Met4Cast

February 12

Worth noting that the May SST link with the following winter was largely debunked & is no longer used by the Met Office as an NAO predictor!

With that though you could see the thinking, i.e SST’s do have impact on the NAO to some extent.

Is the opposite true? Do cold Septembers correlate to cold winters?

February 12

23 minutes ago, Severe Siberian icy blast said:

Background signals have been misinterpreted and the significance of EAMT events working in tandem with the MJO has not been impacted like anticipated, we can point towards the strat warmings for "ruining" things but i don't buy that either.

Haven’t they?

The recent +EAMT & more broadly strongly +ve MT event is one of the reasons we will be seeing a major SSW next week.

Rossby wave packets generated in part due to momentum being deposited directly into the Pacific jet & causing the jet to extend eastwards have allowed for significant heat flux into the stratosphere to finally deliver the knock out punch. Indeed, Tamara mentioned this likelihood a couple of weeks ago and now we’re seeing it play out.

The strongly +MT was signalled quite a while ago as the MJO progressed through the Maritimes & into the Pacific generating strong +FT, MT always follows FT.

In terms of the MJO not impacting as expected, the above is an example of an anticipated consequence of the MJO, the reason we’re not currently seeing blocking despite favourable MJO is because the MJO cannot & should not be used in isolation. Here’s something I posted back on January 22nd:

Quote

What did previous look like a good chance of sustained high latitude blocking during February is rapidly fading.

Despite an increasingly favourable MJO signal into the western Pacific, we’re missing a vital ingredient & that’ poleward propagating +AAM (westerly momentum).

Unfortunately, this time +AAM is increasingly glued to the equator & we’re not seeing this fluxing towards the pole, this helps (despite the MJO) to inflate the European ridge & indeed, a very strong signal for this within NWP through the remainder of January. A flat, mostly mild end to the month with low pressure systems deflected northwards, potentially stormy at times for Scotland.

So actually, this has been rather well sign posted for a couple of weeks now & those of us that subscribe & try to apply the GSDM framework have spoken about this likelihood a few times.

February 12

5 hours ago, North-Easterly Blast said:

I do not think that it is clear that there is any trend between October or November as to the sort of winter that follows, or it is certainly far less clear cut than the warm September = mild winter theory.

It’s not “clear cut” that a warm September = a mild winter either looking at the data shared in here by others.

I think there’s some conformational bias going on here, in a warming world each individual month is more likely to be mild & as such, a mild September may well be followed by a mild winter because mild winters are far more likely these days.

It doesn’t mean there’s a link and the evidence isn’t strong enough to show that there is.

What are the mechanisms? Why does a warm September = mild winter? What drives that? What are the feedback loops that cause it? You have to demonstrate & show a positive feedback loop which influences weather patterns, otherwise it’s not helpful, useful or demonstrable.

Edit: Just read the rest of the thread, I see @Mike Poolemade the same point re: climate change.

February 12

41 minutes ago, TEITS said:

The output this morning is just typical of this winter so far. The 12Z ECM last night gave a glimmer of hope which has quickly faded in the following run. Now the only sign of any cold is the last week of Feb but at the moment that looks more like a cool NW,ly than a bitter N/E,ly.

This winter has been very strange. The model output has been inconsistent, poor ensembles, unsuccessful teleconnection predictions, Met O have been predicting cold N/E,lys since mid Jan!, seasonal and longer range models have been useless.

Obviously something else is causing all these failed predictions. Problem is finding the cause can be just as difficult as making successful predictions. You cannot make future successful predictions until you understand the cause.

Indeed, no surprise to me that modelling hasn't continued with the build of heights northwards yesterdays UKMO/ECM signalled. I do think the GFS is being too progressive with the Atlantic still though & suspect we'll end up closer to a UK high, this mornings ECM probably a good fit.

I think any amplification could come towards the end of the month/into early May but unlikely to see anything of interest re: proper cold/snow before then. It has been a very odd winter, the MetO have done rather poorly with the long-term forecasts. The SSW remains the wildcard & partly the reason there's some hope towards the end of Feb, ensembles certainly show a cooling trend albeit mostly from a Scandi trough again rather than any substantial blocking patterns.

Very odd year.

February 11

Maybe the SSW will bring an early spring instead..

Horrific!

February 11

I often find the NAEFS to be quite a good guide for the broader evolution of the pattern, it's the GEFS and GEM ensembles combined.

This currently suggests steady as we are out until the 19th with the pesky Iberian heights making themselves known.

