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

[Andy8472]

Also 

[bluearmy]

Just now, Mike Poole said:

Indeed.  Massive increase in the number going for the scenario I outlined yesterday - vortex intensification followed by a massive reduction and then reversal.  I reckon it was about 10 members yesterday, huge cluster today.

That’s a big step forward from what you picked out last night Mike 

would love to know how many are displacement and how many see a split. the mean is definitely displacement but that’s no surprise given that the number of runs that don’t reverse 

[Andy8472]

2 minutes ago, bluearmy said:

That’s a big step forward from what you picked out last night Mike 

would love to know how many are displacement and how many see a split. the mean is definitely displacement but that’s no surprise given that the number of runs that don’t reverse 

Could just be a matter of time for a split, not within range atm 

[Mike Poole]

2 minutes ago, bluearmy said:

That’s a big step forward from what you picked out last night Mike 

would love to know how many are displacement and how many see a split. the mean is definitely displacement but that’s no surprise given that the number of runs that don’t reverse 

Yes, I’m minded of the principle the ‘faster it spins the harder it falls’ here.  How many result in a split is indeed the big question.

[sebastiaan1973]

In comparison with the last days. 

[Andy8472]

NOAA Blog

https://www.climate.gov/news-features/blogs/polar-vortex/date-night-stratospheric-polar-vortex

[bluearmy]

13 minutes ago, Andy8472 said:

Could just be a matter of time for a split, not within range atm 

Definitely a trend on the 12z ec suite (inc the op) to follow the gfs op in changing the axis of the spv as it’s squashed by the warming. So it becomes slightly more rounded and trends towards Greenland on that axis. Would suspect this is a point in time and it will continue to stress. Just beyond that chart is when most of the reversals begin on the 46 

[Daniel*]

1 hour ago, Daniel* said:

Good to see geopotential heights this from ECM 12Z, wave 2 attack at the end pinching vortex. I personally think vortex is in serious trouble into early 2024 setting up for a major SSW.

Speak of the devil not surprised myself. I’d expect tomorrow to consolidate it even more. 

[SqueakheartLW]

An update on the SSW for me today and like yesterday it is based on the GFS 12z and GEM 12z

GFS 12z

GFS 12z is really churning out the toasty warm charts today

That's 9 of 32 members of the 12z going for a +4C peak warming but my favourite one is P29 below

A nice toasty +12C warming on this member

GEM 12z

GEM has this nice +384h chart showing on P07

This is the only chart on the 12z's between GFS and GEM that came anywhere close to a split vortex chance

Not as many toasty +4C or above warmings on today's GEM 12z compared with yesterday with only two +4C's

It does make up for it by having a +8C warming chart on P14

Analysing all members of both GFS 12z and GEM 12z (20/12/2023)

GFS
+12     29
+4       02,07,08,11,18
           21,26,28,30
0         Op,Ct,03,06,09
           10,14,20,24,25          Average GFS Warming Peak = -0.250C (-2.625 yesterday)
-4        01,04,12,13,15         (Upgrade of 2.375C compared with 19/12/2023)
           17,19,22,23,27
-8        05,16

GEM
+8      14
+4      04,17
0        01,05,07,08
          13,15,20                     Average GEM Warming Peak = -2.095C (-2.286 yesterday)
-4       Ct,02,03,09,10          (Upgrade of 0.191C compared with 19/12/2023)
          12,16,18,19
-8       06
-16     11

Good news for those wanting a more toasty warming it would seem as both GFS and GEM have upgraded the peak warming temperature, especially the GFS. Seems even more nailed on today and what was telling is how every single member of both GFS and GEM that goes far enough out had a warming of some degree on it.

[Don]

55 minutes ago, Andy8472 said:

Massive drop!

Best chart from the ECM so far?!

[Andy8472]

9 minutes ago, Don said:

Best chart from the ECM so far?!

