Model output discussion - winter proper underway

[frosty ground]

You can't say heights are too high over Europe now can you?

[geordiekev]

Might have a few bookies crying over their sprouts 

Edited December 13, 2017 by geordiekev

[northwestsnow]

3 minutes ago, bluearmy said:

 Can’t even say that op evolution has been spotted in recent ens runs! 

Gets to the eps mean/anomoly for day 14 but via a very different route !! 

GFS seems to be sniffing out a change around the 21st- 8 days away .

Wonder if the MJO is beginning to have an influence in the Atlantic sector Blue..

edit ukmo 144 is similar aside from the eastern seaboard- ukmo has a system coming gfs looks benign, perhaps ukmo will not show the retrogression GFS shows?

Edited December 13, 2017 by northwestsnow

[Methuselah]

And how's that for a Loch Ness Monster!

[Guest]

THE MODELS ARE STARTING TO EXPLORE THE POSSIBILITY OF ANOTHER COLD SPELL

Although I am like many on here, a lifetime "coldie" who seeks out the coldest evolutions, I will "attempt" to provide a little balance in this post! On Monday (in between my main reports) I did a cross model analysis (on page 11) stating what I was looking for with the earliest signs of another cold spell, once this one is over. I said that we need to examine the northern hemisphere charts as the "Europe" view does not show the upstream changes. In particular, I was searching for the earliest signs of a renewed strengthening of the PNA following (what "had" been predicted) a brief period of it going negative. This in turn should show signs of strong ridging towards the North Pole with HP building there and linking with HP from the North Asia/Russia/Siberia region. Then some re-amplification in the mid-Atlantic with HP building north and/or north-east. At that time (just 48 hours ago) many on here were getting very concerned at what "looked like" a long term return to a flatter pattern, a more zonal flow with much milder and more unsettled conditions. Even then, I found some evidence of the signs of what I was searching for. This, of course "was" all into deep FI which I rarely comment on in any detail. When a possible broad pattern change has been indicated in about two weeks time, then all we can do is examine the models in that extended period and then look at how they get there.

Our teleconnection specialists have been indicating for quite a while now that they were seeing some increasing signals for the pattern change to a colder regime. The timing of this change was difficult to nail down but a broad window for this was estimated from somewhere around Christmas to early January. From their most recent updates, there has been no strong suggestion that these signals are weakening or changing and this is very encouraging. (Update: I've just noted @Steve Murr's and @Tamara's excellent and very encouraging posts just now but I appreciate the possible downside risks and we all need to exercise a high degree of caution and patience).

What we have seen in the most recent model output, with their usual lag time, is them just starting to pick up on these possible changes and they are just beginning to explore some colder evolutions. In the meantime, the previously predicted more zonal and much milder interlude for at least next week, has also seen some changes. Most model runs are starting to show higher pressure closer to or even right over the UK. Several runs have then shown this HP ridging north and/or north-east with some even suggesting a much earlier change to a colder pattern. I know many of us would like to have a cold and snowy Christmas holiday but I urge everyone not to get over excited at this stage. The coldest runs might be too progressive. Quite often the models pick up on a new signal and develop it but then drop it on a subsequent run only to show it again several days later. I feel that we are in that phase right now. So, "if" the 12z runs mostly show warmer solutions again, we should not be overly concerned or too disappointed. In fact, I would be surprised if we do not see a period of increased model output volatility. We need to look for any trends and, in time, greater consistency between runs and some general consensus between the different models. 

What I want to do now is to take another look at what the models are showing in the extended period. I will start with the final charts shown for each model:

          GFS 6z T+384 for 0700 Dec 29th                 ECM 0z T+240 for 0100 Dec 23rd               UKMO 0z T+144 for 0100 Dec 19th              GEM 0z T+240 for 0100 Dec 23rd

                       

 

      NAVGEM 6z T+180 for 1900 Dec 20th      JMA 12z (Tues) T+264 for 1300 Dec 23rd  GEFS Control 6z T+384 for 0700 Dec 29th    GEFS Mean 6z T+384 for 0700 Dec 29th

                      

