Stratosphere and Polar Vortex Watch 2020

[sebastiaan1973]

I added the reaction of Simon Lee and the composition of the Greenland Blocking.

[sebastiaan1973]

Well looking at the EC oper output it seems, that a Greenlandblocking at the onset of the SSW is good possible. This is the profile of the SSW composition. In this way not good. Chio pointed out we have to watch at 100 hPa. I question how long will the weak vortex stay there, without 'help' of the SSW.

[sebastiaan1973]

According to this study we have to look to 150 hPa. Which seems to be excellent for downwelling. Further on we need enhanced wave activity propagation to the stratosphere after the onset of the SSW.

Abstract.

Major Sudden Stratospheric warmings (SSW) are striking phenomena of wintertime stratospheric circulation usually defined as a reversal of zonal mean circulation from westerlies to easterlies. SSWs often have significant impacts on tropospheric circulation and cause anomalies in surface climate lasting for up to two months. For this reason, dynamics and predictability of SSW receive considerable attention. It is however well-known that not all SSW cause significant, long-lasting impacts on the troposphere. In order to explain differences in tropospheric impacts following SSWs, several reasons have been previously proposed, including differences in type of SSW (split or displacement), persistence of stratospheric anomalies, preconditioning of the tropospheric circulation, and whether or not SSW was accompanied by a planetary wave reflection in the stratosphere. Here we address the predictability of tropospheric impacts by SSWs by seeking for early precursors of the impacts. We separate mid-winter SSWs into two groups: those which are followed by significant, long-lasting impacts on the tropospheric circulation (defined in terms of anomalous northern annular mode) and those not followed by significant anomalies in the annular mode. We show that SSWs characterised by a more negative Northern Annular Mode index in the lower stratosphere around 150 hPa and enhanced wave activity propagation to the stratosphere during the first few days following the central date have a larger probability to be followed by tropospheric impacts, both in reanalyses and in climate model runs. These anomalies play more important role for the subsequent downward propagation of the signal to the troposphere than the type of SSW: whether it is a split or a displacement, or absorptive or reflective SSW. We propose that using these anomalies as precursors of tropospheric impacts of SSW can enhance climate predictability.

ResearchGate - Temporarily Unavailable

WWW.RESEARCHGATE.NET

 

Edited December 29, 2020 by sebastiaan1973

[Kirkcaldy Weather]

 

[SqueakheartLW]

How has the GFS 12z compared with the 00z and 06z today for new warming prospects

Below I have the summary of how many of both the 00z and 06z fell into each peak warming category as well as the average peak

                    00z GFS          06z GFS          CHANGE

-32                    1                      0                     -1

-28                    2                      0                     -2

-24                    2                      4                     +2

-20                    6                      3                     -3

-16                    8                      7                     -1

-12                    6                      5                     -1

-8                      2                      8                     +6

-4                      4                      3                     -1

+0                     0                      2                     +2

+4                     1                      0                     -1

AV PEAK     -15.13              -12.63

With the average peak getting a little warmer it is clear that the 06z GFS is overall an upgrade on the prospect of a second warming compared with the 00z GFS

This was what was showing earlier. After studying the 12z was it a further upgrade in terms of average peak warming temperature or was it a downgrade? Here are the figures

Below I have the summary of how many of both the 00z and 06z fell into each peak warming category as well as the average peak

                    00z GFS          06z GFS          12z GFS          CHANGE

-32                    1                      0                     0                      0

-28                    2                      0                     0                      0

-24                    2                      4                     3                      -1

-20                    6                      3                     5                      +2

-16                    8                      7                     6                      -1

-12                    6                      5                     8                      +3

-8                      2                      8                     3                      -5

-4                      4                      3                     6                      +3

+0                     0                      2                     1                       -1

+4                     1                      0                     0                       0

AV PEAK     -15.13              -12.63            -12.88

A fairly comparable average peak with the 12z to the 06z so very much no downgrade or upgrade here but we seem to be seeing a large cluster of second warmings with peaks between -20 and -4

I have picked out the warmest or most dramatic ending to warmings charts below

[ALL ABOARD]

I take it this could be the first time in our recorded history that we have a major SSW with a troposphere that is as weak as it is. 

