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Model output discussion - winter proper underway


Paul
Message added by Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

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Posted
  • Location: Bedfordshire
  • Weather Preferences: Seasonal
  • Location: Bedfordshire
1 minute ago, karlos1983 said:

Just out of interest, where did we hear that Glosea is losing the SSW signal? I can’t see any tweets from Ian F about it, and do they mean losing or lost? TIA, 

Can't rememeber if it was a tweet by Ian Fergusson or Chris Fawkes but I think one of those fellas was the source

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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL
1 minute ago, ArHu3 said:

 

1 minute ago, LRD said:

Can't rememeber if it was a tweet by Ian Fergusson or Chris Fawkes but I think one of those fellas was the source

Cheers, well that doesn’t sound like a done deal to me... 

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Posted
  • Location: Camborne
  • Location: Camborne
1 hour ago, bluearmy said:

states much uncertainty (even more so than before I think)  and removes the snow word from the last sentence. That presumably a reflection of glosea removing its ssw 

latest mjo forecasts from NOAA models seem to drift the signal in phase 6 for a while. Ecm not updated since Friday 

Not of major significance i feel

ECMF_phase_51m_full.thumb.gif.92840234f048d32ec071f010c0e4e281.gif

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Posted
  • Location: south london, sutton
  • Location: south london, sutton

It shows you just how much ebb and flows goes on with these models during the NH winter , the situation is so fluid and so finely balanced with regards to the distribution of energy that I doubt we will ever have models capable that can predict more than 10 days with decent certainty . Even something as powerful as Glosea changes with a flip flops all over winter.

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Posted
  • Location: Netherlands close to the coast
  • Location: Netherlands close to the coast
3 minutes ago, FiftyShadesofWine said:

12zs rolling out let's hope for at least Xmas day snow falling somewhere, anywhere:cold::cold-emoji:

Quite big little changes already at 54h, so the run will most likely be completely different from the 6z later on

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Posted
  • Location: Netherlands close to the coast
  • Location: Netherlands close to the coast
3 minutes ago, Hull snow said:

Is the 12z that bad ?

Not if you live in the Philippines, that tropical storm hitting from around the 23rd them in the 6z has completely disappeared 

Edited by ArHu3
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Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth
3 minutes ago, Hull snow said:

Is the 12z that bad ?

This answers your question but it's further down the line where there maybe some interest but these charts would bring a smile to knockers face.

IMG_0196.PNG

IMG_0197.PNG

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Posted
  • Location: Camborne
  • Location: Camborne

H/t MV and also illustrates the strong thermal gradient along the eastern seaboard and thus the 160kt jet that then swings across the Atlantic

Quite the dipole pattern between Alaska-North Pole and the lower 48. Big time Alaska-Arctic warmth with a downstream arctic cold air mass intrusion for the lower 48 the week of Christmas

DRQGYREV4AA2Vuw.thumb.jpg.b1ab441e5635d9d4854784b3b766027a.jpg

Edited by knocker
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MIXED SIGNALS, VARIABLE OUTPUT – A MORE BALANCED ANALYSIS

I fully appreciate that it’s rarely useful to focus too much on the model output in FI and much beyond D10 and even the D6 to D10 period or even before that can often be highly variable. As I said before, my current “obsession” is searching for signs of a broad pattern change to a colder regime as indicated as a real possibility by some of the background signals. I have been examining, perhaps a little too much, the longer term output and the final destination, although I have also looked for any earlier signs of these changes.

On this model discussion thread, we see a whole range of data, charts and graphs posted to assist in understanding and interpreting the output. We all know (or should know) that we must not become fixated on one model and one run. Looking for changes and trends over a few runs and with several models (particularly the “big 3”) can be a good way of analysing the output but quite often one or more of the models pick up on a signal, develop it and then drop it altogether only to pick up on it up again later. This is where the relative merits of studying the ensemble suites and comparing these to the means, control and operational runs can be extremely useful. We can see the possible range of outcomes and how supported these are by grouping them into certain categories. While this usually helps to provide a much better sense of direction it’s not always the case and there are some limitations.

For instance, the GFS operational run can quite often be an outlier and well above or well below the mean. This tells us that we might need to keep in mind that it may be out of kilter for that particular run or it might be leading the way to a new trend having sniffed out a very recent change in the background signals. One of the reasons that the GFS runs in the extended (or less reliable) period can swing quite wildly, is that a minor change in the signals might lead to it switching from one of the coldest to one of the warmest evolutions (or wet to dry or stormy to calmer). Then we look for the support in the ensembles. Usually, these will show us quite a range of outcomes, especially in the extended period. By grouping these, we can see where the operational run might be heading – into a majority or minority solution. The ensembles will also help to show us just how extreme the change of direction might be from run to run.