The GFS at D16 is about the most progressive chart of all but is for the longest period. It not only shows a very positive PNA but has built a strong HP through the Pole and extending across Greenland and Iceland and linking up to HP ridging from Russia to Scandinavia. It also shows lower heights over central Europe. That would be almost the ideal set-up for a prolonged very cold spell. Now we should not get carried away with this eye candy. ECM at D10 shows us under a westerly flow with HP just to our south. The good news it that it is showing signs of a +PNA, HP through the Pole and extending to Siberia and right down into China. UKMO only goes to D6 but also shows a +PNA and HP at the Pole (too early to latch onto a trend). GEM at D10 is similar to but more amplified than the ECM with the Atlantic HP building across us and through to northern Europe. It has a +PNA and an intense HP between Alaska and the Pole ridging down to Greenland. The NAVGEM at only D7/8 is also very progressive with a vast belt of HP over us and ridging all the way up through north-east Europe, north-west Russia and on.through almost all of Asia and Siberia as well as through the Pole with a +PNA.  JMA at D11 also has a +PNA. with strong HP over the Pole, through Greenland and linking with another HP extending north-north-west from the Azores. The GEFS control at D16 has strong HP building north-east from us across into Scandinavia and linking up with even stronger HP over Siberia and Russia as well as ridging across the Arctic and with a +PNA. Even the GEFS mean chart at D16 has a +PNA and HP through the Arctic. 

So far, every model at their far end, show extremely strong evidence of just what coldies are seeking (perhaps not quite with the ECM 0z) but I will go on to look for something for the doubters to latch on to "if" I can find it:

       GFS 6z T+234 for 0100 Dec 23rd                  GEFS 6z T+240 for 0700 Dec 23rd             GFS 6z T+102 for 1300 Dec 17th       GEFS 6z Perturbation 8 T+384 for 0700 Dec 23rd  

                          

The first two charts above show the GFS and the GEFS control run as close as possible to D10 so that they can be compared to ECM (and GEM) at the same time. Both runs are already much more amplified than the ECM. The third chart was the only one on the whole of this morning's GFS 6z run (at T+102) where the PNA was close to neutral, with it being positive before and after that time.I then searched through the GEFS perturbations at D16. The vast majority are close to the "eye candy" for coldie's category. Perturbation 8 was the "warmest" I could find!  This shows a rather strengthened PV with a west-north-westerly flow over the UK but even this has Polar Maritime air in it and the flow looks like it'll veer further towards the north-west later on. The PNA is still slightly positive with some ridging across the Arctic to Siberia. So, even the poorer long term charts look okay!

I'll let you all draw your own conclusions but I'm a happy bunny right now. I am still prepared for less encouraging output over the next few days and will keep looking for a colder trend to be shown with greater consistency. Most important of all will be further updates from Tamara and her colleagues on the background signals. .

. 

Edited December 13, 2017 by Guest
Correct typos and check charts

[tight isobar]

8 minutes ago, northwestsnow said:

GFS seems to be sniffing out a change around the 21st- 8 days away .

Wonder if the MJO is beginning to have an influence in the Atlantic sector Blue..

edit ukmo 144 is similar aside from the eastern seaboard- ukmo has a system coming gfs looks benign, perhaps ukmo will not show the retrogression GFS shows?

The gfs ens12z..

Are now of pivotal importance.

As we can see the guide in momentum' swinging back to colder evo.

The ops have been top seed in signal-setting lately.

So look for continuation in support -ens...

And ecm should offer guidance 168+..

Mild spell...what mild spell??

Edited December 13, 2017 by tight isobar

[comet]

Obviously the greater the Alaskan ridging into the Arctic the greater the impact on the AO and northern hemisphere blocking. At the moment the amount of ridging is changing run to run but if the northerly modelled by the 12z was to be followed by a very strong Alaskan ridge similar to the one modelled in the 06z run then we could really be in business.

[stewfox]

17 minutes ago, terrier said:

well the mild spell doesn't look like lasting long at all on tonights gfs12z. 

