Stratosphere and Polar Vortex Watch 2020

[sebastiaan1973]

Variability in QBO Temperature Anomalies on Annual and Decadal Time Scales.

ABSTRACT: The stratospheric quasi-biennial oscillation (QBO) induces temperature anomalies in the lower stratosphere and tropical tropopause layer (TTL) that are cold when lower-stratospheric winds are easterly and warm when winds are westerly. Recent literature has indicated that these QBO temperature anomalies are potentially important in influencing the tropical troposphere, and particularly in explaining the relationship between the QBO and the Madden–Julian oscillation (MJO). The authors examine the variability of QBO temperature anomalies across several time scales using reanalysis and observational datasets. The authors find that, in boreal winter relative to other seasons, QBO temperature anomalies are significantly stronger (i.e., colder in the easterly phase of the QBO and warmer in the westerly phase of the QBO) on the equator, but weaker off the equator. The equatorial and subtropical changes compensate such that meridional temperature gradients and thus (by thermal wind balance) equatorial zonal wind anomalies do not vary in amplitude as the temperature anomalies do. The same pattern of stronger on-equatorial and weaker off-equatorial QBO temperature anomalies is found on decadal time scales: stronger anomalies are seen for 1999–2019 compared to 1979–99. The causes of these changes to QBO temperature anomalies, as well as their possible relevance to the MJO–QBO.

https://repository.library.noaa.gov/view/noaa/29414/noaa_29414_DS1.pdf 

[Kirkcaldy Weather]

 

[SqueakheartLW]

Looks like we are now officially into the EQBO

When looking at the above chart we can see a clear EQBO now at 30hpa and it is looking close to reaching 40hpa now too. There are also clear signs at 10hpa of a weakening of the EQBO, no doubt a sign of the next WQBO getting ready higher up. Below 40hpa there's not a lot left of the remaining WQBO with a weak peak at 40hpa.

Time to take a more detailed look at the QBO chart itself

1 - Finally after what must be 2 years at least we now appear to have a proper EQBO showing up and there appears to be no signs that this one is going to fail this time around. No sign of the weaker EQBO at 10hpa on this chart though

2 - The last time we came close to an EQBO is still showing on this chart with the weak WQBO and the anomalous easterlies that formed underneath this too which was the main reason for number 3 zone happening

3 - The ongoing WQBO which could have been the deciding factor in our near miss winter 2020/2021. How close we came to a big freeze setup potentially getting going and it just didn't quite come off in the end. What if we had had the EQBO which we should have had during last winter. Would that have just tipped the balance enough to give us a much colder winter than we ended up with.

4 - It seems we have had an EQBO between 10 and 20hpa for ages now at various strengths and still it continues on up here but for how long

[philglossop]

28 minutes ago, SqueakheartLW said:

Looks like we are now officially into the EQBO

When looking at the above chart we can see a clear EQBO now at 30hpa and it is looking close to reaching 40hpa now too. There are also clear signs at 10hpa of a weakening of the EQBO, no doubt a sign of the next WQBO getting ready higher up. Below 40hpa there's not a lot left of the remaining WQBO with a weak peak at 40hpa.

Time to take a more detailed look at the QBO chart itself

1 - Finally after what must be 2 years at least we now appear to have a proper EQBO showing up and there appears to be no signs that this one is going to fail this time around. No sign of the weaker EQBO at 10hpa on this chart though

2 - The last time we came close to an EQBO is still showing on this chart with the weak WQBO and the anomalous easterlies that formed underneath this too which was the main reason for number 3 zone happening

3 - The ongoing WQBO which could have been the deciding factor in our near miss winter 2020/2021. How close we came to a big freeze setup potentially getting going and it just didn't quite come off in the end. What if we had had the EQBO which we should have had during last winter. Would that have just tipped the balance enough to give us a much colder winter than we ended up with.

4 - It seems we have had an EQBO between 10 and 20hpa for ages now at various strengths and still it continues on up here but for how long

Good stuff- the QBO was foxing last year- and last Summer especially with the WQBO down in the Trop. 

 

I think we'll have the E QBO in the Strat for probably the rest of the year- with W starting to appear around the turn of the year. Little doubt this winter will be a mature E QBO- interesting stuff!!!!