Therefore the papers the theories the wills it's or won'ts it can't be answered. 

We can summerize but the weather will make fools of us all. 

Its going to be so interesting to dissect this after the event. 

 

[JeffC]

earth :: a global map of wind, weather, and ocean conditions

EARTH.NULLSCHOOL.NET

---

See current wind, weather, ocean, and pollution conditions, as forecast by supercomputers, on an interactive animated map. Updated every three hours.

here goes!

+2.7C at 10 hpa

 

 

[ItNeverSnowsInWindsor]

1 hour ago, ALL ABOARD said:

I take it this could be the first time in our recorded history that we have a major SSW with a troposphere that is as weak as it is. 

Therefore the papers the theories the wills it's or won'ts it can't be answered. 

We can summerize but the weather will make fools of us all. 

Its going to be so interesting to dissect this after the event. 

 

Probably end up with a Bartlett’s and a long drawn fetch of Southerlies.

[Duane S.]

Impressive looking U wind reversal showing up this morning on the ECM. Much improved from yesterday. No vortex split mid strat but signs of the.  start of a wave 2 resurgence on day 10?

[SqueakheartLW]

My daily stratospheric update

GFS

As always I will begin with the GFS 00z. It appears that GFS is still sticking to its guns and going for a displaced vortex yet again but like with previous updates it is still hinting at another warming event mid January. The least warm warming is first and the warmest ones are last

-24

GFS 00z Member 19

-20

GFS 00z Member 1                                 GFS 00z Member 14                               GFS 00z Member 15

GFS 00z Member 18                               GFS 00z Member 22

-16

GFS 00z Control                                       GFS 00z Member 3                                GFS 00z Member 7

GFS 00z Member 10                               GFS 00z Member 21                               GFS 00z Member 26

GFS 00z Member 28

-12

GFS 00z Member 5                                  GFS 00z Member 6                                GFS 00z Member 8

GFS 00z Member 12                               GFS 00z Member 17                               GFS 00z Member 20

GFS 00z Member 23                                GFS 00z Member 29                             GFS 00z Member 30

-8

GFS 00z Operational                              GFS 00z Member 2                                 GFS 00z Member 4

GFS 00z Member 9                                 GFS 00z Member 11                              GFS 00z Member 16

GFS 00z Member 25                               GFS 00z Member 27

-4

GFS 00z Member 24

+0

GFS 00z Member 13

All 32 runs are going for this second warming yet again and they are starting to come closer than 384 hours in a number of runs now

GEFS Legacy

I haven't featured the GEFS Legacy so far but like with GFS it goes for a displaced vortex first then it too shows this second warming in the control run and its 20 member runs. I have decided to show you the very big warmings showing up in this model and its ensembles

+4

GEFS Legacy 00z Member 3

+8

GEFS Legacy 00z Member 6                  GEFS Legacy 00z Member 10

+12

GEFS Legacy 00z Member 18

That final option is one big warming event and if that comes off it could spell destruction of the vortex

GFS Parallel 06z

GFS Parallel still going for the split by +102 hours away. It also sees another -12C warming at +294 hours away so on the same page as both GFS and GEFS Legacy

JMA

JMA still going for a split by +132 hours away

GEM

After backing off the split idea yesterday it seems GEM is back on board again with a split taking place by +120 hours away

ECM

ECM still going for the displaced vortex today after it backed away from the split yesterday but still going for a decent reversal despite this

Today's updated daily zonal wind data based on ECM charts clearly show this reversal now getting down as far as 30hpa by 10 days away but at the top of the stratosphere the recovery of the vortex is already underway by this stage

OVERALL SUMMARY

GFS - Still going for displaced vortex from first warming and still has strong signal for a further warming mid January

GEFS Legacy - Similar to GFS

GFS Parallel - Still backing a split vortex unlike the main GFS but like GFS it is now showing this second warming mid January too

JMA - Still going for the vortex split

GEM - Has switched back to vortex split today after displacement yesterday. GEM now showing a second warming mid January too

ECM - Has remained on its new displaced vortex path but shows decent reversal

Scores

Displacement     3          Split                      3

Very much still up for grabs then with a 50/50 split between the 6 models I have featured

[snowking]

Thanks as always @SqueakheartLW

Still varying shapes to the vortex across model suites but the one constant is that the pacific wave does not look like going anywhere in the next 15 days or so at 10mb, and this means that any plans the vortex has of trying to return to its default position are pure fantasy, meaning we will see suppressed zonal winds for some time to come through January, with at the very least a displaced stratospheric vortex over towards Scandinavia/Siberia.

