Hunt For Cold: Model Discussion - Heading Into Christmas

[smith25]

4 minutes ago, Stuie W said:

Just look at the total length of, do I say block.

That's the dogs danglies of a chart.

[Guest]

SOME OF TODAY'S UPDATES (JUST OUT) TO THROW INTO THE POT - COLD SPELL YES BUT EXACTLY WHEN AND WHERE?

I just posted this onto a US weather forum "Teleconnections" thread but I wrote it in such a way as it equally applies to Europe and the UK - if not more so.

We have a lot of excitement out there in respect of the upcoming SSW event with some fascinating disagreements between the two main models.  Throw in all the changes in the tropics and we have yet more uncertainty with the models struggling to come to terms with the changes.  Reading the posts from some of our specialists , there is a strong consensus that we'll see the SSW within a week or so but we still are not certain of the type - displacement and/or split SPV, the timing of the impacts, where the blocking will set up and how long the effects will last for.  If we go by GFS we have a displacement which often favours N America and if we go with ECM we have a split which initially tends to favour Europe and usually N America some days later. While that debate continues on the strat thread, we have a more general teleconnections debate on this thread. Some of our specialists here have been looking at the broader patterns and the teleconnection drivers which influence those.  This includes the impact on the stratosphere in the first place to help trigger a major SSW, then how responsive the middle atmosphere is to favour full downward propagation and strat/trop coupling and finally how conducive the surface conditions are.  When all these "play ball" together (quite a rare event) the impacts can be quite dramatic and widespread with much of the Arctic cold displaced towards the middle latitudes and substantial high latitude blocking (HLB).  While a lot does seem to be in place, there is still some uncertainty on timings and extent.  The model uncertainty is even greater in the troposphere than in the stratosphere.  The next few days will be crucial and we may get a lot more answers.  I remain bullish about a predominantly cold January and perhaps beyond that but these timing issues need to be resolved. In this post, I will not draw any conclusions but I'll throw in a load of charts with very brief comments below each one.  Then it'll be back to our specialists to comment further and to pick the pieces out of all this!

 

The total GLAAM anomaly has been rising steadily again for the last 2 weeks. 

  

The relative AAM tendency anomaly spiked again during the last week and seems to have peaked. 

  

FT has continued to fall but looks to be near its lowest point.

 

Global MT (black line) has fallen back slightly but remains +ve as does NAMT (blue).  As expected, EAMT (red) has briefly gone -ve but this is expected to rise strongly again within a few days (if not sooner).  It appears that the last spike in EAMT gave the shot into the strat that was anticipated and we could well see a repeat of this (if it becomes necessary to finisih off the SPV) around Xmas - perhaps impacting on the strat around the New Year.  Meanwhile +ve EAMT can help with the surface patterns too (more below).

 

Since I produced that post on MT, EAMT and especially the extraordinary uplifting properties of the Mongolian Mountains (posted originally in April and repeated in summary form several days ago), it has become clear that Gravity Waves (GWS) and Gravity Wave Drag (GWD) are also part of the uplifting process.  I will keep throwing in this GWD chart which is rarely shown by anyone, as I believe that there "may" be a slight correlation between GWD and EAMT with a few days time lag between GWD and EAMT. Most of all the global GWD produced is over the south and east Asian mountains between 30N and 50N with around 28N  to 33N (Himalayas), 34N to 42N (the Tibetan Plateau) and 43N to 48N (the Mongolian Mountains).  Right now (or 2 days ago, with all these charts published with a 2 day time lag) GWD is -ve over the Tibetan Plateau but is +ve over the Himalayas. At this stage, please take this GWD chart and my comments as part of exploring this theory.  The main thing to look for is +ve EAMT within a few days.

 

The GWO remained +ve and has risen back to phase 5 and has been increasing in amp during the last 2 days. 

  

it's always useful to produce the phase charts as a reminder.  Phase 5 is associated with +ve MT as we have seen with global MT above. 

