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The hunt for cold - Model discussion (late November)


Paul
Message added by 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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Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl
3 minutes ago, Catacol said:

No charts today from me - but a request for a bit of resilience in this thread over the coming few days. I don't think the ridge next week is going to hold: there isn't the background forcing to sustain it, and it really is just an echo from the final phase of the last pacific wave. Let's not throw the toys out if/when battleground scenarios next week get watered down. It is possible we might have a transient snow event - but to my eye it is really only going to be transient.

It is very clear that torques are reengaging now, and that we are going to see a spike in AAM once again over the coming 1 - 2 weeks. This is going to begin the process of enhancing westerlies at 30N and scrubbing them out at 60N. The jet will drop south in that time span, and the extension of the pacific jet specifically will help reengage a high lat block pattern. Signs of this will begin to appear in NWP modelling in the next few days at the extended range, but it will take until the end of the week until we see NWP pick up on this progression consistently. In the meantime don't mourn the shunting east of the scandy ridge in its upcoming form too much. 

I'm confident of this longer term progression and confident that we will see blocking entrench in the second half of this month driven by the new pacific wave. And this is a pattern that will entrench into January. Great news for all snow lovers. The really interesting bit now is just how the impact of this very favourable pacific pattern will combine with top down impacts from a strat warming event. The Siberian high / Aleutian low Nino combo looks to be a pattern that is going to sustain over the medium term at least - and with such sustained pressure it looks unlikely that the vortex can hold its ground. But will it shatter or just wobble badly? I don't think anyone can be confident of that process yet - all the keen minds in other places are agreed on the magnitude of the hit that is coming - but I've not read a single punter willing to put a bet down on just how this will play out. Pacific forcing will not be overridden by the much weakened vortex in its forecast state - but will the shape of upper winds help reinforce that trop led pattern? If it does then we could be in for a very special period of weather. If it doesn't then cold will still come, but less dramatic in its impacts.

Good post - perhaps today marks a downward point - and from here on in, the models and trends will begin to increasingly point to ever colder synoptics more likely to embed themselves - as par for the course at this juncture at such an early stage in the winter - patience being the watchword, frustrating right now, but all quite normal. I like cold and snowy conditions pre-chrismas, but the statistics show, more likely to see such conditions in March and indeed April.. I blame christmas!

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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.
7 minutes ago, Catacol said:

No charts today from me - but a request for a bit of resilience in this thread over the coming few days. I don't think the ridge next week is going to hold: there isn't the background forcing to sustain it, and it really is just an echo from the final phase of the last pacific wave. Let's not throw the toys out if/when battleground scenarios next week get watered down. It is possible we might have a transient snow event - but to my eye it is really only going to be transient.

It is very clear that torques are reengaging now, and that we are going to see a spike in AAM once again over the coming 1 - 2 weeks. This is going to begin the process of enhancing westerlies at 30N and scrubbing them out at 60N. The jet will drop south in that time span, and the extension of the pacific jet specifically will help reengage a high lat block pattern. Signs of this will begin to appear in NWP modelling in the next few days at the extended range, but it will take until the end of the week until we see NWP pick up on this progression consistently. In the meantime don't mourn the shunting east of the scandy ridge in its upcoming form too much. 

I'm confident of this longer term progression and confident that we will see blocking entrench in the second half of this month driven by the new pacific wave. And this is a pattern that will entrench into January. Great news for all snow lovers. The really interesting bit now is just how the impact of this very favourable pacific pattern will combine with top down impacts from a strat warming event. The Siberian high / Aleutian low Nino combo looks to be a pattern that is going to sustain over the medium term at least - and with such sustained pressure it looks unlikely that the vortex can hold its ground. But will it shatter or just wobble badly? I don't think anyone can be confident of that process yet - all the keen minds in other places are agreed on the magnitude of the hit that is coming - but I've not read a single punter willing to put a bet down on just how this will play out. Pacific forcing will not be overridden by the much weakened vortex in its forecast state - but will the shape of upper winds help reinforce that trop led pattern? If it does then we could be in for a very special period of weather. If it doesn't then cold will still come, but less dramatic in its impacts.

I remember how confident you were of the SSW last February and its impact for our part of the globe from quite a long way out, and you were spot on, so fingers crossed!

When you talk about the strat warming, would that be the warming showing up for mid December or more significant warming later? From my understanding of what I've read, the former is expected around mid December and the latter around late December/early January but not sure whether there is still a good level of confidence in that.

