing towards the peak being sooner rather than later.    

[Methuselah]

 Tamara IMO, it's such a shame that all some peeps want to do is blame someone else. . . It's obvious that, despite the veracity of teleconnections, other confounding variables are at play here: our climate is being put under increasing pressure by GHG emissions, so is getting ever more difficult to predict?

I am not about to 'shoot the messenger'! 

Edited February 10 by Methuselah

[raz.org.rain]

 Addicks Fan 1981 the role of sunspot activity is contentious as far as I know. Much like ENSO's theoretical impacts on Europe's climate, there's evidence that supports and goes against the theory of sunspot activity having an influence on our climate. Inevitably we'd have to consider how such an influence would be altered by anthropogenic changes such as the imbalance of heat loss exasperated by heat trapping elements.

[Nick F]

 Tamara That doesn't doesn't give the excuse to be condescending for those that question the GDSM tool. How can it be verified that AAM is implied in more likely being responsible in creating certain patterns and not other drivers? Which begs the question how can you and others be so confident? 

Again, it feels like closed doors to those to question the tool's validity for fear of being shot down because they don't have the hours of learning the subject and all the GDSM updates to hand to draw on to be able to question a prediction. 

I don't doubt that GDSM has It's place, but many of your posts seem mostly centred on the evolution of AAM to make predictions and not talking about other drivers and persuading the reader to disregard model guidance. Then when patterns do not evolve how you suggest, there is no admittance by you why it didn't play out how you predicted.

 

[stewfox]

How do you have a post mortem of winter on 10th Feb ? . End of March for me

[KTtom]

 Nick F Thats a shame, I find this thread truly fascinating in that we can have a good old fashioned debate without it occurring on the MOD thread with various posts going AWOL. 

FWIW im sure the members are 50/50 split on this, personally im in your court. 1 thing is for sure, no matter what your knowledge on x, y and z. It hasnt helped anyone in forecasting our weather over the last year or so..March 2023, August 2023 and this winter are ones that jump at me.

No issues with how strongly people feel about whatever tools you use, but again agree with Nick, some need to work on how they come accross.

Need a similar thread next year.. hopefully not a post mortem one tho.

Edited February 10 by KTtom

[Metwatch]

Another thread here found the other week, although there is a lot of information, can pickout some useful things, mainly from someone named "guest" or David, not sure who that is though, maybe David Gold?

 

7 hours ago, Derecho said:

If we are to see colder winters again though, changes in ocean circulation are required IMO to overcome the expansion of the Hadley Cell. 2009 and 2010 show it is still a possibility.

I'd be interested in knowing more about how the ocean circulation impacted those colder winters in the UK, as a result of increased northern blocking between 2008 and 2010, but I guess other factors like favourable MJO progression and the AAM were important too. Maybe a weaker gulf stream or AMOC? Winter 2009-10 had mod - virtually strong Nino, while 2010-11 was strong Nina, but that doesn't really tell me much on their own.

Edited February 10 by Metwatch

[mountain shadow]

 stewfox Winter runs from December to February and always has.

Whilst March may produce the goods, that is Spring.

So, unless there is some miraculous change in the model output,  there will be no proper cold for the rest of the month and therefore Winter.

[TEITS]

My advice for next winter especially to any newcomers is this.

Do not rely on one forecasting tool i.e model output, or teleconnections. Use all that is available in the following order Model output, ensembles, teleconnections, Met O. If these are all suggesting a similar outlook then take note. However if the teleconnections are suggesting an outlook which isn't supported by the models, Met O etc then in my opinion be very wary. The same applies to using the other methods in isolation.

You also have additional information like the seasonal models, seagulls, seaweed, Berries on a bush, Daily Express, a medium, If you are that desperate then maybe Exacta Weather!!

 

 

[Weather-history]

 reef

Supporters of this, see the data and think that is suffice, they never offer a possible reason why this would be so . Well that is not how science and knowledge advances.  Time to offer theories to why this would be. 

[Met4Cast]

1 hour ago, Nick F said:

Then when patterns do not evolve how you suggest, there is no admittance by you why it didn't play out how you predicted.

Tamara has, in fairness, on several occasions this winter discussed what went “wrong” in terms of the pattern changing vs expectation, as have I, Catacol & various others in the Model Output Thread. 

[Derecho]

 Weather-history

It goes back to the correlation does not equate to causation argument. I can't see how a pattern several months beforehand can lead to something several months later at our latitude.

In the tropics we get some monthly persistence with the likes of ENSO but that's as good as we have right now.

One thing I have noticed since the 2010s is that when we get an Atlantic dominated period, it tends to be associated with high pressure over Spain rather then the Azores. This means rather then a mix of mild and chilly westerlies with a northerly toppler or a ridge never far away. Now it's just endless days of SW'ly winds with a pattern hard to shift once it sets in.

I also think the west-east progression of low pressure systems is slowing down and patterns get stuck for longer.

I wrote a similar post mortem for winter 2018/19 and I still have those same beliefs now. I do think at some point we will shift to a bunch of blocked winters but we are living in changing times.