Edited June 17, 2021 by philglossop

[Don]

22 hours ago, philglossop said:

Good stuff- the QBO was foxing last year- and last Summer especially with the WQBO down in the Trop. 

 

I think we'll have the E QBO in the Strat for probably the rest of the year- with W starting to appear around the turn of the year. Little doubt this winter will be a mature E QBO- interesting stuff!!!!

Yes, lets hope after the 'teaser' winter last year, an E-QBO will allow us to experience the full shebang this year!

[knocker]

The 2019 Southern Hemisphere Stratospheric Polar Vortex Weakening and Its Impacts

Abstract

This study offers an overview of the low-frequency (i.e., monthly to seasonal) evolution, dynamics, predictability, and surface impacts of a rare Southern Hemisphere (SH) stratospheric warming that occurred in austral spring 2019. Between late August and mid-September 2019, the stratospheric circumpolar westerly jet weakened rapidly, and Antarctic stratospheric temperatures rose dramatically. The deceleration of the vortex at 10 hPa was as drastic as that of the first-ever-observed major sudden stratospheric warming in the SH during 2002, while the mean Antarctic warming over the course of spring 2019 broke the previous record of 2002 by ∼50% in the midstratosphere. This event was preceded by a poleward shift of the SH polar night jet in the uppermost stratosphere in early winter, which was then followed by record-strong planetary wave-1 activity propagating upward from the troposphere in August that acted to dramatically weaken the polar vortex throughout the depth of the stratosphere. The weakened vortex winds and elevated temperatures moved downward to the surface from mid-October to December, promoting a record strong swing of the southern annular mode (SAM) to its negative phase. This record-negative SAM appeared to be a primary driver of the extreme hot and dry conditions over subtropical eastern Australia that accompanied the severe wildfires that occurred in late spring 2019. State-of-the-art dynamical seasonal forecast systems skillfully predicted the significant vortex weakening of spring 2019 and subsequent development of negative SAM from as early as late July.

https://journals.ametsoc.org/view/journals/bams/102/6/BAMS-D-20-0112.1.xml

[SqueakheartLW]

Looks like we have reached the peak of the summer "Anti Vortex" strength now at 10hpa based on the ECM 10hpa zonal wind forecast

The only way is up now it would seem but based on the trend line this isn't anything unusual. Haven't research this before but I wonder if there is a link between the QBO and the strength of the summer "Anti Vortex". Maybe EQBO makes for a weaker anti vortex compared with the WQBO as a way for nature to balance itself out.

How is the southern vortex doing which is something that isn't discussed very much at all

Looks like the southern vortex is predicted to be running near record strong values for the foreseeable based on this ECM prediction with no sign of any form of sudden stratospheric warming in sight.

Also noticed what looks like a mistake on the ECM global zonal wind charts today. This is the analysis for 23/06/2021

Compare this with the day before

Unless my eyes are deceiving me here has the QBO suddenly jumped down at least 40 or 50hpa in a single day. That must be a world first if that has happened.

Had to look at the NASA QBO chart to confirm things

It would seem ECM have made a mistake with 23/06/2021's chart. Possible EQBO failure alert averted for now

[knocker]

Prospect of increased disruption to the QBO in a changing climate

Abstract

The quasi-biennial oscillation (QBO) of tropical stratospheric winds was disrupted during the 2019/20 Northern Hemisphere winter. We show that this latest disruption to the regular QBO cycling was similar in many respects to that seen in 2016, but initiated by horizontal momentum transport from the Southern Hemisphere. The predictable signal associated with the QBO’s quasi-regular phase progression is lost during disruptions and the oscillation reemerges after a few months significantly shifted in phase from what would be expected if it had progressed uninterrupted. We infer from an increased wave-momentum flux into equatorial latitudes seen in climate model projections that disruptions to the QBO are likely to become more common in future. Consequently it is possible that in the future the QBO could be a less reliable source of predictability on lead times extending out to several years than it currently is.

