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Paul

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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Sorry guys and girls, feel i may have upset a few people in here tonight, sorry for clogging up the thread with my posts of rubbish. think i may just go back to lurking in here and spending more time in the regional threads. hope you all have a great xmas and a snaw filled new year. take care all.

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1 minute ago, feb1991blizzard said:

I have to say i am a little disappointed with this run TBH, given some of the more stunning output of the last few runs.

Still weeks five and six to come out 

remember that previous runs had troughing just to our west weeks two thru four so to see the block replacing that low anomoly for weeks three and four shows that the model isn’t to be relied upon ! 

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Should re-name this thread to ‘Wake me up, when December ends’.

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8 minutes ago, feb1991blizzard said:

I have to say i am a little disappointed with this run TBH, given some of the more stunning output of the last few runs.

Typical of recent developments really, not going the right way sadly.  Shouldn't come as a surprise.  I'm done for one day!

Edited by Don

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Following my gloomy post earlier, just had a flick through the GEFS 12z between xmas and new year and it's not without wintry interest..there is some cold and indeed snow / snaw..fingers crossed we get a proper wintry spell into early 2019!!!:santa-emoji:

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1 minute ago, bluearmy said:

Still weeks five and six to come out 

remember that previous runs had troughing just to our west weeks two thru four so to see the block replacing that low anomoly for weeks three and four shows that the model isn’t to be relied upon ! 

TBH i think i would have took that run as long as the strat charts in the regular medium range model's and the trop output hd not downgraded recently, added to the fact that the met office are now mentioning its nowhere near a foregone conclusion which suggests the GLOSEA has perhaps downgraded / postponed any split SSW in the last few days, the tide is against us at the moment.

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Just now, Don said:

Typical of recent developments really, not going the right way sadly.

Previous ec 46 runs (whilst being different week 3 and 4) didn’t bring the cold until after week 4 so this renewal is more progressive with the cold by brining it in weeks 3 /4 

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44 minutes ago, Johnp said:

I feel that way about the Exeter 16-30 dayers as well.

What's the harm in making it easier for us all and putting them in one thread?

Basically, in winter I'm interested in

- cold and snow

- how do we get there (strat)

-is there any agreement (Met Office updates)

That's all I'm interested in. 

😎

i agree - mods *please* can we go back to having one model thread!

 

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13 minutes ago, More Snow said:

Sorry guys and girls, feel i may have upset a few people in here tonight, sorry for clogging up the thread with my posts of rubbish. think i may just go back to lurking in here and spending more time in the regional threads. hope you all have a great xmas and a snaw filled new year. take care all.

Don't be silly. I only ever post rubbish and I'm still here! 😁

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Clusters tonight D7: again, showing any Christmas wintryness likely to be a Scottish affair - without heights getting beyond Iceland, unlikely to draw down enough cold to put more southern areas at risk

ec-ens_nat_z500scenarios_2018121712_168.

Onto New Year

ec-ens_nat_z500scenarios_2018121712_360.

Not screaming snowy but could be a very cold high kicking around these parts (not unanimous) 

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1 minute ago, Man With Beard said:

Clusters tonight D7: again, showing any Christmas wintryness likely to be a Scottish affair - without heights getting beyond Iceland, unlikely to draw down enough cold to put more southern areas at risk

ec-ens_nat_z500scenarios_2018121712_168.

Onto New Year

ec-ens_nat_z500scenarios_2018121712_360.

Not screaming snowy but could be a very cold high kicking around these parts (not unanimous) 

The last time we had a cold mostly dry christmas week (25-31 Dec), was 2008, with high pressure coming on the scene just in time for christmas, the cold grew in situ and by new year many places were struggling to get above freezing, with a cold easterly. Some places might have had a bit of snow.

Not saying this will happen, but it will make a refreshing change compared to most recent years. 1992 was another year with a cold frosty christmas period. I'd take that over a wet windy mild one.

 

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18 is shocking , well out to 252 hours anyway, seemingly wants to build a monster PV and hefty euro high..

I dont believe it ,,

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Just now, northwestsnow said:

18 is shocking , well out to 252 hours anyway, seemingly wants to build a monster PV and hefty euro high..

I dont believe it ,,

Perhaps tomorrow will bring something more positive, although I doubt it.

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UPCOMING COLD SPELL - TELECONNECTIONS UPDATE WITH YET MORE ENCOURAGEMENT

I just posted this across the pond on a US weather forum - I copy it here unedited.

