Polar Vortex / Stratosphere Watch 2022 / 2023

[SqueakheartLW]

Weather is cool has upgraded the SSW chances.

Yesterday when I looked it said 1%

Today it says 3% so a small step in the right direction

GFS 00z Op

A nice +8C warming there, shame it doesn't end with a vortex split but signs of another warming getting going at the +384h mark

After looking through all of the GFS 00z and GEM 00z ensembles it appears that today it is GEM that is more keen for a warmer warming and has a few members that split the vortex or at least attempt to do it.

Attempted splits of the vortex on 00z GEM

GEM 00z P06

A decent warming peaking at 0C results in a big stretch of those cold regions but they are still connected in the middle. This one may progress beyond +384 hours with a split but then again the vortex could recover instead.

GEM 00z P16

Another example here with a 0C warming again which like the previous member results in the cold region stretched out once again with the will it or won't it question again. With this one having warmings in 2 places I would imagine this one has more chance to split compared with P06.

Very warm warming member on the GEM

GEM 00z P02

Yet another +16C warming showing up on the models. Yesterday it was GFS that had one of these. Today GEM takes the glory for the warmest warming at +16C again.

GEM 00z P12

Another rather warm member here with a decent +12C warming which looks like it will do something good down the line.

Vortex split options on the GEM

GEM had only 1 of these across the control and 20 members. Today is an upgrade with 4 of the 21 ensemble members showing a split vortex.

GEM 00z P01

After a rather warm +12C warming the result is plain to see with a piece of vortex over the USA and another over Asia. A nice example of a split vortex to start off.

GEM 00z P04

After a warm +4C warming the result is a split vortex again but a more unequal split with a small piece of the vortex over the USA and a much larger piece over Europe. Not sure how that one could turn out for cold prospects but with a large core of cold over Europe you could imagine a lot of cold ending up in Europe so could be good for the UK.

GEM 00z P15

After a more modest 0C warming this results in quite an equal split of the vortex with slightly more of it over Asia however. This should be good for cold prospects down the line.

GEM 00z P20

I've saved what looks like the best one till the end. What starts off as a +4C warming initially just displaces the vortex and at this point it looks like the split is off completely but at the end of the run another warming appears right in the middle of the cold area and pushes them apart. The core of the cold goes the USA direction but that warming is still in progress and could push it further away and into a more favourable position for us.

[Catacol]

Long way off - but the lower strat from here on GFS I think would dissolve

Direction of travel on ECM also clear. Can we get there????

 

[Paul_1978]

This thread is extraordinarily quiet given what is potentially in the offing, so here is a Tweet to get the discussion going.

 

[phil nw.]

Clear signs of reversal of zonal winds in the coming days forecasted almost down to 10hPa

Indeed a dramatic weakening of the vortex is showing with negative anomalies filtering down.

On going wave 1 action continuing to month end

which eventually pushes the spv off it's polar perch.

The trend of a weakening of the vortex looks like continuing and with the ongoing wave 1 warming this will continue with a spv displacement off the pole and the decrease of zonal wind speeds.

The unknown of course is how this plays out lower down at the 500hPa level but if nothing else it keeps the Atlantic jet weaker and amplified so increases chances of colder air spilling into mid-latitudes.As ever we need that bit of good fortune to get it here in the Uk.

 

Edited January 16, 2023 by phil nw.

[Catacol]

19 minutes ago, phil nw. said:

Clear signs of reversal of zonal winds in the coming days forecasted almost down to 10hPa

Indeed a dramatic weakening of the vortex is showing with negative anomalies filtering down.

On going wave 1 action continuing to month end

which eventually pushes the spv off it's polar perch.

The trend of a weakening of the vortex looks like continuing and with the ongoing wave 1 warming this will continue with a spv displacement off the pole and the decrease of zonal wind speeds.

