Stratosphere and Polar Vortex Watch 2020

[Duane S.]

The forecast wave 2 has actually upped in intensity This is one of the strongest I can remember.

The effect of the SPV appears to be negligible. This is right at the top, but the same story down to mid level…

 

I wonder if the fact we have a clear disconnect between the SPV and TPV helps in that respect. If I’m holding a 1 metre piece of thick rope from the top and create circular movements, it takes a lot less effort than if it was a 2 metre piece of rope. If my hand holding the rope got nudged hard sideways, I would be able to get that circular motion through the rope going much more quickly with the short piece, than with the long piece. The longer the rope, the more circular motions within the rope, more susceptible to outside interference than a tighter shorter overall vortex? The analogy sort of works in my head anyway

 

[Chesil View]

16 minutes ago, s4lancia said:

The forecast wave 2 has actually upped in intensity This is one of the strongest I can remember.

The effect of the SPV appears to be negligible. This is right at the top, but the same story down to mid level…

 

I wonder if the fact we have a clear disconnect between the SPV and TPV helps in that respect. If I’m holding a 1 metre piece of thick rope from the top and create circular movements, it takes a lot less effort than if it was a 2 metre piece of rope. If my hand holding the rope got nudged hard sideways, I would be able to get that circular motion through the rope going much more quickly with the short piece, than with the long piece. The longer the rope, the more circular motions within the rope, more susceptible to outside interference than a tighter shorter overall vortex? The analogy sort of works in my head anyway

 

And mine S4L.  That's a great analogy.

[bluearmy]

we can see eps mean 10hpa on their website now 

ECMWF | Charts

APPS.ECMWF.INT

 

gefs is also in this general area 

so a realignment of the spv to bring a the NH trough into the e Atlantic sector from n America is reasonable 

Maybe a good time for the spv and tpv to begin to couple ! 

Edited January 3, 2022 by bluearmy

[JeffC]

Warm sector showing over E Europe at 10 hpa

[Mike Poole]

I haven’t posted much in here this year, and it is because the strat seems to have been played out of the game!  Not sure why, but still, and we are into January now, the strat and trop vortexes are not connected, see todays NAM plot from Stratobserve (GFS 0z data):

Well, yes, while the strats away the trop will play, but it hasn’t benefitted the UK in terms of cold yet.  But it must surely be the case also with the disconnect, that there are no trop precursors to a SSW, because they would have to impact the strat vortex.  So no chance any time soon of a SSW, I think, maybe something will happen in late winter, but by then it is too late for anything other than ruining the Easter holidays.  

[Catacol]

19 hours ago, Mike Poole said:

I haven’t posted much in here this year, and it is because the strat seems to have been played out of the game!  Not sure why, but still, and we are into January now, the strat and trop vortexes are not connected, see todays NAM plot from Stratobserve (GFS 0z data):

Well, yes, while the strats away the trop will play, but it hasn’t benefitted the UK in terms of cold yet.  But it must surely be the case also with the disconnect, that there are no trop precursors to a SSW, because they would have to impact the strat vortex.  So no chance any time soon of a SSW, I think, maybe something will happen in late winter, but by then it is too late for anything other than ruining the Easter holidays.  

There is so much talk about the strat and trop not being connected - but I'm not sure that this concept of a "disconnect" is helpful. To explain this NAM chart a bit further, this text from Colorado State University is useful: "By convention, the high index polarity of the annular modes is defined as lower than normal pressures over the polar regions and westerly wind anomalies along ~55-60 degrees latitude."

When we look at that chart what we are therefore seeing is the extent to which the pressure is constant across the various layers of the atmosphere, and where the pressure is matched vertically it suggests a closer marrying of the circulation pattern, at least partly through friction. When there is a pressure difference between the layers such as has been often talked about this year it suggests less frictional mirroring of the pattern.

However it is a global average at 55-60 degrees and so does not take into account regional difference caused by features such as the north pacific high. It also does not take into account what is happening between 60 and 90 degrees. And in addition an index of -1 or -2 doesn't mean that the stratosphere is having no influence at all on the trop....it means that the influence is not great enough to create a clear marriage of the two. This is very different to saying that the stratosphere and troposphere are "disconnected."  It shows that tropospheric drivers are have MORE of an influence that downwelling stratospheric forcing but be sure that the stratosphere IS STILL having an impact. Pressure at 55-60 degrees at 500hpa can comparatively high compared to the pattern at 30hpa but the patterns at 30hpa you can be sure are impacting to some degree on what happens below. 

