Stratosphere and Polar Vortex Watch 2020

[Singularity]

ECM’s wrap-in from the Atlantic side is similar to what took place to initiate the Jan 2009 split.

Sure is interesting to see so much of a secondary warming. GFS was showing that a number of days back, seemingly as a knock-on effect of the initial polar vortex displacement over Canada. Then it suddenly went off anything more than a faint bit of warming from there.

[SqueakheartLW]

Taken all of the zonal wind speeds from the ECM charts on university of Berlin website and put them in table format and colour coded the speeds to help them stand out

A clear pattern is showing up here at really all levels.

Latest, Day 1 and 2

In general we are at average zonal wind speeds on the latest measurements as well as on days 1 and 2. The usual pattern is also showing with higher speeds the further up we go

Days 3 to 5

In general we see a reduction in zonal winds speeds at all levels during this period. The exact time of the reduction varies by a day here and there depending on the level but all are within this time period

Days 6 and 7

During days 6 and 7 we see a zonal wind recovery of sorts but we never get back to the earlier values. This is no doubt the polar vortex trying to recover after an initial minor warming of the stratosphere but the main event is getting underway at this stage

Days 8 to 10

The last 3 days see a big weakening of zonal winds at all levels and some of the biggest changes are higher up. By day 10 all levels are around 10 m/s or less and at 1hpa we are in reversal and almost in reversal at 2hpa

Is ECM going for the displacement or the split. None of the day 10 charts show what is going to happen yet but give it a day or two and we may start to get a clue as to what ECM is going for

[bluearmy]

06z is another split and probably a gentle reversal but temps remain low in the ne Atlantic basin 

higher up there is a further warming  showing at the end of the run 

[SqueakheartLW]

Looks like the CFS is finally on board with the weakening and/or reversal of zonal winds now

Here are the GFS Ensembles which have for many recent runs pushed down towards 0m/s and some have even had reversals

Up to now the CFS has generally not been on board and has shown a dip in zonal winds before in general sending them upwards again, that is until I looked at todays chart

Here are the CFS runs themselves

I think all 4 runs achieve a reversal at some stage, 3 of them by early Jan whilst the 4th one does it a bit later and dips into the biggest reversal. Overall the runs keep us below the black average line except right at the very end when we just scrape back up to average by the time spring arrives

Here are the so called bias corrected runs

Even all of the bias corrected runs get us into a reversal as some stage between early and mid Jan. Overall on the bias corrected we remain weaker than average but the main difference is that we return to average in February rather than into March

Now this chart caught my eye today and seems to show that the SSW is a 10hpa lead affair

The reversal begins on 5th Jan at 10hpa and starts expanding outwards both up and down. The anomaly chart makes vert good viewing for cold fans with all those blues at really all levels and that very deep blue in the stratosphere is something I really like to see at this time of year

[Catacol]

Strongest wave 2 warming of the season so far modelled at New Year. In truth rather modest...but every bit helps....

[Mike Poole]

Good charts today based on the GFS 0z and ensembles:  -NAM everywhere, extraordinary!

Op and many ensembles go for a reversal:

The ensemble minimaps on Stratobserve:

Many showing the split and in the place that has been supportive of decent block placement in previous events.

 

[Singularity]

Only one of those GEFS members has a split there?

The ECM runs have really got me wondering, though, whether GFS/GEFS have the midrange down right at all. Not enough wave-2 featuring, perhaps.

[Mike Poole]

1 minute ago, Singularity said:

Only one of those GEFS members has a split there?

The ECM runs have really got me wondering, though, whether GFS/GEFS have the midrange down right at all. Not enough wave-2 featuring, perhaps.

Am I reading this wrong, I’m looking at the feint actual contours, not the bold summary ellipses?  

[Singularity]

1 minute ago, Mike Poole said:

Am I reading this wrong, I’m looking at the feint actual contours, not the bold summary ellipses?  

There are a good few stretched and mangled polar vortex shapes, but most still have some connection between lobes rather than two distinct vortexes.

I think that's what the bold lines are intended to show - where there's a clear division in the circulations. It's an important distinction - sometimes you get almost-splits that either never achieve a sufficient reversal or produce results more befitting a displacement event. 

[Singularity]

32 minutes ago, Catacol said:

Strongest wave 2 warming of the season so far modelled at New Year. In truth rather modest...but every bit helps....

That's a bit beyond what Eric Webb was referring to yesterday:

...which makes me wonder if he's overlooking something. Either that or the models are producing spurious wave-2 somehow, with ECM now doing it more than GFS.

[Kirkcaldy Weather]

4 minutes ago, Mike Poole said:

Am I reading this wrong, I’m looking at the feint actual contours, not the bold summary ellipses?  

 

1 minute ago, Singularity said:

There are a good few stretched and mangled polar vortex shapes, but most still have some connection between lobes rather than two distinct vortexes.

I think that's what the bold lines are intended to show - where there's a clear division in the circulations. It's an important distinction - sometimes you get almost-splits that either never achieve a sufficient reversal or produce results more befitting a displacement event. 

