Stratosphere and Polar Vortex Watch 2020

[SqueakheartLW]

What a difference a week makes

ECM

Last Week

Predicted 60N 10hpa zonal winds were expected to be back to average by 4th November before going above average for a while before then maybe getting back to around average by December

Today

It would seem the ECM is backing away from powering up the zonal winds back to average so quickly as it was and now has us returning to average by around the 11th instead. Not only that we only just barely scrape above average for about a week before we weaken the zonal winds again and go some way below the average into December now.

GFS

Only wish the GFS was more bullish in backing off it's return to average then above average zonal winds too. Have seen many charts like the one below recently with a big strengthening of the zonal winds at most levels of the atmosphere at the stratospheric level at least.

[Griff]

13 minutes ago, Griff said:

Mustn't grumble! 

Don't @ me you groovie cats! 

 

8 minutes ago, sebastiaan1973 said:

Thanks Griff. We don't see a stratospheric vortex on fire. New warming after 15th of november.

Yes, some interesting days ahead  

[bluearmy]

1 hour ago, SqueakheartLW said:

What a difference a week makes

ECM

Last Week

Predicted 60N 10hpa zonal winds were expected to be back to average by 4th November before going above average for a while before then maybe getting back to around average by December

Today

It would seem the ECM is backing away from powering up the zonal winds back to average so quickly as it was and now has us returning to average by around the 11th instead. Not only that we only just barely scrape above average for about a week before we weaken the zonal winds again and go some way below the average into December now.

GFS

Only wish the GFS was more bullish in backing off it's return to average then above average zonal winds too. Have seen many charts like the one below recently with a big strengthening of the zonal winds at most levels of the atmosphere at the stratospheric level at least.

Apples and oranges 

ec is taking the zonal winds above average in a fortnight.  So is gfs .  Take out the straggling ec 46 runs and the mean would take the flow to the same levels as gfs. 30/35 m/s.  
 

it now looks as though ec is not keen to maintain the flow above average.  I saw a tweet earlier that showed glosea at 30hpa and that showed an average November being followed by a gradual reduction to below average as we head through the second half of dec 

Onto Mondays run now !

[Catacol]

3 hours ago, Griff said:

 

Yes, some interesting days ahead  

If ECM is to be believed we are seeing an embedding of the right pressure pattern through November for vortex disruption. Note the semi permanent sceuro high anomaly and a stubborn low pressure anomaly in the North Pacific. Things might just be beginning to fall into place….

500 hPa Z: Weekly mean anomalies

APPS.ECMWF.INT

---

Weekly-mean 500hPa geopotential anomaly for the ensemble mean

500 hPa Z: Weekly mean anomalies

APPS.ECMWF.INT

---

Weekly-mean 500hPa geopotential anomaly for the ensemble mean

500 hPa Z: Weekly mean anomalies

APPS.ECMWF.INT

---

Weekly-mean 500hPa geopotential anomaly for the ensemble mean

 

Edited October 29, 2021 by Catacol

[jules216]

9 hours ago, Catacol said:

If ECM is to be believed we are seeing an embedding of the right pressure pattern through November for vortex disruption. Note the semi permanent sceuro high anomaly and a stubborn low pressure anomaly in the North Pacific. Things might just be beginning to fall into place….

500 hPa Z: Weekly mean anomalies

APPS.ECMWF.INT

---

Weekly-mean 500hPa geopotential anomaly for the ensemble mean

500 hPa Z: Weekly mean anomalies

APPS.ECMWF.INT

---

Weekly-mean 500hPa geopotential anomaly for the ensemble mean

500 hPa Z: Weekly mean anomalies

APPS.ECMWF.INT

---

Weekly-mean 500hPa geopotential anomaly for the ensemble mean

 

Semi permanent Sceru high How did I know this back on 14.10 it will rule the pattern. How did I know this will excite folks for a potential of 2 week cold in February based on SSW,.

My take away from this is, how are you going to get cold enough weather with Sceuro/Western Russian permanent high pressure? This has a potential of the ugliest pattern that exist, that NAO blocking will arrive, western Europe will get cold but only cold enough for rain so your bills will be high and Alps will get plastered over 1000m asl. How does that sound?  I dont mean to be offensive, just we have been here before.

