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Hunt For Cold: Model Discussion - Heading Into Christmas

Paul

If you're hunting for cold potential in the model output, this thread is for you. But if you'd like to look more widely at the models, please head over to the general model discussion thread.

This is a model related thread, so a general, frequent theme of the model output is a given, but it will not be strictly enforced:

  • Some topic drift, humorous responses etc are fine
  • Posts likely to lead the thread off on an entirely off topic tangent are not ok. For example (but not solely limited to): Posts entirely or mainly about Met Office, BBC or media forecasts with little or no model context, and posts solely asking for a weather forecast in a specific location.
  • Posts which start with something like 'I know this is off topic but ...' are not ok.
  • Posts which break the forum guidelines are not ok (eg trolling, troll-hunting, weather guilt tripping, overly defensive/aggressive, abusive, disrespectful to others)

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I for one don't really mind a less than perfect Christmas ,because the real prize looks like it's on the horizon.

if ,as anticipated,we have a stonking January ,I would like to thank all contributors to the forum,and the mods as it may not be a peaceful new year for them.

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GFS importing mainland air as we head through christmas week, 850s look rubbish but its classic inversion stuff with temps struggling !!

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14 minutes ago, ... said:

Is this Project Fear?

No thats the day after tomorrow or 2nd week of jan in may terms becausr tomorrow never comes

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3 minutes ago, starstream said:

I for one don't really mind a less than perfect Christmas ,because the real prize looks like it's on the horizon.

if ,as anticipated,we have a stonking January ,I would like to thank all contributors to the forum,and the mods as it may not be a peaceful new year for them.

This is what I posted 9th Dec, and I can't read charts :

I am going to make a prediction, not based on charts but purely on what seems to be a pattern. The cold will be showing on the charts just before Christmas for around New Year, 1st week in January. Maybe I a imaging it but it seems to me that Christmas is just a week or so too early nowadays.

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Well one thing we can say about GFS is its dry and cold after christmas eve!!

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gfs-0-312.png?12

 

Finally making its moved

gfs-0-348.png?12
Get your barometers calibrated 

Edited by frosty ground

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2 minutes ago, northwestsnow said:

Well one thing we can say about GFS is its dry and cold after christmas eve!!

Boring

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Strat split on the 12z not as gung ho as the 06z but still there 

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UK HP D6-D15 and possibly a blocked pattern:

gfseu-0-384.thumb.png.ebd58af98b14cd0f7c0906c5ea53dbc9.png

Not really what I was hoping for and can only hope background signals move it to a more productive placement as further waves from the Azores at D16 look to reenforce!

Edited by IDO

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High pressure get that flow right just for the newbies even though it shows +5c uppers under that high could be bitter.... 

Cool the ground down enrich the cold in time for the easterly... 

HA! 

Beats mild mush all day long.. Freezing nights freezing fog frosts winter weather at last in sight... Just 

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Here we go... this is a trend we want to see repeat and improve as we head to new year-

gfsnh-0-336-1.thumb.png.6ff33984ee072f829b463b8b5253c230.png

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Can't access my old account - have emailed about it.

So "first" post from this account.

As we all know, the likelihood of anything verifying 6/7+ days out is unlikely but so long as come Thursday/Friday the cold making its way towards us hasn't disappeared off the charts then we may have a little hope in seeing some snow in places... or a frost at least.

I have been keeping an eye more so on this week as I am off to Latvia in a couple of days - Riga Thurs-Sat then Berzpils (not far from Russian border) for the remainder - and back on 2nd Jan. Wanted to make sure no snow would impact on my travel there.

Thankfully snow has fallen where I'll be going and should remain below 0 so I can enjoy it.

I do believe based on today's charts that we will see temps below the average for Christmas here and I hope for all of you staying put for Christmas that you see some snow.

My other half and I have exchanged some Christmas gifts we won't be taking with us... she's only gone and bought me a weather station! Currently showing Thunderstorms forecast... I hope she kept the receipt.

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A high centred over or to the west of the UK is a theme that is being repeated in FI. Gives some decent cold for my location. 

gfs-0-384 (2).png

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1 minute ago, Radiating Dendrite said:

Greece yet again in the freezer! Haha

I'm sure the Greek weather geeks must love a GB high cell in Winter.

