Stratosphere and Polar Vortex Watch 2020

[Catacol]

18 minutes ago, chionomaniac said:

 

Zoiks - responses flying in. Going to update this post when I've got time later to chew through more of the links....

Edited November 9, 2021 by Catacol

[Catacol]

47 minutes ago, knocker said:

or here

https://ozonewatch.gsfc.nasa.gov/monthly/NH.html

Thanks Knocker - and thanks also @chionomaniac. Doing a chew through the data, and especially the NASA site here it is clear that we are in an uncommon ozone position this year, but not one I would describe as rare. Early November does not usually feature quite so much ozone and October 2021 looks above average as a month compared to other Octobers, but there are other years where early November sees similar concentrations and patterns. In the recent records the current November profile is most similar to Nov 2009 and Nov 2010 though Nov 2021 through this first week or so is more intense than both of those. Nov 2016 also featured uncommonly large concentrations of Ozone.

If you are of a pattern matching persuasion it is good news. Nov 09 and Nov 10 both led to good winter spells, Nov 16 not so good. But 2 out of 3 ain't bad......

I'll keep an eye on this as we go through November. Looking at the record ozone levels usually rise a bit as November progresses so it will be interesting to see if the high levels continue or even intensify. 

Those that like the images - 

5 Nov 2021

 

5 Nov 2010

 

5 Nov 2009

 

5 Nov 2016

 

And meanwhile a much more common look for early November would be this from last year

5 Nov 2020

Edited November 9, 2021 by Catacol

[bluearmy]

Today’s ec46 builds a high anomoly over W Canada period around 20th dec which then reduces. The zonal flow is above average throughout nov but drops back a little in dec and still no strong steer for the final month of the year. 

[Eagle Eye]

Did the further research I said I would do on SSW's
Small direct quote : 
"Major Winter Weather Disruptions at Lower Latitudes

If all SSW's did, was affect the upper or middle stratosphere over the pole or even the equator (as shown in the chart above), they would remain an interesting atmospheric curiosity or mystery much as Scherhag found them in 1951. What we've learned in the past few decades however, is that they have enormous and profound effects (especially the larger ones) on the entire weather patterns of the Northern Hemisphere winter. These effects begin with the descending air and increasing pressure that comes with the sinking air over the pole.  Here is the pressure anomaly chart of the January 2013 SSW:

Along with this sinking air, we see the corresponding disruption of the Arctic polar vortex as shown in the zonal wind anomaly chart from winter 2013:

"
Now, I feel it's best if I word it as best as I can whilst keeping the scientific terms from here

When there is a large SSW and the PV breaks down, the normal westerlies are reversed and wind comes from the east, as the chart above shows. When the winds come from the east they typically bring colder air and of course snow etc. In terms of the winter of 2013, we can retrace back the change in England's weather that winter to the day of the large SSW event over the north pole. If you look at the chart above for the SSW which peaked around the 6th of January, and then take a look at the Central England Temperature for that 2013 winter, you'll see this:

Generally high pressure over the pole tends to lead to a negative AO index and the reverse for the opposite. When the AO index turns negative it is likely that colder weather is possible for you snow lovers out there. When a large SSW event occurs such as there was  n 2013, warm, descending air over the pole compresses and warms even more, disrupts the vortex (as talked through above) and turns the AO Index negative. What needs to be clear however is that the AO Index is in fact a tropospheric reading, and the SSW begins in the stratosphere and the pressure effects can work their way down into the troposphere and last over a period of many weeks. 

Here' the most revealing chart showing a direct comparison of the timing of the early January 2013 SSW seen in the normalized zonal GPH anomaly (top) aligned with the AO Index (centre), and the Central England Temperature (bottom) from January 1, 2013 through to April 1, 2013:

 

There is a remarkable correlation between all three of them and directly related to the initial event-- the SSW that began early January when England's weather turned cold and the prevailing wind began to blow from the east as the vortex was broken in a way and the AO Index turned to the negative.

Now this potential of the association between SSW's, the disruption of the Arctic vortex and a negative AO index does not attempt suggest that SSW's are the only thing that affects the AO index, just like it would be wrong to suggest that all low pressure and rain over the Gulf of Mexico is related to hurricanes. What it does show, is that when a large SSW event occurs (which is every couple years on average) will tend to dominate the Arctic weather and lower latitudes during the period when the SSW is happening.