Towards the end of the month, and perhaps more broadly it signals a trough returning to Scandinavia, perhaps introducing colder air as a result but still not exactly blocked. Perhaps something similar to the recent colder spell, i.e Scandi trough led rather than blocking led.

In any case - It's currently difficult to make an argument for widespread cold/snowfall, if anything that remains a very low probability looking at NWP modelling. It becomes perhaps even lower when factoring in the teleconnections, despite an up-coming major SSW.

Lets hope for some changes in the coming week.

February 11

Derecho

On 10/02/2024 at 10:57, Derecho said:

It's an interesting response but the winter months of 2010 saw the complete opposite. Warm air often moving into western Africa and southern Spain with anomalous warmth in the SE North Atlantic. So what made 2023/24 so different?

Just to go back to this, here are the SST's during early January 2010 compared with the current SST's.

both El Nino years and both had anomalous warmth in the SE Atlantic, one major difference however is the strength of the tripole, much colder waters stretched across the central Atlantic in 2010 vs this years, I suspect this perhaps helps to explain why we saw a cold winter in 2010 vs this year.

Not to say the anomalous warmth is the entire reason for this winters broadly mild weather, but certainly an argument could be made that the warmth helped to inflate the Iberian high this year.

MJO was also broadly more favourable through February in particular.

February 11

16 minutes ago, TEITS said:

You mention no sign of any cold spell for the next 2 weeks and yet UKMO/ECM at +168 disagree. I don't need any teleconnections to tell me that the +168 charts will go on to develop towards a cold spell for the UK.

Yes, because following the whims of individual det runs through this winter has been a complete success..

I can't say I care much for what the det runs show if I'm honest, they could show the next BFTE and feet of snow across the whole of the UK but if it's beyond day 3 it may as well not exist.

February 11

There’s currently no real sign of anything colder reaching the UK in the next 2 weeks. I think we can *probably* write those off.

There is the potential for something colder late Feb/early March on the basis of a downwelling SSW, extended ensembles do show a switch to colder weather albeit not very confidently at present.

In terms of background forcing, the MJO remains favourable however the AAM does not, two different forcing coming out of the tropics/sub tropics makes forecasting more uncertain & nailing broadscale patterns difficult, especially when you factor in an increasingly unstable polar field (SSW).

February 11

36 minutes ago, jules216 said:

ts actually quite simple. Its easy to follow GSDM on Victor Gensini website and it takes about a week to realize that even the GLAAM/GWO forecasts are as prone to get IT wrong as numerical models like GFS day 16 lol. When I followed the GWO graph it went from high AMP. Phase 7 to almost COD in a space of few days.

Those CFS forecasts are completely useless, I can't say I ever look at them beyond mild curiosity, I certainly don't factor what they show into my predictions within the GSDM space.

The (almost) real time plots produced by David Gold are more useful in determining the broader direction of travel, there's typically a 14-20 lag between initiation & pattern changes so it's often more useful to see what's happening *now* vs what might happen in the future re: AAM. For example, we have seen and are continuing to see subtle equatorward fluxing of both +ve and -ve AAM anomalies, this generally favours stronger Iberian/S European heights and indeed that's what we're seeing represented quite well within broader NWP modelling, despite on the face of it a favourable MJO for blocking and despite the fact we remain in a high GWO orbit. This is the reverse of what we saw through December with anomalies instead fluxing poleward reaching the realisation with the blocking early-mid January.

Worth noting though that the polar field is very important to factor in as well, the stratosphere can dominate or disrupt expected patterns at relatively short notice that no amount of applying the GSDM or various other teleconnections can help with, the mid-late January period was a good example of this, that SSW reshuffled the trop pattern and sent energy from the Canadian vortex eastwards across the Atlantic sector, instead of the blocking that had been expected we saw the pattern flatten & a stormier, milder period of weather ensue, as Tamara said "expect the unexpected".

Indeed the opposite was true for the December cold spell, broadly the GSDM was not in favour of blocking but the jet stream hitting road blocks as it crossed the Atlantic allowed for blocking to amplify, so, it’s not perfect by any sense of the imagination but it can and absolutely does provide context to NWP modelling and give a much broader picture of what’s driving our weather.

More often than not, the direction of travel re: AAM tendency is more important than the aggregated total AAM in the atmosphere. But, perhaps this isn't the right thread for this kind of discussion re: future forecasts and is better left in the Mod thread, just wanted to perhaps add some context for those reading the thread and wish to learn.

