Stratosphere and Polar Vortex Watch 2020

[bluearmy]

Just now, Nick F said:

Steady as she goes ...

Would like to see EC come on board though, their extended zonal mean zonal wind at 10 hPa updates today, though not sure when we'll get to see it: 

ECMWF | Charts

APPS.ECMWF.INT

Question is, if we do get a SSW, what with the strat decoupled from the trop atm, will we see the effects from it on our weather patterns?

around 9:45 pm nick

no indication at day 10 that the gfs strat and ec strat are far apart

[Vikos]

 

  ---> 

To understand

We need this blue area like this

 

One can see a punch from up above forwarding down

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  -----> 

 

Zonal winds are slowly (!) weaking in 10hpa and 30hpa, but nothing extraordinary (by now!), maybe at 0 by end of January, but that could (!) than already be the (very early) final warming

Strat. temps forecast shows a significant rise at 60°N in 10hpa around 1.1.2021, 90°N isn't affected (yet)

 

Feel free to correct me. I would love to see the SSW coming, also in prefer an Vortex split just for the possible outcomes (beast of the east you call it, in Germany we call it the Russian Whip)

[southbank]

5 minutes ago, Vikos said:

 

  ---> 

To understand

We need this blue area like this

 

One can see a punch from up above forwarding down

----> 

 

  -----> 

 

Zonal winds are slowly (!) weaking in 10hpa and 30hpa, but nothing extraordinary (by now!), maybe at 0 by end of January, but that could (!) than already be the (very early) final warming

Strat. temps forecast shows a significant rise at 60°N in 10hpa around 1.1.2021, 90°N isn't affected (yet)

 

Feel free to correct me. I would love to see the SSW coming, also in prefer an Vortex split just for the possible outcomes (beast of the east you call it, in Germany we call it the Russian Whip)

great to see other folks in Europe posting - just shows you weather nuts are universal - welcome to Netweather btw Vikos

[Vikos]

8 minutes ago, southbank said:

great to see other folks in Europe posting - just shows you weather nuts are universal - welcome to Netweather btw Vikos

Well, thank you

GFS is onto something, and that is want I want to see, as it is a significant part of the SSW puzzle

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[Vorticity0123]

To get a quick idea of the 3D-structure evolution of the stratospheric polar vortex, I like to use the 'ellipse profile' plots found here. The GFS-forecast for the upcoming warming episode nicely show how the polar vortex might behave both horizontally and vertically during the next 10-15 days. Note that the plots are from Sunday 20-12, as the plots from 21-12 were not yet available.

At first (situation 20-12), you can see the polar vortex is nicely structured - it is both vertically well-stacked and circular in shape.

GFS ellipse Polar Vortex profiles from the run of 20-12, valid 20-12, 00Z

However, at about 10 days out (30-12, see below), the vortex has become much less well-stacked, with the upper vortex centered near Siberia while the lower vortex is offset towards Russia.

GFS ellipse Polar Vortex profiles from the run of 20-12, valid 30-12, 00Z

The vortex elongation and distortion only increases from that point. At 14.5 days out (outside the reliable timeframe, but nice to illustrate the diagnostics), the vertical displacement of the vortex decreases a little. However, the vortex becomes much more elongated at the upper levels. Especially at 3 and 5 hPa, the vortex is far from circular. This is also nicely shown in the large aspect ratio diagnostic of the vortex at these pressure levels (see rightmost plot below).

GFS ellipse Polar Vortex profiles from the run of 20-12, valid 03-01-2021, 00Z

Curious to see whether the warming and resulting polar vortex distortion will result in a SSW sometime early January!

[Snowy Hibbo]

1 hour ago, Nick F said:

Steady as she goes ...

Would like to see EC come on board though, their extended zonal mean zonal wind at 10 hPa updates today, though not sure when we'll get to see it: 

ECMWF | Charts

APPS.ECMWF.INT

Question is, if we do get a SSW, what with the strat decoupled from the trop atm, will we see the effects from it on our weather patterns?

It’s interesting that we already see quite a -AO in the troposphere, before we even start to see the plausible effects downwelling to the surface. So the dynamic there could be interesting.

It’s quite possible that we might have the troposphere try to briefly balance itself out, as the SSW occurs, returning to neutrality or even a slight positive in the first week of Jan. Before the SSW comes down to the surface on the 2nd and 3rd weeks of Jan. And you should be able to maintain a mostly cold -AO/-NAO look through there.

[Snowy Hibbo]

1 hour ago, Vikos said:

Zonal winds are slowly (!) weaking in 10hpa and 30hpa, but nothing extraordinary (by now!), maybe at 0 by end of January, but that could (!) than already be the (very early) final warming

Got some decent heat flux into the SPV. It’s just a matter of whether it’s enough for a technical SSW. 
 