To quote again from the same university blog:

"For decades, the prevailing wisdom was that stratospheric processes respond to but do not impact the tropospheric flow. But recent observations and model results done in the context of the annular modes suggest the coupling is two-way."

A two way relationship can never be disconnected.

 

 

Edited January 6, 2022 by Catacol

[Mike Poole]

5 hours ago, Catacol said:

There is so much talk about the strat and trop not being connected - but I'm not sure that this concept of a "disconnect" is helpful. To explain this NAM chart a bit further, this text from Colorado State University is useful: "By convention, the high index polarity of the annular modes is defined as lower than normal pressures over the polar regions and westerly wind anomalies along ~55-60 degrees latitude."

When we look at that chart what we are therefore seeing is the extent to which the pressure is constant across the various layers of the atmosphere, and where the pressure is matched vertically it suggests a closer marrying of the circulation pattern, at least partly through friction. When there is a pressure difference between the layers such as has been often talked about this year it suggests less frictional mirroring of the pattern.

However it is a global average at 55-60 degrees and so does not take into account regional difference caused by features such as the north pacific high. It also does not take into account what is happening between 60 and 90 degrees. And in addition an index of -1 or -2 doesn't mean that the stratosphere is having no influence at all on the trop....it means that the influence is not great enough to create a clear marriage of the two. This is very different to saying that the stratosphere and troposphere are "disconnected."  It shows that tropospheric drivers are have MORE of an influence that downwelling stratospheric forcing but be sure that the stratosphere IS STILL having an impact. Pressure at 55-60 degrees at 500hpa can comparatively high compared to the pattern at 30hpa but the patterns at 30hpa you can be sure are impacting to some degree on what happens below. 

To quote again from the same university blog:

"For decades, the prevailing wisdom was that stratospheric processes respond to but do not impact the tropospheric flow. But recent observations and model results done in the context of the annular modes suggest the coupling is two-way."

A two way relationship can never be disconnected.

 

 

Thanks for the reply.  But actually I do agree that the relation goes both ways, which is why I assert that while the two vortexes seem to be doing different things, while that may mean the trop vortex has more latitude to split and move as forces down here dictate, also, I think that means there is much less chance of the trop precursor patterns for a SSW to take hold, which is why I have thought for some time now that there won’t be a SSW.  At least in any timeframe where it could influence late winter.  We will see…

[mb018538]

Last night's ECM update shows the PV on steroids throughout! The mean stays at or above the 90th percentile right through to February after next weeks slight drop from nearly 60 m/s.

[Don]

3 hours ago, mb018538 said:

Last night's ECM update shows the PV on steroids throughout! The mean stays at or above the 90th percentile right through to February after next weeks slight drop from nearly 60 m/s.

It has been showing a crazy PV for some time now, has been consistent with it and this is all during an E-QBO!

Edited January 7, 2022 by Don

[georgiedre]

2 minutes ago, Don said:

It has been showing a crazy PV for some time now, has been consistent with it and this is all during an E-QBO!

Yup and it's hardly been stormy really. It's a weird world weather wise

[northwestsnow]

8 hours ago, mb018538 said:

Last night's ECM update shows the PV on steroids throughout! The mean stays at or above the 90th percentile right through to February after next weeks slight drop from nearly 60 m/s.

Gutted.

PV on steroids , guess the eQBO has done absolutely  nothing to help  us out.

[mountain shadow]

8 minutes ago, northwestsnow said:

Gutted.

PV on steroids , guess the eQBO has done absolutely  nothing to help  us out.

You can guarantee that all that deep cold will come our way in April!

[Don]

21 minutes ago, northwestsnow said:

Gutted.

PV on steroids , guess the eQBO has done absolutely  nothing to help  us out.

Strange times with the QBO at the moment!

[SqueakheartLW]

On 07/01/2022 at 15:56, Don said:

Strange times with the QBO at the moment!

Solar activity too high for EQBO to help out.

I did see someone post a chart here some time back showing what happens to the polar vortex with the QBO and solar activity.

I think it was:

Low solar activity and EQBO = Weak Polar Vortex

Low solar activity and WQBO = Strong Polar Vortex

High solar activity and EQBO = Strong Polar Vortex

High solar activity and WQBO = Weak Polar Vortex

What I can say about this is we could have really done with the EQBO for winter 2020/2021 when solar activity was lower and switched over to a WQBO for this winter, a bit more like it worked out for winter's 2009/2010 (EQBO) with low solar activity and 2010/2011 (WQBO) when solar activity was higher.

