Model output discussion - winter proper underway

[ACCOUNT DELETED]

High pressure with milder temperatures looks to be the story of next week so there could be some decent spells of weak winter sun around for the run up to Christmas, much better than heavy rain, gales, floods etc anyway IMO

[Methuselah]

4 minutes ago, mountain shadow said:

Based on what evidence?

None at all, MS...That's the point - if a Bartlett is 'displaced' it's not a Bartlett, is it?

[phil nw.]

An Interesting and very marked departure around the Christmas period from the gfs op runs compared to the ens suite

 

A repeating FI pattern from the American model wrt the Azores high building into Scandinavia.So far the majority of both ens suites are having nothing to do with it for now.The one constant though is the Alaskan ridging which shows quite strongly right out to week 2.Just signs that those ht anomalies are building to our east at the end which keeps open the possibility of a cross polar link up of heights splitting the vortex beyond Christmas.

Will need to continue to monitor the ens in the coming days to see if this becomes a trend.

[Purga]

23 minutes ago, Ed Stone said:

I'm starting to worry that we might heading towards a dreaded 'displaced Bartlett'. 

1947 freeze started from a 'displaced Bartlett'

whatever the term is supposed to mean???

Edited December 14, 2017 by Purga

[ribster]

1 hour ago, bobbydog said:

of course, its a long way off and plenty of time for things to change but the background signals, teleconnections and drivers have been hinting at this for some time. we now have this repeatedly shown in the models at the projected timeframe. coincidence?....

Indeed, if it was against a background of noise or contradictory signals then I would tend to agree. However, it's not and I certainly wouldn't be betting against.

[Purga]

23 minutes ago, phil nw. said:

An Interesting and very marked departure around the Christmas period from the gfs op runs compared to the ens suite

 

A repeating FI pattern from the American model wrt the Azores high building into Scandinavia.So far the majority of both ens suites are having nothing to do with it for now.The one constant though is the Alaskan ridging which shows quite strongly right out to week 2.Just signs that those ht anomalies are building to our east at the end which keeps open the possibility of a cross polar link up of heights splitting the vortex beyond Christmas.

Will need to continue to monitor the ens in the coming days to see if this becomes a trend.

Not for this thread, I realise - but the updated METO further outlook today makes 'interesting reading'. Monitoring the ENS will be hopefully an enjoyable pastime for coldies. Comes with a health warning of course....

[comet]

May have been a little slow on the uptake here regarding the struggle the models are having with longer term outlook. There has been a reasonable warming and more importantly strong geopotential height rises from 10mb down across northern and north eastern Canada. Below are the geopotential heights at 30b on11/12                   70mb 

I presume the ridging we are seeing in the PNA /EPO locale is the models interpretation of how this warming and heights will play out as they filter down into the troposphere. If we see a slow propagation then the impacts will probably be far less dramatic than if we see a faster propagation. Scandinavian height rises make sense rather like a counterbalance wave 2 effect. Then as the heights move clockwise we will see a cross polar flow setting up with wave 1 heights in the Pacific and wave 2 ridging north so perhaps a transition from east /north easterly into northerly.

The stratosphere gfs instant weather maps give an indication which way the heights are expected to travel. It is only towards the end of the run that I think we see the possible forcing (warming) from MJO related wave breaking.

Feel free to add/correct if my analysis is off.

 

 

 

Edited December 14, 2017 by comet

[bluearmy]

21 minutes ago, Purga said:

Not for this thread, I realise - but the updated METO further outlook today makes 'interesting reading'. Monitoring the ENS will be hopefully an enjoyable pastime for coldies. Comes with a health warning of course....

no way the clusters at day 15 would lead you to think that 30 dayer was coming.  I have seen this before on the extended and I suspect that either glosea is firming up on a SSW or they are happy to take the MJO into 7 and 8 as being strongly likely. perhaps both !! 

[Daniel*]

GFS continues to be bullish regarding height rises to N/NE I’d take this seriously. GFS is known to be the first to get a whiff, very little support amongst ENS but a few are very cold, we need this to grow.

[Guest]

10 minutes ago, bluearmy said:

no way the clusters at day 15 would lead you to think that 30 dayer was coming.  I have seen this before on the extended and I suspect that either glosea is firming up on a SSW or they are happy to take the MJO into 7 and 8 as being strongly likely. perhaps both !! 

Have seen it said in this thread many a time that an SSW buys us a lottery ticket but it doesn't always win us the jackpot... they do use the 'confidence is low' but other than that it is a rather bullish update. so maybe the models they have that we don't get to see are showing really strong signals for this cold period very interesting times ahead for sure.