 

Now it's always difficult to compare like with like. We have GFS which has (or had) a known -ve bias but Victor Gensini has been producing bias corrected charts.  However, there have been ongoing technical issues with the GFS output.  They take GLAAM into -ve territory but this looks very suspect given the current actual level of AAM which is +ve.  The AAM shown on the GWO/FNL chart above, always looks to be much more accurate and is a corrected "final" analysis" of the current position (2 day time delay) but it is not a forecast chart.

 

Then we have the CFS forecast charts which have a known +ve bias!  One thing is certain, GFS and CFS are in complete disagreement!  Just as much as GFS and ECM wrt the type of upcoming SSW. it's very frustrating for us when we have to make allowances for the biases quite apart from the differing output. Even the trends are in opposite directions!

 

I know that there has been a debate of the relative usefulness of the RMM MJO plots, which tend to be pretty unreliable beyond week 1, the filtered VP200 maps and filtered potential velocity phase space diagrams and all of these have been shown today on this thread but all forecasting tools have their uses. Today's RMM chart was shown earlier with all the models but given the uncertainties, I wanted to focus on the ensemble spreads for a number of models.  The GEFS bias corrected chart has the MJO stalling in phase 5 but at decent amp. the ens spread is interesting with a good number maintaining decent amp (none dive into the COD) and some going for increasing amp towards phase 6 (which is what we want to see and at a slowish pace so that we can get towards phases 6, 7, 8 and 1 at decent amp in early January to coincide (perhaps) with the main SSW impacts and propping up HLB.  The darker grey (the focused ens spread) also points towards slow progression towards phase 6 at increasing amp.  Things may change significantly during the next few days. 

 

Meanwhile ECM are more progressive with almost perfect timing but the mean suddenly takes a turn towards the COD or at least reduced amp during week 2.  There is quite a spread in the ens members, reflecting the uncertainty.  Some members do just what we want to see - progression toward phase 7 at decent amp by early January.  Remember the almost record high amp phase 7 that coincided with the impacts of the last SSW!  Overall, slowish progression will be a good thing if we can maintain or increase amp.  

 

The other models produce variations around the theme somewhere between the big boys.

 

 

  

This one was produced on Dec 18th

  

The BOMM (Australian model) is 4 days out of date and covers a 6 week period.  Given the unreliability of just week 2 in all the MJO models, I do wonder why they continue to produce such long term output.  I just pay attention to the week 1 forecast for detail and week 2 (with caution) for changes in the general trend.  Ignoring the vast spread of ens members (which tend to cover most bases in the extended outlook!) the shorter term does look promising but will their Dec 20th output maintain the amp or not? 

Next, my new favourite charts for the important east Asian region and looking for +ve EAMT.  Here's the link to the animation of the jet stream there from now to T+180.  http://www.stormsurfing.com/cgi/display_alt.cgi?a=nindi_250

 

There have been some changes on this model's output but they are still forecasting a powerful jet streak over the Himalayas and southern Tibeten Plateau around Xmas day. Now that would be a nice Xmas prezzie! From studying these charts in relation to the MT charts and the EAMT responses + the theories in the Mongolian Mountain and Tibetan Plateau papers, EAMT in that region should be strongly +ve up to 2 days or so after the strongest jet streak has passed through.  That would be around Dec 26th/27th.  Then we have a further time lag to impact on the strat of around 5 to 7 days. Again this points towards January 3rd.  It may be coincidence but it is in line with the ECM strat splitting forecast.  I shall keep posting updates from time to time on these to scrutinise the results. It's very much an evidence gathering exercise.  I'm not sure yet how reliable the StormSurf modelling is but given that we're only really looking for fairly short term jet stream impacts, I see no reason to dismiss it. I did look into this and found that they use some of the NOAA output - here's a statement from their website:

Stormsurf significantly upgraded all our Wave Models in early 2009 and the Weather Model are poised for release shortly. We built these tools with the goal of providing full global coverage of the ocean-atmosphere interface from several perspectives ranging from global to local.  This has been an evolutionary process driven by a combination of our developing skills at using the tools to build the images, and NOAA's steady march forward at improving the underlying mathematics/physics of models themselves all fueled by the dropping price of computer memory and steep increase in CPU power. The result has been nothing but fabulous for the end user.  With these upgrades nearterm performance of the models are much improved and zoomed-in inspection of local conditions becomes a reality.    