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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull
23 minutes ago, blizzard81 said:

Certainly many variables at play which makes meteorology so fascinating. With regards to sst's in the Atlantic  and it's affect on the nao, the met office used this as one of their main driver's for UK winter weather forecasts for many years - sst's off the eastern seaboard of US in May corresponding to those during the following winter. The met office then abruptly changed this method of forecasting about 8 to 10 years ago due to little evidence of this theory having any bearing on UK winter patterns at all. 

They used to use May SSTs for upcoming winter forecasts. It's still a factor to consider but forecasts have become more sophisticated since then and we have had the research into SSWs which we are only now beginning to appreciate the importance of.

The SSTs now right though are key. If you have cold continental air pouring out of Canada and moving above warm SSTs, you are going to see rapid deepening of low pressure systems, its basic physics as you get steep lapse rates under such setups.

In 2010 the SST pattern was the opposite of what we see now. It has a big bearing, its just difficult to forecast because the way in which SSTs are influenced by cold air over NE Canada. Anyhow look at how December 2018's SST pattern compares to 2010.

image.thumb.png.fa34fc6176db3b688c00d4c2787f5c76.png December 2018

image.thumb.png.b63c39559b9c950540d5c04e2d190ac1.png Early January 2011

 

I personally am apprehensive of a snow event next week. It will be a nice bonus if it happens. I'm more interested in when the NE Canada cold pool dissipates as I expect the Atlantic to wind down if it happens,

Edited by Quicksilver1989
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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.
2 minutes ago, Quicksilver1989 said:

They used to use May SSTs for upcoming winter forecasts. It's still a factor to consider but forecasts have become more sophisticated since then and we have had the research into SSWs which we are only now beginning to appreciate the importance of.

The SSTs now though are key. If you have cold continental air pouring out of Canada and moving above warm SSTs, you are going to see rapid deepening of low pressure systems, its basic physics as you get steep lapse rates under such setups.

In 2010 the SST pattern was the opposite of what we see now. It has a big bearing, its just difficult to forecast because the way in which SSTs are influenced by cold air over NE Canada. Anyhow look at how December 2018's SST pattern compares to 2010.

image.thumb.png.fa34fc6176db3b688c00d4c2787f5c76.png December 2018

image.thumb.png.b63c39559b9c950540d5c04e2d190ac1.png Early January 2011

So those current colder than average SSTs off the eastern seaboard should go against cyclogenisis when cold air from eastern Canada moves over that area? On the other hand, the temperature gradient between those anomalously cold SSTs and anomalously warm SSTs further south/south east would probably boost cyclogenisis. 

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Posted
  • Location: Winterbourne, South Glos
  • Location: Winterbourne, South Glos
1 hour ago, blizzard81 said:

You were direct with your reply there and each to their own. Now allow me to be just as direct when I say that I totally disagree with your assumptions on this subject.

Quicksilver1989 didn't state any assumptions.

Edited by kumquat
Got my facts wrong
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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull
5 minutes ago, MattStoke said:

So those current colder than average SSTs off the eastern seaboard should go against cyclogenisis when cold air from eastern Canada moves over that area? On the other hand, the temperature gradient between those anomalously cold SSTs and anomalously warm SSTs further south/south east would probably boost cyclogenisis. 

Correct. I consider cold air in NE Canada as our winter gremlin as it helps spew up some deep Atlantic lows. The only time it doesn't work against us is when we have a big Scandi high, AKA the beast last February.

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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.
4 minutes ago, Quicksilver1989 said:

Correct. I consider cold air in NE Canada as our winter gremlin as it helps spew up some deep Atlantic lows. The only time it doesn't work against us is when we have a big Scandi high, AKA the beast last February.

Can also help increase the wintriness of any north westerly though. Last winter I saw quite a bit of snow from the North West thanks to colder than average SSTs in that area. Swings and roundabouts!

Edited by MattStoke
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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
12 minutes ago, Quicksilver1989 said:

They used to use May SSTs for upcoming winter forecasts. It's still a factor to consider but forecasts have become more sophisticated since then and we have had the research into SSWs which we are only now beginning to appreciate the importance of.

The SSTs now right though are key. If you have cold continental air pouring out of Canada and moving above warm SSTs, you are going to see rapid deepening of low pressure systems, its basic physics as you get steep lapse rates under such setups.