The unknown of course is how this plays out lower down at the 500hPa level but if nothing else it keeps the Atlantic jet weaker and amplified so increases chances of colder air spilling into mid-latitudes.As ever we need that bit of good fortune to get it here in the Uk.

 

Good post. The potential negatives of this are that the rather vague Scandy block signal we have been faced with through January has reduced the potential for a wave 2 event - and that means a displaced vortex sat over our sector that then looks like it might recover into February could work to scupper tropospheric opportunities for high lat blocking to take hold. Very fine lines.

The future of winter sits right here I think. Displaced wave 1, swift recovery (any reversal is looking very very short lived at the moment) and my pessimistic head sees mid lat blocking at month's end replaced by westerlies and a mobile month ahead. A full on split and the current shape of vortex forecast works in favour of snow as high lat blocking gets established with plenty of cyclonic activity to undercut.

I fear - and I hate to say it - that the second scenario backed by my heart is on the brink of being overwhelmed by the first scenario sitting within my head. Just not convinced we have seen enough action in the Ural sector to promote wave 2. Last gasp Scandy/Ural impacts of this current phase peak over the weekend and through the first part of next week. Fingers remaining crossed.

 

Edited January 16, 2023 by Catacol

[phil nw.]

7 minutes ago, Catacol said:

Good post. The potential negatives of this are that the rather vague Scandy block signal we have been faced with through January has reduced the potential for a wave 2 event - and that means a displaced vortex sat over our sector that then looks like it might recover into February could work to scupper tropospheric opportunities for high lat blocking to take hold. Very fine lines.

The future of winter sits right here I think. Displaced wave 1, swift recovery (any reversal is looking very very short lived at the moment) and my pessimistic head sees mid lat blocking at month's end replaced by westerlies and a mobile month ahead. A full on split and the current shape of vortex forecast works in favour of snow as high lat blocking gets established with plenty of cyclonic activity to undercut.

I fear - and I hate to say it - that the second scenario backed by my heart is on the brink of being overwhelmed by the first scenario sitting within my head. Just not convinced we have seen enough action in the Ural sector to promote wave 2. Last gasp Scandy/Ural impacts of this current phase peak over the weekend and through the first part of next week. Fingers remaining crossed.

 

Yes a displacement is never as good as full blown split. Not sure how much mileage we will continue to get from the current wave 1 warming before as you suggest the spv looks to return to it's home.

Looking at the latest forecast of the new mjo cycle doesn't hold much promise for any tropical help later on.This can change of course but i can appreciate your concern that the next week or so could be crucial for any further cold pattern to develop before we start to lose the coldest(supposedly) part of the year

[Don]

5 hours ago, Catacol said:

The future of winter sits right here I think. Displaced wave 1, swift recovery (any reversal is looking very very short lived at the moment) and my pessimistic head sees mid lat blocking at month's end replaced by westerlies and a mobile month ahead. A full on split and the current shape of vortex forecast works in favour of snow as high lat blocking gets established with plenty of cyclonic activity to undercut.

I fear - and I hate to say it - that the second scenario backed by my heart is on the brink of being overwhelmed by the first scenario sitting within my head. Just not convinced we have seen enough action in the Ural sector to promote wave 2. Last gasp Scandy/Ural impacts of this current phase peak over the weekend and through the first part of next week. Fingers remaining crossed.

This would be inline with today's Netweather monthly outlook leading to a lacklustre winter overall if it were to come off!

[Bricriu]

A noob question here: Are wave 2 warmings more likely to lead to a split in the Vortex. Is the potential problem with these  current warmings  that they are mostly wave  I could be mistaken but I thought I saw it mentioned that wave 1 warmings tend to lead to displacements of the Vortex instead of a split. 

Edited January 17, 2023 by Bricriu

[phil nw.]

49 minutes ago, Bricriu said:

A noob question here: Are wave 2 warmings more likely to lead to a split in the Vortex. Is the potential problem with these  current warmings  that they are mostly wave  I could be mistaken but I thought I saw it mentioned that wave 1 warmings tend to lead to displacements of the Vortex instead of a split. 