The Weather Models provide animated forecast imagery for the atmosphere while the Wave Models focus on the oceans surface. It is the interaction of the atmosphere on the ocean in the form of wind that generates waves, so the focus of the Weather Models is naturally surface wind. Likewise the result of that wind blowing on the oceans surface is chop, which can build into windwaves, sometimes reaching monstrous proportions if the wind is strong enough, lasts long enough and covers a large enough area.  Those windwaves eventually migrate away from the fetch area that created them, and as the raw components dissipate, swell emerges. It is swell that make the best surf, and is what is most sough after by surfers. 

The models also depict these natural processes at a deeper level with the entire wind-to-sea-to-wave lifecycle supported. Wind is generated by differences in surface pressure, with air flowing from areas of higher pressure towards regions of lower pressure in an attempt to create equilibrium. As wind moves over the oceans surface it produces seas or swell, which in-turn have energy. That energy is quantified by it's period (which increases as the swells propagate away from their source). As swells move into shallow waters they begin to break creating surf, and those waves size can be predicted based on the interaction of the swell/sea size and period. More details concerning these processes can be found in the tutorials (see navigation bar above) with a rudimentary understanding of that information helpful if you want to dive into the deep end.

Our models are broken down into 4 geographic categories:

Global (whole planet),

Hemispheric (e.g. North Pacific, South Atlantic, North Atlantic, etc)

Regional (e.g. Northeast Pacific, East Indian Ocean, Tasman Sea, etc)

Locals (Margaret River, Hawaii, South California, Central Florida, West South Africa etc).

So depending on your need, the data is available at the macro or micro level.

This is and will remain a work in progress with more detailed Wave Model imagery constantly being developed. How much actually makes it the public webserver will depend mostly on whether the existing content is used. Each set of images requires computer CPU cycles and bandwidth, which in turn costs money. So we focus on images that will benefit a wide audience first and are working our way down to more targeted detailed charts last.

I also found their south Pacific pressure charts particularly useful during the summer and fall/Autumn when posting on the build up to the El Nino and the battle with the colder currents being driven northwards into the east tropical Pacific by the -ve SPO (South Pacific Oscillation). So it's well worth exploring their whole site.

Finally, StormSurf's pressure charts for Asia.  Here's the link to the animations:  http://www.stormsurfing.com/cgi/display_alt.cgi?a=nindi_slp

  

Again the Xmas Day chart.  The west Russian HP has been replaced by LP but that's part of the expected transition. A very intense new HP cell (CP circa 1054mb) is developing over northern Asia, central Russia and western Siberia. We have the further theory (many papers on this part of  the subject) of strong northern Asian blocking as a precursor to SSW events - perhaps another piece in the jig saw?  In my last post on this subject, I suggested that the stronger jet streaks around 30N often coincided with the strongest blocking further north - hardly surprising as the LP further south is effectively propping up the HP to the north. I have a strong feeling that a number of these precursor theories to SSWs are actually strongly correlated.  I'll make this a new project to study more deeply in the New Year.

Overall, I'm still very bullish about a cold spell for both Europe and the eastern CONUS and eastern Canada but the precise timing is still too tough to call.  The models are really going to struggle for at least several more days - perhaps longer than that.  This is such a fascinating period for anyone studying the background signals and loads of potential for those of us seeking a decent cold spell and all this for January not March/April   David 

Edited December 20, 2018 by Guest
check charts, links and correct typos

[Singularity]

How very interesting - the last couple of times I've emphasised no expectation of anything substantial from the current round of potential (in this case the pre-lagged SSW impacts round), GFS has immediately undergone an exciting adjustment. Go figure .