[Catacol]

1 hour ago, sebastiaan1973 said:

Hi Catacol, where can we find these composites? Thanks!

For now I use a fairly broad brush tool broken down by month and MJO phase. Better composites are done by including ENSO phase and then specifying specific years that might fit other teleconnective features - but that requires a database of information and a load of time I haven't found yet. One day....

In the meantime this JMA link is useful for general guidance.

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html

[Glacier Point]

GEFS mslp anomalies for days 1-5, 6-10 and 11-15 over Siberia:

Add that to already observed:

Strong +ve anomaly over Siberia.

Comparable with December 2005, but interestingly the Aleutian Low not so classical this time round.

January 2006 featured a major mid winter warming..

The Aleutian Low conduit working to effect on wave 1 there.

This time round, maybe not so much Wave 1 likely to impact the vortex into January, but perhaps more Wave 2 a possible driver for a strat warming event (QBO was stronger in 2005/6).

[tight isobar]

Slp..

Gefs postage stamps.

Xmas day 25th.

Highlighting a likely 'still slightly milder set up .

However @decembers conclusion' ..perts are blocking-a plenty.

Some eye watering synoptics via operationals running upto xmas for the begining of the new year...one would suspect!!!

Obviously from one suite-one run...

But signaling the pattern(perhaps)

 

25dec

30 dec

Edited December 14, 2017 by tight isobar

[Nick L]

Folks, since we've had one instance of it this afternoon, just a warning. One of the biggest bug bears on this forum from moderators and other members alike is those who post off topic posts in here with a disclaimer of "Sorry mods, off topic but...". There are no buts about it, just don't post it. 

[Catacol]

46 minutes ago, comet said:

 

I presume the ridging we are seeing in the PNA /EPO locale is the models interpretation of how this warming and heights will play out as they filter down into the troposphere.

The stratosphere gfs instant weather maps give an indication which way the heights are expected to travel. It is only towards the end of the run that I think we see the possible forcing (warming) from MJO related wave breaking.

 

Not sure about this - who leads the dance between trop and strat is always a subject of some debate, but this season so far a trop led pattern has impacted on the lower levels of the strat, and the eQBO appears to have helped prevent much influence from upper strat activity filtering down. I'm not convinced we are seeing a pattern "filter down" - instead I think we are seeing an imprint extend upwards and that the Alaskan ridge, assisted by MJO phase, is driving a wedge up into the atmosphere.

So far warming at levels from 30 - 70mb has helped shift the vortex to Asian side and ensured further reduced impact on trop patterns particularly in the atlantic.

Where do we go from here? I think again GP has made that pretty clear today - Alaskan ridge shifting polewards working into an already passive trop and lower strat vortex, helping increase warming further. MJO forcing meanwhile encourages a Scandy High creating possibly cross polar ridge and - who knows - a complete split of the trop vortex... with that pattern set to release plenty of cold air into Europe particularly if retrogression occurs.

[Guest]

CONTINUING THE SEARCH FOR THE NEXT COLD SPELL

While the longer term output from the GFS and GEFS models that go as far as the D11 to D16 period continues to produce some mouth watering charts for coldies, this is, of course what we "usually" call deep FI and the highly unreliable period. As I said in my post yesterday (on page 31), what we are looking for at this stage are signs that the models are starting to factor in what the teleconnection signals have been indicating - a broad pattern change to a generally colder regime. In that post I did a cross-model analysis of the end of run charts for each of the main models (+ several others). What we need ideally is all the models doing this:

                                                                                                                                                                

Now we know that this would be wishful thinking and highly unlikely much beyond D7. Indications of a reasonable consensus with the model output trending towards a similar broader solution is probably the best that we could ever hope for. The window for the pattern change that has been suggested by our excellent teleconnection specialists (especially @Tamara, @Glacier Point, @Catacol and @chionomaniac)  to be somewhere from around Christmas time until early January. Some model runs are likely to be more progressive (or perhaps too progressive) while others will show a slower evolution (or even find a different solution altogether).

