Stratosphere and Polar Vortex Watch

[Dennis]

some is brewing

[Mattias]

The gfs ensemble now goes for a reversal at 10 hPa 60N.

Still very far out in the forecast and latest GFS not as extreme, but it seems to be good agreement regarding the increased wave 1 activity, latest gfs shown below.

 Interesting times ahead!

[KyleHenry]

Brewer Dobson Unit analysis.

 

24/11/2017.

25/11/2017.

30/11/2014.

24/11/2010.

 

Deviations of Ozone % in key geographical areas during both cold and mild NW European winters, I will let the reader decipher the differences on their own. 

 

Edited November 26, 2017 by KyleHenry

[Catacol]

The obvious question from this is which leads which. Pattern is clear - but my knowledge of ozone impact on trop pressure patterns or the vortex above is weak. Does ozone concentration provide a forcing that helps alter the pattern, or is it simply reflective of a dominant pattern that shifts the ozone to suit?

[KyleHenry]

47 minutes ago, Catacol said:

The obvious question from this is which leads which. Pattern is clear - but my knowledge of ozone impact on trop pressure patterns or the vortex above is weak. Does ozone concentration provide a forcing that helps alter the pattern, or is it simply reflective of a dominant pattern that shifts the ozone to suit?

I'm observing ozone concentration in terms of relationship to other ongoing key factors. 

There is currently no Stratosphere/Troposphere coupling. 

Tropopause has extended In height through Autumn.

Low solar.

Northern Hemispheric Ozone concentration percentage is up in comparison to years without key factors.

Ongoing wave activity which will displace PV off default position.

Most significantly, less BDU above PV default position in atmosphere above Greenland results in less cooling, lessens convection at heights inside PV and in turn the PV is weakened by being unable to anchor at its default position. 

Noted that in years without these factors ozone transfer from Southern Hemisphere doesn't occur until mid Jan onwards. 

Ozone is not an overriding factor but in a specific alignment of key components, it becomes an assisting factor.

* Not inferring this winter will be like 2010. Using it as an extreme example. 

 

Edited November 26, 2017 by KyleHenry

[Catacol]

26 minutes ago, KyleHenry said:

 

Most significantly, less BDU above PV default position in atmosphere above Greenland results in less cooling, lessens convection at heights inside PV and in turn the PV is weakened by being unable to anchor at its default position. 

 

Ah - ok - this bit is particularly relevant. So it is a specific driver that impacts on vortex intensity and position. Best I add that to my teleconnective forecasting arsenal - I've rather ignored BDC when looking at pattern development. Rather good news then - and considerably better than 2010 especially if we want to see scandy heights rise also.

[Ruben Amsterdam]

Still rather impressive output this morning (GFS 06z in FI). Does anyone have any info on December SSWs? I believe there are rare and FU Berlin reports such events only in '87, '98, and 2001. These were not exactly impressive winters...

Edited November 26, 2017 by Ruben Amsterdam

[Summer Sun]

 

[lorenzo]

https://esrl.noaa.gov/csd/groups/csd8/sswcompendium/majorevents.html

Butler, A. H., J. P. Sjoberg, D. J. Seidel, and Karen H. Rosenlof, A sudden stratospheric warming compendium, Earth Syst. Sci. Data, doi:10.5194/essd-9-63-2017, 2017

Event Name	NCEP-NCAR	ERA40	ERA-Interim	JRA-55	MERRA2	ENSO	QBO 50mb
DEC 1965	8-Dec-65	16-Dec-65		18-Dec-65		E	E
DEC 1981	4-Dec-81	4-Dec-81	4-Dec-81	4-Dec-81	4-Dec-81	N	E
DEC 1987	8-Dec-87	8-Dec-87	8-Dec-87	8-Dec-87	8-Dec-87	E	W
DEC 1998	15-Dec-98	15-Dec-98	15-Dec-98	15-Dec-98	15-Dec-98	L	E
DEC 2001	2-Jan-02	31-Dec-01	30-Dec-01	31-Dec-01	30-Dec-01	N	E
Total Events	36	29	24	37	23
Frequency: Events/Decade	6.2	6.4	6.5	6.4	6.4

[Interitus]

2 hours ago, Ruben Amsterdam said:

Still rather impressive output this morning (GFS 06z in FI). Does anyone have any info on December SSWs? I believe there are rare and FU Berlin reports such events only in '87, '98, and 2001. These were not exactly impressive winters...