Anyway... 

With the propagating MJO back on the H-W diagrams after a mysterious absence yesterday, confidence in getting what we need to boost our chances by just a few days into Jan has increased.

GFS possibly swinging a bit too vigorously, ECM perhaps not enough so; +168 I've noticed a positive trend in heights within the AO region, and this almost facilitates a link-up with the UK ridge at +192 on the 12z. Even with that falling short, it seems to take enough out of the Atlantic westerlies (via messing up the tropospheric vortex lobe) that the following two days see the main Atlantic trough splitting against the UK high instead of just riding up over it as one large system. That brings the UK high a step closer to being able to make use of the launch pad that's the tropical + stratospheric sequence coming together, perhaps very well indeed if we get a bit of luck.

[brmbrmcar]

Not much of a split from the FV3 12z

[Methuselah]

Looks like the tail-end of the FV3 is also showing signs of not getting to grips with things:

[northwestsnow]

For those interested EC DET is pretty cold again,esp Christmas Eve/Christmas day, tho Boxing day onwards goes a lot less cold(even mild perhaps).

[karlos1983]

So many conflicting posts on Twitter about the GFS splitting the PV or not...... who the hell does one listen too 

[Mike Poole]

FV3 12z final strat chart

Hint of split, not anywhere near previous run.  

So the situation re the strat seems to be

• GEFS favouring wind reversal every run 25-26 Dec.  Has been for days.
• GFS totally inconsistent
• FV3 more consistent towards split, but when?  Usually end of run. Day 16.
• ECM reversal within 10 days, and signs of split at that time (that's yesterday's 12z on the Berlin site, may have changed this morning).

My conclusion is that the GEFS is just wrong, GFS doesn't know, FV3 has an inkling but the timescale is wrong, ECM will prove vaguely correct.  What I really mean is that is it possible that the SSW will happen but will be a split from the get go, rather than displacement and later warming causing split.   What does anyone else think? 

Edited December 20, 2018 by Mike Poole

[feb1991blizzard]

3 minutes ago, karlos1983 said:

So many conflicting posts on Twitter about the GFS splitting the PV or not...... who the hell does one listen too 

None of them, stick with this thread and view the charts.

[Stuie]

3 minutes ago, Mike Poole said:

FV3 12z final strat chart

Hint of split, not anywhere near previous run.  

So the situation re the strat seems to be

• GEFS favouring wind reversal every run 25-26 Dec.  Has been for days.
• GFS totally inconsistent
• FV3 more consistent towards split, but when?  Usually end of run. Day 16.
• ECM reversal within 10 days, and signs of split at that time (that's yesterday's 12z on the Berlin site, may have changed this morning).

My conclusion is that the GEFS is just wrong, GFS doesn't know, FV3 has an inkling but the timescale is wrong, ECM will prove vaguely correct.  What does anyone else think? 

Low double figures in the south, single figures in the North...

[karlos1983]

3 minutes ago, Mike Poole said:

FV3 12z final strat chart

Hint of split, not anywhere near previous run.  

So the situation re the strat seems to be

• GEFS favouring wind reversal every run 25-26 Dec.  Has been for days.
• GFS totally inconsistent
• FV3 more consistent towards split, but when?  Usually end of run. Day 16.
• ECM reversal within 10 days, and signs of split at that time (that's yesterday's 12z on the Berlin site, may have changed this morning).

My conclusion is that the GEFS is just wrong, GFS doesn't know, FV3 has an inkling but the timescale is wrong, ECM will prove vaguely correct.  What does anyone else think? 

Not a clue!! I don't think anyone does 

[nick sussex]

It’s like the Star Trek Voyager episode The Void!