Could be if we get even higher solar activity next winter 2022/2023 and the expected WQBO and maybe a predicted Modoki El Nino on top we could be in a better position than this winter.

[karyo]

31 minutes ago, SqueakheartLW said:

Solar activity too high for EQBO to help out.

I did see someone post a chart here some time back showing what happens to the polar vortex with the QBO and solar activity.

I think it was:

Low solar activity and EQBO = Weak Polar Vortex

Low solar activity and WQBO = Strong Polar Vortex

High solar activity and EQBO = Strong Polar Vortex

High solar activity and WQBO = Weak Polar Vortex

What I can say about this is we could have really done with the EQBO for winter 2020/2021 when solar activity was lower and switched over to a WQBO for this winter, a bit more like it worked out for winter's 2009/2010 (EQBO) with low solar activity and 2010/2011 (WQBO) when solar activity was higher.

Could be if we get even higher solar activity next winter 2022/2023 and the expected WQBO and maybe a predicted Modoki El Nino on top we could be in a better position than this winter.

Even if that happens, another variable can go wrong that can prevent a cold winter from happening. Climate change is extra ugly for cold lovers.

[Don]

8 hours ago, SqueakheartLW said:

Solar activity too high for EQBO to help out.

I did see someone post a chart here some time back showing what happens to the polar vortex with the QBO and solar activity.

I think it was:

Low solar activity and EQBO = Weak Polar Vortex

Low solar activity and WQBO = Strong Polar Vortex

High solar activity and EQBO = Strong Polar Vortex

High solar activity and WQBO = Weak Polar Vortex

What I can say about this is we could have really done with the EQBO for winter 2020/2021 when solar activity was lower and switched over to a WQBO for this winter, a bit more like it worked out for winter's 2009/2010 (EQBO) with low solar activity and 2010/2011 (WQBO) when solar activity was higher.

Could be if we get even higher solar activity next winter 2022/2023 and the expected WQBO and maybe a predicted Modoki El Nino on top we could be in a better position than this winter.

I had not heard that  high solar activity combined with a W-QBO increased the chances of a weaker vortex and vice versa?  Could be in a better position next winter, but as Karyo alluded to, a permanent feature going against the chances of a cold winter is climate change!

Also, the QBO has been acting strangely since 2016 with two easterly phases failing.  I imagine this is likely to also be a symptom of climate change?

[SqueakheartLW]

This isn't promising at all. Look at all those red positive zonal wind anomalies on the latest chart.

A stark contrast to a year ago around this stage.

All those blue weaker than average areas and even some in reversal at times.

Guess we can rule out strat help this season by the looks of things.

[georgiedre]

29 minutes ago, SqueakheartLW said:

This isn't promising at all. Look at all those red positive zonal wind anomalies on the latest chart.

A stark contrast to a year ago around this stage.

All those blue weaker than average areas and even some in reversal at times.

Guess we can rule out strat help this season by the looks of things.

Does it make a difference with a disconnect ? I haven't got a clue btw

[sukayuonsensnow]

3 hours ago, SqueakheartLW said:

This isn't promising at all. Look at all those red positive zonal wind anomalies on the latest chart.

A stark contrast to a year ago around this stage.

All those blue weaker than average areas and even some in reversal at times.

Guess we can rule out strat help this season by the looks of things.

Do we need a SSW for a cold spell? We are still in an interesting position synoptics wise.

Also if things start to become favourable, would a SSW late January or February undo that and give us something much milder?

[SqueakheartLW]

4 hours ago, georgiedre said:

Does it make a difference with a disconnect ? I haven't got a clue btw

It's better to have a disconnect in the situation we have this year if cold is what you are after. Raging zonal winds high up need to stay there so they don't get us into a never ending mild train like we got in "Polar Vortex of Doom" winter 2019/2020.

A disconnect can result in a pot luck kind of winter where tropospheric patterns lead the charge instead. This can result in a what appears to be an unlucky so far missing out winter like our current one or we can hit the jackpot like we did in 1995/1996 when we had a strong stratospheric vortex that remained disconnected from the troposphere..

1 hour ago, sukayuonsensnow said:

Do we need a SSW for a cold spell? We are still in an interesting position synoptics wise.

Also if things start to become favourable, would a SSW late January or February undo that and give us something much milder?

