Model output discussion - 1st December onwards

[chrisbell-nottheweatherman]

Apologies for my bluntness, I could (and should) have phrased it a bit more diplomatically.  What I should have typed was "...massively over-excited by something that was never going to happen as yesterday's more extreme outputs showed." i.e. a once-in-a-decade easterly with a couple of feet of snow or whatever people were inferring.  I'm probably a bit short on patience at present as I'm concerned regarding flooding in the north today and possible damaging winds during the middle of the week.  Sadly, in a (perfectly understandable) desire to see some wintry weather rather than the mild, wet conditions we've been enduring, or, in some cases, enjoying, for this past couple of months, I'm annoyed that the more important and pressing modelling is being ignored.

 

MODS, is there an argument, particularly for situations like this where lives may be at stake, to divide this thread into "under +144h" and "Fi" in order that model outouts relevant to this week can be separated from the "search for cold", please?

Edited December 26, 2015 by chrisbell-nottheweatherman

[gottolovethisweather]

Re: a couple of posts above my own, move along the bus please, nothing to see here.  Private mails between members are always best for these one to one discussions, Thank you kindly. As otherwise they add nothing to this thread, furthermore there is a LOT of weather discussion to be had, is there not?

 

Overall, I'm pleased to witness an increasing likelihood of something completely different being offered up, come the New Year. Heights are lowering over parts of Europe as soon as the 30th December and once we get there, we will know whether the change and that hyped up Easterly is a-coming to our shores. This is the first piece of a very big puzzle, alongside this we need that second/third low during the upcoming days to dive SE into Western Europe, or at least fill/stall/peter out due South of the UK and then it'll be a good sign of a game-changer which will hopefully set about a new pattern for a number of days in January. A lot of water under the bridge to come yet, quite literally.

 

Stay safe all, Happy Boxing Day and play and stay safe. 

Edited December 26, 2015 by gottolovethisweather

[ukpaul]

People are not believing charts are going to happen exactly as they come out and getting 'overexcited', pretty much everyone knows that they are not going to happen exactly like that. What is good is the likelihood of a change which takes us away from these awful floods and unseasonal warmth and that is worth being pleased about it's no help when people go on about what others already know, it's just patronising.

Edited December 26, 2015 by ukpaul

[nick sussex]

Re my last post and for those interested in the MJO the smoothed out version does throw up perhaps more interest in the outputs we're currently seeing.

The smoothed out version seeks to remove the Kelvin wave component of the MJO, although Kelvin waves connect with the MJO especially in the early stages we need to be able distinguish between them because the KW is centred nearer to the Equator and travels faster. Looking at the dynamical forecast models they already have the MJO in phase 6 you can see the smoothed out version has this still in phase 5. It could be assumed that what we're seeing in the dynamical models is some interference from the KW.

Below from research into the MJO sums things up very well:

This prefiltering removes Kelvin wave signals, which contribute significantly to the standard RMM PCs in a manner that would invalidate the composite analysis because it might specify some of the Kelvin wave signal (Roundy et al. 2009).

So the question is the NWP reacting too soon or too slow comes to mind, effectively the main instigator of NH changes hasn't even reached the higher amplitude phase 6 if you go by the smoothed out version. The logical conclusion is that we might see even more changes in the NWP over the coming days.

 

Edited December 26, 2015 by nick sussex

[knocker]

5 minutes ago, IDO said:

Yes no sign of the GEFS moving towards an Easterly, like the 0z run a very small cluster of only 3 by D9, so we need that to start moving in the right direction. Again the op has 2 other members with support but the op is far and away the best out of that small cluster for cold. The control is a train of lows and fronts crossing the UK from D9, a strong zonal run. The ENS temp shows the op as an outlier and a colder run from early on: 

Looking at the GEM ENS, there are 4/5 Easterly's by D10, so again a small cluster. With IF suggesting 10% for the ECM then this remains a low chance, probably what you would expect when a wave amplifies the pattern (normal errors). The latest CFS w2 suggests the HP cell being pushed east and an Atlantic flow re-establishing and w3 and w4 offers more of the Euro high/Atlantic trade off:

   

The most likely solution is the HP cell being slowly pushed East as the lower heights moving in overwhelm the block. Still a few days to resolve this so could go the other way.

