Autumn & Winter 2023---2024 Stratospheric Polar Vortex. Events, Analysis, Discussions AND Outlooks

[Eagle Eye]

1 hour ago, lorenzo said:

@Eagle Eye adding your post here too given the work undertaken and quality of content, this thread slightly more slow moving than the main Model Disco.

Also given your keen insight, and mind miles beyond my own - recommend this paper as one of the best on Stratospheric internal vacillation. This is something we have mentioned a lot in historic stratosphere threads but one that the community is still trying to understand.  Given the fact the paper is now 15 years old probably speaks to the complexity of where some dynamics of our old winter foe the Polar Vortex just remain elusive.. Enjoy https://journals.ametsoc.org/view/journals/clim/22/6/2008jcli2365.1.xml

 

Thank you, it's quite hard to find papers on topics like this. Agreed that the amount of papers show just how complex of a topic it is. The amount of work that goes into understanding cold or hot is something non-weather enthusiasts won't understand unfortunately. I have a lot of respect for everyone here, trying to understand a 3D vortex is very difficult and almost everyone here probably knows more about the troposphere than me because there's very little papers on it and I don't have the 'experience' (not to make people feel old) with the troposphere especially. There's a lot more about the stratosphere and I've sort of specialised in trying to understand it because the SSW was one of the first events I heard about here. I think the more you understand, the more you realise that we really don't understand much at all, that's what makes it fun though. 

[Mike Poole]

Yesterday’s ECM 12z, technical SSW at T96, with reversal 60N 10hPa:

Seems to count as a split, however short, and it’s come from the trop up, you can see it at 50 hPa T0, 30hPa T24, 10hPa T72 and 7hPa T96:

Unusual to say the least, my theory is that it is down to the Canadian warming in early December which caused such a significant weakness in the strat vortex, that it didn’t form properly, and that has allowed the amplified trop patterns to do things they wouldn’t normally be able to do, such as propagate splits up to 10hPa.  And finally (maybe) register a technical SSW by the bottom trapdoor.  What are peoples’ thoughts?

Edited January 13 by Mike Poole

[Anthony Burden]

Marco patanga on twitter just stated major SSW on knife edge,could get very interesting in the next few weeks possible short mild interlude for UK  before northern blocking shows its hand.

[Kiwi]

2 hours ago, Anthony Burden said:

Marco patanga on twitter just stated major SSW on knife edge,could get very interesting in the next few weeks possible short mild interlude for UK  before northern blocking shows its hand.

 

[Summer Sun]

 

[Summer Sun]

 

[Windysun1]

23 minutes ago, Summer Sun said:

 

Just for the history books. Thats about it.

[Anthony Burden]

Evening all,could be a very significant 24 hrs if reversal takes place weather wise,northern blocking could make the next possible cold spell very interesting.

[Don]

54 minutes ago, Anthony Burden said:

Evening all,could be a very significant 24 hrs if reversal takes place weather wise,northern blocking could make the next possible cold spell very interesting.

Will it be enough though, or too brief?

[stodge]

Evening all

My theory (which is mine and which belongs to me) is the current cold spell has been broken by the PV being forced back to Canada/Greenland by the powerful Siberian warming. From there. cold air has flooded south into Canada and engaged with warmer air over the United States firing up the jet, leading to rapid cyclogenesis and a return (for us) to the usual pattern of westerly-based Atlantic dominated weather.

Now, I don't know if this is anything approaching a passable theory but as soon as I see warming from Siberia, I count 10 days before the PV is back with us. Oddly enough, there's no sign of any significant renewed warming on the 12Z and this encourages me - yes, the PV can reform (it is only January) but the elements which can push it over to Siberia (of which there seem to be many) can be at work towards the end of the month and hopefully keep it there. 

With half of winter remaining there's plenty of time for the PV to move or weaken further as we move into February.