Plain Language Summary

The quasi-biennial oscillation (QBO) consists of a regular switching between eastward and westward winds in the tropical stratosphere. The oscillation has persisted at least since its discovery in the 1960s, over which time its period averages about 28 months with some variability from cycle to cycle. Recently, during the Northern Hemisphere winters of 2015/16 and 2019/20, remarkable departures from this regular behaviour occurred that have no precedent in the observational record. Both the 2015/16 and 2019/20 QBO disruptions occurred when large horizontal fluxes of momentum intruded into the tropics from higher latitudes. Using climate model projections we find these horizontal fluxes are likely to increase in future, suggesting an increased future likelihood of QBO disruptions and a concomitant loss in QBO predictability.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093058#.YNg4QBDZZIY.twitter

[SqueakheartLW]

Anyone who has hopes of an EQBO winter 2021/2022 may not want to see this latest update which may just set the alarm bells ringing that we could be entering another WQBO by the time winter arrives. The only reason I have these thoughts is because of what is currently happening up at the 10hpa level above the equator right now. Take a look at this screenshot from earth nullschool.

You can clearly pick out what looks to me like a displaced EQBO north of the equator at around 10N at 10hpa but look at what is happening above the equator itself. The winds are generally slack here and in some spots a few possible signs of a new WQBO are now showing up above some spots. Not a good sign that the EQBO wants to start ending so soon. Hope this is more related to how dominant the southern vortex is at 10hpa and above when taking a look at this next chart.

1 - A new WQBO can clearly be seen here between 10hpa and 2hpa above the equator and this has been building over the last few weeks. The big question is will it weaken again and turn back easterly like it does at this level more often than lower down or is this going to start pushing downwards and bringing an early end to the EQBO lower down?

2 - The displaced EQBO can clearly be seen here roughly above 10N between 10hpa and 40hpa with weaker easterlies below which are probably not related to the QBO at all. Will this push over to the southern side when the northern hemisphere gets it's dreaded vortex later in the year

3 - Although the 10hpa southern vortex is weaker than average at present the vortex is a beast higher up and at times these charts have gone up to 140 m/s at 1hpa at times. Compare that with the maximum the northern vortex saw last winter which was around 70 m/s at most.

These other QBO charts also show up the slowing down / stalling of the EQBO at 10hpa too

Quite easy to see here on both the plot and the QBO chart the neutral QBO at 10hpa. Hope this is more of a side effect of the southern vortex rather than a sign the WQBO is on it's way back already

[Don]

18 hours ago, SqueakheartLW said:

Quite easy to see here on both the plot and the QBO chart the neutral QBO at 10hpa. Hope this is more of a side effect of the southern vortex rather than a sign the WQBO is on it's way back already

Lets hope so, but it appears something strange has been occurring with the QBO during the last five years!  Not the update we wanted to see but we will just have to watch how things unfold during the coming months!

Edited July 3, 2021 by Don

[mb018538]

Just for you winter fans - the annual birth of the PV is around 3.5 weeks away. Silly season isn’t far off  

[Kiwi]

 

[northwestsnow]

Marco suggesting an EQBO for Winter...

Weak ENSO would be nice ...

Of course it's only August but first METO long ranger comes out in Sept I think..

Might be interesting....

[philglossop]

The QBO is something I’ve really got into the last few years- the eQBO failure last winter whilst strange wasn’t that unexpected- it was the powering up of the wQBO in the trop that was the surprise. 
 

It may have done us as favour- as all things being equal, we should now be seeing a new WQBO developing in the Strat and whilst we’ve got some minimum development it’s nothing to worry about having done some checking- and this winter will hopefully be a developing strong EQBO.

As northwest snow highlights if we get a weak or Western based enso El Niño that will influence some long range forecasts.

I just personally wish the Pacific was a lot colder than it is currently - that’s a real fly in the ointment…..

[summer blizzard]

1 hour ago, philglossop said:

The QBO is something I’ve really got into the last few years- the eQBO failure last winter whilst strange wasn’t that unexpected- it was the powering up of the wQBO in the trop that was the surprise. 
 

It may have done us as favour- as all things being equal, we should now be seeing a new WQBO developing in the Strat and whilst we’ve got some minimum development it’s nothing to worry about having done some checking- and this winter will hopefully be a developing strong EQBO.

As northwest snow highlights if we get a weak or Western based enso El Niño that will influence some long range forecasts.