Yes you have pretty much summed it up Bricriu.

We need a 2 wave attack on the strat.vortex to squeeze into it from opposite sides.

At strong enough event will find the pinch point and split it .

A wave 1 attack will,as you suggest, create a displacement and can push the spv off the pole.

We are seeing forecasts for such a displacement currently.

How this affects the troposphere is still to be decided at this stage.

[Catacol]

8 minutes ago, Bricriu said:

A noob question here: Are wave 2 warmings more likely to lead to a split in the Vortex. Is the potential problem with these  current warmings  that they are mostly wave  I could be mistaken but I thought I saw it mentioned that wave 1 warmings tend to lead to displacements of the Vortex instead of a split. 

Spot on. Wave 2 promotes a split - think of pinching a balloon between 2 fingers. Wave 1 displaces. What we have occurring at the moment is a strong wave 1 event driven out of the Alaskan region but a much softer reciprocal event driven out of Russia. It isnt a done deal yet - but if we are to see the real benefits of a wave 2 vortex split we need the warming from the Russian side to be a bit more than is currently modelled.

[Bricriu]

16 minutes ago, Catacol said:

Spot on. Wave 2 promotes a split - think of pinching a balloon between 2 fingers. Wave 1 displaces. What we have occurring at the moment is a strong wave 1 event driven out of the Alaskan region but a much softer reciprocal event driven out of Russia. It isnt a done deal yet - but if we are to see the real benefits of a wave 2 vortex split we need the warming from the Russian side to be a bit more than is currently modelled.

So is it the Ural High not playing ball in that regard? if that Russian/ Scandi high that was shown on the GFS a few days ago came about and move westwards a bit would that help our case? 

[mountain shadow]

1 hour ago, Bricriu said:

A noob question here: Are wave 2 warmings more likely to lead to a split in the Vortex. Is the potential problem with these  current warmings  that they are mostly wave  I could be mistaken but I thought I saw it mentioned that wave 1 warmings tend to lead to displacements of the Vortex instead of a split. 

Probably worthwhile posting what Mushyman's research has discovered. A displacement through Wave 1 is just as likely to produce a UK impacted cold and snowy spell as a Wave 2 split. Bare in mind, that there is more chance a split or displacement will not give us a cold and snowy spell but just puts us in the game.

[mushymanrob]

3 hours ago, mountain shadow said:

Probably worthwhile posting what Mushyman's research has discovered. A displacement through Wave 1 is just as likely to produce a UK impacted cold and snowy spell as a Wave 2 split. Bare in mind, that there is more chance a split or displacement will not give us a cold and snowy spell but just puts us in the game.

to be fair though, it was only a cursory bit of research, and didnt take into account cold spells with little/no snow, but only what the Bonacina site reported. So its only a guide, a more in depth study might tweek the general findings other ways, plus i didnt take into account ENSO or QBO.

[BruenSryan]

Singularity did this 2m temp reanalysis of periods following PV displacement and PV split events. Clearly the signal for cold in Europe and indeed North America is significantly stronger following a PV split compared to a displacement. The signal doesn't favour colder or milder than avg following displacement in western Europe but there's a great difference over Greenland following both. Much colder following displacement there indicative of +NAO whilst much warmer following split indicative of -NAO. 

As he says though you would have thought there'd be a greater signal for cold in NA following a displacement than what this analysis shows.

 

[Singularity]

I subsequently improved my SSW analysis with better targeted 'impact periods' for the historical events. That reduced the difference between displacement and split type events with respect to temperatures across NW Europe , though the latter remain the more conducive to cold conditions.

From reading around over the years, my impression is that split type events tend to produce longer-lasting, less marginal cold spells compared to displacements. Enough so that the cases where a cold spell stops short of the UK are outweighed in the mean for split type events but not displacement type ones where it balances out.