Quoting MV I cannot get this out of the back of my mind.

Strongest signal in the ECMWF Week 4 height anomaly is yet another massive Aleutian low pressure system

Starting to see a blocked up pattern about the N. Pole in the medium-range. Happened in 1997-1998 too.

[Polar Maritime]

5 minutes ago, chrisbell-nottheweatherman said:

MODS, is there an argument, particularly for situations like this where lives may be at stake, to divide this thread into "under +144h" and "Fi" in order that model outouts relevant to this week can be separated from the "search for cold", please?

There is a storm thread already open, And as long as it's discussion based around the Model Outputs in here then that's fine. Please Pm me any further discussion on this, Thanks.

[blizzard81]

I believe momentum has swung away this morning from any possible easterly in a week's time. The possibility was only small to start with so I am not too down beat about it. People may say that the pendulum may swing back but if I am going to be brutally honest, from past experience on easterly's, if the baton is not picked up and the momentum does not gain rapidly, you can kiss goodbye to it. Just my honest thoughts.

[bluearmy]

39 minutes ago, knocker said:

Just to make sure I'm with what you are saying blue are you talking this

 

Yes Knocks  - not the detail but the neg AO and polar profile plus what would follow for our part of the world 

[nick sussex]

12 minutes ago, blizzard81 said:

I believe momentum has swung away this morning from any possible easterly in a week's time. The possibility was only small to start with so I am not too down beat about it. People may say that the pendulum may swing back but if I am going to be brutally honest, from past experience on easterly's, if the baton is not picked up and the momentum does not gain rapidly, you can kiss goodbye to it. Just my honest thoughts.

I would say I agree with your first part in as much as when an easterly is mentioned in here people equate that with convective snow showers. For an easterly we'd need to see the troughing to the west disrupt more and be edged west. We clearly haven't seen this suggested in any operational run. This initial battle of block versus trough is the first one and any proper easterly would take some time to develop.

At this time I think its more a matter of where the battle lines might be drawn than no battle at all. The modelling of this is likely to change. For the timebeing I think its best to keep an open mind, to be honest at the moment I'm more interested in at least removing the Euro slug high so am keen to see high pressure hang on to the ne and help force the jet se.

Anything after that IMO is a bonus, we'll see over the next few days. The key thing is that the Scandi high doesn't sink or if it does it becomes separated by another high pressure lobe near Svalbard.

Edited December 26, 2015 by nick sussex

[Nouska]

23 minutes ago, chrisbell-nottheweatherman said:

 

MODS, is there an argument, particularly for situations like this where lives may be at stake, to divide this thread into "under +144h" and "Fi" in order that model outouts relevant to this week can be separated from the "search for cold", please?

Liam (SubZero) does a sterling job of keeping people appraised of these situations - both in generic and specific threads.

As far as discussing the likelihood of extreme charts in the far reaches of low-res - why not? It is a legitimate discussion and it is just possible the few stragglers are right against the majority odds. The cold spell at the end of November was highlighted by a few such stragglers that people were wont to dismiss very quickly.

I have empathy/sympathy for those whose homes are currently being destroyed by another episode of extreme weather. It was well modelled and well warned but we can do very little about it. We don't need to don the hair shirts - these things happen and if we can help, we will.

[forecaster]

16 hours ago, CreweCold said:

RE ensembles...which is why they're next to useless. 

 

This is just hyperbole. The meteorological (both operational and research) consensus is strongly in favour of ensembles. They are not crystal balls but they are essential to forecasting. 