This is an update to my last two main posts:

From  December 11th entitled "Looking Great for Extended Cold Spell in Europe and East CONUS from Xmas Onwards" 

(direct link:  https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=110591 ) 

From December 13th entitled "A Major Sudden Stratospheric Warming (SSW) Later This Month?  Testing an Important Recent Theory" 

(direct link:  https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=110901 )

Since then, I have read numerous posts on several threads and many of which IMHO are showing far too much negativity and this seems to be largely due to the model uncertainty which is often at its greatest just before some important broad scale pattern changes.  I hope to allay many of those posters' and readers' fears in this post.

In the last few days we have seen some great posts by our Teleconnections and Stratosphere specialists with a real consensus firming up of the anticipated cold spell.  Today we have seen some great updates from Tams @Tamara, Tom @Isotherm, Zac @Snowy Hibbo, John @earthlight and James @Singularity as well as some others. Everything looks good to me and there is some remarkable agreement on the forthcoming cold spell and if anything, the view is even more bullish than just a few days ago.  The only differences are over precise timing issues.  I'll run through some of the charts with brief comments below each one. 

  mt21.thumb.PNG.4c856047270fdc57eb6053f5c22ac126.PNG

The GWO looks to be looping back up again and we'll be back in phase 5 and rising again quite soon.  Note that the total GLAAM anomaly has remained +ve.

  mt16.thumb.PNG.d0d5704a9b0ab2dad2498b25abc6f050.PNG

GLAAM fell back and then rose again and has levelled off.

  mt15.thumb.PNG.b3ae608ae5079f7cd4a68a9fa99fd452.PNG

Relative AAM tendency, nose dived and then spiked briefly before falling back slightly but with a renewed spike already underway.

 mt14.thumb.PNG.b55597f1c3bdf3f2f45fe6b071ba837d.PNG

FT has stopped falling and has levelled off.

 mt13.thumb.PNG.b7e9e45e168ffdf76638489534be9d09.PNG

The huge spike in global MT (black line) had already ended when I last reported on it but it looks like it has already turned upwards again without going -ve.  The key regional torque, EAMT (red line) peaked last week and is falling back as expected.  It may go briefly -ve but it looks set to rise strongly again within a few days.  Note that the previous strong spike was the one that should have created that powerful uplift from the Tibetan Plateau and Mongolian Mountains with those very strong vertical rossby waves which should impact on the stratosphere around Dec 22nd-24th. The further spike may well produce a similar response in very early January  (more below on that).

 mt19.thumb.PNG.15f5c74655ca309b86aee13b7eaa74fb.PNG

Jet stream looks strong over Himalayas and Tibet now (above) and again (predicted) at T+180 (below).  Link to gif for animations:

http://www.stormsurfing.com/cgi/display_alt.cgi?a=nindi_250

 mt20.thumb.PNG.44c62c3073aa62e21f5071748439e32f.PNG

Remember from the paper that I referred to - the lower part of the jet is obstructed by the very high Himalayan peaks and is partly channeled and funneled across the Tibetan Plateau and rushes northwards until it is uplifted by the Mongolian Mountains.  It is that range (the Altai in particular) that is believed to generate the greatest uplift of all and it was probably no coincidence that the strongest EAMT (the red blob on the MT chart centred around 40N to 45N) was right over that range last week.  The lower charts suggests a repeat in about 7 to 8 days time and if this is roughly correct, that should coincide with the next spike in EAMT in that area (more below).

 mt17.thumb.PNG.762b54150f1bc8e3f4aa3ec0a7d7304d.PNG

As I said a few days ago, the Russian HP is hanging on - in fact it is building slightly. As our specialists have said, some HLB looks likely to be in place "before" we get the "top up" benefit from the SSW itself.  Link to these two charts for animation:  http://www.stormsurfing.com/cgi/display_alt.cgi?a=nindi_slp

 mt18.thumb.PNG.15e4663d5631d7e5f4e3cfcda96423a6.PNG

W Russian HP builds and a new even stronger cell develops from the north and from the south.  The lower troposphere and the surface look nicely prepared and conducive to further blocking.

mt23.thumb.PNG.2d20260e01673ae5da3d6a8c765a7c38.PNG 

The MJO is playing ball too. It's progressing though the "Maritimes" phases 4 and 5 at decent amp. ECM take it to phase 6 and towards phase 7 around the New Year - further supporting HLB.  Given the other background signals, it's quite likely that we may see a further increase in the week 2 amp. 

 mt22.thumb.PNG.408018c4adf7ab6cb44655838512608c.PNG

GEFS is similar - perhaps slightly higher amp but holds it in phase 5 for longer.  Several other models are more progressive and closer to the ECM forecast. Expect further evolution during the next few days - week two MJO forecasts are notoriously unreliable and the main models have still not factored in the broader pattern changes in any event. 