About 4 hours if you base it on the mood of this thread

Interesting 18Z GFS pub run coming up... is it free drinks for everyone and a lock in ?

 6Z GFS was more amplified then 0Z  GFS ..where diluted  tomato juice was on offer and the cold was written of for the rest of the month.

 

[Daniel*]

GFS once more is giving coldies a reason to be joyful temporarily - does anyone know what this may be? 

 

[Methuselah]

11 minutes ago, Bring Back1962-63 said:

THE MODELS ARE STARTING TO EXPLORE THE POSSIBILITY OF ANOTHER COLD SPELL

Although I am like many on here, a lifetime "coldie" who seeks out the coldest evolutions, I will "attempt" to provide a little balance in this post! On Monday (in between my main reports) I did a cross model analysis (on page 11) stating what I was looking for with the earliest signs of another cold spell, once this one is over. I said that we need to examine the northern hemisphere charts as the "Europe" view does not show the upstream changes. In particular, I was searching for the earliest signs of a renewed strengthening of the PNA following (what "had" been predicted) a brief period of it going negative. This in turn should show signs of strong ridging towards the North Pole with HP building there and linking with HP from the North Asia/Russia/Siberia region. Then some re-amplification in the mid-Atlantic with HP building north and/or north-east. At that time (just 48 hours ago) many on here were getting very concerned at what "looked like" a long term return to a flatter pattern, a more zonal flow with much milder and more unsettled conditions. Even then, I found some evidence of the signs of wthat I was searching for. This, of course "was" all into deep FI which I rarely comment on in any detail. When a possible broad pattern change has been indicated in about two weeks time, then all we can do is examine the models in that extended period and then look at how they get there.

Our teleconnection specialists have been indicating for quite a while now that they were seeing some increasing signals for the pattern change to a colder regime. The timing of this change was difficult to nail down but a broad window for this was estimated from somewhere around Christmas to early January. From their most recent updates, there was been no suggestion that these signals are weakening or changing and this is very encouraging. (Update: I've just noted @Steve Murr's and @Tamara's excellent and very encouraging posts just now but I appreciate the possible downside risks and we all need to exercise a high degree of caution and patience).

What we have seen in the most recent model output, with their usual lag time, is them just starting to pick up on these possible changes and they are just beginning to explore some colder evolutions. In the meantime, the previously predicted more zonal and much milder interlude for at least next week, has also seen some changes. Most model runs are starting to show higher pressure closer to or even right over the UK. Several runs have then shown this HP ridging north and/or north-east with some even suggesting a much earlier change to a colder pattern. I know many of us would like to have a cold and snowy Christmas holiday but I urge everyone not to get over excited at this stage. The coldest runs might be too progressive. Quite often the models pick up on a new signal and develop it but then drop it on a subsequent run only to show it again several days later. I feel that we are in that phase. So, "if" the 12z runs mostly show warmer solutions again, we should not be overly concerned or too disappointed. In fact, I would be surprised if we do not see a period of increased model output volatility. We need to look for any trends and, in time, greater consistency between runs and some general consensus between the different models. 

What I want to do now is to take another look at what the models are showing in the extended period. I will start with the final charts shown for each model:

          GFS 6z T+384 for 0700 Dec 29th                 ECM 0z T+240 for 0100 Dec 23rd               UKMO 0z T+144 for 0100 Dec 19th              GEM 0z T+240 for 0100 Dec 23rd

                       

 

      NAVGEM 6z T+180 for 1900 Dec 20th      JMA 12z (Tues) T+264 for 1300 Dec 23rd  GEFS Control 6z T+384 for 0700 Dec 29th    GEFS Mean 6z T+384 for 0700 Dec 29th

                      