Check out the SSW compendium for a full list of dates from reanalyses - https://www.esrl.noaa.gov/csd/groups/csd8/sswcompendium/majorevents.html

Since 1958 there have been 5 with 1981 perhaps most well known - winter 1981/2 was famously cold for the UK.

FWIW this forecast event is very similar to 1998.

edit: pipped to the post, lol

Edited November 26, 2017 by Interitus

[lorenzo]

Brilliant site and here are some of the re-analysis plots from 98.

 

Edited November 26, 2017 by lorenzo

[Interitus]

1998

 

[Northern Sky]

Apart from Dec 81/ Jan 82 none of those winter months were cold. In fact most were mild. Should we be careful what we wish for?

[ArHu3]

17 minutes ago, Interitus said:

1998

 

That was a really sucky winter, as were 1960, 68, 77, 88,  and 2004 (winters with december or early to mid January warmings) 

Edited November 26, 2017 by ArHu3

[lorenzo]

The 10hPa run through bears similarity to 98 in terms of eventual vortex locale, flatlined flux this yr in comparison.

https://acd-ext.gsfc.nasa.gov/Data_services/Current/arctic/anim_EPV_0800.html

And, yes nothing ever guaranteed in terms of the eventual cold spillage as result of Strat Event.

[lorenzo]

Reckon that would trouble the vortex...

[Ruben Amsterdam]

2 hours ago, Interitus said:

Check out the SSW compendium for a full list of dates from reanalyses - https://www.esrl.noaa.gov/csd/groups/csd8/sswcompendium/majorevents.html

Since 1958 there have been 5 with 1981 perhaps most well known - winter 1981/2 was famously cold for the UK.

FWIW this forecast event is very similar to 1998.

edit: pipped to the post, lol

Would I be correct in stating this would also be a Canadian Warming? I.e. anomalies in early winter in the Canadian sector are Canadian Warmings, but only some of these also classify as a full-SSW?

[JeffC]

1 hour ago, lorenzo said:

Reckon that would trouble the vortex...

Looks like a lamb...hopefully it's frozen lamb!

[Weather-history]

2 hours ago, ArHu3 said:

That was a really sucky winter, as were 1960, 68, 77, 88,  and 2004 (winters with december or early to mid January warmings) 

Has the state of the tropospheric vortex at time of Canadian warming event taking place been considered?

For instance this was from December 1998, looks far more organise than it does now

Edited November 26, 2017 by Weather-history

[ArHu3]

21 minutes ago, Weather-history said:

Has the state of the tropospheric vortex at time of Canadian warming event taking place been considered?

For instance this was from December 1998, looks far more organise than it does now

Nope, this was just looking at major warmings and hellmann number (in De Bilt but that location seems to be a reasonable reference here on this forum) 

[Singularity]

  
  

The 30 hPa sequence from the GFS 12z. Great consistency with previous runs, and the kick-off moving closer in time rather than being put back to stay at the same range each day.

The scale of vortex displacement and stretching depicted looks sufficient to my eyes for encouraging a tropospheric reverse zonal flow response (after approx. 14-20 day lag) across N. Eurasia, likely including much or all of the UK.

We can easily see, however, the risk that exists should the event not reach this magnitude; the reverse zonality line ends up drawn NW of the UK, much as was the case during the middle part of the week just gone but for a longer period, and we're stuck with unsettled conditions and temps between near average and very mild depending on the trough orientation.

So my interpretation is "high risk, high reward" when going along this route.

Has EPS been suggesting (or at least hinting at) anything like this magnitude and configuration of warming and height rises?

 

I can see something in the works on the ECM day 10, although that was based on yesterday's 12z and I imagine the 00z produced something more pronounced based on the tropospheric charts? TIA

 

Edited November 26, 2017 by Singularity

[Mattias]

1 hour ago, Singularity said:

  
  

The 30 hPa sequence from the GFS 12z. Great consistency with previous runs, and the kick-off moving closer in time rather than being put back to stay at the same range each day.

The scale of vortex displacement and stretching depicted looks sufficient to my eyes for encouraging a tropospheric reverse zonal flow response (after approx. 14-20 day lag) across N. Eurasia, likely including much or all of the UK.