In this post, I am going to bring my cross model analysis into the middle time frame, around D7/8, drawing on each model's most recent run. Several posters have suggested that this may be a key period in the very early stages of the widely predicted pattern change and I agree with them. As I have said a few times before, it's essential to look at the "northern hemisphere" charts as the "Europe" view does not show the full upstream pattern. The latter (Europe) charts come into their own when one wants to look at the finer detail around the UK. So let's have a closer look:

     GFS 6z T+180 for 1900 Dec 21st              ECM 0z T+192 for 0100 Dec 22nd           UKMO 0z T+144 for 0100 Dec 20th          GEM 0z T+180 for 1900 Dec 21st  

                                       

 

  NAVGEM 6z T+180 for 1900 Dec 21st      JMA 12z T+192 for 1300 Dec 21st   GEFS 6z Control T+180 for 1900 Dec 21st   GEFS 6z Mean T+180 for 1900 Dec 21st 

                                         

The GFS 6z was not quite as progressive as the 0z in the earlier stages. Nevertheless, it shows a strengthening +PNA (Pacific North America) with HP just starting to rebuild across Alaska into the Canadian Arctic. There is a broad belt of HP over northern Russia and Siberia ridging into the Arctic and also south-westwards into north-east Europe and towards Scandinavia. The HP centred just south of the UK is ridging east-north-eastwards into north-west Europe. There are lower heights over eastern Europe. The ECM 0z run has a stronger +PNA with HP ridging into the Arctic towards the Siberian side. The HP in the Atlantic is much closer to the UK, just over south-west England. UKMO only show charts up to T+144. The T+168 "west Atlantic view" charts barely show the UK let alone the Arctic, Europe and Asia. The UKMO is rather more amplified than its recent earlier runs. It too has the PNA going positive with a strong HP ridge over the Arctic and getting close to linking up with HP over Siberia and northern Russia. Like the ECM, it has HP close to the UK and just over the south-west but the orientation is better with it showing signs of ridging north-eastwards into north-west Europe (not quite Scandinavia). Like some of the others (not ECM) it also has rather lower heights over eastern Europe.

GEM 6z, which has possibly been the least consistent over the last few runs showing quite diverse evolutions, is broadly similar to UKMO in respect of the +PNA and HP across the Arctic but that it has the Atlantic HP a little further south of the UK and significantly, it has a strong ridge pushing northwards through Iceland into Greenland and develops yet another northerly - although this one dives into central Europe (if this occurred it would certainly help to build a cold pool there). NAVGEM is also quite similar to UKMO and being 36 hours later "might" have some indication of how UKMO might evelove slightly later on. It has the UK HP building gently north-east towards Scandinavia. It's too early to say if it will establish there but it does show rather lower heights over central and southern Europe as well as a large belt of HP of central Asia, ridging westwards towards Europe and north-eastwards through Russia, Siberia and towards the Arctic. Yesterday's JMA has the Atlantic HP further south of the UK but with it ridging northwards towards its frequently exaggerated Greenland heights (unadjusted to sea level values for the high plateau there). It also has the HP ridging east-north-eastwards into central Europe, again with rather lower heights over eastern Europe and western Russia. It also has a strong expanse of HP across central Asia and north-east into Siberia and into the Arctic and just showing signs of ridging right across the Arctic with the PNA going positive. 

The GEFS control run is broadly similar to the GFS in the 6z run - they have often shown quite different evolutions on recent runs.The mean chart is not that different suggesting that on this run the control is closer to the mean (often not the case). To explore this further, let's have a look at 4 quite diverse perturbations:  

GEFS 6z T+180 for 1900 Dec 21st:

                   Perturbation 1                                           Perturbation  9                                           Perturbation  11                                         Perturbation 13

                                         

An encouraging feature on almost all 20 perturbations is the +PNA. and on some of them it's going strongly positive. Most, but not all, all of them have HP ridging across the Arctic and there is generally a large belt of HP across central and north Asia, Russia and Siberia. The greatest variations are closer to home, particularly in the position and strength of the HP in our vicinity. Perturbation 1 (and several others) have the HP south of the UK with a fairly mild westerly flow across us - some show this flow on a more west-north-west/east-south-east trajectory with various degrees of Polar Maritime air in the mix. Many more perturbations have the HP much closer to or right over the UK. Perturbation 9 is typical of a few of them that has a more intense HP with it ridging into Scandinavia. Another group of them, like perturbation 11, have a very strong build of pressure over western Russia and already showing signs of linking to the UK HP across northern Scandinavia with lower heights across northern Europe. Perturbation 13 and several like it, also have the HP over the UK but not quite such progressive building north-east "at this stage". The slight delay may produce even better outcomes later on as there is a strong belt of HP from Alaska through to Siberia building and perhaps available to link up to.  