So now that we've taken a look at some of the effects of SSW's on the NH winter weather let's get to the causes of SSW.

We follow the warm air back to Asia

Direct quote

"There are a few clues that one can use to trace the origin of the descending warm air over the pole, but before looking at that, let's talk about that descending air in general. Of course the rapid descent of air in the stratosphere compresses and warms, but a key clue comes from knowing that it was already anomalously warm before it began to be compressed. What warmed it and where?

Thanks to satellite reanalysis data, we can in fact see exactly where the warm air came from before reaching the polar latitudes. As this animation so excellently displays, a wave of warm air moved up from
South Central Asia in the weeks prior to the SSW event that occurred in early January 2013. This wave in fact seems to almost "explode" up into the stratosphere, almost like the warming you'd get from a volcanic eruption (again, hence the reason for early theories on SSW's looking for a volcanic connection)."

Continuing with the analysis



This warm bubble rises due to the thermal wave that's over central Asia around the 21st December, the fact that this rises up so quickly indicates a very strong dynamical event which forced warm air up into the stratosphere from the troposphere.  It then moves northeast at 10 hPa stratospheric levels and higher. Here's different view of the thermal wave on December 28, 2013:

Here's another perspective on this wave that shows both its origin at lower latitudes, as well as it's progress toward the north. Remember, that this is occurring at the 10 hPa mid-stratosphere level:

This is a typical 'standard fingerprint' of an SSW, here's another one from an SSW in 2002 - 2003

Similar development in the thermal waves when it was developing at lower latitudes that year as well, there are similar waves before any SSW events as far as I know no example of it beginning in anywhere other than Asia, for example January 2009

 

When considering the development of these thermal waves at mid-stratospheric levels over Asia, there are several factors that must be considered. First, such of a rapid build-up of rising warm air can obviously not come from evaporation as normal adiabatic cooling would occur and we would see the exact opposite condition such as we find associated with the normal convective processes in thunderstorms or on a much larger scale in Hadley Cells.

Secondly, the consideration is that the rapidity necessary to bring such a large mass of warm air upward into the stratosphere. Some process must essentially "launch" this warm air up to the stratosphere, as we see it seems to "explode" into the stratosphere. The air has to be relatively warm to begin with (anomalously warm relatively to normal stratospheric temperatures at 10 hPa), for no matter how rapidly it is launched or how warm it was, it will expand and cool by some amount, no matter what. So in our search for the source of the thermal wave, we are looking for a source of warm air and a mechanism by which that air is launched rapidly upward into the stratosphere.

This is why some researchers suggested that volcanoes may be to blame for these waves though there isn't much evidence to support that.
 

Then we look for a High Positive Omega

The vertical rising or falling of air in the atmosphere is known as omega and is measured in Pascals per second (Pascal/s). A high positive omega over a geographic region would indicate that a significantly large mass of air was rapidly moving upward in that region, and likewise, a negative omega would indicate that a mass of air that was falling or moving downwards. 

In the formation of a thermal wave in the stratosphere over South Central Asia we would be looking for a region in the troposphere within the same rough region with an unusually high positive omega. It would have to be an area that displayed what would be much like vertical jet stream or plume of warm air moving rapidly upward in the troposphere, then through the tropopause, to form the thermal wave in the stratosphere.

"In looking at the omega reanalysis data for the period around the formation of the thermal wave that formed over Asia in December 2012, we find the following very interesting data that displays the average omega across the entire troposphere from 1000 hPa up to 100 hPa. This chart was further constrained to show the region of interest, namely South Central Asia from 60E to 110E longitude and 0 to 70N latitude: "

When looking at this reanalysis chart we see three regions of high positive omega. These regions represent areas where air was moving rapidly upwards across the troposphere averaged over the entire month. For the sake of simplicity, I chose to narrow my analysis down to the area which has the highest positive omega of the three, which was the one furthest north and west.  Here's a closer view of the omega in that region during December 2012:

Again, for a clearer understanding of omega when looking at the preceding diagram, you could imagine a stream of air moving right out of the centre of the red  area, outward from the model area. This stream would be flowing up through the entire depth of the troposphere during the month of December 2012. For the sake of comparison, here's the omega for the exact same region during the month of July 2012:

When we begin comparing the two, we see that the high omega over this region in December 2012 truly is at least a monthly anomaly and not a year-round feature of this region. So we at least now have a potential area for a vertical stream of air moving into the stratosphere to form the thermal wave in December 2012. 