[Catacol]

1 hour ago, jules216 said:

Semi permanent Sceru high How did I know this back on 14.10 it will rule the pattern. How did I know this will excite folks for a potential of 2 week cold in February based on SSW,.

My take away from this is, how are you going to get cold enough weather with Sceuro/Western Russian permanent high pressure? This has a potential of the ugliest pattern that exist, that NAO blocking will arrive, western Europe will get cold but only cold enough for rain so your bills will be high and Alps will get plastered over 1000m asl. How does that sound?  I dont mean to be offensive, just we have been here before.

Jules - the days of alternative options for the U.K. have gone. CC has produced a context (warming oceans, warming Arctic, cooling stratosphere, northerly shift in the Hadley Cell) that means (in my opinion) that proper cold in Western Europe will not arrive without vortex disruption. You live in a part of Europe that has a different local context and continental cold can and will still strike….but not for us unless we can break the frictional domination of the stratospheric vortex. Being a U.K. site this means looking for opportunities for vortex disruption to benefit the U.K. in the longer term and to my eye the signs we can get some are increasing thanks to that ScEuro anomaly. 
 

Two weeks of February cold are not to be sniffed at in the U.K. these days. 2 weeks of proper cold has become a very rare event away from high ground in the usual sweet spots. We got unlucky last year with the impacts of vortex stress - hopefully we can get a bit luckier this year if a SSW strikes. And if there is no SSW we will have an average to mild winter in the U.K.

[jules216]

8 minutes ago, Catacol said:

Jules - the days of alternative options for the U.K. have gone. CC has produced a context (warming oceans, warming Arctic, cooling stratosphere, northerly shift in the Hadley Cell) that means (in my opinion) that proper cold in Western Europe will not arrive without vortex disruption. You live in a part of Europe that has a different local context and continental cold can and will still strike….but not for us unless we can break the frictional domination of the stratospheric vortex. Being a U.K. site this means looking for opportunities for vortex disruption to benefit the U.K. in the longer term and to my eye the signs we can get some are increasing thanks to that ScEuro anomaly. 
 

Two weeks of February cold are not to be sniffed at in the U.K. these days. 2 weeks of proper cold has become a very rare event away from high ground in the usual sweet spots. We got unlucky last year with the impacts of vortex stress - hopefully we can get a bit luckier this year if a SSW strikes. And if there is no SSW we will have an average to mild winter in the U.K.

But isnt the UK cold potential ever augmented by not enough cold source in central Europe because of that stubborn high pressure to the east that its been praised as good pattern now? I dont recall any situation where UK has benefited from snow where we have been missed in central Europe appart from some synoptic from Feb 2009 and parts of winter 2009/10.

[Catacol]

1 hour ago, jules216 said:

But isnt the UK cold potential ever augmented by not enough cold source in central Europe because of that stubborn high pressure to the east that its been praised as good pattern now? I dont recall any situation where UK has benefited from snow where we have been missed in central Europe appart from some synoptic from Feb 2009 and parts of winter 2009/10.

Broadly speaking you are right. But aside from the freakish Dec 2010 when was the last time the U.K. tapped into substantive cold without an SSW? Extremely hard to get a high latitude block in a winter where the vortex takes control. So given it is only November anything that can set the vortex up for a fall is good news for U.K. snow chances over the season to come. 

Edited October 29, 2021 by Catacol

[jules216]

2 hours ago, Catacol said:

Broadly speaking you are right. But aside from the freakish Dec 2010 when was the last time the U.K. tapped into substantive cold without an SSW? Extremely hard to get a high latitude block in a winter where the vortex takes control. So given it is only November anything that can set the vortex up for a fall is good news for U.K. snow chances over the season to come. 

Given its November and La Nina me on other hand would like to cash in on early cold as snow in Novembers here used to be so typical of La Ninas - 1995,1998,1999,2005,2007,2010,2011,2016 to a degree and most of these did not hurt our later season snow chances at all. Its Amazing but we had even more bad luck with snow here then UK did since 2012/13, which seen 50+cm from BFTE. The Ural high or Sceuro high whichever you call it did nothing but bring misery. No wonder why there were 4 out of 5 last winters SSW, it usualy means we in central Europe have to take it on the chin while USA and Western Europe/Alps or Scandi are laughing. The biggest cold events here do not require -NAO synoptics but do require Ural high to bugger of