It’s rare for a major change in the operational output to have little or no support from the previous run’s ensemble suite and it’s equally rare for the vast majority of the current run’s ensemble suite to lurch strongly from one solution to another. There can be exceptions and we have just had one with the last three GEFS runs. Most of the regulars on here will have witnessed the big swings in the GFS operational output for the last few days (from cold to warm and back) but the GEFS ensemble output was much more consistent with a reasonable size grouping supporting either main solution with only smaller changes from run to run. I had noted a good number of colder solutions, with a disrupted or split PV, HP through the Pole and some showing a Scandi HP with one or two already showing easterlies. Yesterday’s 0z, 6z 12z and 18z groupings only showed slight variations in the support for either of the main two (colder or milder) evolutions (although there are other minority solutions, such as a rather cold zonal type). Then this morning’s 0z run showed “almost all” the ensemble members switching away from the split PV and Scandi HP evolutions – ie: the op, the control, the mean as well as almost all the ensemble members had dropped the signal for a pattern change to a colder regime. Then on this morning’s 6z output (which I cover below) goes back to a larger grouping showing a disrupted or splitting PV again with a few Scandi HPs back in the mix too.

What can we make of this, when almost an entire model’s output and supporting ensembles lurch from one position to another and back again? It didn’t look like a simple timing issue or one run being too progressive and another being far less progressive. In fact, I feel that it meant that GFS had temporarily dropped almost any notion of the pattern change to cold and then reverted back to it. We have been told that the conflicting background signals have been difficult to interpret (although yesterday’s updates had suggested that things might be becoming somewhat clearer) and that the models with struggle for a while with these and each model has varying degrees of biases, particularly when dealing with a pattern change that would go against the climatological norm for (possibly) an extended period (reminder: it’s the background signals that drive the model output, not the other way around).

All this tells me that we need to be particularly cautious right now and with this in mind I move onto my cross-model analysis. I shall start by having a look at the much closer term where I can compare all the main models. I use the most recent output for each model at D5, aiming for the position at 0100 on December 22nd:

          UKMO 0z T+120                     ECM 0z T+120                       GFS 6z T+114                     GEM 0z T+120

   UN120-21.GIF    ECH1-120.GIF    gfsnh-0-114.png?6?6    gemnh-0-120.png  

          NAVGEM 6z T+114              JMA 12z T+132               GEFS 6z T+114 Control          GEFS 6z T+114 Mean

   navgemnh-0-114.png    JN132-21.GIF    gensnh-0-1-114.png     gensnh-21-1-114.png

     GEFS 6z T+114 Ensemble Suite   gens_panel_asz2.png

I picked this date as I detected some very early signs in some of the models showing the PV already coming under some pressure. Most of models show at least relatively HP around the Pole, HP ridging from around Alaska into the Arctic and a large belt of HP across central and Northern Asia. Some models are rather more progressive than others. Good to see the ECM starting to agree on this possible evolution with slightly greater amplification. Very early days and far too early to draw any definitive conclusions.

Next I move onto D8 output for December 24th/25th (UKMO not available at this range):

            ECM 0z T+192                      GFS 6z T+180                     GEM 0z T+192                  NAVGEM 6z T+180

   ECH1-192.GIF    gfsnh-0-180.png?6?6    gemnh-0-192.png    navgemnh-0-180.png

            JMA 12z T+204             GEFS 6z T+180 Control        GEFS 6z T+180 Mean

   JN204-21.GIF    gensnh-0-1-180.png    gensnh-21-1-180.png 

 

   GEFS 6z T+180 Ensemble Suite  gens_panel_cfg5.png

I picked this date as further changes appear around this time. Note that most models have progressed only slightly but there are signs of the PV coming under rather more attack, albeit nowhere near a split (JMA perhaps the closest). So, still nothing to confirm a trend but perhaps rather more agreement at this stage than only a few days ago.

Finally, I move onto D16 for January 2nd :

          GFS 6z T+384                GEFS 6z T+384 Control       GEFS 6z T+384 Mean

   gfsnh-0-384.png?6?6      gensnh-0-1-384.png      gensnh-21-1-384.png

 

GEFS 6z T+384 Ensemble  Suite gens_panel_kjr5.png 

Okay, another FI distant period but at least one can see the evolution from the earlier charts. Study the ensemble suites and follow them through the three time snaps I've selected. There are some split PVs, some nearly there, some with it disrupting and only a few with a stronger and better developed PV.

