Stratosphere and Polar Vortex Watch

[ghoneym]

Reading about the varying trop responses associated with SSW's. This article separated SSW's into two types. Reflecting (characterized by a quick termination of the warming episode due to the reflection of planetary waves in the stratosphere, which leads to an amplification of tropospheric planetary waves) and absorbing (longer timescale as well as a larger meridional extent due to the persistent incoming planetary waves from the troposphere.)

It appears to me from what I have read and what we are currently seeing, is that we are looking at a reflecting type of SSW which is not what we seen in 2010's SSW's ? (which most of us remember as being a recent strat/trop event  for UK wide cold / snow)

A wee extract from the document.

 

For the absorbing type (such as the SSWs in February 1999, January 2009, and January 2010), the deceleration

of zonal winds starts in the subtropical upper stratosphere. The decelerating zone shifts poleward from the

subtropics and then the warming descends in the polar region. The poleward and downward penetration

is similar to the polar night jet oscillation.  In this respect, it is also noticeable that

a cooling occurs prior to the SSW in the polar stratosphere in association with the strengthening of the polar

night jet. The tropospheric response associated with this type of SSW appears through changes in the polar

night jets, and thus appears as a negative AO-like pattern.

 

For the reflecting type (the SSWs in February 1979, December 1998, February 2007, and February 2008.), the

deceleration of stratospheric zonal winds is confined mainly to the polar region. Warming is rapidly terminated

by reflection of planetary waves, which induces downward propagation of the wave packets.

Fluctuations, including intermittent warming periods, precede or follow the major warming. The tropospheric

response of this type of SSW appears as an amplification of the tropospheric planetary wave in the

recovery phase of the SSW. In particular, a deepening trough over the North Atlantic and an enhancing ridge

in the North Pacific sector are evident. The latter enhancement provides a favorable condition for a blocking

formation over the North Pacific.
 

 

[Blessed Weather]

Here's an animation of the Polar Vortex split as forecast by the latest GEFS run (0z Mon 5th Feb). At the start of the run (5th Feb) the PV u-mean zonal wind at 10 hPa 60N is running at 45 m/s. This goes negative (reverses to easterly) on 12th Feb and by 14th Feb hits -21 m/s. Then a slow recovery so by the end of the run is -4 m/s.

5th - 20th Feb:  As a graph:

Upcoming deterministic runs awaited with anticipation as models get to grip with the impact down here on the ground!

Charts courtesy of http://weatheriscool.com/

P.S. I notice recent tweets that have been posted in this thread, including mine, have lost any pictures/charts that were originally included and are now displayed as just text, completely losing the impact. Does anyone have any idea what is happening? Thanks.

[lorenzo]

Oh why not & for archive purposes - here is the Berlin view of the beast getting taken down this morning... not sure about the Twitter embedding, sry.

[Summer Sun]

 

[Gray-Wolf]

Do folk expect the PV to reform or will this just rumble through 'till the final warming?

We've seen early finish date over the last decade and the U.S. lobe looks like it will not be the vortex to try and reform so are we to just see some lazy lolling and then a final warm up as we head into spring and sunlight again impacts 90N at height?

[lorenzo]

That second blow torch on the 'big sister' vortice still prevalent on the latest GFS, be interesting to see if this is maintained and whether the ECM grabs hold of a similar solution..

[bluearmy]

32 minutes ago, lorenzo said:

That second blow torch on the 'big sister' vortice still prevalent on the latest GFS, be interesting to see if this is maintained and whether the ECM grabs hold of a similar solution..

earlier on the last two op runs tony. by day 9/10.

[chris55]

37 minutes ago, lorenzo said:

That second blow torch on the 'big sister' vortice still prevalent on the latest GFS, be interesting to see if this is maintained and whether the ECM grabs hold of a similar solution..

From a laymans perspective this upcoming warming looks very well placed to deliver some colder easterly conditions to the UK if the trip follows suit. And that second warning says ' Canadian PV....your time is done ....see you next winter"

interesting times, and the first official SSW for years  

[Daniel*]

Wow that is really quite something 

 

[ALL ABOARD]

 

 

[Day 10]

Is there any kind of link between a high hurricane season and a sudden stratospheric warming with extra heat being transferred to the pole?