 

[Midlands Ice Age]

17 minutes ago, stodge said:

Evening all

My theory (which is mine and which belongs to me) is the current cold spell has been broken by the PV being forced back to Canada/Greenland by the powerful Siberian warming. From there. cold air has flooded south into Canada and engaged with warmer air over the United States firing up the jet, leading to rapid cyclogenesis and a return (for us) to the usual pattern of westerly-based Atlantic dominated weather.

Now, I don't know if this is anything approaching a passable theory but as soon as I see warming from Siberia, I count 10 days before the PV is back with us. Oddly enough, there's no sign of any significant renewed warming on the 12Z and this encourages me - yes, the PV can reform (it is only January) but the elements which can push it over to Siberia (of which there seem to be many) can be at work towards the end of the month and hopefully keep it there. 

With half of winter remaining there's plenty of time for the PV to move or weaken further as we move into February.

 

I share your theory, Could we call it the StodgeM theory?  

Not  sure of the warming in Siberia its just the weakness of the vortex overall IMO, with the 'touchdowns' of the warming from above occurring pretty randomly.

MIA

Edited January 15 by Midlands Ice Age

[Summer Sun]

 

[bluearmy]

17 hours ago, stodge said:

Evening all

My theory (which is mine and which belongs to me) is the current cold spell has been broken by the PV being forced back to Canada/Greenland by the powerful Siberian warming. From there. cold air has flooded south into Canada and engaged with warmer air over the United States firing up the jet, leading to rapid cyclogenesis and a return (for us) to the usual pattern of westerly-based Atlantic dominated weather.

Now, I don't know if this is anything approaching a passable theory but as soon as I see warming from Siberia, I count 10 days before the PV is back with us. Oddly enough, there's no sign of any significant renewed warming on the 12Z and this encourages me - yes, the PV can reform (it is only January) but the elements which can push it over to Siberia (of which there seem to be many) can be at work towards the end of the month and hopefully keep it there. 

With half of winter remaining there's plenty of time for the PV to move or weaken further as we move into February.

 

The gefs are showing a renewed slowdown later week 2 

the cfsv2 is all in on a marked reversal in feb 

The ec46 found a small cluster yesterday that looked to headed back down again so watching that later

we are seeing modelling showing a new ural ridge upcoming and some Aleutian troughing so if that verifies the I wouldn’t expect the spv to survive the warmings that are generated by that. 

of course we can expect downwelling waves in February anyway from the warmings and reversals seen in first half jan - we run the risk of a neg AO from a downwelling wave either being interfered with by a new tech reversal ssw or not downwelling because of interference.  I think we can guess how this might play out !

 

[Don]

22 minutes ago, bluearmy said:

The gefs are showing a renewed slowdown later week 2 

the cfsv2 is all in on a marked reversal in feb 

The ec46 found a small cluster yesterday that looked to headed back down again so watching that later

we are seeing modelling showing a new ural ridge upcoming and some Aleutian troughing so if that verifies the I wouldn’t expect the spv to survive the warmings that are generated by that. 

of course we can expect downwelling waves in February anyway from the warmings and reversals seen in first half jan - we run the risk of a neg AO from a downwelling wave either being interfered with by a new tech reversal ssw or not downwelling because of interference.  I think we can guess how this might play out !

 

Is it a case of guessing or expecting?! 

[TSNWK]

30 minutes ago, Summer Sun said:

 

And a fat load of good that is.. as we go mild and zonal for rest of month thanks in no small part to this warming and reverse 

[bluearmy]

54 minutes ago, Don said:

Is it a case of guessing or expecting?! 

Sod’s Law innit! 