This isn't some "elitist cult" and I'd be more than happy to help anyone wishing to learn more about this, just as @Tamara has often very kindly and patiently helped me, though admittedly I'm still very much a novice.

February 10

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.

February 10

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.

February 10

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.

February 10

Earthshine

I plan to go back through my own posts this winter & do a more in depth write up on what I said about the AAM/MJO & compare to what actually happened & then compare that with the weather outcomes when I get a bit of time.

I’ll likely wait until winter is actually over though.

February 10

Derecho

It might be worth looking at the MJO from that year & comparing it with this year, i’ll see if I can find the AAM from 2010 too, be interesting to compare the different variables & try to “diagnose” it, so to speak!

I have to go to work now though so no time to do that today!

February 10

Weather-history

Indeed, i’m not saying it’s quite that linear but we had more variables for a cold winter vs against this year and we still came out in the top 10. But then again the UK is a tiny island, difficult to upscale that.

Obviously it’s more complicated than A+B=C as this winter (and the winters you mentioned) show!

In terms of solar activity - I think the link there is rather tenuous, it may help in some aspects but I don’t think it’s a driver of global weather patterns, at least not one that can dominate other earth based forcing!

February 10

jules216

-QBO does more than just increase SSW probabilities, it generally helps to promote a weaker sPV overall, which we have seen throughout this entire winter.

But that’s just 1 variable, there were plenty of other variables favouring increased likelihood of blocking going into this winter, declining IOD should have helped the MJO gain more traction, that didn’t happen.

What we did see is the anticipated rise in AAM/GWO to link the Nino base state with the atmosphere. We did see periods of fairly deep -NAO and -AO which was again, anticipated going into this winter. We did see a south shifted jet stream, most of the drivers talked about going into winter did “come off” and have the effects that were expected, from a UK point of view though it didn’t produce & i’m sure there’ll be lengthy discussions on why.

For northern Europe it absolutely did produce, Scandinavia for example has been absolutely bitter as have many other Nordic countries.

February 10

northwestsnow

The fact this winter is likely to come out in the top 10 mildest winters is pretty telling.

-QBO, El Niño, two, soon to be three SSW’s, weak strat throughout, declining IOD, on paper this winter should have been absolutely bitter.

In reality? Not even close.

February 10

1 minute ago, jules216 said:

There is múch better chance of cold winter next year when/if analogs like 1998/99, 2005/06 or 2016/17 would still hold merrit

We hear this every single year. “next year will be better”, it was said last year about this year. It was said the year before last about last year.

Analogues categorically do not work anymore, last winter was a great example of analogues utterly failing. The climate is shifting too quickly for them to work, the baseline has changed, comparing winter to years gone past may have worked (somewhat) in the past but i’m firmly of the opinion that it doesn’t anymore, our climate isn’t the same as it was 20 years ago, let alone 50-100 years ago.

February 10

MJB

I was speaking with James Peacock on Twitter and he thinks that the anomalous warmth in the SE Atlantic has propped up/strengthened Iberian heights this winter, given the link between climate change & an expanded Hadley cell it does make me wonder if this winter was a “real time” example of the type of winters we can expect in the future.

Getting decent cold spells into the UK is becoming increasingly difficult.

February 10

8 hours ago, Nick F said:

Does comes across to me like GDSM forecasting is an exclusive club who's members have secret access to AAM charts. Where do the rest of us find them?

It's certainly not an exclusive club and I'm sure if you reach out to David Gold he would be happy to provide the username & password to the site where the charts are hosted. Unfortunately when Ed Berry passed away (the founder/main researcher of the GSDM) NOAA shut down the AAM pages where all the charts were publicly hosted. There used to be a forum on 33andrain specifically about teleconnections with a hell of a lot of research from both pro mets and people like Tamara, Blessed Weather etc trying to understand and build up a library of scientific papers but unfortunately the forum shut down without any real warning and so all that work was unfortunately lost.

Besides that one site there's very little information or data available now, there's this CFS based AAM maproom but it's not very good.

AAM/GWO Mapwall

ATLAS.NIU.EDU

Weatherbell also offer AAM/GSDM charts within their top tier subscription, though you're looking at >£100 per month so not particularly accessible or justifiable just to access some charts.

There is still a lot to learn about the GSDM of course, it's certainly not perfect as this winter has perhaps shown but perhaps this winter isn't a good example of it's use, it's been a bit of a strange one in terms of the MJO, the stratosphere and just our luck here in the UK really. Despite a south shifted jet for much of winter, despite -NAO and -AO we just haven't been able to get things in the right places for the UK despite what looks to be an almost record breaking cold winter across N Europe.