[Mattias]

Nice to see the great action in the stratosphere! Will be interesting to see the tropospheric response. Could also be fun to compare with previous events and to make the comparison easier we have added a new product to weatheriscool.com that might be of interest. The product can be found from the website or following this link: http://weatheriscool.com/index.php/interactive-comparison-gfs-era-interim/ . The product will make it possible to plot charts with geopot. and temperature data at 10 hPa from the ERA interim record and compare it side by side with a chart from the latest GFS forecast. Both charts will have the same projection, colormaps and contour intervals to make the comparison as easy as possible. At the moment only January and February data from ERA Interim is available, but December and March will be added as soon as possible. The product might also have some bugs but hopefully someone finds it useful anyway. For each GFS forecast timestep we have also tried to calculate the most similar geopotential field in the ERA interim record (based on a simple Euclidean distance calculation) and the corresponding date is written out in the box at the bottom of this images: http://weatheriscool.com/index.php/stratosfaren-temp-geopot-height-10hpa/  . The calculation is very simple, just comparing the snapshot of the predicted geopot. field for each timestep, and does not take the dynamical background and so on into account so the result is of course far from perfect but maybe it could give some hints of analouge events. 

[ghoneym]

29 minutes ago, Mattias said:

Nice to see the great action in the stratosphere! Will be interesting to see the tropospheric response. Could also be fun to compare with previous events and to make the comparison easier we have added a new product to weatheriscool.com that might be of interest. The product can be found from the website or following this link: http://weatheriscool.com/index.php/interactive-comparison-gfs-era-interim/ . The product will make it possible to plot charts with geopot. and temperature data at 10 hPa from the ERA interim record and compare it side by side with a chart from the latest GFS forecast. Both charts will have the same projection, colormaps and contour intervals to make the comparison as easy as possible. At the moment only January and February data from ERA Interim is available, but December and March will be added as soon as possible. The product might also have some bugs but hopefully someone finds it useful anyway. For each GFS forecast timestep we have also tried to calculate the most similar geopotential field in the ERA interim record (based on a simple Euclidean distance calculation) and the corresponding date is written out in the box at the bottom of this images: http://weatheriscool.com/index.php/stratosfaren-temp-geopot-height-10hpa/  . The calculation is very simple, just comparing the snapshot of the predicted geopot. field for each timestep, and does not take the dynamical background and so on into account so the result is of course far from perfect but maybe it could give some hints of analouge events. 

 

This is cool Mattias, thanks!

[Summer Sun]

 

[Blessed Weather]

In his updated weekly blog Dr. Cohen has a go at predicting the impact of the imminent SPV split based on 'best fit' analogues and a recent study.

I would say that the best analog was early January 1985 (central date of January 2) followed by early February 1991..... The temperature response across northern Eurasia was more consistent including Europe. For both January 1985 and February 1991 cold was widespread across much of Europe...... We showed in our recent BAMS study that the temperature response to significant PV disruptions similar to the one predicted this week is most robust across northern Eurasia. I include Figure 4 from the study in Figure i. Cold temperatures are widespread across northern Eurasia including Europe.

Figure i:

Finally in an earlier version of the BAMS study we had an alternate plot to Figure i where we present the NH temperature anomalies for the three weeks following a significant PV disruption broken out by week, which I present in Figure ii.

Figure ii:

Full blog (note: updates each week): https://www.aer.com/science-research/climate-weather/arctic-oscillation/

 

[ALL ABOARD]

Just read online that the 10hPa 60N zonal mean wind is due to stay easterly for over 10 days and 

""This would *not* fit the criteria of a mid-winter SSW defined in Charlton and Polvani (2007). They specify events in which the zonal winds stays easterly for more than 10 consecutive days as final warmings.""

 

[Snowy L]

11 minutes ago, ALL ABOARD said:

Just read online that the 10hPa 60N zonal mean wind is due to stay easterly for over 10 days and 

""This would *not* fit the criteria of a mid-winter SSW defined in Charlton and Polvani (2007). They specify events in which the zonal winds stays easterly for more than 10 consecutive days as final warmings.""

 

Would be one of the earliest final warnings ever surely?

[ALL ABOARD]

3 minutes ago, Snowy L said:

Would be one of the earliest final warnings ever surely?

I have no idea, hopefully one of the more knowledgable can explain later in a bit more detail. 

Im guessing a final warming in winter may lead to some fancinating charts but I may be way wide of the mark. 

[chionomaniac]

20 minutes ago, ALL ABOARD said:

Just read online that the 10hPa 60N zonal mean wind is due to stay easterly for over 10 days and 

""This would *not* fit the criteria of a mid-winter SSW defined in Charlton and Polvani (2007). They specify events in which the zonal winds stays easterly for more than 10 consecutive days as final warmings.""

