Stratosphere and Polar Vortex Watch 2020

[bluearmy]

12z gfs op was a tech ssw by day 15 

I guess you can’t say this isn’t a consistent signal .......

[Mike Poole]

1 hour ago, bluearmy said:

12z gfs op was a tech ssw by day 15 

I guess you can’t say this isn’t a consistent signal .......

Well that isn’t a surprise given last couple of days output.  GFS 12z T384

Strat vortex RIP

What’s left of it looks a bit like a bra, to be honest

Edited December 19, 2020 by Mike Poole

[virtualsphere]

24 minutes ago, Mike Poole said:

Well that isn’t a surprise given last couple of days output.  GFS 12z T384

Strat vortex RIP

What’s left of it looks a bit like a bra, to be honest

Always a good sign when the vortex resembles a ninja turtle.

[ghoneym]

Does anyone have an explanation for this? I think PSC 2's in the artic are only formed by ice rather than the chemical reaction in the antarctic. At 30hpa I'm only imagining warming kicking off up there.

 

[bluearmy]

Last Two gfs ops have backed off from tech ssw’s although the picture remains pretty much the same 

[ALL ABOARD]

1 hour ago, bluearmy said:

Last Two gfs ops have backed off from tech ssw’s although the picture remains pretty much the same 

Not this one. 

 

 

Renewed warming showing up. 

[Vikos]

2 hours ago, bluearmy said:

Last Two gfs ops have backed off from tech ssw’s although the picture remains pretty much the same 

By now, it's more a strong minor warmig regarding that a major warming is defined like a rise of 30-40K within 48-72h, reversal of the climatological westerly zonal-mean zonal winds at 60°N/10hpa. Regarding temperture, we must reach a positive number. Until there is nothing on the ECMWF horizon, we should just wait for the outcome.

Wind

Forecast-> 

Temperature

Forecast ->   

 

Until now, I would say a displacement is more to come than a real split

Edited December 20, 2020 by Vikos

[wellington boot]

17 minutes ago, Vikos said:

By now, it's more a strong minor warmig regarding that a major warming is defined like a rise of 30-40K within 48-72h, reversal of the climatological westerly zonal-mean zonal winds at 60°N/10hpa. Regarding temperture, we must reach a positive number. Until there is nothing on the ECMWF horizon, we should just wait for the outcome.

Wind

Forecast-> 

Temperature

Forecast ->   

 

Until now, I would say a displacement is more to come than a real split

Wow I had no idea the ECM was showing so little in the way of warming. or negative wind anomalies. Seems a stark contrast with the GFS output. Can anyone shed light on the relationship and reliability of these two models when it comes to strat forecasting?

[sebastiaan1973]

Stratospheric influence on North Atlantic marine cold airoutbreaks following sudden stratospheric warming events.

 

https://wcd.copernicus.org/articles/1/541/2020/wcd-1-541-2020.pdf

[Vikos]

 

NASA +240h, displacement

  

 

JMA, seems to get back to "normal"

 

ECMWF +240h

GFS +240h, +384h

 

 

This seems to be a (weak) split

  

 

 

Edited December 20, 2020 by Vikos

[ghoneym]

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

[sebastiaan1973]

Incredible GFS12h-run for the stratosphere. We see a split SSW.

[Vikos]

2 minutes ago, sebastiaan1973 said:

Incredible GFS12h-run for the stratosphere. We see a split SSW.

That's what GFS shows, but it's the last chart of this run. For a SSW, we need some more parameters like zonal wind change, ozone concentration, downstream developments and so on.

We should wait for further analysies charts from ECMWF

noaa_21496_DS1.pdf

[Singularity]

Consistently, GFS shows displacement of the polar vortex partially across North America followed by strong warming over the North Atlantic sector.

It appears that the displacement is setting the stage for the secondary warming that then drives the split.

Such an internally-driven event explains the high consistency of the model's output lately. If it was reliant on uncertain troposphere dynamics, we'd see a lot more variation between runs.

This gives me reason to be more confident than usual in what the model shows for the 12-16 day range.

No such confidence when it comes to whether the outcome features enough wave-2 to drive a rapid downward propagation of a negative NAM, though!

That was the big lesson taught by 2019's failed downward propagation. That SSW was huge, featuring some record-breaking vertical wave activity flux, but predominantly wave-1 driven.

In such a situation, it seems to be much less likely that the vertical structure of the stratosphere aligns in a way that permits rapid downward propagation.

Instead we're left looking for 'drip-down' of anomalously warm stratospheric temps to produce a negative NAM (i.e. negative AO in the troposphere), which tends to produce smaller-scale impacts that more easily miss the UK. It can also be stalled by an unreceptive troposphere, much as we saw in Jan-Feb 2019.

In a wave-2 dominated SSW, there's still no guarantee of the rapid downward propagation, but at least some slower propagation seems to be very likely and the resulting cold weather outbreaks tend to cover wider areas and persist for longer. Of course, the UK can still miss out, being such a narrow slither of the hemisphere.

[bluearmy]

That 12z gfs op is nuts as it reverses to about -25m/s by day 15

Not surprisingly the reversal looks to be heading down to the trop on that run  - although we already have a neg AO in any case 

[ICE COLD]

26 minutes ago, bluearmy said:

That 12z gfs op is nuts as it reverses to about -25m/s by day 15

Not surprisingly the reversal looks to be heading down to the trop on that run  - although we already have a neg AO in any case 

What’s the ECM like high up nick at day 10 ? Is going the same way as the gfs ? Cheers . 