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8 minutes ago, Spah1 said:

Boring

Maybe but as a coldie which I know you are Surely cold and dry is better than 12c

And rain all about opinions but I know what I prefer.

C.S

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possibly some agreement starting on the first attempt at the ridge / area of above average heights around Christmas (so possibly a cold dry and frosty Christmas)

gfsnh-12-168.thumb.png.6a48fbd55451b074ebf61a2b47a47ab1.pnggfsnh-0-168.thumb.png.512931f09100d3331c0426adc7dc8930.pngiconnh-0-168.thumb.png.92f830ec6f672da7a30a85b396eef095.pnggemnh-0-168.thumb.png.334a60fbda15d42099de92a652dd2401.pnggemnh-12-168.thumb.png.e70cd664dba1e79d4b582b12ae8d2a1d.png 

then its a question of how far north / north west / north east this gets and if it can lead to a northerly or easterly at the first time of asking, probably not but good to see this as a possibility so quickly

the calm before the snowstorm? 😜

Just waiting to see if any of the GEFS 12z's go cold / blocked

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8 minutes ago, mountain shadow said:

I'm sure the Greek weather geeks must love a GB high cell in Winter.

Not the ones that live in the UK! lol

Anyway, good to see another split in the stratosphere.

Edited by karyo

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3 minutes ago, Seasonality said:

A high centred over or to the west of the UK is a theme that is being repeated in FI. Gives some decent cold for my location. 

gfs-0-384 (2).png

The large cell...will/should likely retro-or expand and try to plot directly into the pole!..

Raw assumption's still in a non decipher/elevated stage.

.....but are gaining/getting there..

Slowly slowly catchy.....

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9 minutes ago, Radiating Dendrite said:

Greece yet again in the freezer! Haha

Not suprised  really  given the large continental  landmass thats around them 

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7 hours ago, Interitus said:

A couple of observations - 'uplift' from mountains doesn't produce 'vertical Rossby waves'. These would be orographic gravity waves - oscillations in the vertical which are restored to equilibrium through the density of the air parcels acting under gravity. They can increase in amplitude with height and reach a point where they break depositing their energy (possibly in the strat). But they are not planetary waves (wave 1, 2 etc) or Rossby waves. Rossby waves act in the horizontal plane perpendicular to the flow with the restorative force being the gradient of potential vorticity (typically north-south). This applies to the stationary waves from mountain torques also, where the height of the topography increases the amplitude of the wave, speed of the flow determines wavelength.

For winter 2009/10, the UK did experience cold weather after the SSW with a deeply negative AO - however the lowest AO and coldest UK weather occurred before the SSW on Feb 9th, as shown in the graph below (windspeed left axis, AO and CET right axis), with a healthy mid and upper strat vortex at the time -

2009-10.thumb.png.7e68f8e9abee6532907062a022df956d.png

 

 

I feel that I must respond to you as I largely disagree. Before I start, I should say that you have a most unfortunate habit of either misquoting long posts, cherry picking and quoting out of context or missing the main points being delivered in the post. You have actually managed to achieve all of these in only two paragraphs of your "observations"! While I respect that you have been specialising in the stratospheric processes for much longer than myself, some of your arguments are based on earlier theories which do not always reflect the latest thinking. Some of the interaction between the lower tropospheric teleconnective drivers and how they combine to influence the stratosphere, has, as I'm sure you realise, undergone significant change in recent years with an evolution of the understanding and considerable research being undertaken. This is gathering momentum with a number of new papers being published and a whole raft of them in the pipeline - not least various investigations into the early 2018 SSW events. As you have responded on this thread, I shall do likewise but I will copy this across to the strat thread afterwards so that other strat specialists can comment on this new theory and I will be facinated to hear what they have to say.. 

Much of my last two main posts were centred around putting the recent theory on the influence of the Mongolian Mountains in helping to trigger major SSW events to the test. For those who wish to follow where we're at and the audit trail, here they are:

My post on page 6 of this thread was entitled: "UPCOMING COLD SPELL - TELECONNECTIONS UPDATE WITH YET MORE ENCOURAGEMENT". 

Here's a direct link: https://www.netweather.tv/forum/topic/91032-hunt-for-cold-model-discussion-heading-into-christmas/?do=findComment&comment=3941269

My previous post entitled from December 13th was on page 295 of the previous model thread:  "A MAJOR SUDDEN STRATOSPHERIC WARMING (SSW) LATER THIS MONTH?  TESTING AN IMPORTANT RECENT THEORY".  