There's not much else I can add that @MattH didn't cover in his post in response to what you said.

February 10

18 minutes ago, Nick F said:

I've lost faith in using the MJO passage through the phases as precursor to changes in weather patterns towards cold or mild. Following 'warm phases' of 3-4 in early Jan we saw a 2-week cold spell, we've seen the MJO recently pass through 6 and now loitering and weakening through 7, but very little amplification in the upper flow at mid-to-high latitudes to show for it in the models. What high lat blocking that has been showing and will likely continue to be shown down to changes in the strat, i.e. downwelling of weakening winds.

And I don't get this obsession with using AAM as tool on its own, it seems that when ever it rises all falls we are told to look out for changes but it seems, like when the MJO moves through the historically 'colder' and 'milder' phases, many other drivers are at play, some not so obvious, drowning it out much influence from it over the N Atlantic sector / Europe. Though the biggest interference in what we would expect in lag to certain MJO phases being climate change.

The state of the stratosphere is one driver, when it couples with the troposphere, still one to keep an eye on though.

Be glad not hear about the MJO for several months, until the next cold season. I've given up talking about how it may influence patterns, as it makes me feel like a Snake Oil Salesman!

You're talking about the MJO & AAM as if they are two separate things, but they're not.

AAM is simply a measurement of how much westerly momentum is in the atmosphere, the MJO influences this via frictional & mountain torques, i.e driving positive MT increases westerly momentum. More westerly momemum tends to = a more perturbed jet stream and thus, a higher likelihood of high latitude blocking but it's equally important to see which direction those anomalies are travelling. The MJO is taken in isolation too much in this forum & more generally, it's just 1 variable of the global windflow budget so it's no real surprise that looking at the MJO, checking the composite & expecting the atmosphere to respond and look like the composite isn't really working, the whole point is to view the MJO as part of the windflow budget, the MJO is incorporated into the GWO.

The AAM, or GSDM isn't supposed to be used to determine regional specific weather but to help diagnose global weather patterns, it's essentially the best tool we have for medium-extended range forecasting.

GSDM (which incorporates processes like the MJO) > Global NWP modelling > High res modelling

The GSDM provides context to NWP modelling in the same way NWP modelling provides context to more localised high resolution modelling. You're right, the MJO is currently in a phase which if you view in isolation and look at the composites, does favour high latitude blocking, but that's not the entire story.

AAM is positive at the moment indicating a good link between the +ve ENSO state & the atmosphere, however as discussed here in recent days fluxing of positive (and negative) anomalies are and have been equatorward rather than poleward, this serves to inflate the Iberian/S Euro high, whereas poleward fluxing (see early Jan) helps to amplify high pressure into the Arctic regions.

The current state of AAM fluxing helps explain the current patterns we've been seeing despite, on the face of it, a favourable MJO. I do wonder if the very warm SErn Atlantic waters has perhaps helped to extend the Hadley cell this winter and thus inflate the Iberian high regardless of other forcings such as the AAM, it seems very much to have been the default, base state through much of this winter despite seemingly (and often) favourable teleconnective forcing. Climate change is without doubt changing the dynamics.

I don't think we should just ditch the MJO, GSDM etc just because it hasn't performed with pre-determined outcomes. If anything, this winter has been a fantastic learning point on this, but it is important not to take them in isolation or out of context.

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5035355

February 9

14 hours ago, Nick F said:

I've lost faith in using the MJO passage through the phases as precursor to changes in weather patterns towards cold or mild. Following 'warm phases' of 3-4 in early Jan we saw a 2-week cold spell, we've seen the MJO recently pass through 6 and now loitering and weakening through 7, but very little amplification in the upper flow at mid-to-high latitudes to show for it in the models. What high lat blocking that has been showing and will likely continue to be shown down to changes in the strat, i.e. downwelling of weakening winds.

And I don't get this obsession with using AAM as tool on its own, it seems that when ever it rises all falls we are told to look out for changes but it seems, like when the MJO moves through the historically 'colder' and 'milder' phases, many other drivers are at play, some not so obvious, drowning it out much influence from it over the N Atlantic sector / Europe. Though the biggest interference in what we would expect in lag to certain MJO phases being climate change.

The state of the stratosphere is one driver, when it couples with the troposphere, still one to keep an eye on though.

Be glad not hear about the MJO for several months, until the next cold season. I've given up talking about how it may influence patterns, as it makes me feel fraudulent!