49 minutes ago, TSNWK said:

And a fat load of good that is.. as we go mild and zonal for rest of month thanks in no small part to this warming and reverse 

the tech ssw is merely the end point of the reversals that have been ongoing since Jan 2nd above 70N.  The fact that they actually get to 60N 10hpa is merely a technicality.  You could say that the mild and zonal renews as the warmings and reversals end. We will have had almost two weeks of blocking by this point. Sadly, not quite in the right place for our small island.  We saw late nov and into December that the warmings then took a pretty strong flow high up and brought it below average. There are those that would say the past two weeks of blocking are down to that warming with a month delay on the downwelling wave. Not sure about that. 

we can expect ramifications through feb and possibly march on the back of this past two weeks of reversals in the higher latitudes. Whether that’s enough to deliver at our latitude would be the question.  
 

as for the next couple of weeks, it looks like an MJO imprint phases 4 and 5 with a week or so lag. And the strat vortex segments rejoining together to our north is never a good sign for the northern arm. Put together it’s no surprise to see the Atlantic in full flow for at least a week.

[Anthony Burden]

Evening all,very encouraging news from Marco Patanga with QBO easterly looking a good bet while encouraging northern blocking and -NAO could well be a short milder interlude before things start to look very positive regarding another round of very cold temperatures get established by the end of the month.

[Cloud 10]

Scraping the bottom of the barrel regarding technical SSW's,but there it is!

 

 

Should be plenty of interest to come heading through the next few months with a weak looking strat.

 

[Mike Poole]

There’s a question mark in my mind over how this SSW will affect things going forward.  I think there are two things with an SSW.  In an energetic split vortex SSW, where the zonal wind doesn’t just touch 0 at 60N 10hPa but goes substantially negative and remains easterly for some time, that can downwell and affect the trop weather at our latitude over the next couple of months, maybe eked out in discrete stages.  That’s not really on the table with this one, which brings me to the other thing, which is the lack of the strat vortex westerlies driving the trop pattern - it seems to me that’s largely been the case since the Canadian warming, and should continue.

Which means, for me, it is up to the trop to drive the pattern it wants, unfettered from above.  In which case, it is good that rising AAM and a favourable MJO phase might be driving the pattern into February in the direction of a -AO/-NAO, i.e. in a couple of weeks.  But if that does happen, I wonder how much of that will be attributed directly to the effects of the SSW, and whether or not that would be correct…

 

Edited January 16 by Mike Poole

[stodge]

59 minutes ago, Mike Poole said:

There’s a question mark in my mind over how this SSW will affect things going forward.  I think there are two things with an SSW.  In an energetic split vortex SSW, where the zonal wind doesn’t just touch 0 at 60N 10hPa but goes substantially negative and remains easterly for some time, that can downwell and affect the trop weather at our latitude over the next couple of months, maybe eked out in discrete stages.  That’s not really on the table with this one, which brings me to the other thing, which is the lack of the strat vortex westerlies driving the trop pattern - it seems to me that’s largely been the case since the Canadian warming, and should continue.

Which means, for me, it is up to the trop to drive the pattern it wants, unfettered from above.  In which case, it is good that rising AAM and a favourable MJO phase might be driving the pattern into February in the direction of a -AO/-NAO, i.e. in a couple of weeks.  But if that does happen, I wonder how much of that will be attributed directly to the effects of the SSW, and whether or not that would be correct…

 

Inasmuch as recent perturbations have weakened the stratospheric vortex, yes, I entirely agree.

I'm hoping the tropospheric mechanisms will be more relevant going forward (as they often can be in early winter) and the hints tonight offered by FI on the GFS 12Z suggest a possible path which demonstrates having a strong PV isn't the be-all and end-all (it wasn't in 62-63 after a much stronger Canadian warming). 

[Don]

6 hours ago, bluearmy said:

Sod’s Law innit! 

Is there more to it now though?  Is CC adding further complications, is it just bad luck, or a combination of the two perhaps? 

[bluearmy]

13 hours ago, Mike Poole said:

There’s a question mark in my mind over how this SSW will affect things going forward.  I think there are two things with an SSW.  In an energetic split vortex SSW, where the zonal wind doesn’t just touch 0 at 60N 10hPa but goes substantially negative and remains easterly for some time, that can downwell and affect the trop weather at our latitude over the next couple of months, maybe eked out in discrete stages.  That’s not really on the table with this one, which brings me to the other thing, which is the lack of the strat vortex westerlies driving the trop pattern - it seems to me that’s largely been the case since the Canadian warming, and should continue.