Winter 2009/2010 and December 2010

We don't need SSW's to get cold spells. Perfect examples are winter 2009/2010. There was no SSW that winter although the vortex itself was generally weak throughout the season.

An even better recent example of no SSW and a cold spell is December 2010.

Vortex stayed strong but there was a big disconnect between strat and trop so blocking ruled in the trop and zonality in the strat. They did connect eventually by February 2011 however and that month was mild and wet.

February 2018

SSW's can tip the balance towards cold. February 2018 is the most recent good example when in early to mid Feb there was a SSW then the beast from the east came at the end of the month.

Winter 2001/2002

It can also work against us too. The main one I can think of was in winter 2001/2002. December 2001 was colder than average, especially the second half of the month when we had a couple of notable northerly outbreaks with snow. The SSW happened late December 2001. This shook up the pattern and instead of reinforcing blocking it just pushed the vortex over to where we don't want it to be around Greenland and the rest of that winter was mild and zonal.

Winter 2008/2009

Although the SSW in January 2009 has often been claimed to have brought the easterlies we saw in early February 2009 I think in fact it was the SSW that brought that winter to an end early as the pattern had been generally cold and blocked throughout that winter up to when the SSW hit and I think in fact it was the SSW that like with the 2001/2002 example shook up the pattern and in the 2008/2009 case I think it moved blocking away from our part of the hemisphere to another location and put us into mild SW winds from around mid February 2009.

Edited January 10, 2022 by SqueakheartLW

[sukayuonsensnow]

Have a feeling if we get SSW end of January/beginning of February it may not work in our favour (if it is cold/snow you are after).

But also something piqued my interest when I re-read the Netweather Seasonal Forecast. There was more of a leaning towards northern blocking in the second half of the winter, and a weakening SPV, but with uncertainty regarding when or if a SSW occurs. 

Could the timing of a SSW be crucial for our Winter prospects? ie. the sooner we get one the more likely it could work in our favour. 

There is also the La Nina side of things, with it becoming more east-based and leading to a more likely chance of being colder second half of the winter. 

Either way it will be an interesting few weeks on this thread. SSW doesn't necessarily mean cold, snowy weather, could mean the opposite.

 

[feb1991blizzard]

2 hours ago, SqueakheartLW said:

It's better to have a disconnect in the situation we have this year if cold is what you are after. Raging zonal winds high up need to stay there so they don't get us into a never ending mild train like we got in "Polar Vortex of Doom" winter 2019/2020.

A disconnect can result in a pot luck kind of winter where tropospheric patterns lead the charge instead. This can result in a what appears to be an unlucky so far missing out winter like our current one or we can hit the jackpot like we did in 1995/1996 when we had a strong stratospheric vortex that remained disconnected from the troposphere..

Winter 2009/2010 and December 2010

We don't need SSW's to get cold spells. Perfect examples are winter 2009/2010. There was no SSW that winter although the vortex itself was generally weak throughout the season.

An even better recent example of no SSW and a cold spell is December 2010.

Vortex stayed strong but there was a big disconnect between strat and trop so blocking ruled in the trop and zonality in the strat. They did connect eventually by February 2011 however and that month was mild and wet.

February 2018

SSW's can tip the balance towards cold. February 2018 is the most recent good example when in early to mid Feb there was a SSW then the beast from the east came at the end of the month.

Winter 2001/2002

It can also work against us too. The main one I can think of was in winter 2001/2002. December 2001 was colder than average, especially the second half of the month when we had a couple of notable northerly outbreaks with snow. The SSW happened late December 2001. This shook up the pattern and instead of reinforcing blocking it just pushed the vortex over to where we don't want it to be around Greenland and the rest of that winter was mild and zonal.

Winter 2008/2009

Although the SSW in January 2009 has often been claimed to have brought the easterlies we saw in early February 2009 I think in fact it was the SSW that brought that winter to an end early as the pattern had been generally cold and blocked throughout that winter up to when the SSW hit and I think in fact it was the SSW that like with the 2001/2002 example shook up the pattern and in the 2008/2009 case I think it moved blocking away from our part of the hemisphere to another location and put us into mild SW winds from around mid February 2009.

There was an SSW around early Feb 2010 i believe.

Edited January 10, 2022 by feb1991blizzard

[SqueakheartLW]

2 hours ago, feb1991blizzard said:

There was an SSW around early Feb 2010 i believe.