As you point out the GFS is becoming quite consistent with another significant warming episode towards day 12, serving only to weaken what remains of the stratospheric vortex further - indeed the last 2 GFS runs have gone on to show this further warming coupled with the continued forcing from the pacific wave and just some very minor pressure from the Atlantic leading to a stronger split in the latter stages.

Will be interesting to see as the next warming episode comes in to the day 10 range whether we see this on the ECMWF too.

All of this is suggestive that we will likely continue to see a suppressed zonal wind profile through the stratosphere over the next 3 weeks or so (and increasingly likely perhaps beyond that too). So it’s over to the troposphere to set up whatever it is going to set up pattern wise - whatever pattern is set up is unlikely to shift around too much without some significant forcing from the tropics I would suggest.

If we did end up with a stratospheric imprint on the troposphere, the weird looking, almost summer-like (in their longwave set up rather than temperature profile I should clarify!) charts with the atlantic side of the hemisphere almost entirely devoid of low heights might not be too far off the mark. The general set up I would anticipate in such a scenario remains the same - higher heights to our north/west, and lower heights to our east.

[summer blizzard]

It would be interesting to see any historical strat charts from Jan 04 since the Dec pattern and timing is quite good.

[SqueakheartLW]

These are some of the +384 hours charts from the 06z GFS. They all have one common theme as you will see

These were the 10 charts with the most split or destroyed vortex on them. Member 22 is the weakest of all. Where's the vortex on that chart?

[sebastiaan1973]

2 hours ago, snowking said:

Thanks as always @SqueakheartLW

Still varying shapes to the vortex across model suites but the one constant is that the pacific wave does not look like going anywhere in the next 15 days or so at 10mb, and this means that any plans the vortex has of trying to return to its default position are pure fantasy, meaning we will see suppressed zonal winds for some time to come through January, with at the very least a displaced stratospheric vortex over towards Scandinavia/Siberia.

As you point out the GFS is becoming quite consistent with another significant warming episode towards day 12, serving only to weaken what remains of the stratospheric vortex further - indeed the last 2 GFS runs have gone on to show this further warming coupled with the continued forcing from the pacific wave and just some very minor pressure from the Atlantic leading to a stronger split in the latter stages.

Will be interesting to see as the next warming episode comes in to the day 10 range whether we see this on the ECMWF too.

All of this is suggestive that we will likely continue to see a suppressed zonal wind profile through the stratosphere over the next 3 weeks or so (and increasingly likely perhaps beyond that too). So it’s over to the troposphere to set up whatever it is going to set up pattern wise - whatever pattern is set up is unlikely to shift around too much without some significant forcing from the tropics I would suggest.

If we did end up with a stratospheric imprint on the troposphere, the weird looking, almost summer-like (in their longwave set up rather than temperature profile I should clarify!) charts with the atlantic side of the hemisphere almost entirely devoid of low heights might not be too far off the mark. The general set up I would anticipate in such a scenario remains the same - higher heights to our north/west, and lower heights to our east.

ongoing wave activity a couple of days after the onset of the SSW and negative NAM at 150 hPa means downwelling. You see it already at the EC oper output. So Domeisen can write about not downwelling, we see at EC it does. So, I wonder what's going on.

[georgiedre]

2 minutes ago, sebastiaan1973 said:

ongoing wave activity a couple of days after the onset of the SSW and negative NAM at 150 hPa means downwelling. You see it already at the EC oper output. So Domeisen can write about not downwelling, we see at EC it does. So, I wonder what's going on.

It's 2020 anything is possible.  What's your take on next stage if you could make an informative guess 

[sebastiaan1973]

 

[sebastiaan1973]

1 hour ago, georgiedre said:

It's 2020 anything is possible.  What's your take on next stage if you could make an informative guess 

Based on the 2010 analogue, we see a continuation of the GL blocking, after 3 weeks followed by an Atlantic trough. 