Which means, for me, it is up to the trop to drive the pattern it wants, unfettered from above.  In which case, it is good that rising AAM and a favourable MJO phase might be driving the pattern into February in the direction of a -AO/-NAO, i.e. in a couple of weeks.  But if that does happen, I wonder how much of that will be attributed directly to the effects of the SSW, and whether or not that would be correct…

 

Agree substantively with this Mike but I would add that we’ve seen repeated warmings since the back end of December and actual strong reversals above 70N through the first half of jan. These look to be done by 21st. you would expect those reversals to drive repeating waves over the next six weeks.   I appreciate that the quick downwelling of these seen at high latitudes with a weak strat to resist may mean that there are less of these through feb than might be expected.   But my point is that we should expect negative flow support for the trop from the strat at some points over the next month above 70N.  On its own that perhaps wouldn’t help bring deep cold far enough south across the NH (re our latitude) but it may push some cold pools far enough south to interact with blocking that may not be able to gain quite the traction that we’d look for.   We should be aware that feb could easily end up quite frustrating for us. 
 

Edited January 17 by bluearmy

[Bricriu]

As someone  said the weakest major ssw  ever that it shouldn't even really be called one. I can't see us having a proper high latitude block in February as a consequence. From what the UKMO are saying I think we will have a mid latitude  block to the east that  starts  to sink which let's the Atlantic  back in through  the back door.  I won't be surprised  if we see  the ec46  change to a less blocked outcome. I will be delighted if I am wrong about all this  

[bluearmy]

1 hour ago, Bricriu said:

As someone  said the weakest major ssw  ever that it shouldn't even really be called one. I can't see us having a proper high latitude block in February as a consequence. From what the UKMO are saying I think we will have a mid latitude  block to the east that  starts  to sink which let's the Atlantic  back in through  the back door.  I won't be surprised  if we see  the ec46  change to a less blocked outcome. I will be delighted if I am wrong about all this  

I think too much emphasis is placed on the reversal at 10hpa/60N regarding consequences. 
if we had a  strong sustained  reversal at 65N then we would expect some positive consequences for the mid latitudes over the following month (with downwelling waves if they propagate ). A tech ssw isnt a magic bullet. 

we’ve seen repeated notable reversals above 70N last two weeks and these continue up till around the 21st.   Would be amazing if these didn’t have consequences in feb but our worry is that they mean the wintry patterns don’t  get far enough south.  think west based neg NAO as an example. how many times have we seen the retrogression take the blocking west at a latitude that’s no good for nw europe ? 

hence my earlier comment about feb possible being a v frustrating month, 

 

 

[Bricriu]

2 minutes ago, bluearmy said:

I think too much emphasis is placed on the reversal at 10hpa/60N regarding consequences. 
if we had a  strong sustained  reversal at 65N then we would expect some positive consequences for the mid latitudes over the following month (with downwelling waves if they propagate ). A tech ssw isnt a magic bullet. 

we’ve seen repeated notable reversals above 70N last two weeks and these continue up till around the 21st.   Would be amazing if these didn’t have consequences in feb but our worry is that they mean the wintry patterns don’t  get far enough south.  think west based neg NAO as an example. how many times have we seen the retrogression take the blocking west at a latitude that’s no good for nw europe ? 

hence my earlier comment about feb possible being a v frustrating month, 

 

 

But that's the key with a major ssw like we saw in 2018 there is more likely to be proper downwelling that propagates. Although the irony is that might have been too good as we ended  up with a west based nao in the end, but alot of Irish People didn't  mind as there was a historic Snowstorm out of it. An event  that probably won't be seen again in our lifetime