[snowking]

20 minutes ago, bluearmy said:

That 12z gfs op is nuts as it reverses to about -25m/s by day 15

Not surprisingly the reversal looks to be heading down to the trop on that run  - although we already have a neg AO in any case 

Bonkers run.

Anyone want to play spot the vortex? That’s it, over there in the pacific...what’s left of it anyway.

Vortex annihilated at the top from as early now as T+324. As a result, split down as far as 30mb, and as you say downwelling with some real purpose through the trop.

Incidentally I’m not sure why there’s been some disheartened posts about the ECM strat output - I’m liking what I’m seeing so far and certainly up to day 10 the dynamics of the warming at 1mb looks very similar to recent GFS output. Will try and post an update on this tomorrow once I’ve seen the 12z runs on the Berlin site

[snowking]

20 minutes ago, ICE COLD said:

What’s the ECM like high up nick at day 10 ? Is going the same way as the gfs ? Cheers . 

Okay well as you asked  , easiest to show things at 2mb to give you a demonstration of how it’s looking. Days 9 and 10 from yesterday’s 12z:

 

what you can see here is:

1. The “H” is a stratospheric high pressure, or ‘wave’ pushing the vortex towards the Atlantic. This is the Wave 1 attack at the top of the stratosphere.

2. You can see the orange and red colours wrapping around the vortex - this is the warmer temperatures flowing around the surf zone of the vortex - what we want to see (and what we go on to see from the GFS days 10-16) is this temperature wave breaking the surf zone and into the core of the vortex, further weakening it and allowing it to be pushed around even more. The further away from the pole the vortex get pushed by the Wave 1, the more susceptible it becomes to any subsequent warming temperature wave  - so in this instance, with the Wave 1 having pushed the vortex away from the pole, it stands a much better chance of having the temperature wave break the surf zone.

Of course this is all right at the top of the stratosphere. The next thing we want to see are these dynamics downwelling towards the bottom of the stratosphere and into the troposphere. And the GFS currently is suggestive of this happening (as posted above).

The stratosphere is a lot more complicated than just looking at whether the wind direction reverses at 60-65N - whilst that delivers a technical SSW, one is not always required to give us a desirable result in the troposphere - and particularly when we are starting from the point of a very weak tropospheric vortex already. Any damage which can be applied from above will only help the cause.

Edited December 20, 2020 by snowking

[SMU]

51 minutes ago, bluearmy said:

That 12z gfs op is nuts as it reverses to about -25m/s by day 15

Not surprisingly the reversal looks to be heading down to the trop on that run  - although we already have a neg AO in any case 

My new AO formula

-AO + -AO = -AO2 !!

[Singularity]

Here's an earth.nullschool.net snapshot I saved from the SSW of early Jan 2019. As you can see, there was only one substantial area of warming at 10 hPa - not the two that GFS is consistently predicting for early Jan 2021.

 

Now here's one from 2018 and a forecast chart that I kept hold of too. Two areas of warming converging, but originating in different locations to what we're seeing predicted for early 2021.

Still, we see the important difference between 2019 & 2018 and that 2021's predictions are more like 2018, a genuine split of the polar vortex.

[Mike Poole]

Well if GFS 0z predictions are right, we shouldn’t be worried about the AO or NAM at any level!

I’m sure the 12z would be even more extreme!

[ICE COLD]

27 minutes ago, snowking said:

Okay well as you asked  , easiest to show things at 2mb to give you a demonstration of how it’s looking. Days 9 and 10 from yesterday’s 12z:

 

what you can see here is:

1. The “H” is a stratospheric high pressure, or ‘wave’ pushing the vortex towards the Atlantic. This is the Wave 1 attack at the top of the stratosphere.

2. You can see the orange and red colours wrapping around the vortex - this is the warmer temperatures flowing around the surf zone of the vortex - what we want to see (and what we go on to see from the GFS days 10-16) is this temperature wave breaking the surf zone and into the core of the vortex, further weakening it and allowing it to be pushed around even more. The further away from the pole the vortex get pushed by the Wave 1, the more susceptible it becomes to any subsequent warming temperature wave  - so in this instance, with the Wave 1 having pushed the vortex away from the pole, it stands a much better chance of having the temperature wave break the surf zone.

Of course this is all right at the top of the stratosphere. The next thing we want to see are these dynamics downwelling towards the bottom of the stratosphere and into the troposphere. And the GFS currently is suggestive of this happening (as posted above).

The stratosphere is a lot more complicated than just looking at whether the wind direction reverses at 60-65N - whilst that delivers a technical SSW, one is not always required to give us a desirable result in the troposphere - and particularly when we are starting from the point of a very weak tropospheric vortex already. Any damage which can be applied from above will only help the cause.

Thanks kris (it is kris isn’t it ?) very nice reply and easy to understand. Appreciate it

[lorenzo]

That vortex looks pretty toasted 

 

:)

[Nick F]

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?

[southbank]

5 minutes 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?

its interesting that i remember Steve Murr posting a chart at the beginning of dec/ late November? that had a COBRA run which showed a rapid and marked deacceleration in wind speeds