Skipping a bit here as this is beginning to get quite long explaining an SSW in clear effect

Direct quote
 

"SSW's are marked by rapidly descending air over the polar region.  This air warms as it descends but we've seen that it was warmer than normal to begin with. Through reanalysis, we have seen that the air travelled to the high latitudes as a stratospheric thermal wave at 10 hPa. In looking at the origins of this thermal wave we find high omega areas just south of the Taklamakan Desert in the Kunlun Shan and Altun Mountains. When prevailing north to south winter winds blowing across the Taklamakan desert (and including possible energy from jet stream winds) are directed toward the Tibetan Plateau under the right conditions, the perfect topological lifting conditions occur, allowing the warmer air from the desert to ascend rapidly into the stratosphere where it builds into a thermal planetary wave of warmer air that is carried north by prevailing upper level winds.

Upon reaching the higher latitudes of the Arctic, the warmer air begins to descend rapidly, warming even more but also carrying enough momentum during the descent to drag mesospheric air down into the stratosphere as well. This intrusion of mesospheric air during SSW events has been well documented, but is outside the scope of my research. Suffice to say it has been measured by many researchers and can be identified through its unique chemical signature. One excellent recent source for more information on this is Kvissel et al., 2012. As illustrated earlier, the rapidly descending air in the stratosphere over the Arctic has effects or teleconnections that reach some 9,000 km away to the equator. Here we see that the momentum of the polar descending air pulls the air in the stratosphere up at the equator, such that this air cools and expands and creates a temporary temperature and pressure anomaly.

Again, here's another example of this from the large SSW event that occurred around January 21, 2009 where, in this equatorial stratosphere profile of temperature, you can readily see the effect of air being drawn upward into the stratosphere: "

 

Other Causal Elements of SSW's: The Winter Tropopause

I have only briefly mentioned the tropopause so far but it shouldn't be taken out of any discussion of the full dynamics of SSW's. The intrusion of rapidly ascending warm air into the stratosphere from the troposphere means that this stream must penetrate through the tropopause as it ascends.

There are also some topological circumstances with location of the Taklamakan desert next to the Tibetan Plateau. The desert provides the ideal source of warm air to be "launched" upward and the rapid and steep mountain Kunlun Shan and Altun Mountains are the perfect launch pad for this 'launch' as it were. With the winter winds prevailing from the desert toward the mountains in this region, it only takes the right set of circumstances to initiate the precursor events to an SSW. 

"We must however add the additional factors of the lower winter tropospheric height and the fact that the Kunlun Shan and Altun Mountains are at an ideal position for penetrating the tropopause with warm air from below as the tropopause drops down rapidly between 30 and 40 degrees, as seen in this simple illustration (B. Geerts and E. Linacre, 1997):"

 

Not only does the tropopause lower in the winter, it also drops down dramatically just at the point where the Kunlun Shan and Altun Mountains ranges are located and therefore this is ready to provide the necessary launch platform for warm air from the Taklamakan desert. It is quite possible that had these mountain ranges been located four to five hundred hundred kilometres further south where the tropopause is higher, that the character of NH SSW's and NH winters might be completely different, that is why such small things can have such massive changes across an entire Hemisphere's Winter for quite a few years.

 

"Investigating numerous SSW events using reanalysis data has shown that in every event that I could find reliable data on, the initial locus of the warm air has come from South Central Asia. I investigated one potential source of this warm air among several-- namely at the point where the Taklamakan Desert meets the Tibetan Plateau in the Kunlun Shan and Altun Mountain ranges. 