I just personally wish the Pacific was a lot colder than it is currently - that’s a real fly in the ointment…..

Fairly sure he means weak La Nina. The sub-surface profile means a near zero likelyhood of El Nino development. 

[Cheshire Freeze]

The early winter period looks to have potential to me, hence my question about the 2010-2011 analogue @summer blizzard

EC seasonal looks decent for early winter

[Catacol]

3 hours ago, CreweCold said:

The early winter period looks to have potential to me, hence my question about the 2010-2011 analogue @summer blizzard

EC seasonal looks decent for early winter

Very early yet….and these graphs can be misleading. Core of winter 500 equivalent

and probability in December for upper tercile 500hpa

Nothing remarkable yet. Best evidence so far is QBO state and chance again of a weak Nina season.

 

[bluearmy]

Ec seasonal has a mid Atlantic/greeny high anom both upper and slp for dec.  This less clear for jan and feb looks very +nao 

[Cheshire Freeze]

On 05/08/2021 at 22:47, bluearmy said:

Ec seasonal has a mid Atlantic/greeny high anom both upper and slp for dec.  This less clear for jan and feb looks very +nao 

Would suit me. Much prefer my winter in December in the run up to Christmas and when the days are at their shortest...

FWIW a front loaded winter is what I'd plump for at present. I'm thinking Nov and Dec may be the coldest (in comparison to the average) months of the 'cold season'.

Edited August 6, 2021 by CreweCold

[jules216]

I would not mind if December is to be the month with greatest winter potential. I would 100 take the core of cold to be concentrated from last 10 days of November through the most of December.

[Weather-history]

4 hours ago, CreweCold said:

Would suit me. Much prefer my winter in December in the run up to Christmas and when the days are at their shortest...

FWIW a front loaded winter is what I'd plump for at present. I'm thinking Nov and Dec may be the coldest (in comparison to the average) months of the 'cold season'.

I thought last winter was perfect, well for my area anyway, the coldest wintry spell came from Christmas up to mid February, the heart of winter. The trouble with 2010-11, it was more or less all over by Christmas and it was then a long haul from then onwards. 

[Catacol]

4 hours ago, jules216 said:

I would not mind if December is to be the month with greatest winter potential. I would 100 take the core of cold to be concentrated from last 10 days of November through the most of December.

Haha it’s August and we are already talking winter

For the U.K., away from continental cold, I tend to feel that 2010 has skewed perceptions. Cold in December here is all too often a slushy, marginal affair. The ground is too warm, the oceans are too warm, and the near continent is usually still cooling down. In 2010 we got a direct northerly hit from a vortex shard that I think (without checking) was unique in the modern record and since then front loaded winters have become a wishbone. Not for me. Winter needs colder air sources than December usually supplies us, and the extra week or 3 of continental cooling is key regardless of solar factors. So…any signal pointing to a +NAO in the second half of winter is a kick in the privates.

But there is soooooooo much time to come yet and early seasonal predictions now are about as much use as a chocolate teapot. Once we get to September the chase can begin in a little more earnest.

Edited August 6, 2021 by Catacol

[summer blizzard]

8 hours ago, jules216 said:

I would not mind if December is to be the month with greatest winter potential. I would 100 take the core of cold to be concentrated from last 10 days of November through the most of December.

How was winter 10/11 for Europe. Did the cold melt away in Jan as it did here.

[Cheshire Freeze]

On 06/08/2021 at 07:07, Weather-history said:

I thought last winter was perfect, well for my area anyway, the coldest wintry spell came from Christmas up to mid February, the heart of winter. The trouble with 2010-11, it was more or less all over by Christmas and it was then a long haul from then onwards. 

True but it was memorable even if it was over by Christmas. Christmas Day 2010 was the most magical of my lifetime with deep snowcover and a temperature not getting above about -4 all day. Would take it again in a heartbeat.

[daz_4]

On 06/08/2021 at 16:07, summer blizzard said:

How was winter 10/11 for Europe. Did the cold melt away in Jan as it did here.

Well, compared to 81-10, January was 0,9C above average and February 1,5 below average so it wasn't bad but also pretty unremarkable snow wise if I remember correctly. All the fun happened in December.