Note the different story in the eastern US where displacements tend to hit harder. I believe this is due to a propensity for such events to place a stratospheric high near or over Canada, leading to an Arctic High regime over N. America. Unlike here in the UK, though, both type of events tend to result in notable cold spells (but over different timeframes - often it turns cold in the US at around the time that it becomes less cold in Europe).

[BruenSryan]

1 hour ago, Singularity said:

I subsequently improved my SSW analysis with better targeted 'impact periods' for the historical events. That reduced the difference between displacement and split type events with respect to temperatures across NW Europe , though the latter remain the more conducive to cold conditions.

From reading around over the years, my impression is that split type events tend to produce longer-lasting, less marginal cold spells compared to displacements. Enough so that the cases where a cold spell stops short of the UK are outweighed in the mean for split type events but not displacement type ones where it balances out.

Note the different story in the eastern US where displacements tend to hit harder. I believe this is due to a propensity for such events to place a stratospheric high near or over Canada, leading to an Arctic High regime over N. America. Unlike here in the UK, though, both type of events tend to result in notable cold spells (but over different timeframes - often it turns cold in the US at around the time that it becomes less cold in Europe).

Somehow I missed this, bloody algorithm, thanks! That's much more like what you'd expect, was flabbergasted by the original results. 

So both events do create blocking but the tendency for the cyclone track following a displacement event tends to be further northward over Europe giving that unreliable nature - more of a west based -NAO? 

[Singularity]

10 hours ago, BruenSryan said:

Somehow I missed this, bloody algorithm, thanks! That's much more like what you'd expect, was flabbergasted by the original results. 

So both events do create blocking but the tendency for the cyclone track following a displacement event tends to be further northward over Europe giving that unreliable nature - more of a west based -NAO? 

The wonders of Twitter!

Pretty much yes, in fact when the response is highly amplified the result can be exceptionally warm yet dry as well, late Feb 2019 being a prominent example in the wake of a Jan displacement, with the widespread record highs.

I expect such is also possible after a split type if factors such as the MJO are strongly opposed to high-latitude blocking high positions. If only I had the time to study what happened after each and every historical event! Perhaps I will find it at some point.

[mountain shadow]

Temps on the rise at 10hpa(still below average).

But has not filtered down to 30hpa yet.

 

[summer blizzard]

Out of interest but is there any data regarding the phase of the MJO during a SSW. We have a relatively amplified Phase 2/3 forecast about the time we are seeing this which seems a tad odd to me. 

[bluearmy]

Eps mean at day 15 not far from gfs ops with the vortex displacement to nw Norway below 70N 

I’m still not overly fussed about a split - infact, given that we could see a segment post split end up over s greeny, a weak upper strat with the spv over Norway (stretched towards Asia) and imprinting down through the strat would surely be acceptable 

[Mike Poole]

9 hours ago, bluearmy said:

Eps mean at day 15 not far from gfs ops with the vortex displacement to nw Norway below 70N 

I’m still not overly fussed about a split - infact, given that we could see a segment post split end up over s greeny, a weak upper strat with the spv over Norway (stretched towards Asia) and imprinting down through the strat would surely be acceptable 

Would it imprint down effectively though? 

Given this winter has largely been trop led (and, mutter, has been disappointing compared to what we might expect given that!), is a displacement warming enough to change that?

[mountain shadow]

Is the expected target start date for the SSW (major or minor) still around the 27th January 2023?

Thanks

[Kirkcaldy Weather]

12zs looking very impressive again

GEM Ens 

 

 

 

 

gefs

 

 

 W.O.W  

 

 

 

 

 

 

[Kirkcaldy Weather]

 

 

 

 

 

 

 

 

 

Trend definitely continues to increase for split 

[Coopsy]

Canadian forecasters are being quite bullish about a very cold February due to an SSW and subsequent split and a chunk of PV sitting over Canada as a result. Not sure what that would mean for the UK though.