Here's a direct link: https://www.netweather.tv/forum/topic/90862-the-hunt-for-cold-model-discussion-late-november/?do=findComment&comment=3938049

I also referred back to two very long posts that Malcolm @Blessed Weather and I produced on a US forum Teleconnection thread back in April.  In fact you challenged Malcolm and myself to prove some of the links between Mountain Torque (MT) and SSW events back in February/March 2018 immediately after that SSW.  We had been looking into a number of papers on earlier SSWs.  Since then we have not only found some extremely strong evidence but we have built up a library of many 100s of Teleconnection related papers on the US forum. Here's a link to the main topics index (just click on the heading):   INDEX TO PAPERS AND PRESENTATIONS  . It has become so big that we have had to split it into two this week.

The main paper that we're both referring to is:  Orography and the Boreal Winter Stratosphere: the Importance of the Mongolian mountains  (click on the title for a link to the portal abstract where there's a link to the full paper).

This amazing paper was researched and published "before" the 2018 SSW but so much of the theory almost perfectly fitted into the timing of teleconnection interactions in the build up to and the triggering of the major SSW and the secondary warming.  I note that you referenced this paper about 3 months after Malcolm found it and I reviewed it. - so you must have read it but it seems that you are dismissing some of the findings although you do not directly say that - very puzzling. I will not repeat my very detailed review of that paper again now but I will quote from it in relation to several of your rather erroneous comments. 

This on rossby/planetary waves and gravity waves:  

"3.3 Impacts on Wave Activity Orography induced anomalies in EP flux divergence can be caused either by a change in wave activity amplitude or by changes in wave propagation pathways. If changes in wave amplitude were the dominant cause of the orography induced anomalies in EP flux divergence, then the pattern of anomalous EP fluxes would be nearly identical to that in the control just with reduced amplitude. Figures 2f and g show that, near the band of latitudes spanned by the mountains (⇠30-55N), the presence of the Mongolian or Tibetan mountains produces a strong increase in wave activity propagating upwards from the surface into the upper troposphere; however the orography induced EP flux anomalies have generally different propagation pathways from the troposphere to the upper stratosphere than the climatology (c.f. Figures 2f and g with Figure 2d). Mountains thus also induce changes in wave propagation paths. Additionally we find that orography induced anomalies in wave amplitudes for Z at 10 hPa (for wavenumbers k = 1, 2) are inconsistent with the changes in EP flux divergence across the three experiments (see supplemental Figure 196 S2), further suggesting that the orography induced changes in EP flux divergence cannot be attributed solely to the orography acting as an additional source of Rossby waves. –7– Confidential manuscript submitted to Geophysical Research Letters. Since changes in wave amplitude alone cannot explain the changes in EP flux divergence, we examine orography induced anomalies in KS (Figures 2f-h), which can alter wave propagation pathways and thus EP flux divergence. Between ⇠55-80 200 N and 10 hPa the Mongolian mountains induce a change in KS with a positive poleward gradient. This would act to deflect wave activity poleward relative to the control case and thus cause an increase in EP flux convergence poleward of ⇠50N, consistent with the orography induced anomalies in EP flux vectors and convergence in this region (Figure 205 2b). The mountains also generally increase KS in the stratosphere, which will allow more wave activity to propagate vertically into the stratosphere, where it can converge. Orography induced changes in KS are primarily due to changes in the meridional gradient of potential vorticity (qy ) and the zonal wind (u), and not changes in buoyancy ( f 2 0 /4N2H2).  The change in KS due to the Tibetan mountains has a similar spatial structure to the changes due to the Mongolian mountains, but are of smaller magnitude (Figure 2g), consistent with the smaller changes in EP flux divergence and u. Compared to Mongolia or Tibet, the Rockies have a much smaller impact on KS (Figure 2h), consistent with the small impact of the Rockies on the stratospheric zonal wind. These results indicate that changes in refractive index are of central importance for the impact of orography on the wintertime stratospheric circulation. The changes in KS stem from changes in the circulation of the upper troposphere associated with the various orographic features. As shown by White et al. [2017], the Mongolian mountains have a greater impact on the upper tropospheric wintertime circulation than the Tibetan plateau."