The GFS at D16 is about the most progressive chart of all but is for longest period. It not only shows a very positive PNA but has built a strong HP through the Pole and extending across Greenland and Iceland and linking up to HP ridging from Russia to Scandinavia. It also shows lower heights over central Europe. That would be almost the ideal set-up for a prolonged very cold spell. Now we should not get carried away with this eye candy. ECM at D10 shows us under a westerly flow with HP just to our south. The good news it that it is showing signs of a +PNA, HP through the Pole and extending to Siberia and right down into China. UKMO only goes to D6 but also shows a +PNA and HP at the Pole (too early to latch onto a trend). GEM at D10 is similar to but more amplified than the ECM with the Atlantic HP building across us and through to northern Europe. It has a +PNA and an intense HP between Alaska and the Pole ridging down to Greenland. The NAVGEM at only D7/8 is also very progressive with a vast belt of HP over us and ridging all the way up through north-east Europe, north-west Russia and on.through almost all of Asia and Siberia as well as though the Pole with a +PNA. JMA at D11 also has a +PNA. with strong HP over the Pole, through Greenland and linking with another HP extending north-north-west from the Azores. The GEFS control at D16 has strong HP building north-east from us across into Scandinavia and linking up with even stronger HP over Siberia and Russia as well as ridging across the Arctic and with a +PNA. Even the GEFS mean chart at D16 has a +PNA and HP through the Arctic. 

So far, every model at their far end, show extremely strong evidence of just what coldies are seeking (perhaps not quite with the ECM 0z) but I will go on to look for something for the doubters to latch on to "if" I can find it:

       GFS 6z T+234 for 0100 Dec 23rd                  GEFS 6z T+240 for 0700 Dec 23rd             GFS 6z T+102 for 1300 Dec 17th       GEFS 6z Perturbation 8 T+384 for 0700 Dec 23rd  

                          

The first two charts above show the GFS and the GEFS control run as close as possible to D10 so that they can be compared to ECM (and GEM) at the same time. Both runs are already much more amplified than the ECM. The third chart was the only one on the whole of this morning's GFS 6z run (at T+102) where the PNA was close to neutral, with it being positive before and after that time.I then searched through the GEFS perturbations at D16. The vast majority are close to the "eye candy" for coldie's category. Perturbation 8 was the "warmest" I could find!  This shows a rather strengthened PV with a west-north-westerly flow over the UK but even this has Polar Maritime air in it and the flow looks like it'll veer further towards the north-west later on. The PNA is still slightly positive with some ridging across the Arctic to Siberia. So, even the poorer long term charts look okay!

I'll let you all draw your own conclusions but I'm a happy bunny right now. I am still prepared for less encouraging output over the next few days and will keep looking for a colder trend to be shown with greater consistency. Most important of all will be further updates from Tamara and her colleagues on the background signals. .

. 

Top notch stuff BB62-63!

But you have, IMHO, made one egregious error...you haven't included the mighty BOM among you musings...

[carinthian]

8 hours ago, carinthian said:

latest gfs chart at day 10. Still a chance to recue Christmas. The quasistationary pattern now changing over Central Russia, so always a chance of the Low over Northern Russia to sink. Its an outside option but not one to be totally ignored. ECM  charts look the worse outcome. Maybe GFS holds out for the best options to advance cold into Euroland at least.  Blighty on the outside but not totally without a 40% chance I would think as it stands now at day 10.

 C

I think most who want the cold to return will settle for this latest run from GFS. Chart below at t210 . In relation to the above post I earlier sent, we need to see those lower heights showing to the NE to drop. I think now that the holding pattern over Central Russia is becoming less abnormal this process is possible and would allow pressure to rise to the north again. Good to see at this stage and room for much more colder scopes over the Christmas and New Year period. Blighty still on the outside but a cold Christmas now upgraded from 40% to 50 %. I am pleased to see heading in the right direction.

C

[northwestsnow]

1 minute ago, ShortWaveHell said:

Don’t shoot a newbie ! But is this a reaction to a stronger MJO signal in the models? I.e 7 into 8  , I read four days ago they were dealing with a COD MJO signal ?!?!? #imclueless  

Yes its possible the MJO is now showing its hand- in GFS operationals at least-

I'd love to see EC show something similar at 168 onwards tonight- its all about the Atlantic sector..

[The Northern Ramper]

37 minutes ago, feb1991blizzard said:

Here comes the slider.

Sliders can do one unless forecast for Scotland allowing for a 200 mile correction south near to the time ?