Thats the void of nothingness for the next ten days as the limpet high to the south  meanders about driving us nuts!

After that the GFS goes into warp drive delivering a semblance of excitement !

Make it so ! 

[northwestsnow]

168 the crucial timeframe on EC tonight- hoping for some members seeing the high getting further north..

Tony has just posted the day 10 Strat latest from EC and WOW!!

Edited December 20, 2018 by northwestsnow

[tight isobar]

19 minutes ago, karlos1983 said:

So many conflicting posts on Twitter about the GFS splitting the PV or not...... who the hell does one listen too 

None pal...

Would be my advise..reaserch/view yourself...and independently...decipher/interp..yourself also.

[No Balls Like Snow Balls]

 

[feb1991blizzard]

10 minutes ago, northwestsnow said:

168 the crucial timeframe on EC tonight- hoping for some members seeing the high getting further north..

Tony has just posted the day 10 Strat latest from EC and WOW!!

I would like to see the 1mb chart, i dont think the 10mb split is getting any wider from the last run.

[matt111]

14 minutes ago, northwestsnow said:

Tony has just posted the day 10 Strat latest from EC and WOW!!

So that's where everyone vanished to, the Strat thread. Encouraging. 

Edited December 20, 2018 by matt111

[northwestsnow]

1 minute ago, feb1991blizzard said:

I would like to see the 1mb chart, i dont think the 10mb split is getting any wider from the last run.

Its chalk and cheese to GFS mate ..surely.

[Badgers01]

26 minutes ago, karlos1983 said:

So many conflicting posts on Twitter about the GFS splitting the PV or not...... who the hell does one listen too 

Dr Amy H Butler.  @DrAHButler always good on twitter ..

[feb1991blizzard]

Just now, northwestsnow said:

Its chalk and cheese to GFS mate ..surely.

Put it this way i don't think i have ever seen such chaotic NWP output in terms of strat modelling, i wonder if Tony, chionomaniac or someone is around to say if there has ever been a situation like this before.

[Catacol]

20 minutes ago, karlos1983 said:

So many conflicting posts on Twitter about the GFS splitting the PV or not...... who the hell does one listen too 

Holding pattern at present. The extent of the hit to the vortex, and whether it splits or not will be a now cast event. However there has been a lot of gloom in here today, and the usual suspects who love to shout “told you so” with little to no understanding of actually what they are telling us have appeared in force. Always makes me chuckle to read posts from those who enjoy pointing out the the UK rarely gets a sustained cold spell and that mild/wet is our default setup....as though we don’t know that already. Really tiresome to have to filter out that twaddle.

We didn’t get our block this week - but it was a close run thing. Torques set to re engage very shortly....and the second bite at Pacific led forcing to shunt a block up to the north will be in the period between Xmas and New Year. The fact that a UK high looks likely to be the end product of the current negative torque phase is good news....a much better starting point for the next +MT impacts to work off than the rather nasty trough we had anchored to our west last week.

All good still. Strong signals very much in place....but angle of any potential vortex split really will dictate whether we get cold shots or the chance of a properly sustained cold spell of easterly feeds. There are no guarantees here....but we still potentially stand on the cusp of a spell of special January wintriness....

[SMU]

59 minutes ago, karlos1983 said:

So many conflicting posts on Twitter about the GFS splitting the PV or not...... who the hell does one listen too 

The GFS is not a high top strat model-

The ECM has better height resolution hence will be better when resolving a split -

However for reference the overnight suite has slightly reduced the splits down to 13- GEFS has minimal if any

Note the consistency of the 'oval' shape from the green GFS indicating no split-

Moving onto the SSW the GFS 00z operational is disguarded for day 10

It has no split, & no SSW @+3.84 M/S V A suite of 20 members with EVERY SINGLE ONE AS A SSW day 10-

In this scenario the ECM is usually supreme- We are awaiting todays 12z ECM however yesterdays day 10 was A split & a SSW of -3.6M/S

The models are expectes to respond to the SSW with a QTR appearing at the later stages of the runs in the next 5 days- assuming we do land a split the ECMs PV lobes location indicate an opportunity of an atlantic ridge alligned towards svalbard ...