Now I won't for one minute admit to understanding the maths and equations (perhaps you do) but I always read the abstract, the introduction and conclusions when I read any paper and if I wish to learn more then I carefully read the full text. I discussed this with Malcolm and this is a decent short summary of that section:   

  • Rossby Waves are a bit of a red herring and (in hindsight) probably shouldn't have been mentioned although many authors do not distinguish between Rossby waves and Planetary waves..
  • Planetary Waves 1 and 2 impacting on EP-Flux convergence/divergence is what it relates to. 
  • This is NOT the amplitude of the Waves but by the mountains altering the propagation pathways of the waves poleward and by also allowing more waves to propagate vertically into the stratosphere.
  • Gravity waves can be part of the process but it is much more than that - there's another whole section on that

 

The main points here and also described in several other recent and some earlier papers which I reviewed in my very long April post, is that the Himalayas obstruct the southerly Asian jet stream. It's the interception by the high Himalayan peaks which are easily high enough to penetrate the lower portion of the jet stream. It doesn't matter whether it's a due west to due east jet flow (as recently and now) or a more south west to north east flow.  I feel that this is where several scientists have misunderstood this "new" theory (or in some cases are not prepared to entertain something that rather challenges conventional wisdom). The recent theory is not suggesting that the jet stream passes directly over the Mongolian range. In fact it very rarely does. It's the channeling and funneling which guides the flow northwards as it rushes down the lee side of the highest Himalayan peaks across the high Tibetan Plateau until it hits the Altai range and this where the extraordinary uplifting is produced (my long post back in April thoroughly examined the whole unique geography of the region with many maps and charts). It simply cannot be a coincidence that the strongest EAMT usually appears at 40N to 45N precisely where the Altai range blocks the flow.  I also explained that the traditional thinking of "only" mountain ranges which are perpendicular to the largely west to east jet stream (like the Rockies and Andies) is not the be all and end all to mountain torque and vertical propagation - in fact very far from it.  Back in 2002 the leading proponent of the GSDM (Global Synoptic Dynamic Model) and the GWO (Global Wind Oscillation) Dr Klaus Weickmann realised that EAMT (East Asian Mountain Torque) had far more impact on vertical propagation than NAMT (North American Mountain Torque) and he even refers to the unique properties of the Tibetan Plateau.  Following through on the development of the latest theories makes for fascinating reading right through to this Mongolian Mountain paper. The authors are currently completing even more research in this field and I imagine the early 2018 SSW and the highly likely late 2018 SSW events will feature heavily as they present further evidence to back up their theories..

Aside from this paper, there also appears to be a link between gravity wave drag (gwd) and EAMT.  Here's a gwd chart that I've rarely seen shown in any post with the MT chart for the same date alongside:

grw1.thumb.PNG.8589a19c2440b5cf11ab36bf671abb2a.PNG   mt13.thumb.PNG.daa5669d414a7b8be0c43b476a2634e6.PNG

They are at their global greatest in the east Asian mountains.  In fact almost all the activity or gwd appears in the sub tropics - mostly in the N Hem (all year round) but in the S hem to a lesser extent in their winter where I've noted some over Antarctica in July and a little around 70S to 75S on the edge of that continent (some pretty high mountain there), mostly in their winter but a little at other times (as can be seen). More recently, most gwd has centred around 40N and there is a partial correlation with EAMT which seems to follow changes in gwd several days afterwards.  Follow the blue and yellow blobs at 30N to 50N right through.  Overall, the point here is that whatever the more significant factor (which might well vary during different episodes) the strongest EAMT spikes appear over the Mongolian Mountains and especially the Altai range.  The vertical propagation on occasions can be so strong that it influences the lower mesosphere and with waves breaking from very high levels.  A prolonged +ve EAMT event (over a few days) can potentially send up successive or multiple impacts with breaking from above and below.  It is essential that this new theory is thoroughly investigated.  I said in my posts that I am putting this theory to the test with the upcomng anticipated SSW.  