This is at the end of the run (the numbers start to increase before then) have been gradually increasing over the last few days including the numbers of splits, does look like an interesting situation also whether it’s worth any note I seen a few saying on twitter the other day that the GEM seemed to be the most keen on the split ideas. Also worth noting these charts don’t show the ECM or indeed the one the Met office use.

10hpa 

50hpa 

[Singularity]

Good stuff KK. The outcome of this is going to be very informative - which model will look the most dignified come mid-January?

[Griff]

I probably should have posted this here... 

[Catacol]

1 hour ago, Griff said:

I probably should have posted this here... 

yep - SSW near certain now. All eyes on the nature of the pattern and how downwelling impacts land.

[lorenzo]

[Windysun1]

1 hour ago, Catacol said:

yep - SSW near certain now. All eyes on the nature of the pattern and how downwelling impacts land.

What date are you thinking that its effects will be felt in the British isles?

[bluearmy]

And still gfs-gefs v ecm/gem on day 9/10 temps and heights at 10hpa. Ec trends the spv towards Canada and gfs to n scandi. Both stretching 

Surprised this remains - on similar page heights day 8 but temps already off quite early in the runs 

[snowking]

GEFS 35 day ensemble mean takes us into negative territory - as Nick says above, still a fascinating stand off between GFS and ECM, which is even more bizarre when you consider the GFS seemed to pick up on the initial warming the ECM is now showing, before changing its mind.

Either the FV3 core of the new GEFS is the new leader of the pack when it comes to the stratosphere, or the GFS is going to have to come some way back to it’s original solution.

ECM op still looking wonderful 

[SqueakheartLW]

My latest set of data from university of Berlin shows a pincer movement on the vortex by day 10

We see the higher wind speeds initially although not as high as they were followed by a drop off as the initial warming has an effect. We then see a slight recovery of sorts which propagates downwards to an extent before attacks on the lower vortex begin combined with attacks at the top too. By day 10 a clear two pronged attack is visible with reductions in zonal winds speeds pushing upwards from 150hpa and much bigger reductions coming down from the top too

10hpa day 10

Looks like the vortex is about to get pulled apart here. One piece of cold has moved down to southern Asia, the other looks as if it is headed in the direction of the USA and the Pacific. Hopefully the vortex itself will do the same too

1hpa Latest

 

The warming is clear to see here at 1hpa and this is the warming expected in the next few days at 10hpa showing itself now at 1hpa but if the ECM charts are to be believed another warming is due to take place

1hpa day 10

The vortex at 1hpa is much reduced in size by this stage and with another dramatic warming showing up here it seems what remains of the vortex is going to be destroyed completely

[SqueakheartLW]

1 hour ago, snowking said:

GEFS 35 day ensemble mean takes us into negative territory - as Nick says above, still a fascinating stand off between GFS and ECM, which is even more bizarre when you consider the GFS seemed to pick up on the initial warming the ECM is now showing, before changing its mind.

Either the FV3 core of the new GEFS is the new leader of the pack when it comes to the stratosphere, or the GFS is going to have to come some way back to it’s original solution.

ECM op still looking wonderful 

Wouldn't you just love a reversal to take place that ends up as fast as those winds at 1hpa in the southern hemisphere at around 20S?

[Duane S.]

I can some already posting these charts but I’m posting the again because it’s Xmas and because they are so

Happy Christmas from the ECM...

 Squeeeeeeeeeeze

  Reversal on way down

 

 

 

 

[Catacol]

12 hours ago, Windysun1 said:

What date are you thinking that its effects will be felt in the British isles?

A tough call, but I’d go for a fast downwell this time, so broadly speaking last third of January. Until then ongoing trop forcing is what will direct our weather - and a very disturbed and amplified trop it is. If that amplification sticks around until after mid month and then taps into the downwelling effects of the SSW then, with a lucky dice roll or two, we get the potential for proper intensification of the cold that is already looking to bed in. 

[Catacol]

Important to me that modest wave 2 impacts are still in the mix. Again not a big forecast here, but enough I hope to provide the anvil to break the vortex upon. 

However as has been mentioned in other places the flux we are seeing this year battering the vortex is mainly sourced from the Ural side....and so if we end up with a displacement we would hope it won’t be the sort that we have seen before initiated from the pacific and with an end result that vortex energy is thrust into the Atlantic.

Should we end up with a displacement that forces the vortex back over to the pacific side (rather than split it, one shard to US and one shard to eastern Siberia) then I am less certain of tropospheric impacts. Lots to follow and muse over....

[Bricriu]

Happy Christmas to all.

 

A question for the experts, are ye fairly confident of a split happening instead of a big displacement. Also are you confident that any warming will downwell sufficiently through the layers for us to benefit from?

Edited December 25, 2020 by Bricriu

[bluearmy]

1 hour ago, Bricriu said:

Happy Christmas to all.

 

A question for the experts, are ye fairly confident of a split happening instead of a big displacement. Also are you confident that any warming will downwell sufficiently through the layers for us to benefit from?

I’m not an expert but I am confident that none of the experts can answer either of your questions yet .....