Overall, I feel that the models are now factoring in at least some of the teleconnection signals pointing to a colder regime. The timing is still very uncertain but there is quite widespread evidence of a trend developing from much of the recent output with the "early" signs showing up as soon as a week from now. There are still likely to be some big swings in the output from run to run and the background signals might still change. It looks like we should be looking more to our east for the next cold spell rather than to the north. Although a further shot or two of Arctic air cannot be ruled out while the main pattern evolves. Just how cold it will get is also very uncertain. I covered that topic in part 2 of my last main report (on page 17 of this thread) when I looked at the European and Asian temperature and snow cover profile. As  @Nick F said in one of his excellent posts earlier today, there isn't that much cold in Europe right now. In my recent report I noted that following some unusually warm conditions in much of Russia it "had" cooled off, particularly in north-west Russia. This cold has already weakened as can be seen in the charts below:

GFS 6z T+6 for 1300 Dec 14th:

                  2m Surface temps                                                  850 temps

                          

There is some good news to counter this. A week ago, the models were generally predicting that the jet stream would strengthen and blow right across us and well into Europe. This has now changed and virtually no runs show this happening. This will give western Russia and Europe a chance to see any colder air stagnate (this can happen very quickly with the long nights and very low sun this time of year). If heights do slowly build to our north-east, then much colder air will slowly filter down from Siberia and through Russia. The longer that pattern persists, the deeper the cold air should become. I will be posting my next Eurasia temperature profile report early next week and I look ahead to what some of the models are predicting.

Finally, several posters have asked (with tongue in cheek, I think!) why I do not included other models in my cross-model analyses, such as BOM, ICON and CFS - well most of the time they are rather less reliable!  I will, however close with this chart:

         CFS T+1692 for Feb 22nd 2018

      

It looks like I can look forward to a shot of Polar Maritime air for my 65th birthday. What could possibly go wrong!

 

Edited December 14, 2017 by Guest
Correct typos and check charts

[Ali1977]

Just catching up, that is one of the best (for coldies) METO update I've read I think - if it's not an SSW I'm guessing what the GFS is showing in FI has support using their models . I'd sacrifice a cold Xmas for a very cold Jan any day !! 

[Daniel*]

24 minutes ago, Ali1977 said:

Just catching up, that is one of the best (for coldies) METO update I've read I think - if it's not an SSW I'm guessing what the GFS is showing in FI has support using their models . I'd sacrifice a cold Xmas for a very cold Jan any day !! 

Ian F used to share behind the scenes stuff about MOGREPS highly likely it has caught up on something. 

[northwestsnow]

2 minutes ago, Daniel* said:

Ian F used to share behind the scenes stuff about MOGREPS highly likely it has caught up on something. 

well if the update is on the ball then i would expect the 15% cluster discussed with Blue (from ext eps) to start gaining momentum over the next few days.

Could be some dreamy synoptics coming into view across the NWP-

Yes i know i'm a cold ramper but i genuinely believe things are about to get interesting!!

[West is Best]

Been out all day. But anyone despondent, don't be. These ensembles give considerable grounds for dreaming:

There are plenty of cold members. Interesting times ahead ... we may soon start to see the odd coldfest operational crop up.  The key though is for some consistency to appear with fewer routes out of the cold. 

 

[West is Best]

Northwest snow: snap

[northwestsnow]

Well here comes 12z...

Again i think we have to accept the pre christmas period probably will not look pretty-

Its really post christmas the 'drivers' hopefully will get to work, GP must be reasonably confident after his earlier musings pretty much backed up by Exeter...

WRT Glosea5, one would assume the latest update reflects a flip in the long range model as the 3monthly update only last week did not look inspiring at all...

 

 

[shaky]

Hmmm more anticyclonic across england and wales early next week compared to last run!!high has edged further north on this run!!

[nick sussex]

The GFS 12hrs run looks more amplified over the USA than the 06hrs. The issue is whether shortwave energy in the mid Atlantic will complicate any WAA into Greenland as happened this morning.

Shortwave behaving so far!

 

Edited December 14, 2017 by nick sussex

[bluearmy]

20 minutes ago, northwestsnow said:

Well here comes 12z...

Again i think we have to accept the pre christmas period probably will not look pretty-

Its really post christmas the 'drivers' hopefully will get to work, GP must be reasonably confident after his earlier musings pretty much backed up by Exeter...

WRT Glosea5, one would assume the latest update reflects a flip in the long range model as the 3monthly update only last week did not look inspiring at all...

 

 

That was for an extended period of months though ??

jan could have a very cold three weeks and that forecast could still be spot on

gfs 12z slower off the esb with the trough and more amplification than the 06z 

looking to see how far west the northerly can get day 7/8