[Catacol]

11 minutes ago, jules216 said:

Given its November and La Nina me on other hand would like to cash in on early cold as snow in Novembers here used to be so typical of La Ninas - 1995,1998,1999,2005,2007,2010,2011,2016 to a degree and most of these did not hurt our later season snow chances at all. Its Amazing but we had even more bad luck with snow here then UK did since 2012/13, which seen 50+cm from BFTE. The Ural high or Sceuro high whichever you call it did nothing but bring misery. No wonder why there were 4 out of 5 last winters SSW, it usualy means we in central Europe have to take it on the chin while USA and Western Europe/Alps or Scandi are laughing. The biggest cold events here do not require -NAO synoptics but do require Ural high to bugger of

Ha - well you won't get much sympathy on here if you are able to reel off eight Novembers since 1995 when it snowed properly. I've seen snow personally in November once that I can remember in my lifetime, and that was 2005. I was in South Wales coaching on a rugby tour, and for once it was not the weather I wanted as both games were cancelled. I cant ever remember November snow other than this, and I have passed the half century....

And panic not. I was fortunate enough to be in the MetO red warning area for BFTE in 2018 and away from high ground 50cm was not what we got.

I will hope for an extended ScEuro high that stresses the vortex enough to cause an almighty split in Xmas week. And if one vortex shard can spin its way from Asia into Western Europe while a ridge builds over Greenland then we can all cash in on the fun..... 

[jules216]

55 minutes ago, Catacol said:

Ha - well you won't get much sympathy on here if you are able to reel off eight Novembers since 1995 when it snowed properly. I've seen snow personally in November once that I can remember in my lifetime, and that was 2005. I was in South Wales coaching on a rugby tour, and for once it was not the weather I wanted as both games were cancelled. I cant ever remember November snow other than this, and I have passed the half century....

And panic not. I was fortunate enough to be in the MetO red warning area for BFTE in 2018 and away from high ground 50cm was not what we got.

I will hope for an extended ScEuro high that stresses the vortex enough to cause an almighty split in Xmas week. And if one vortex shard can spin its way from Asia into Western Europe while a ridge builds over Greenland then we can all cash in on the fun..... 

I would say this type of setup would be well overdue and I mean still within winter months not spring like past post SSW years.

[summer blizzard]

November snow did used to be pretty common until about 2010, every few years. 

[Dorsetbred]

On 29/10/2021 at 16:16, Catacol said:

I will hope for

1) an extended ScEuro high

2) that stresses the vortex enough

3) to cause an almighty split

4) in Xmas week.

And

5) if one vortex shard

6) can spin its way from Asia

7) into Western Europe

8)) while a ridge builds

9) over Greenland

then

we can all cash in on the fun..... 

I don't think that sounds too much to ask for......do you?

[Tom Clarke]

7 hours ago, Catacol said:

Broadly speaking you are right. But aside from the freakish Dec 2010 when was the last time the U.K. tapped into substantive cold without an SSW? Extremely hard to get a high latitude block in a winter where the vortex takes control. So given it is only November anything that can set the vortex up for a fall is good news for U.K. snow chances over the season to come. 

This is interesting, so when we used to have much colder winter spells - 70s,80s, were they result of these SSWs - which I understand to be fairly rare ? 

[summer blizzard]

20 minutes ago, Tom Clarke said:

This is interesting, so when we used to have much colder winter spells - 70s,80s, were they result of these SSWs - which I understand to be fairly rare ? 

Full SSW's only occur every few years but almost every winter has a period of weaker than normal zonal winds or the zonal wind profile displaced favourably for the UK. In many winters the background teleconnection profile has also been relatively kind. 

Moral of the story is that even with climate change we will always see periods like the mid 80's or late 10's where a collection of winters stack up.

[Catacol]

9 minutes ago, summer blizzard said:

Full SSW's only occur every few years 

Not really. If you look at Amy Butler’s research there were 15 SSWs between 1998 and 2013. Each different, each offering lagged tropospheric impacts. The issue with many of them though is timing - a good number happen late in February meaning impacts are swallowed up in Spring.

[virtualsphere]

39 minutes ago, Tom Clarke said:

This is interesting, so when we used to have much colder winter spells - 70s,80s, were they result of these SSWs - which I understand to be fairly rare ? 