 

http://onlinelibrary.wiley.com/doi/10.1002/wea.2069/epdf

 

" Practical experience and statistical verifications indicate that the average (or median) output from the ensemble is indeed the superior provider of ‘the most likely outcome’. The spread around this average tells how much trust can be put into this output, and, converted into probabilities, can warn about high-impact weather developments. It would therefore be quite possible to base the entire weather forecast guidance on the EPS. "

Edited December 26, 2015 by forecaster
Added link

[Borei]

1 hour ago, fergieweather said:

Quite so. Presently, the E/SE'ly cold solutions courtesy of the diffluent block out east - as offered by some recent deterministic output across various suites - is rated as 10% PROB. Whilst a mobile/zonal pattern remains the stronger and thus more favoured signal out beyond d10-15, clearly any mean fields will be skewed by these energetic ENS members (& with inevitable tendency to lean back towards climatology) versus those stamps (presently a minority) showing the opposite. I know we hammer on about this, but inspection of individual stamps is critical, rather than pronouncements based solely on ENS mean.  As it stands, indication of an eventual change to the pattern has bolstered slightly, rather than diminished. But it's clearly all highly tentative for now.

Those of you who like to base analysis primarily on ensemble means might like to remember Ian's well made point a little more often.

 

 

Edited December 26, 2015 by Borei

[Jason M]

2 minutes ago, forecaster said:

 

This is just hyperbole. The meteorological (both operational and research) consensus is strongly in favour of ensembles. They are not crystal balls but they are essential to forecasting. 

Yep, I agree. I think they do have value. It's important to look at the individual stamps though. I tend to look across all 20 at 168, 240 and 300 hours. The trouble with the means is that as Fergie says they don't show much of value. The 850 graph can also be misleading.

 

[bluearmy]

3 minutes ago, forecaster said:

 

This is just hyperbole. The meteorological (both operational and research) consensus is strongly in favour of ensembles. They are not crystal balls but they are essential to forecasting. 

I suspect you may have access to far more detailed  information than we do re the ens data.  I believe that if ecmwf would allow the general public to see the full ens suite for a few runs (inc clusters and probabilities), we  would have a lot more faith in the seven day + forecasts from Exeter which are led by ens suites. 

[knocker]

21 minutes ago, bluearmy said:

Yes Knocks  - not the detail but the neg AO and polar profile plus what would follow for our part of the world 

Cheers blue, I thought that was the case

[forecaster]

4 minutes ago, Borei said:

Those of you who like to base analysis primarily on ensemble means might like to remember Ian's well made point a little more often.

 

 

 

Using the mean along with well calibrated probabilities is quite sound in many situations. The mean smooths things out, the probabilities tell you about what's been removed by the smoothing. If you care about cold spells, you can do things like showing the mean and % of members showing 850hPa T < xC. Even 5% will then provide you with a hint. Cascading probabilities of multiple thresholds and parameters then give you a pretty good view of the ensemble. 

My only wariness of stamp maps themselves is that you are overloading the human with information and they may sometimes filter it out subconsciously. Clustering is probably superior IMO, unless you are looking at a very specific feature, in which case stamp maps are the king (I remember seeing ECMWF stamps for a famous low in 1999 or something like that, it was very interesting).

Bad times to use the mean are if you have very distinct possible outcomes, with the mean simply provided a physically meaningless and non-representative "MOR solution". In this case it's very dangerous, and misleading. But it's also rare.

[Mucka]

Personally I love the enthusiasm in this thread and feel there is a good balance of posters for people to get a real feel of the type of weather we may be facing.

I know people get frustrated with the chase for cold and snow, more times than not any signal will fail, nature of the beast, but any idea we should write off any Easterly or cold signal in FI, "As never going to happen", would be the real hyperbole. - not the discussion of the signal itself and its possibilities. If people feel it will never happen then that of course can be a valid part of the discussion so long as they make a reasoned argument based on the output.

 The reality is any cold has always been the least likely outcome on balance but if anything the probabilities improved over the last few days. As an analogy it is like going  from having to roll a  double six to rolling a total of 11 or more. Significant improvement but still a long shot.