 

Edited February 10 by Derecho

[Tamara]

 Nick F

This is my last response on this subject as your latest resply tells me you didn't read the (albeit very brief) explanation about wind-flow, torque, angular momentum (and what it means in parlance of weather patterns)

. It should be clear from that, that the jetstream is influenced by the basis science of what causes acceleration of momentum, or conversely, deceleration of momentum in the atmosphere and a background to the waxing and waning & movement of cyclones and anticyclones across the globe. It might be technical in its GSDM  data sets with a lot of acronym speak, but it is actually in truth a basic starting point for getting a structure of the global patterns. If it is not understood what influences basic jet stream patterns,and also the cyclical nature of teleconnection phenomena (which is another part of the equation) then how can any of the other drivers be placed in the jigsaw?.

I am more and more convinced that if this winter had produced more widespread and sustained snowfall this thread would never have been triggered. I resent being implied as some kind of cherry picking soothsayer and equally that there is some arrogance about being right and not admitting errors.

Why is it my responsibility to be held account for the lack of desired winter weather? I have produced continuity analysis throughout my more recent years on this site, for the very purpose of being transparent. In an effort to stand up for myself, I am going to say that these continuity analyses have left little room for conspicuous error and so the latest charge of yours of not admitting any error is deeply untrue, unfair & unreasonable and I am not going to stand for it. And yes this is defensive, and yet you winder why!...

I have not been paid to contribute anything on this site, and while we all (including you actually!) make mistakes, none of us, including me (though sometimes I wonder!) have any particular obligation to be apologist to anyone.

 

It just so happens that I have been pro-wintry weather patterns for this particular season. The truth, which I am not going to be pressured into conceding on, is that very fine lines have driven the outcomes of this winter. It *should* have been, or it should be, a spectacle of interest and discussion as to outcomes and not a scapegoat seeking exercise for those, like you, who want to vent their frustrations onto other people.

As far as I am concerned the present evolution of the pattern between troposphere and stratosphere are playing out accordingly to expectations. Feel free to go pick out the recent summaries and dismantle them to pieces if you wish. Tropospheric +EAMT pathway in tandem with eastward propagating tropical convection triggering rossby wave perturbing of the stratosphere ( upcoming) and amplified state mid latitudes. Now, what that means in respect of cold air advection to mid latitudes, and where, remains uncertain and there are complex and somewhat countervailing aspects of fluxing between the stratosphere & troposphere- but it does NOT debunk the GSDM mechanisms which have played a part, already, in creating the evolution of the pattern underway.

 

Edited February 10 by Paul

[Met4Cast]

1 hour ago, Metwatch said:

Another thread here found the other week, although there is a lot of information, can pickout some useful things, mainly from someone named "guest" or David, not sure who that is though, maybe David Gold?

 

Just skimmed through the first few pages, this thread is a fantastic resource for those wishing to learn more about the teleconnections/drivers of our weather, including the GSDM, AAM/GWO/torques etc. 

“Guest” is “Bring Back 1962-1963”, not David Gold but a different David. Wonder why his username isn’t showing? 

Regardless, @Nick F& anyone else who wishes to delve into things more, this is a good starting point. 

[Paul]

 Met4Cast

This is another good resource

And more generally

https://community.netweather.tv/learning/research/

 

[Paul]

Just for the avoidance of doubt, this thread was started by the team, splitting out posts which had been made in the model thread, which would have taken it way off topic.

Obviously as a 'post mortem' it's somewhat premature, but since there's obviously some appetite to discuss this now, it's better to have a thread then have those discussions spread about elsewhere.

The purpose of it is not to have it turn into a name calling session or some sort of blame game. The aim is for it to be a place for some reasoned discussion on this winter, along with the forecasts, models and teleconnections during the season, so we can hopefully learn more about them and understand where, how and why things have gone both right and wrong with them all.

There's already been at least some of that, so hopefully that theme can continue and we can have a constructive, useful debate. 

 

[Derecho]

For those who are intrigued some interesting MJO periods from the past. For each cold month the key analogues for the most amplified phases during that month.

Oct - Dec 1981. December 1981 phases 5 and 6

Jan - Mar 1985. January 1985 phases 8 and 1

Feb 1986 phases 8 and 1

Jan 1987 - Phases 2 and 3

Feb 1991 -Phases 5 and 6

Dec 1995 - Phases 7 and 8

Feb 2005 - Phase 6 and 7

Jan 2010 - Phase 7

Phase 4 and 5 - Dec 2010

Feb 2018 - Phase 7, 8 and 1

A pretty good record there. Maybe not for Dec 2010 or Feb 1991 though. A lot of the times 'it failed' were because people read the composites incorrectly or assumed it would go into a favourable phase when uncertainty was high.

No way are they bulletproof but they were just a tool to examine whether we could get out of a SW'ly rut and it did pretty well. To say it's something used by snake-oil salesmen is pretty harsh against the academic research that has gone into it.

Edited February 10 by Derecho

[RJBingham]

Well, I appreciate the time and effort people have put in regarding the teleconnections, I'm sure you must wonder why you bother sometimes.