[SMU]

Guys keep an eye on this high pressure day 7/8- it’s angle is pitching North West going against the flow- Greenland High pressures come from highs that either ridge North out of the Azores or North West from the uk ( circa 2010 )

I’m not saying it will however...

Edited December 13, 2017 by Steve Murr

[SMU]

22 minutes ago, Daniel* said:

GFS once more is giving coldies a reason to be joyful temporarily - does anyone know what this may be? 

 

I would hazard a guess to say cold clustering from the east...

[West is Best]

Well well well.

The 12z GFS chases away those who were gloomy. This has been on the cards, or rather the ensembles, for a few days as so many cold members, and huge scatter, were showing which suggested that sooner or later the operational might join them. The 6z ensembles showed a definite trend to more cold members and that's the thing I'm really looking for: more cold members and less scatter.

How incredibly exciting this is. A start to winter like of old. Here's hoping.

 

[West is Best]

41 minutes ago, Man With Beard said:

And here comes your December 25th slider - and the Daily Star's prediction of a White Christmas comes off - what could possibly go wrong?!

    

 

Must admit I saw that headline this morning and laughed.

No longer. It's still wishcasting but this 12z GFS does back it up.

[Summer Sun]

Pretty solid agreement on the short ens for milder air to move in early next week after a chilly weekend though probably not as cold as it was earlier this week

[chrisbell-nottheweatherman]

5 minutes ago, Summer Sun said:

Pretty solid agreement on the short ens for milder air to move in early next week after a chilly weekend though probably not as cold as it was earlier this week

Even before the end of the graph, though, the temperatures are heading gradually downwards at both 850hPa and 500hPa, suggesting that the warmest conditions might not last for a significant period, though that isn't to suggest that it won't stay on the mild side for a while.

[Summer Sun]

Full ens now out lots of scatter developing from around the 22nd mean indicating a drop closer to the average

[chapmanslade]

1 minute ago, Summer Sun said:

Full ens now out lots of scatter developing from around the 22nd mean indicating a drop closer to the average

It is unusual you see the op and control runs so similar but out of kilter with the ensembles - somethings brewing !

[BLAST FROM THE PAST]

Interest grows, and as posted other day with my ‘let’s not get ahead of ourselves’ post and see where we are come Friday.  Already we are seeing signs of changes afoot or probably more like the route ahead isn’t full on zonal.  So still looking forward to seeing what the runs show come then....more ridging is on my mind consolidating what GFS is hinting at.

I am very interested by GPs 22nd Dec.  I have highlighted that date in the LRF thread with an update I did last week that we could well have a strong solar wind burst hitting Earth and I anticipate a wild meandering / split jetstream as a result over festive period.

 

BFTP

Edited December 13, 2017 by BLAST FROM THE PAST

[bluearmy]

19 minutes ago, Steve Murr said:

I would hazard a guess to say cold clustering from the east...

The run came out Monday evening so not sure what is so strange that we haven’t heard from anyone about it for nearly 48 hours !!

 

[East_England_Stormchaser91]

19 minutes ago, chapmanslade said:

It is unusual you see the op and control runs so similar but out of kilter with the ensembles - somethings brewing !

December 1962 had an early cold spell around a very similar time to this, delivered in pretty much the same way (short potent northerly blast), only for milder conditions to briefly take over before December 25th... who says lightning can't strike twice! 

 

Looking at that NH chart, you wouldn't believe what was to occur just less than a week away.. 

Edited December 13, 2017 by East_England_Stormchaser91

[The PIT]

20 minutes ago, West is Best said:

Well well well.

The 12z GFS chases away those who were gloomy. This has been on the cards, or rather the ensembles, for a few days as so many cold members, and huge scatter, were showing which suggested that sooner or later the operational might join them. The 6z ensembles showed a definite trend to more cold members and that's the thing I'm really looking for: more cold members and less scatter.

How incredibly exciting this is. A start to winter like of old. Here's hoping.

 

Sadly well out in la la land could go the same way as those blow torch south westerlies did not so long ago. If it's still there next Wednesday I may sit up a bit more and take notice.