Several of the EAMT/Asian Monsoon papers I've read focused heavily on gwd and affirmed that much of the uplift was generated by the EAMT/gwd combo. This is far more in relation to tropospheric impacts and more in the summer half of the year. I've also read a paper on gravity waves and their impact in the tropics and in relation to ENSO and that's another area to study (gws and kelvin wave activity). These are the papers on gws and gwd which are in the Research Portal.  Again just click on the title for a link to the abstract where there's a direct link to the paper:

Gravity Waves (and Gravity Wave drag):

A comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings

Circumglobal Propagation of Successive MJO Events in MERRA-2 - Presentation

Convective Adjustment, Gravity Waves and Diurnal Regulation of Tropical Cyclogenesis - Presentation

Coupling of Stratospheric Warmings with Mesospheric Coolings in Observations and Simulations

Dynamical control of the mesosphere by gravity wave drag

Effects of Parameterized Orographic Drag on Weather Forecasting and Simulated Climatology Over East Asia During Boreal Summer

Gravity wave drag

Gravity Wave Effects on Polar Vortex Geometry During Split-Type Sudden Stratospheric Warmings

Gravity wave refraction by three-dimensionally varying winds and the global transport of angular momentum

Improving weather forecasts via impacts of turbulent orographic form and small-scale orographic gravity wave drag on boundary layers

Interannual variability in the gravity wave drag – vertical coupling and possible climate links

Kelvin Waves - A Learner's Guide

Mountain Waves and Downslope Winds

On the importance of gravity waves in the middle atmosphere and their parameterization in general circulation models

Parameterized Gravity Wave Momentum Fluxes from Sources Related to Convection & Large-Scale Precipitation Processes in Global Atmosphere Model

Propagation of planetary‐scale disturbances from the lower into the upper atmosphere

Regional Variations in Gravity Waves, Latent Heating, and the Tropical Circulation

Role of gravity waves in vertical coupling during sudden stratospheric warmings

Studies of atmospheric angular momentum

The Challenge of Classifying Propagating Synoptic Disturbances in the African Tropics – Examples from the DACCIWA Field Campaign - Presentation

The physics of orographic gravity wave drag

The roles of planetary and gravity waves during a major stratospheric sudden warming as characterized in WACCM

The whole atmosphere response to changes in the Earth’s magnetic field from 1900 to 2000

Toward a Physically Based Gravity Wave Source Parameterization in a General Circulation Model

Variability of African Easterly Wave Structures- Presentation

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

Why do Earth's equatorial waves head east?

I will not review any of these papers now (some readers will be relieved to hear) but in due course some of them can be reviewed on the teleconnections threads (here or across the pond). .

Finally, the part where you misquoted me the most was my reference to the 2009/10 winter. Firstly, as we know, every SSW is different and one should use analogue years with great caution.  The references that I made to that winter was in relation to how well primed the troposphere and surface was to SSW impacts. The difference in the main SSW itself was, as you say, the upcoming event (assuming it does happen which now seems almost certain) will be over 1 month earlier.  I have been referring to the blocking in Russia (right now and expanding HP to come over the next week to days) and another precursor to an SSW is the Asian blocking - probably no coincidence that the powerful jet streak over south and east Asia is propping up that HP.  Then I added in the MJO, AAM, torque factors plus the major "pattern re-set" and a fairly cold and blocked period is expected even without the assistance of an SSW.  To get an early season SSW plus these other teleconnections playing ball more or less simultaneously is particularly encouraging for those looking for cold.  Overall, I am prepared to accept that you may have misunderstood my comments in relation to the 2009/10 winter but most of your "observations" were really pretty wide of the mark.  David 🙂   

Edited by Guest
check charts, links and correct typos

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Looks like the models are toying with a scandi high between 144 and 168 hours and with this warming taking effect theres all the chance in the world that the ridge heads even further north and west and we end up with a full on cold flow from the east!!!lookin for upgrades from here on in!!

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An unsettled end to what's been a very wet Autumn in South Wales with some flooding from 'stuck rainbands' some producing 100-200mm in a day over high ground at times. It's been often windy with gales on the coast in the last few weeks but mostly mild except for frosts during October half term week but these were followed by mostly sunny days. Sunshine recorded in my location is just 8.2 hours so far this month, well below normal. 

However the first week of Winter does look like we'll see a pattern change in time for the Christmas holidays with high pressure near or over us allowing the saturated ground to begin drying out somewhat and possibly more sunshine around as the evenings are now very slowly getting lighter again ☀️☀️☀️😎

image.png

image.png

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