SSWs are relatively frequent (60% of years between 1958 and 2019 according to this paper), but getting one in the heart of winter is rarer, and getting one which results in a cold outcome for the UK isn't guaranteed either - in some instances the UK seems to have had more cold weather from the precursor pattern leading to the SSW than after the event itself.  EQBO seems to increase the chance of a SSW (90% according to the paper I posted).

Looking at this, there were SSW events in Feb '79, Feb '80, Mar '81, Dec '81, Feb '84, Jan '85, Jan '87, Dec '87, Mar '88 and Feb '89: there was then no further SSW until 1998.  Thinking of how some of the memorable UK cold spells of this period fit in, 1979 was cold from January suggesting the precursor pattern may have had an impact; the Dec '81 SSW was at the beginning of the month so may have led to that cold December and early Jan '82; the SSW on 1 Jan '85 may have aided the cold Jan and Feb that year.  The Jan '87 SSW was on 23rd, which was slightly after the famous deep cold spell.  1987/88 and 1988/89 were both mild winters.  There was no SSW in 1990/91 or 1995/6 which both saw cold weather.

'

[Catacol]

52 minutes ago, Tom Clarke said:

This is interesting, so when we used to have much colder winter spells - 70s,80s, were they result of these SSWs - which I understand to be fairly rare ? 

A very good question. The evidence is rather conflicting. Some of our great spells were preceded by an SSW - BFTE in 2018, March 2013….there was an SSW in Dec 81 and one in Jan 85. A Canadian Warming in Dec 62 was followed by an SSW in Jan 63. But equally we have had cold spells such as Feb 91, Feb 96 and the famous Dec 2010 where there wasn’t an SSW. Jury is out. But there is a difference between a displaced and a split vortex, and for my part in any case I think weather patterns have changed. What used to happen in the 60s-80s I don’t think is relevant anymore. Since 2010 I think it is possible to argue that our cold has only really come from an SSW, and the relative infrequency of SSWs from 2010 to 2020 matches a run of pretty dire winters, 2013 and 2018 excepted when SSWs tipped cold in our direction.

We will see. Watching the weather move through phases and prove us wrong at every turn is half the fun…

Edited October 29, 2021 by Catacol

[damianslaw]

8 hours ago, Catacol said:

Broadly speaking you are right. But aside from the freakish Dec 2010 when was the last time the U.K. tapped into substantive cold without an SSW? Extremely hard to get a high latitude block in a winter where the vortex takes control. So given it is only November anything that can set the vortex up for a fall is good news for U.K. snow chances over the season to come. 

If you look back pre 2010 I doubt there were many cases when UK benefited from cold without vortex disruption or SSW... scandi heights only.. Greenland heights tend to occur under vortex disruption. Perhaps Feb 91 and Jan 87 when vortex was strong but heights were stronger to the east.

[Mike Poole]

9 hours ago, Catacol said:

Broadly speaking you are right. But aside from the freakish Dec 2010 when was the last time the U.K. tapped into substantive cold without an SSW? Extremely hard to get a high latitude block in a winter where the vortex takes control. So given it is only November anything that can set the vortex up for a fall is good news for U.K. snow chances over the season to come. 

 

1 hour ago, Catacol said:

A very good question. The evidence is rather conflicting. Some of our great spells were preceded by an SSW - BFTE in 2018, March 2013….there was an SSW in Dec 81 and one in Jan 85. A Canadian Warming in Dec 62 was followed by an SSW in Jan 63. But equally we have had cold spells such as Feb 91, Feb 96 and the famous Dec 2010 where there wasn’t an SSW. Jury is out. But there is a difference between a displaced and a split vortex, and for my part in any case I think weather patterns have changed. What used to happen in the 60s-80s I don’t think is relevant anymore. Since 2010 I think it is possible to argue that our cold has only really come from an SSW, and the relative infrequency of SSWs from 2010 to 2020 matches a run of pretty dire winters, 2013 and 2018 excepted when SSWs tipped cold in our direction.