This combination provides an ideal topographically forced "launching pad" for warm air to be lifted up through the lowered winter tropopause into the stratosphere. This air is then advected as a thermal wave toward the northern latitudes where it eventually descends, warms further, and creates an SSW event. This diagram illustrates the overall dynamics of this entire process:

 

In addition to the extensive reanalysis data, there appears to be tangential corroborating evidence in support of this overall dynamic, such as the high level of dust in Greenland ice cores that has an origin point in the Taklamakan desert and Tarim Basin. This dust could be part of the thermal wave that descends over the Arctic during the SSW and is eventually deposited in Greenland ice.

Future research could focus on gathering mid-stratosphere air samples at 10 hPa during one of the thermal wave episodes, just prior to the SSW event. A high level of dust inside that thermal wave that could be identified through isotopic analysis as coming from the Taklamakan Desert and Tarim Basin would be strong evidence of the origin of the warm air. Other avenues of research should include the analysis of other regions of South Central Asia that also show high positive omega values in the days leading up to the formation of the 10 hPa thermal wave. It is quite possible that several high positive omega areas could be involved simultaneously or each during different SSW events. 

Finally, a close analysis of the regions involved in high positive omega events should be conducted to see what meteorological conditions exist to create the wind field energy necessary for topographic lifting. In addition to pressure zones and prevailing winds, energy from the lowering of the tropopause and the jet stream during winter could be an important source of energy for high positive omega events and the precursors to SSW's."

A lot of this has been direct quote's because I feel it better to quote than try changing it and explaining it further as it was already efficiently explained

Now that we know what is most likely the main cause for an SSW we can look at where this is and other factors which could possibly effect us longer and why a split PV could reset this change

So as we can see, Asia has had an effect on previous years as to the extent of bringing cold and snow to the extent of many of Britain including me down south. Having looked at previous years it does seem that in SSW years the Geopotential height has shown the more extreme cold to typically stay on the western side of the origin of the Asian rising warm air as per the reversing westerlies (although low's can build near Siberia as per the usual Winter) 
7 February this year
 
2020

2019

850Pa (m)
2021

2020

2019

And it at the moment

I think I probably need to wrap this up with a conclusion fort the effects possible on this Winter from the effects of the SSW properly now. An SSW is still most likely having effects this far into the year with it being hard to reverse, despite the retreat of the stronger geopotential height east of Siberia you can see that it is still having effects possibly coming back from hibernation where there was little going on to change it within the Summer and so the natural change to Winter brought back the effects of this SSW to the point where unless we have a splitting PV I think we could see the effects of this weakening the Winter potential this year (doesn't mean there's not the chance for a good Winter if a split PV doesn't come off)
 
 
As you can see the effects of the SSW can be most clearly seen on the H500 right now with the changes east of Siberia most noticeable but also the effects of the amplified Pacific is quite easily seen within these charts. Now I don't pretend to be an expert nor know much this is purely from some recent research but IK do see the chance of a split PV to happen getting closer, despite the effects of it rapidly changing on the models on whether it's going to happen or not creating the flip flop effect as it were, I do see the chances of the amplification over far Siberia perhaps pushing up the split PV potential hence why it's still on the models drifting ever so closer. This is what's increasing the chances of a northern based flow and why the SSW last year seemingly causing the amplification towards Siberia could have a positive effect for the people who want snow although still far out it is something to look at, as having looked through the months since the SSW you can see the clear effects of it and if we look recently we can perhaps see why a split PV is being shown mid model run right now.

You can already see the first effects of the re-amplification east of Siberia beginning to allow for a split PV to occur sometime within the future though definitely nowhere near guaranteed, so that's the post finished, though there is still a lot more to be explored but that's all well above where I am now, hence why I'm dealing in if's and maybe's. As you can see the way to find out the effects is pretty much looking at why it happens and see what sticks.
This is what I have understood and may not be correct but if you made it all the way through in 1 take, congratulations, I didn't, this is about my 4th take with all the take backs and writing that I did in my notepad guessing what was going to happen in my notepad to get through the day with no access to models except what I remember about the models and the writing online.
Xander

 

 

 

 

[SqueakheartLW]

Looks like the next WQBO is making its move now. Those brown colours are now starting to descend down from 10hpa.