Cheers

 

 

Edited December 20, 2018 by Steve Murr

[Stuie]

4 minutes ago, Steve Murr said:

The GFS is not a high top strat model-

The ECM has better height resolution hence will be better when resolving a split -

However for reference the overnight suite has slightly reduced the splits down to 13- GEFS has minimal if any

Note the consistency of the 'oval' shape from the green GFS indicating no split-

Moving onto the SSW the GFS 00z operational is disguarded for day 10

It has no split, & no SSW @+3.84 M/S V A suite of 20 members with EVERY SINGLE ONE AS A SSW day 10-

In this scenario the ECM is usually supreme- We are awaiting todays 12z ECM however yesterdays day 10 was A split & a SSW of -3.6M/S

The models are expectes to respond to the SSW with a QTR in the next 5 days- assuming we do land a split the ECMs PV lobes location indicate an opportunity of an atlantic ridge alligned towards svalbard ...

Cheers

 

 

Steve, an exceptional post and will maybe not be greatly received from everyone that has gone all in on this development. I have been in the let`s see camp rather than chasing this and without any of this information. I knew the basics but this post just shows a walk in the park this is not.

Being a snow chaser I am going by models and will continue to do so and would love these developments to aid in that (models will/would show a response) but we could evolve into that scenario without this event. 

Top work mate.

[Nick F]

12z EPS splits the SPV a little earlier than the previous run, at odds with GEFS, but the ECWMF apparently has better resolution at higher levels of the atmosphere, so I think the earlier panic should be unfounded for now. 

Strong signal from 12z GEFS and EPS z500 mean day 10 and also going on the earlier 00z EPS clusters for a strong ridge of high pressure to build N across UK as we end the year, just a waiting game IMO for this to build over Scandi then eventually retrograde if we see the MJO cycle go into colder phases and downwelling of strat warming combine in January.

Edited December 20, 2018 by Nick F

[lorenzo]

I agree with the above @Catacol - in terms of want does everyone what for 'Xmas Day' things have improved markedly in the last 12-18 hrs with the models 'cleaning out' what was original a pretty uninspiring high. Cleaner high, cleaner cold, chance to wake up on Xmas day with very seasonal temps , blue skies, a frost etc...( Stop Press - EC delivers junk).

As for other events, there is no way.... 100% no way this winter will be ordinary after 01 Jan... we have well programmed MJO artefacts to play through from both directions - 

1) the phase 3 imprint on the strat ( again ) will slowly downwell over 30-50 days to create a u wind wave driving event on a crippled vortex.

2 the current MJO phase space and thinking about the forthcoming MJO phases predicating Greenland blocking - well given the easterly QBO in lower atmosphere - this alone would make folks salivate.. http://www.meteonetwork.it/models/mjo/ regardless of any Strat Activity - the trop does what it wants too !

Check Nino January plots on that link for 5-6-7-8..

All of the above - PLUS a monster warming.

Not withstanding whether it meets the 'classic' definition this is still remarkable. i.e. even if at the advertised point we pull back from the C&P u wind reversal at 10hPa.

The level of heat flux, the loading of MJO trop blocking precursors almost makes the SSW a 'cherry on top' or indeed a moot point.

At this point we can see GFS go bonkers, FV3 really show it's hand as a model to take seriously into 2019..

I think what cements the above is the ever cautious Met Office and the contingency update, these are know for the poker faced slant and candour - they never hyperbole anything. Given that steer - today's update one could consider as a proper ramp...

Edit : See Strat thread for ECM

Second Edit : 'Normally - this is peak VI Vortex intensification period... now that will become a cool question.'.

 

 

Edited December 20, 2018 by lorenzo