This morning has not seen favourable output overall with the less disruption of any lows crossing the Atlantic. It is a situation finely balanced in that respect with big swings still possible because the knock effect of any disruption and energy heading under the block early has the high further West and higher latitude which means the next low has a better chance of disrupting favourably against the block in terms of energy distribution (or buckling and splitting of the jet if you prefer) and so on.

I posted a couple of days ago about what people new to all this should look for if they want to join in watching the output roll out.

Here are the 72h charts UKMO, GFS ECM 00z (So no FI here!)

 

Look carefully at the SW tip of the UK and hopefully you will be able to see that UKMO has a little more energy pushing SE attempting to "undercut" the developing high. The more pronounced this is the better the evolution of the run will be in general terms.

As more spin off the trough to our West they will meet the block and while we cannot predict with precision the timing and maturity/strength of these lows we can predict that the further Wet and better aligned our high is when they meet it the more likely they are to disrupt and send energy under the block which in turn  prevents it from being forced SE and the cold diverted away from our shores.

A perfect solution with good disruption (stretched out low pressure rather than balls of energy) will bring an Easterly to the UK. (least favoured solution IMO)

A halfway solution with some disruption and energy heading SE will result in the cold being forced North of the UK but it will at least get low pressure into Europe with possibility of a different route to cold from there. (Currently favoured solution IMO)

The other possibility, the worse for coldies, is of course that we get little or no energy heading Se under the block which would result in a flattening of the pattern and cold being forced back east although with a slight positive of lower heights in Europe - at least temporarily.

 So although any cold is in FI, what develops in the much earlier time-frames will naturally dictate what develops later, it is just those minor early differences have a huge impact on what we get later in these situations. I hope that explains why nothing is solved yet but may soon well be. 

 

[knocker]

The recent Hres Modis says it all

[Mucka]

31 minutes ago, knocker said:

The recent Hres Modis says it all

Looks a bit like a raging waterfall - fitting.

[geminitracie]

 

Flood sirens going off in Appleby , Cumbria 

[Frosty.]

19 minutes ago, geminitracie said:

 

Flood sirens going off in Appleby , Cumbria 

It's a recurring nightmare for folk in the northwest of the UK and it makes our hunt for cold pale into insignificance, our thoughts are with them.

Edited December 26, 2015 by Frosty.

[nick sussex]

Always the problem with mild conditions . Rarely do they ever come with dry settled conditions in the UK during winter. Of course every extreme has an impact on peoples lives but the best thing about colder weather is that you generally have less moisture available. I'm sure the people of Cumbria would rather be dealing with snow than these ghastly floods.

 

[ukpaul]

47 minutes ago, Frosty. said:

It's a recurring nightmare for folk in the northwest of the UK and it makes our hunt for cold pale into insignificance, our thoughts are with them.

I'm up here on the Lancs/Cumbria border at the moment and the rain is incessant. In truth a search for cold is also potentially what they need, as the Euro high pushing into the South East where I usually am is also pushing the rain their way again and again. High pressure would be very, very nice if it pushed further and further west, those systems stalling west of the U.K. are exactly what is needed.

Edited December 26, 2015 by ukpaul

[cyclonic happiness]

43 minutes ago, Frosty. said:

It's a recurring nightmare for folk in the northwest of the UK and it makes our hunt for cold pale into insignificance, our thoughts are with them.

It's very strange how all the rainfall in the UK seems to be concentrated on North Wales and Cumbria, have you seen the MET office rainfall anamoly chart, it's very dry most everywhere else, but the northwest is being drowned (no, not Kanye and Kim's kid).

Why is all the moisture so stuck in that rut? It's a tiny area on a global, and even a European scale?

I know the geological reasons for it, but it's just very strange that it's so intense in such a small area and for such a long period of time.

 

We can only hope for a change to drier and colder weather (hopefully, what's being shown in FI) although you can bet that it'll be blizzards that would bury the poor folk of Cumbria then :-(

[Jason M]

GFS para coming out at the moment.

ive seen worse charts at this timeframe 

http://www.meteociel.fr/modeles/gfse_cartes.php?runpara=1