At the end of the day, it’s just a technicality and ultimately it’s about whether it’s impacts whether a SSW or just a moderate weakening can be seen on the surface in the NH circulation. And the fact we are already seeing a -AO phase helps.

[Vikos]

Has anyone a link to QBO-Charts? My link is outdated/dead

[ghoneym]

54 minutes ago, Vikos said:

Has anyone a link to QBO-Charts? My link is outdated/dead

The Quasi-biennial Oscillation (QBO)

ACD-EXT.GSFC.NASA.GOV

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Plots of the QBO

 

[Vikos]

2 minutes ago, ghoneym said:

The Quasi-biennial Oscillation (QBO)

ACD-EXT.GSFC.NASA.GOV

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Plots of the QBO

 

Thank you  

so qbo goes east...  

[jules216]

1 hour ago, Snowy Hibbo said:

It’s interesting that we already see quite a -AO in the troposphere, before we even start to see the plausible effects downwelling to the surface. So the dynamic there could be interesting.

It’s quite possible that we might have the troposphere try to briefly balance itself out, as the SSW occurs, returning to neutrality or even a slight positive in the first week of Jan. Before the SSW comes down to the surface on the 2nd and 3rd weeks of Jan. And you should be able to maintain a mostly cold -AO/-NAO look through there.

Have look at similarities with Baldwin/Dunkerton 2001

[JeffC]

The first glimmerings of the Siberian warming?

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

EARTH.NULLSCHOOL.NET

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

 

[phil nw.]

Not much to add to some very good information in recent posts,Just to show the 00z gefs zonal wind forecasts tied in with the bias corrected cfs trends.

Based on the above we should expect a big drop off as we enter January where hopefully the vortex will by then be in a increasingly stressed state.

ECM should be showing this soon i guess as their outputs come into the 10 day range.

Sill good wave 1 action ongoing and forecasted to extend forward.

All good news at the moment.

 

 

Edited December 21, 2020 by phil nw.

[Snowjokes92]

What are the potential effects down the line with an ssw on top of the already -ao in the trop anyway. We are already seeing blocking in play in the trop now let alone without a ssw? I know things go wrong and an ssw isnt always a gold ticket. Surely the implifications could be unheard of if things fall in favourthe pv is already getting smashed. Hope to see some biblicial charts soon. We have a lot in are favour here. Could we still be at a point where some runs throw up some unseen set ups we dont really see? 

Edited December 21, 2020 by Snowjokes92

[Singularity]

The wave-2 is a little slower on the 06z and 12z GFS runs today. The usual slowdown showing its hand? The model often proves a bit too efficient with the WAFz, causing it to show SSWs a week or two earlier than actually happens, if it does to begin with.

I can see some historical splits that worked out fine without requiring the wave-2 to be very strong - but I sense that the probability of hitting the jackpot is lower than when the wave-2 is comparable to the wave-1 in terms of peak stratosphere temp increase and ridge development.

[Griff]

I'm not taking credit for checking ecm myself tonight for a change but did spot this... 

 

[Bullseye]

Some movement now towards GFS, need this to continue but pretty good sight to see 

[ghoneym]

On 20/12/2020 at 16:05, ghoneym said:

A few replies to my question re - PSC 2 formation on twitter. Might belong in the model tweet thread, or still relevant here? 

Some further discussion regarding the record breaking forecasted drop in temperature in the Stratosphere. (in a very particular area, not to be taken as a large proportion of area) A potential temperature of - 99 still being forecast on the nasa ozone site. A gravity wave off the South tip of Greenland potentially being the culprit for this phenomena. 

Edited December 21, 2020 by ghoneym
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[chionomaniac]

The time we are most likely to see PSCs is during significant strat events when the colder core of the vortex is displaced southwards and wave activity introduces moisture.  Hopefully we can witness this

[bluearmy]

The gfs op seems to have backed off the quick reversal and it currently remains unlikely before two weeks is out. However, it is still coming according to that model and it sees a split at the moment trending to vortices nw Russia and ne Canada .....some way to go yet .....would be good if we knew what the ec 46 clusters or eps were seeing on their deceleration of the zonal flow ref any split or displacement 

[Uncertainty]

2 hours ago, bluearmy said:

The gfs op seems to have backed off the quick reversal and it currently remains unlikely before two weeks is out. However, it is still coming according to that model and it sees a split at the moment trending to vortices nw Russia and ne Canada .....some way to go yet .....would be good if we knew what the ec 46 clusters or eps were seeing on their deceleration of the zonal flow ref any split or displacement 

Does that infer BA that the split is between those two vortices e.g through the NA/NW Europe?

More GEFS members going for the a reverse too, almost half and a cluster goes really deep!