Shouldn't be any issues for this coming winter but it would seem this EQBO is going to be a shorter than average one by the looks of things unless we see a repeat of the EQBO then WQBO descent we experienced between 1999 and 2001 where it took a long time to get the EQBO down from 10hpa to 100hpa and as a result the following WQBO got delayed too, taking until late 2001 to get down to below 30hpa

[Benny123]

 

[philglossop]

21 hours ago, SqueakheartLW said:

Looks like the next WQBO is making its move now. Those brown colours are now starting to descend down from 10hpa.

Shouldn't be any issues for this coming winter but it would seem this EQBO is going to be a shorter than average one by the looks of things unless we see a repeat of the EQBO then WQBO descent we experienced between 1999 and 2001 where it took a long time to get the EQBO down from 10hpa to 100hpa and as a result the following WQBO got delayed too, taking until late 2001 to get down to below 30hpa

Funny just looking at the Singapore soundings and I thought exactly the same- just as the E QBO hits the magically 21km and firmly into the Troposphere. It's taken its time but seems to be descending  very quickly now. Early days but it's nailed on EQBO winter this year.

[Griff]

Not as bad as the latest GFS run! 

[knocker]

wrong thread

 

Edited November 15, 2021 by knocker

[bluearmy]

2 hours ago, Griff said:

Not as bad as the latest GFS run! 

Surprised to see so much placed behind a single gfs run!

the ec46 has steadily drifted away from a weaker than average spv and is now pretty solidly behind one that is on the stronger than average side as we head through December. 

[Catacol]

14 hours ago, bluearmy said:

Surprised to see so much placed behind a single gfs run!

the ec46 has steadily drifted away from a weaker than average spv and is now pretty solidly behind one that is on the stronger than average side as we head through December. 

We have lost the signal for the ScEuro High and Aleutian Low a bit - and that is working through the long term forecast I think. What will be interesting to see will be the impact of the solidly eQBO on the vortex as we head through December and whether it sets it up more readily for knocking or splitting as we move into January. The early Nina ridge promoting a scandy trough didnt feel like a useful precursor to strat disruption early season - a mid January SSW has been my best guess and it is built on the expectation that early cold in December will moderate and fade into a pattern by the second half of the month that sees the ScEuro or Ural High return. We will see.

[lorenzo]

Given the upcoming cold developments thought this thread would be more suited to a slower paced post.. 

First off the a caveat -  Physical Sciences Laboratory have stymied some composite activity as : Change: The ability to use your own http address for custom files is no longer supported due to security restrictions. This is frustrating as the daily composites allow a little more precision than using the months where variables are suitably in range. If anyone knows of a similar portal that accepts an ftp transfer of a date.txt file to render a composite - please drop me a note!

Looking at existing variable and considering the NAO- in the immediacy - sought to examine the pre 2000 and post 2000 eQBO / Nina base state, then layer in MJO loosely for P4/5 for a review. The pre and post yr. 2000 composites are below, clearly some differences last century.

These conditions are then rolled forward for the dates used to extrapolate - where we might head next..

Not strat. related I hear you say.. okay so based on the years in question which built the composites, I think the lead would be for a February SSW.

That being said right in the midst of the February action we have this odd season where things doubled up via a displacement and a split

View the action here for December - Displacement

ECMWF Analyses

WWW.METEO.PHYSIK.UNI-MUENCHEN.DE

 

And here for February - Split

ECMWF Analyses

WWW.METEO.PHYSIK.UNI-MUENCHEN.DE

November composites for months featuring since 2000 in the original daily set for later comparison to where this November finishes.

An exciting start to the season, having watched many animations the Greenland Block is nearly always the one that tips the balance and creates the most chaotic solutions / eventually knocks the strat off it's perch. Will be intriguing to watch how this plays into vortex development from here...

[philglossop]

I think looking at the soundings for QBO- the signs of the Westerly QBO are appearing very clearly in the Strat now and starting to both power up and start the long slide down. Won't affect this winter as highlighted in posts above- but will make 2022 a strengthening WQBO.   

The failure about 14 months ago seems to have done us a favour going forward......

Edit- did some digging on QBO and it appears the fabled failure of 2016/2017  and 2019 may, may have happened back in autumn of 1964 with a descending EQBO being cut off (not too dissimilar to 2019 with the WQBO strengthening from surface to Strat. This led to a very long WQBO in the Strat from 1964 to 1967 before descending. 