 

That's wrong.

This classifies as a SSW and it remains to be seen whether we would get a final warming. This would be unlikely given the timeframe. I think that there must be an error regarding west and east. Final warmings are only classified by a lack of consecutive westerlies over a ten day period before the end of April following a period when easterlies have been prevelant.

Edited February 6, 2018 by chionomaniac

[ALL ABOARD]

Thanks chio ✅?

[zdlawrence]

27 minutes ago, ALL ABOARD said:

Just read online that the 10hPa 60N zonal mean wind is due to stay easterly for over 10 days and 

""This would *not* fit the criteria of a mid-winter SSW defined in Charlton and Polvani (2007). They specify events in which the zonal winds stays easterly for more than 10 consecutive days as final warmings.""

 

Yeah, this was just a mistake that was posted on Twitter. The Charlton & Polvani 2007 paper specifically says:

"... cases where the zonal mean zonal winds become easterly but do not return to westerly for at least 10 consecutive days before 30 April are assumed to be final warmings, and as such are discarded. This criterion ensures that following SSWs, a coherent stratospheric vortex is reestablished."

The upcoming event will classify as a mid-winter SSW. How quickly the stratospheric circulation "recovers" after it remains to be seen, but forecasts (ensembles included) show it taking anywhere from 4-10+ days before circulation returns to westerly. 

 

[chionomaniac]

2 minutes ago, zdlawrence said:

Yeah, this was just a mistake that was posted on Twitter. The Charlton & Polvani 2007 paper specifically says:

"... cases where the zonal mean zonal winds become easterly but do not return to westerly for at least 10 consecutive days before 30 April are assumed to be final warmings, and as such are discarded. This criterion ensures that following SSWs, a coherent stratospheric vortex is reestablished."

The upcoming event will classify as a mid-winter SSW. How quickly the stratospheric circulation "recovers" after it remains to be seen, but forecasts (ensembles included) show it taking anywhere from 4-10+ days before circulation returns to westerly. 

 

I think I have read those 2 papers a lot in my time that I probably could recite them, lol!

[lorenzo]

Latest from the Dow Jones Vortex chart... 

Stunning

 

Sam Lillo tweet re reversal - always a wizard with charts!

And for old times sake - remember looking at these ones

 

Edited February 6, 2018 by lorenzo

[Gray-Wolf]

I get a tad concerned that with such a 'new' science folk might be busy trying to retrospectively understand the Stratosphere and its workings when changes in Arctic Sea Ice are possibly driving WACCy alterations to its very functioning?

What has become apparent is the anomalous nature of the warming that I have seen tweeted with temp anoms off the chart?

I had already ruminated over the fate of the Canadian vortex as it keeps on looking like it will not recover post the split but will rather keep on warming and fade

 So we would be left with half a vortex and possibly 2 weeks before we might expect an early end to the season?

If the vortex tries to reform but is not centred over the pole will not the higher reaches of the strat be in sunlight? Does this not alter things a tad? 

All in all maybe we are seeing a 'new' expression of the strat and its working under a novel forcing? I take it the reason for the vortex being ripped into two is not geographically common relying upon WACCy generated Lp's slamming into Barentsz after clashing with the eastern heights of Greenland?

As with 'weather' generally there are a limited number of ways it can express itself but the forcings driving those expressions can take many differing forms?

Anyhoo's , all we can do is watch and wait now eh?

EDIT: So now the timing for us to see impacts is also anomalous?

Edited February 6, 2018 by Gray-Wolf

[lorenzo]

The 800K animation is worth a watch on the GSFC site.. imagine that played out in regular old NWP, think we would have a party..

Potential Vorticity circa 10hPa  https://acd-ext.gsfc.nasa.gov/Data_services/Current/arctic/anim_EPV_0800.html

10hPa temps animation            https://acd-ext.gsfc.nasa.gov/Data_services/Current/arctic/anim_T_0010.html

As you go down through the levels you can see the transfer east of the weaker lobe is less instantaneous. Good viewing nonetheless!

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

 

Actually this is bloody cool too showing the stratospheric highs doing their dance. t72 and the Atlantic Stratospheric High goes for it..

http://www.atmos.albany.edu/student/hattard/realtime/dt_500/DT_500.php

 

 

Edited February 6, 2018 by lorenzo