We will see. Watching the weather move through phases and prove us wrong at every turn is half the fun…

I agree with you, in recent years (since 2010) all but one of the proper cold snaps in my location in Oxfordshire have been as a result, one way another, of a SSW (the exception being 10/12/17 which was very M4 marginal!!).  But I don’t think it follows that SSW is the only game in town, 2010 is too recent for there have been too much of a further reduction in likelihood of such things, it may be that such non-SSW cold events are less frequent, I’d buy that, but it doesn’t mean they can’t happen, and while from your posts, I infer you are looking down the SSW route for cold this year, I am not at this stage, I still think there is a meridional hangover from last winter that’s lasted through summer, and may, if the strat vortex can be held at bay, give cold early doors.  We will see…

Edited October 29, 2021 by Mike Poole

[Blessed Weather]

Dr Amy Butler has updated her plot showing the occurrence of SSW years by easterly/westerly QBO and by La Nina/El Nino ENSO. It's worth recording the new plot and Amy's narrative in this thread. I've highlighted in bold the key take-out from the data:

Thought I'd update this plot since I'm getting retweets of older versions. I've added/changed some things; here using NDJ QBO 50 hPa and Nino 3.4 from CPC. Solid dots = corresponding winters (Nov-Mar) with SSWs, empty dots = winters with no SSWs.

I've added the frequency of #SSWs for each quadrant (QBO +/-, Nino 3.4 +/- 0.5), and the barplots show the frequency of SSWs in each "bin" of either Nino 3.4 or QBO phase. The black dashed line on the histogram shows the overall frequency 0.63 SSWs/yr in JRA-55 reanalysis.

This shows we get the most #SSWs during La Nina winters and easterly #QBO. But [the occurrence of] this combination also happens by far the least (only 6 NDJs in a 64 year record!). It also shows that you get increased SSWs in both phases of ENSO relative to neutral, and for strong easterly QBOs.

Currently, it's looking possible to get the elusive #LaNina, easterly #QBO this winter, but it's hard to say for sure because QBO at 50 hPa is still westerly and taking its sweet time changing to easterly.

The final takeaway from this figure is that it's possible to get a #SSW in any phase of ENSO/QBO. It's just more likely in some phases compared to others.

Note the years refer to the "Jan" of the NDJ period- so, for example you can see 2021 on the chart- that is NDJ of 2020-21.

Source: Twitter @DrAHButler 26th Oct2021

[Catacol]

7 hours ago, Blessed Weather said:

Dr Amy Butler has updated her plot showing the occurrence of SSW years by easterly/westerly QBO and by La Nina/El Nino ENSO. It's worth recording the new plot and Amy's narrative in this thread. I've highlighted in bold the key take-out from the data:

Thought I'd update this plot since I'm getting retweets of older versions. I've added/changed some things; here using NDJ QBO 50 hPa and Nino 3.4 from CPC. Solid dots = corresponding winters (Nov-Mar) with SSWs, empty dots = winters with no SSWs.

I've added the frequency of #SSWs for each quadrant (QBO +/-, Nino 3.4 +/- 0.5), and the barplots show the frequency of SSWs in each "bin" of either Nino 3.4 or QBO phase. The black dashed line on the histogram shows the overall frequency 0.63 SSWs/yr in JRA-55 reanalysis.

This shows we get the most #SSWs during La Nina winters and easterly #QBO. But [the occurrence of] this combination also happens by far the least (only 6 NDJs in a 64 year record!). It also shows that you get increased SSWs in both phases of ENSO relative to neutral, and for strong easterly QBOs.

Currently, it's looking possible to get the elusive #LaNina, easterly #QBO this winter, but it's hard to say for sure because QBO at 50 hPa is still westerly and taking its sweet time changing to easterly.

The final takeaway from this figure is that it's possible to get a #SSW in any phase of ENSO/QBO. It's just more likely in some phases compared to others.

Note the years refer to the "Jan" of the NDJ period- so, for example you can see 2021 on the chart- that is NDJ of 2020-21.

Source: Twitter @DrAHButler 26th Oct2021

Thanks Malcolm - brilliant chart. Certainly shows the impact of a strong eQBO regardless of ENSO.......

[Catacol]

And for those wondering how far the eQBO has descended - current chart is here. Looks to be down to around 45hpa now...

 

And remember this old tool? Not a bad 30hpa temperature profile over the pole at all as we move into the vortex intensification phase.....

Edited November 1, 2021 by Catacol

[sebastiaan1973]

EC46-update. 

[bluearmy]

1 minute ago, sebastiaan1973 said:

EC46-update. 

Quite a spread but certainly retains our interest ….