Just checked as I was sure we just had a weak vortex and no reversals or major warmings in 2009/2010 but saw this

Where was the vortex after this warming. Want to play spot the vortex?

Edited January 10, 2022 by SqueakheartLW

[damianslaw]

5 hours ago, SqueakheartLW said:

It's better to have a disconnect in the situation we have this year if cold is what you are after. Raging zonal winds high up need to stay there so they don't get us into a never ending mild train like we got in "Polar Vortex of Doom" winter 2019/2020.

A disconnect can result in a pot luck kind of winter where tropospheric patterns lead the charge instead. This can result in a what appears to be an unlucky so far missing out winter like our current one or we can hit the jackpot like we did in 1995/1996 when we had a strong stratospheric vortex that remained disconnected from the troposphere..

Winter 2009/2010 and December 2010

We don't need SSW's to get cold spells. Perfect examples are winter 2009/2010. There was no SSW that winter although the vortex itself was generally weak throughout the season.

An even better recent example of no SSW and a cold spell is December 2010.

Vortex stayed strong but there was a big disconnect between strat and trop so blocking ruled in the trop and zonality in the strat. They did connect eventually by February 2011 however and that month was mild and wet.

February 2018

SSW's can tip the balance towards cold. February 2018 is the most recent good example when in early to mid Feb there was a SSW then the beast from the east came at the end of the month.

Winter 2001/2002

It can also work against us too. The main one I can think of was in winter 2001/2002. December 2001 was colder than average, especially the second half of the month when we had a couple of notable northerly outbreaks with snow. The SSW happened late December 2001. This shook up the pattern and instead of reinforcing blocking it just pushed the vortex over to where we don't want it to be around Greenland and the rest of that winter was mild and zonal.

Winter 2008/2009

Although the SSW in January 2009 has often been claimed to have brought the easterlies we saw in early February 2009 I think in fact it was the SSW that brought that winter to an end early as the pattern had been generally cold and blocked throughout that winter up to when the SSW hit and I think in fact it was the SSW that like with the 2001/2002 example shook up the pattern and in the 2008/2009 case I think it moved blocking away from our part of the hemisphere to another location and put us into mild SW winds from around mid February 2009.

Some good analysis here, no mention of 2012-2013 the early Jan SSW had major implications for quick change to cold mid-late Jan, and more notably from mid Feb onwards with the exceptional March.

Barring winter 09-10 and Dec 10, our last two notable periods of cold have come courtesy of a SSW, March 2013 and late Feb-early March 2018. Last years short very cold spell in Feb also came on the back of a SSW. There is a clear correlation between SSW and enabling very cold conditions to happen in recent years at least.

The reference to winter 95-96 is interesting, in December I was seeing potential for another Dec 95 late on alas heights to the north didn't position themselves in the same position. Interestingly, the first 3 weeks of Jan were mild and generally atlantic driven but quite dry, we then saw easterlies from 21st and the rest of the winter was often cold and snowy. Not saying we will see a similiar transition this year, but interesting to note - it also came in the midst of a very blocked period, that had started in March 95.. we have been a blocked non-atlantic dominated spell since Dec 2020 I would say..

[Catacol]

9 hours ago, damianslaw said:

Some good analysis here, no mention of 2012-2013 the early Jan SSW had major implications for quick change to cold mid-late Jan, and more notably from mid Feb onwards with the exceptional March.

Barring winter 09-10 and Dec 10, our last two notable periods of cold have come courtesy of a SSW, March 2013 and late Feb-early March 2018. Last years short very cold spell in Feb also came on the back of a SSW. There is a clear correlation between SSW and enabling very cold conditions to happen in recent years at least.

The reference to winter 95-96 is interesting, in December I was seeing potential for another Dec 95 late on alas heights to the north didn't position themselves in the same position. Interestingly, the first 3 weeks of Jan were mild and generally atlantic driven but quite dry, we then saw easterlies from 21st and the rest of the winter was often cold and snowy. Not saying we will see a similiar transition this year, but interesting to note - it also came in the midst of a very blocked period, that had started in March 95.. we have been a blocked non-atlantic dominated spell since Dec 2020 I would say..

Yes - I think the 1995/96 analogue is our best analogue for chances of cold weather in the later stages of this winter. Nina continues to edge east, and there is much less evidence of a zonal February when Nina is east based. We will see. However one thing is for sure - the strong vortex is a substantial problem when looking for high latitude blocking, regardless of NAM charts illustrating a less connected state than might be the case.