We can easily see, however, the risk that exists should the event not reach this magnitude; the reverse zonality line ends up drawn NW of the UK, much as was the case during the middle part of the week just gone but for a longer period, and we're stuck with unsettled conditions and temps between near average and very mild depending on the trough orientation.

So my interpretation is "high risk, high reward" when going along this route.

Has EPS been suggesting (or at least hinting at) anything like this magnitude and configuration of warming and height rises?

 

GFS 12z seems to be a bit extreme, some more images shown below, but GFS ensemble also has a very strong signal with a majority of the members now going for a reversal at 10 hPa 60N.

. 

[Allseasons-Si]

 

[Interitus]

16 hours ago, Ruben Amsterdam said:

Would I be correct in stating this would also be a Canadian Warming? I.e. anomalies in early winter in the Canadian sector are Canadian Warmings, but only some of these also classify as a full-SSW?

Ok, the Mystery of the Canadian Warming....

The origin of this probably goes back to the 1977 paper Interannual Variability of the Winter Stratosphere in the Northern Hemisphere http://journals.ametsoc.org/doi/abs/10.1175/1520-0493(1977)105<0762:IVOTWS>2.0.CO;2

by Karin Labitzke of Berlin Free University which is the source of data and ECMWF charts that regularly feature in this forum. This was still quite early on in stratosphere research, but there was enough data from 30mb and some from 10mb to study 12 winters from 1964/5 - 1975/6. Two of the indices are familiar from the Berlin site today - wave 1 and 2 height and wave 1 temperature (wave 2 considered comparatively insignificant by the author). The third index however was daily values of zonal kinetic energy (KZ), integrated from 90-15°N and between 10-50mb. This is basically an angular momentum equation to describe the strength of the vortex and while there will be a correlation with wind strength, how closely it matches the 60°N zonal wind is unclear which likely affects their SSW dates. Lastly, there is the temperature difference between 80 and 50°N.

From this, the author was able to determine three types of stratospheric disturbance - "major", "minor" and "Canadian" warmings.

In a nutshell, the defining qualities were as follows -

Major

Commonly 2 phases - first pre-warming - high KZ = vortex strong and well developed. Temperature wave peaks, larger at 10mb than 30mb. Wave 1 height also peaks with a pronounced minimum in wave 2 height. The contrasting wave 1 and 2 heights also noted lower down at 200mb (i.e troposphere). Then comes the breakdown phase - rapid decay of wave 1 simultaneous with development of wave 2 splitting the vortex - concurrent reversal of temperature gradient and marked drop of KZ. It was noted that breakdown may occur without the wave 2 development, and an intense "final warming" is similar to a major but leading to reversal from winter to summer circulation.

Minor

Similar to a major with similar wave 1 height, but no breakdown of the vortex. Key difference observed - during pre-warming, amplitude ratio of wave 1 and 2 at 30mb is about 10:1 for a major but typically 2:1 (or wave 2 actually larger than wave 1) for a minor. Suggestion that large wave 2 in this phase retards the process of vortex breakdown (in agreement with Holton 1976) and synoptically there is a difference between wave 2 in the height field of an elongated cold vortex, or a "cold wave 2" (no marked drop in KZ or temp reversal) and wave 2 developing at same time as temp reversal and the drop of KZ leading to breakdown.

Canadian

Three key characteristics - 1) Reversal of temperature gradient alongside large wave 1 geopotential. 2) Wave 1 temperature clearly larger at 30mb than 10mb (contrast to major warming). 3) Zonal kinetic energy KZ increases while wave 1 decays. These 3 characteristics occur with typical intense development and vacillation of the Aleutian high, which moves polewards towards Canada and and forces the vortex to Siberia. There may be net easterly zonal winds and meet the criteria for major warming, but no vortex breakdown and KZ recovers with waning wave 1. Finally, satellite radiance data shows intensity decreases with height with little activity in upper stratosphere.

So it can be seen with the more typical use of 60°N zonal wind and more data in the 40 years since this paper that Canadian warmings may have been absorbed into the collection of SSW and minor warmings as general displacements, but Labitzke was always keen to stress that they were synoptically different, affecting the middle stratosphere and not destructive to the vortex. No mention is made of time of occurrence during the winter and though they are typically early winter, the paper has the example of 1966/7 with one in December and a second at end Jan / start February - curiously this isn't shown in the list of winters on the Berlin website where they're all in November or December.

Edited November 27, 2017 by Interitus

[knocker]

 

Edited November 27, 2017 by knocker