 

[ICE COLD]

2 hours ago, bluearmy said:

The gfs op seems to have backed off the quick reversal and it currently remains unlikely before two weeks is out. However, it is still coming according to that model and it sees a split at the moment trending to vortices nw Russia and ne Canada .....some way to go yet .....would be good if we knew what the ec 46 clusters or eps were seeing on their deceleration of the zonal flow ref any split or displacement 

We should know soon if there is gonna be a technical SSW ? As in the wording should start to change at the back end of the METO 30 dayer . Chance of cold Easterly winds etc . That’s what happened on the previous 2 SSW , obviously doesn’t mean we’re hit the jackpot (2018) BFTE we could end up like last year and not get anything. But this year feels as tho something special could happen . 

[SqueakheartLW]

Have decided to look through all of the GFS and its ensembles in regards to the outcome of the predicted SSW. I have only used the 00z, 06z and 12z since I have generally missed the 18z output for the stratosphere. Here are the percentage chances of each outcome based on what I have seen so far as well as the date this outcome has either been achieved or was achieved just before the date given.

The main categories are:

Displacement - Polar vortex displaced but in one main vortex centre but generally weakened too

Split - Vortex ends up in 2 separate pieces, weakened and in different locations

Unknown - The warming has taken place but the outcome isn't clear by the end of the run

None - A none event where the warming has taken place but the vortex is still in one piece and generally near the pole or Greenland, maybe weakened a bit in a number of these outcomes

20/12/2020 00z, 06z and 12z Stratospheric 10mb run outcomes

TYPE                    CHANCE  DATE               CHANCE IGNORING UNKNOWN OUTCOMES

Displacement     21.8%     05/01/2021     36.2 %

Split                      25.0 %    05/01/2021     41.4 %

Unknown            39.6 %     05/01/2021     N/A

None                    13.6 %     05/01/2021     22.4 %

On the first day of my assessment most options were not fully resolved by the end of the run with 39.6 % in the unknown category. Of those that were resolved it seemed that the vortex split option was the most likely end outcome at 25 %. Displacement wasn't far behind however at 21.8 % so between these outcomes it is still very much up for grabs. The none event was last at 13.6 % but not insignificant in terms of the share of the resolved outcomes. Ignoring unknown outcomes gives a more clear idea of the spread from the 00z, 06z and 12z runs on 20/12/2020. In theory the unknown outcome should see less and less options falling in it as the event gets closer.

21/12/2020 00z, 06z and 12z Stratospheric 10mb run outcomes

TYPE                    CHANCE  DATE               CHANCE IGNORING UNKNOWN OUTCOMES     CHANGE FROM 20/12/2020

Displacement     35.4%     06/01/2021     45.9 %                                                                       +9.7 %

Split                      30.2 %    06/01/2021     39.2 %                                                                       -2.2 %

Unknown            22.9 %     06/01/2021     N/A                                                                            N/A

None                    11.5 %     06/01/2021     14.9 %                                                                      -7.5 %

My second stratospheric assessment has seen an expected drop in unknown outcomes as predicted dropping in percentage terms from 39.6 % to 22.9 % but where has the dice fallen with these extra outcomes. It would seem most moved towards the displacement option as it now has the biggest share of the other outcomes at 35.4 %. Split is still taking a good fair of the share however at 30.2 % so don't rule out a split vortex taking place. The good news for cold fans is that the none event outcome has seen a drop in its share down to 11.5 %. When ignoring the unknown outcomes Displacement is almost half of the options from 21/12/2020 at 45.9 %, an increase of 9.7 % from 20/12/2020. Split has dropped to 2nd position with 39.2 % of outcomes, a small drop of 2.2 % of the share. The none events are still in last place but a more distant last place now at 14.9 %, a drop of 7.5 % compared with 20/12/2020.

ECM Stratospheric Forecast

The GFS has been going full on for this SSW event but is the ECM also playing ball too

Here are the 10mb forecast charts for the next 10 days

Current                                                       Day 1                                                         Day 2

Day 3                                                           Day 4                                                          Day 5

Day 6                                                           Day 7                                                          Day 8

Day 9                                                            Day 10

At first there is a small warming event between the present time and Day 5 that makes little impact but then the main event is starting to show up around Day 6 and 7 which by days 8 to 10 is beginning to really get going. This shows that ECM is on board with the idea too and is getting the core warming up to around 0C like the GFS is doing.

We shall have to wait and see if ECM goes for a displacement or split event

[sebastiaan1973]

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081091

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.

[Kirkcaldy Weather]

Have continued to look at the GEFS strat splits and to avoid clogging the thread up I created a gallery of the charts from the last few days, a few are the same ensemble just tried to show how it played out and some show the second area of warming more as a continued displacement at least at that stage like I mentioned a couple of days ago, it all continues to be really interesting to see how it unfolds  

Strat warming

IBB.CO

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Strat warming album hosted in ImgBB