In 2010 the SST pattern was the opposite of what we see now. It has a big bearing, its just difficult to forecast because the way in which SSTs are influenced by cold air over NE Canada. Anyhow look at how December 2018's SST pattern compares to 2010.

image.thumb.png.fa34fc6176db3b688c00d4c2787f5c76.png December 2018

image.thumb.png.b63c39559b9c950540d5c04e2d190ac1.png Early January 2011

 

I personally am apprehensive of a snow event next week. It will be a nice bonus if it happens. I'm more interested in when the NE Canada cold pool dissipates as I expect the Atlantic to wind down if it happens,

As Matt Stoke has just inferred, if the sst theory is put to the test, then it explains why our winter went off the rails after Dec 10. However, if anything there looks to be a lesser temp gradient this month off the eastern us seaboard so you would expect less cyclogenesis. Again this takes me back to the beginning of this debate - solar influences!

 

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Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
2 minutes ago, MattStoke said:

Can also help increase the wintriness of any north westerly though. Last winter I saw quite a bit of snow from the North West thanks to colder than average SSTs in that area. Swings and roundabouts!

Yes - and as Roger has pointed out: there's a lot of unusually cold air over the Canadian arctic this season. Any NW element could carry a real punch if not moderated by warm oceans too much...

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1 minute ago, blizzard81 said:

As Matt Stoke has just inferred, if the sst theory is put to the test, then it explains why our winter went off the rails after Dec 10. However, if anything there looks to be a lesser temp gradient this month off the eastern us seaboard so you would expect less cyclogenesis. Again this takes me back to the beginning of this debate - solar influences!

 

Lol you might eat your words

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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.
7 minutes ago, Catacol said:

We are seeing wave 2 warming hit a peak in about 5 days

ecmwfzm_ha2_f120.thumb.gif.40acb7213a67c031c698c8e79870e198.gif

and then wave 1 to follow

ecmwfzm_ha1_f240.thumb.gif.5825194f6d2efcd05709076c07492a1b.gif

From there we have extended modelling seeing that continue - courtesy of the Nino SH/AL combo

gfs_Tz10_nhem_27.thumb.png.f7ec6c26b2e5aef1542e837dfae1ab9f.png

All of this looks a given at the moment - BUT the exact shape and position of the vortex once all this has occurred (312 hours being on the cusp of Xmas) is hard to visualise at the moment. GP has gone for a technical warming 3 days after the last image above which may well prove to be close to the mark. What we need to help make some really special synoptics is the vortex post-warming to end up more on the Siberian side and not over the atlantic. Over the atlantic will not help reinforce the high lat blocking pattern that I think will establish there....instead we want vortex influence below 50hpa to sit more over to the east to help invigorate any troughing that could can help sustain an east-west flow under the block. Alternatively (but less beneficial I think) would be vortex energy dropping over the US to encourage that southerly tracking jet to bump underneath the block in a more "normal" west to east fashion with battleground potential. But for us down here in the SW that's not so good!!! Too much scope for marginality. What happened in February was near perfect - almost total vortex destruction with a shard dropping over Siberia and creating that remarkable reverse flow in March.

It's all up for grabs. But the foundations are there to build on from the timing, size and central pacific shape of the forecast ENSO/MJO conditions over the next 6 weeks. 

Fascinating stuff.

 

So the current warming at the 10hpa level being shown over towards Asia is in a decent position for us? Or would it be better if the warming was over our side of the globe? That's something I don't really understand. Can be some great warming showing up on the GFS at that level but not sure whether it's in the right place to enhance our chances of cold.

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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull
8 minutes ago, MattStoke said:

Can also help increase the wintriness of any north westerly those. Last winter I saw quite a bit of snow from the North West thanks to colder than average SSTs in that area. Swings and roundabouts!

Yup it certainly is! I remember the winter of 2014/15 was one of the most westerly on record yet the CET was close to normal. NW'lies can carry a punch but the flipside is that if you see SW'lies they will be warmer then usual because of the sharp SST gradient e.g. December 2015.... yuk

From a NIMBY perspective I'd rather see some Scandi highs  

Edited by Quicksilver1989
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Posted
  • Location: Southside Glasgow (135m)
  • Weather Preferences: Beginning with S ending with W ;)
  • Location: Southside Glasgow (135m)
6 minutes ago, Catacol said:

We are seeing wave 2 warming hit a peak in about 5 days

ecmwfzm_ha2_f120.thumb.gif.40acb7213a67c031c698c8e79870e198.gif

and then wave 1 to follow

ecmwfzm_ha1_f240.thumb.gif.5825194f6d2efcd05709076c07492a1b.gif

From there we have extended modelling seeing that continue - courtesy of the Nino SH/AL combo

gfs_Tz10_nhem_27.thumb.png.f7ec6c26b2e5aef1542e837dfae1ab9f.png

All of this looks a given at the moment - BUT the exact shape and position of the vortex once all this has occurred (312 hours being on the cusp of Xmas) is hard to visualise at the moment. GP has gone for a technical warming 3 days after the last image above which may well prove to be close to the mark. What we need to help make some really special synoptics is the vortex post-warming to end up more on the Siberian side and not over the atlantic. Over the atlantic will not help reinforce the high lat blocking pattern that I think will establish there....instead we want vortex influence below 50hpa to sit more over to the east to help invigorate any troughing that could can help sustain an east-west flow under the block. Alternatively (but less beneficial I think) would be vortex energy dropping over the US to encourage that southerly tracking jet to bump underneath the block in a more "normal" west to east fashion with battleground potential. But for us down here in the SW that's not so good!!! Too much scope for marginality. What happened in February was near perfect - almost total vortex destruction with a shard dropping over Siberia and creating that remarkable reverse flow in March.

It's all up for grabs. But the foundations are there to build on from the timing, size and central pacific shape of the forecast ENSO/MJO conditions over the next 6 weeks. 

Fascinating stuff.

 

Thanks for this Catacol. Looks like we could be looking at most interesting winter since 2009 or 2010 especially with this occurring around start and into heart of winter. In regard to the strat, are we also seeing somewhat of a Canadian warming in next week to 10 days looking at some charts?

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
3 minutes ago, Mokidugway said:

Lol you might eat your words

Forgive me if I am being a little dim but please elaborate.

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Posted
  • Location: Chevening Kent
  • Location: Chevening Kent

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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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull
8 minutes ago, blizzard81 said:

As Matt Stoke has just inferred, if the sst theory is put to the test, then it explains why our winter went off the rails after Dec 10. However, if anything there looks to be a lesser temp gradient this month off the eastern us seaboard so you would expect less cyclogenesis. Again this takes me back to the beginning of this debate - solar influences!

 

The plot for December 2018 shows a sharp SST gradient just to the east of North America/ to the south of Greenland and that is the problem for the moment. It's the reason why we are seeing some deep lows forming next week.

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Posted
  • Location: Winterbourne, South Glos
  • Location: Winterbourne, South Glos
19 minutes ago, MattStoke said:

So those current colder than average SSTs off the eastern seaboard should go against cyclogenisis when cold air from eastern Canada moves over that area? On the other hand, the temperature gradient between those anomalously cold SSTs and anomalously warm SSTs further south/south east would probably boost cyclogenisis. 

Can we see some sst charts from Eastern Canada and the Eastern Seaboard? I honestly don't know where to look. Meteociel?

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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull
3 minutes ago, kumquat said:

Can we see some sst charts from Eastern Canada and the Eastern Seaboard? I honestly don't know where to look. Meteociel?

anomnight.12.6.2018.gif Latest SSTs

https://www.ospo.noaa.gov/Products/ocean/sst/anomaly/ 

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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)

some tidy charts beginning to appear towards the later stages of the GFS on this side of the pond which could have a positive knock effect for cold across UK after xmas

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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
5 minutes ago, Quicksilver1989 said:

The plot for December 2018 shows a sharp SST gradient just to the east of North America/ to the south of Greenland and that is the problem for the moment. It's the reason why we are seeing some deep lows forming next week.

Based on the past met office sst theory you would take those Dec 18 sst anomalies all day long if wishing for a cold UK winter.

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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
3 minutes ago, blizzard81 said:

Based on the past met office sst theory you would take those Dec 18 sst anomalies all day long if wishing for a cold UK winter.

looks like a tripole that = a positive NAO signal for the winter months

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Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
10 minutes ago, Bullseye said:

Thanks for this Catacol. Looks like we could be looking at most interesting winter since 2009 or 2010 especially with this occurring around start and into heart of winter. In regard to the strat, are we also seeing somewhat of a Canadian warming in next week to 10 days looking at some charts?

Certainly signs of the warming emphasis circulating west to east on the Berlin charts - by day 10 there is a Canadian element to the warming pattern - yes. May help shift the weakening vortex over towards Siberia rather than mid atlantic in the longer term. Could we then see a Euro side warming event on the back of this long lasting autumn Euro/Scandy high pattern emerge to strike straight through its heart? Possible....but I'm not going to speculate quite as far as that yet. Don't have the skill.

My confidence at present is mostly grounded in pacific forcing. Impacts from the strat are the next stage......

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