I have also been following the changes in the PNA and the predictions. This “may” be one of the key influences and early indicator of the pattern re-alignment suggested for early January). I noted that Knocker posted the GEFS 0z graph this morning (the run where almost all the ensembles temporarily dropped the PV coming under attack). I copy that chart below:

 PNA:  GEFS 0z Ensemble Graph          gefs_pna_00.png.0f16bd4b1eb299f5edc52d48

@knocker always provides us with some excellent updates and analysis. He posted this chart this morning and correctly stated that the PNA is negative right now and for a while going forward. Remember that our teleconnection specialists have suggested that some of the key background signals might suggest a short negative phase for perhaps 2 weeks or so prior to the PNA likely to go positive again around the New Year or into early January (I also noted Knocker's comments about the similar trends in the last few winters - so caution as usual about both any changes and also any impacts). You can see the GFS control run as negative throughout 14 days period shown but it’s steadily rising closer to neutral towards the end. A few ensemble members go positive much earlier and rather more later on, although (for this 0z run) there are some members which are trending down towards the end.

It strikes me that it would be very useful for the foreseeable future to compare this particular chart for each (or at least once a day) GEFS ensemble suite so that we can monitor the changes and the trend. I feel that the 6z chart is likely to show far more members going positive towards the end. Now, many of us know that Knocker is most certainly NOT one of the “coldie brigade” and I would fully understand it if he does not wish to support those of us desperately wanting this cold regime change to come to fruition. I believe that this chart is not available on a “free to view” basis (please correct me if this is not the case). Perhaps someone else (should Knocker not be willing to) would kindly post these specific charts or give me a free to view source? It would be much appreciated.

What I can obtain are the NOAA PNA forecast daily updates as shown below:

NOAA (GFS) PNA 10 Day Forecast from Dec 16th  pna.sprd2.gif

These charts average out the readings from each of the last three days using the running mean (probably based on Dec 13th to 15th input. So, although extremely useful, do not relate to the very latest position. Some of members stay positive, most go negative and some recover again towards the end of the 10 days (Dec 26th). 

I'll be back soon (may be after a short break for a couple of days) with further updates and reports.

Edited by Guest
Correct typos and check charts
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Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth
3 minutes ago, knocker said:

H/t MV and also illustrates the strong thermal gradient along the eastern seaboard and thus the 160kt jet that then swings across the Atlantic

Quite the dipole pattern between Alaska-North Pole and the lower 48. Big time Alaska-Arctic warmth with a downstream arctic cold air mass intrusion for the lower 48 the week of Christmas

DRQGYREV4AA2Vuw.thumb.jpg.b1ab441e5635d9d4854784b3b766027a.jpg

As illustrated.

IMG_0198.PNG

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield
6 minutes ago, feb1991blizzard said:

Another Kieron run, another nail in the coffin.

Indeed. The polar blocking and flow is incredible tho!!!Some massive changes on gfs from this morning. Looks at best odd to me !!!:cc_confused:

Edited by swfc
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Posted
  • Location: Tullynessle/Westhill
  • Weather Preferences: Cold and snowy or warm and dry
  • Location: Tullynessle/Westhill

Maybe not what we are looking for but quite impressive in it's own way...

gfsnh-0-288.png?12 gfs-2-288.png?12

 

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Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL

I’m seeing nothing overly mild on GFS 12z.

I keeping hearing about next week being very mild I’m not seeing it myself largely near average I’d say with frost risk not going away, perhaps milder further north. I think some of our more northern members with some elevation *boom* might be a tad excited - on what’s being shown, I however am not. 

B9D5C94B-D7E0-4DD7-A8AB-EEDDA0AF8978.thumb.png.9ea4942d782eee975b91d67ba380cd03.png

Edited by Daniel*
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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire

To be frank, the 12z gfs is like a kick in the gonads! The Euro high returns with a vengeance in the 7 to 8 day timeframe. Not a welcome sight at all. I Just hope the ecm doesn't follow suit. 

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire

Well, the meto got the forecast for the end of December very wrong. It was gunning for blocking but it looks like the opposite is going to happen. 

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Posted
  • Location: St rads Dover
  • Weather Preferences: Snow, T Storms.
  • Location: St rads Dover
5 minutes ago, blizzard81 said:

Well, the meto got the forecast for the end of December very wrong. It was gunning for blocking but it looks like the opposite is going to happen. 

tbh the outlook looks very blocked on the 12z just not quite in the right place for us. I'm personally not looking that far ahead yet though, let's see what the high coming over us soon does.

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Posted
  • Location: South Norwood, London
  • Weather Preferences: Snowy Cold Winters & Warm Dry Summers
  • Location: South Norwood, London
8 minutes ago, blizzard81 said:

Well, the meto got the forecast for the end of December very wrong. It was gunning for blocking but it looks like the opposite is going to happen. 

Although the met office are good, they aren't that good and can't get a forecast wrong for a time period that hasn't happened yet ;-)

Only time will tell but various options have been presented over the last few days from mild to cold so we will have to wait and see.

Edited by Jayces
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Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

Probably Snowing on the mountain tops in Scotland but otherwise mild for xmas day. The main interest in lala land is the 28th which looks fairly stormy, Otherwise nothing in locker for coldies just with most of the cold air missing us.

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