All the above is already suggestive of a fairly blocked pattern becoming established even without the help of a major SSW.  In fact most of our strat specialists should note that the  troposphere would appear to be even more conducive to a decent strat/trop coupling than it was in the early 2018 events. The latest strat charts (GFS and ECM) and comments seem to be going beyond just a wave 1 displacement and the repeated attacks on the SPV will be reinforced by lasts week's EAMT spike around this weekend.  That may well be enough to trigger a major SSW with splitting. Some wave 2 action is starting to look more likely and reasonably early on. So, the SSW perhaps starting over Xmas and reversal and surface impacts perhaps around New Year. The renewed spike in EAMT should help to finish off the SPV as we enter January if it manages to survive the Xmas attack. 

This time the trop patterns + the repeated strat attacks look very likely to produce a much longer cold spell compared to the early 2018 events.  There is so much to be excited about for those seeking cold.  We still need to wait for the precise timing - it may be a few days later than I suggested. Then we need to see exactly where the troughs and ridges set themselves up.  Given the vast Russian HP, it seems highly likely that we shall see that push westwards. It may retrogress to Iceland or Greenland for a while too.  According to several specialists, this may well follow the pattern set up during the 2009/10 SSW when we saw many weeks of cold and snow in both Europe, the UK and the eastern CONUS. Too early to be certain of that yet.    

So, the next few days are likely to see a flatter pattern with higher temps and pretty unsettled and windy at times too but that is all part of the build up to the "re-set".  If anything this more zonal pattern is looking to be even briefer than suggested a week ago.  Watch out for some big changes in the models later this week with some exciting charts showing up for just beyond Xmas.   

David :) 

 

Edited by Guest
check charts, links and correct typos

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3 minutes ago, northwestsnow said:

18 is shocking , well out to 252 hours anyway, seemingly wants to build a monster PV and hefty euro high..

I dont believe it ,,

I'm not overly surprised about this - it's basically increasing a signal we've seen building in the last few days and producing something of a large Euro High - I cannot say I don't believe this nor am I surprised. 

If we're looking for just a bit of something from a real cold perspective - it may well be a good few weeks down the line into the new year as that high pressure growing up over the top of the country looks like a bit of a heavy weight to shift - but it's not going to last forever and it'll be interesting to see what does happen after it retires out the way. I feel either one extreme or the other.

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@Bring Back1962-63 amazing post, lots to look out for and to look forward too.

looking forward to future updates.

fromey

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Expecting the models to show various fayre over coming days with regard to the location of heights set to build into the UK in time for christmas - so don't be surprised to see some sinking it south, some building it out west and some north, whilst others show it over the UK - take the models with lots of uncertainty right now.

 

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GFS OP has now given up on the SSW. Deep cold recovering quickly after a minor warming. What do the GEFS say?

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8 minutes ago, Bring Back1962-63 said:

 

So, the next few days are likely to see a flatter pattern with higher temps and pretty unsettled and windy at times too but that is all part of the build up to the "re-set".  if anything this more zonal pattern is looking to be even briefer than suggested a week ago.  Watch out for some big changes in the models later this week with some exciting charts showing up for just beyond Xmas.   

David :) 

mt23.PNG

Thank you so much for such an informative post. I may not get all of it but I still learn from it and your research and knowledge is most gratefully received!!! What a little gem you are to have in our forum!!!😀

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Bring Back1962-63

Great post much appreciated and gives us all pointers on things to look out for. And not to get to hung up on the models at present. Thankyou.

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Many thanks for this @Bring Back1962-63. Would be great if this could be pinned at top of page! 

I also noticed @Tamara had a slight ramp if we can call it that with regard to NY pattern onwards. Model mayhem as they try to figure out what will happen after strat warming - doubt it will be what GFS 18z run shows with PV locked in over Greenland and expanding.

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5 minutes ago, Snowy L said:

GFS OP has now given up on the SSW. Deep cold recovering quickly after a minor warming. What do the GEFS say?

Sorry, which planet are you referring to?

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4 minutes ago, bobbydog said:

Sorry, which planet are you referring to?

10Hpa temps are at -80 in the vortex core at day 16

gfsnh-10-384.png?18

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