 

Interestingly- the next EQBO was 1968-69- and was much shorter as well (as appears to be happening this year)

 

Osprey et al..pdf (hawaii.edu) has the paper. Interesting stuff.

Edited November 18, 2021 by philglossop

[Griff]

Ecm zonal latest, pretty much on the mean / average just about, all things considered not terrible... 

[MattStoke]

On 18/11/2021 at 20:04, Griff said:

Ecm zonal latest, pretty much on the mean / average just about, all things considered not terrible... 

[lorenzo]

This years prediction competition is up and running in the Twittersphere. 

10 part tweet thread from Daniela Domeisen here contains lots of great detail.

 

[Cheshire Freeze]

On 18/11/2021 at 20:04, Griff said:

Ecm zonal latest, pretty much on the mean / average just about, all things considered not terrible... 

That mean is dragged down by the few strong reversals. Looks to me that the main grouping is above average?

[Griff]

6 minutes ago, CreweCold said:

That mean is dragged down by the few strong reversals. Looks to me that the main grouping is above average?

Equally the mean is being dragged up by a few above average members... No doubt more will be revealed come Monday.  

[SqueakheartLW]

There may be some doom and gloom from some who are disappointed the polar vortex has become stronger than average but need not panic when taking a look at how 60N zonal winds have trended vs last year

We have on the most part trended slower with zonal winds than last year and are predicted to become weaker than last year on the zonal wind front if the GEFS are to be believed

[Catacol]

End of the month - good looking wave pattern for strat disruption. Rockies and Urals in action.

Nothing showing up yet on the strat charts to suggest any disruption - but won't be too far away now.....

[bluearmy]

9 hours ago, Catacol said:

End of the month - good looking wave pattern for strat disruption. Rockies and Urals in action.

Nothing showing up yet on the strat charts to suggest any disruption - but won't be too far away now.....

More than just signs on extended gfs/gefs of the spv being displaced back to n Asia 

[Catacol]

3 hours ago, bluearmy said:

More than just signs on extended gfs/gefs of the spv being displaced back to n Asia 

Ideal. Push it off its axis into Asia, fire up a huge +NAO signature running up against a ScEuro signal as we move into the second half of December, and drive a warm spear up into the displaced vortex over Xmas while the Aleutian Low hangs on and keeps the pressure up. Massive split, vortex shard drop into Europe, cold air spilling out everywhere in January. Effectively the 2018 pattern but 2 months earlier.

Not too much to ask, is it?!

[Rollo]

I shall take that as gospel!!

[Mike Poole]

5 hours ago, Catacol said:

Ideal. Push it off its axis into Asia, fire up a huge +NAO signature running up against a ScEuro signal as we move into the second half of December, and drive a warm spear up into the displaced vortex over Xmas while the Aleutian Low hangs on and keeps the pressure up. Massive split, vortex shard drop into Europe, cold air spilling out everywhere in January. Effectively the 2018 pattern but 2 months earlier.

Not too much to ask, is it?!

You make it sound so easy!  But as I have said before it is putting all our chips on a SSW for jam tomorrow when there may be other options closer to now.  I know you have said that cold is very unlikely these days without a SSW, so, effectively why bother!,  but I think the early part of this winter will test that.  Although the Greenland heights suggested by the models a week or so are watered down (it was never modelled a true Greenland high anyway), there is equally nothing to suggest a return to zonal.  A return to zonal after about 10 months now.  So I want to see that one out first, before chasing a SSW because I don’t think the trop precursors are there at the moment.  

Edited November 21, 2021 by Mike Poole

[Mike Poole]

Stratobserve charts for todays GFS 0z run ridiculous:

Not sure what caused that.  Assuming that is a one off, strat vortex remains strong.  ECM T240 from Berlin:

I know others think otherwise but I favour a strong vortex now while it is not coupled to the trop.  One reason, that will make it less likely to couple sooner and to give the current trop patterns, which are interesting, to play out.  Second, if a SSW is going to do anything for us this year, it would be as a split, and I think that is more likely when the strat vortex is obliterated from a strong not weak base.  My bet SSW 15/1/22.