EC46 supports this vision. So we have an article which shows Atlantic through, a analogue of 2010 with the same deceleration and EC46 pointing out to this direction.

Edited December 30, 2020 by sebastiaan1973

[Mike Poole]

Well the GEFS very much joining the split SSW party on todays chart from Stratobserve T384:

Even those that don’t quite make the cut (not sure what the algorithm the software uses is) you can see from the contour plots (faint blue) that many are well on the way.  

[Mike Poole]

GFS // 12z take on the SSW:

I’m struck that the split is what we have seen on many models but ends up a displacement to Europe.  Thoughts?  

[snowking]

To answer my own question from earlier, the ECM ensembles fairly keen on the GFS suggestion of a split in the extended range, and even without a full split the displaced vortex is so stretched that it will have very little effect on anything. We manage to get a sneaky view of the 0z ensembles courtesy of Twitter:

I make that 26 members with a split, and several more right on the verge of one.

[Flake news]

43 minutes ago, Mike Poole said:

GFS // 12z take on the SSW:

I’m struck that the split is what we have seen on many models but ends up a displacement to Europe.  Thoughts?  

It might be weak but it's very nimble.  It's like trying to grab a bar of soap.

[sebastiaan1973]

57 minutes ago, Mike Poole said:

GFS // 12z take on the SSW:

I’m struck that the split is what we have seen on many models but ends up a displacement to Europe.  Thoughts?  

EC12h-oper showed the same. With the vortex at the Atl. Ocean. Which is not good.

[Kirkcaldy Weather]

4 hours ago, Mike Poole said:

Well the GEFS very much joining the split SSW party on todays chart from Stratobserve T384:

Even those that don’t quite make the cut (not sure what the algorithm the software uses is) you can see from the contour plots (faint blue) that many are well on the way.  

Just had a little look numbers similar to how they have been before the end of the run around 5/6 etc for splits but end of the run jumps up to 20 at 10hpa  and here’s 50hpa 

wonder if there are any previous years that have had what the models appear to be hinting at - split (possibly brief) followed by another attempt at a split not too long after? 

[SqueakheartLW]

My favourite ensemble stratospheric charts from the 12z GFS

GFS 12z Member 11

I think I will begin with the warmest warming within the 12z GFS today. Even before this warming shows up the vortex is in quite bad shape and all this warming does is pushes what's left of the vortex to Europe and the other section near the USA even further away.

Even then there is still a modest warming showing up at +384 hours so more damage could still be done to the European piece of the vortex

GFS 12z Member 24

This is only a modest warming at a peak of -24 and you would think that would do little to the vortex but it is already in bad shape after the first main warming. The end result of this -24 warming is the following

The main surviving piece of the vortex has ended up over Siberia and a small warming is still taking place close to this. The already weaker section of the vortex has all but gone and is just a thin stripe of blue over the Atlantic

GFS 12z Member 23

Here is a relatively decent warming of -16 taking place on an already displaced and weaker vortex after the first warming. The end result took me quite by surprise

The vortex never splits but look how much damage was done to it by that second warming. That is one weak vortex spread out over quite a wide area. Not the most favourable location for UK cold but with been so weak it may have little impact

GFS 12z Member 10

Last but by no means least my favourite of the collection

This is how the vortex looks on Member 10's run by the time the second warming reaches its peak -16 temperature. What follows is a thing of dreams for cold weather fans in the UK

The vortex gets shredded apart completely by the end of this run. It is stretched all the way out in a thin weak zone right from the USA, through the Atlantic and Europe and all the way up to eastern Siberia

[Catacol]

2 hours ago, snowking said:

To answer my own question from earlier, the ECM ensembles fairly keen on the GFS suggestion of a split in the extended range, and even without a full split the displaced vortex is so stretched that it will have very little effect on anything. We manage to get a sneaky view of the 0z ensembles courtesy of Twitter:

I make that 26 members with a split, and several more right on the verge of one.

Fine and dandy. I’d love to bin my sense yesterday that displacement was the direction of travel....