Yes i would say

[BLAST FROM THE PAST]

1 hour ago, Mike Poole said:

Indeed.  Massive increase in the number going for the scenario I outlined yesterday - vortex intensification followed by a massive reduction and then reversal.  I reckon it was about 10 members yesterday, huge cluster today.

Hence the current early SUPER COLD up there currently.  Not unknown but pretty unusual.  Could be very interesting come early Jan

 

BFTP

[Andy8472]

Interesting thoughts from Dr amy butler about lead times

https://twitter.com/DrAHButler/status/1737581154423943512

 

[snowsummer]

5 hours ago, Norrance said:

If those are the similar to nacreous clouds they have been visible both yesterday afternoon and today in Dundee. 

Aah. These are the clouds i was asking about on the mod thread earlier. But they were called rainbow clouds in the article i read. I also read that they're only seen in the uk in winter when the strat is really weak. Its the last sentence  i was wondering about, and if there was a connection  anywhere  between them and a SSW. 

[lorenzo]

Now then... stunning EC progression and a 'Sudden' jump in and of itself.

Am completely intrigued by this one as looking at 'LOTS' of different charts it feels nearly there in terms of the warmings moving from a

1 perhaps technical SSW with u reversal but main vortex remains robust and just a minor visit to negative u, to, 

2 full SSW with the warmings over-whelming the vortex and full blows SSW...

Still right now for me the vortex looks concentric, yes tilted via the W1 but core is stable and heat flux is flying around the surf zone, so much so filaments are echoing off to create a PV incursion for North America c end of first week Jan. Yet, you cannot ignore such a consolidated forecast from our best wx model..

1 Last night's runs at 70hPa saw infiltration of this pulse into core of vortex, tonight it has eased off a little, the SSW solution is firmly in the mix though.

2 10hPa from GEOS at the edge of the modelling out to the 30th shows the next pulse - right on a cliffhanger - will the vortex swallow the red pill? 

3 From CPC the much maligned CFS - which happens to have a nose for technical SSWs into the left side of it's legend after 1st week in Jan. It's going to be a close run thing.

Technical reversal perhaps for now is maybe 65 / 35 on that EC U - but the caveat is the mean and how quickly it recovers, could be a function of a really strong displacement. It still feels to me like a robust vortex based on image 2..

 

[Norrance]

1 hour ago, snowsummer said:

Aah. These are the clouds i was asking about on the mod thread earlier. But they were called rainbow clouds in the article i read. I also read that they're only seen in the uk in winter when the strat is really weak. Its the last sentence  i was wondering about, and if there was a connection  anywhere  between them and a SSW. 

They need very cold air very high up in the stratosphere and the clouds have very small ice particles. I have read that under-78C  is needed so most associated with the far North in Winter. Some say they precede a cold snap but I not sure if there is any association with an SSW.
Also known as mother of pearl clouds and sometimes rainbow clouds. 

Edited December 20, 2023 by Norrance

[lorenzo]

Polar stratospheric clouds (PSCs) play a central role in the formation of the ozone hole in the Antarctic and Arctic. PSCs provide surfaces upon which heterogeneous chemical reactions take place. These reactions lead to the production of free radicals of chlorine in the stratosphere which directly destroy ozone molecules.

PSCs form poleward of about 60°S latitude in the altitude range 10 km to 25 km during the winter and early spring. The clouds are classified into Types I and II according to their particle size and formation temperature.

Type II clouds, also known as nacreous or mother-of-pearl clouds, are composed of ice crystals and form when temperatures are below the ice frost point (typically below −83°C).

The Type I PSCs are optically much thinner than the Type II clouds, and have a formation threshold temperature 5 to 8°C above the frost point. These clouds consist mainly of hydrated droplets of nitric acid and sulphuric acid.

Polar stratospheric clouds – Australian Antarctic Program

WWW.ANTARCTICA.GOV.AU

---

Polar stratospheric clouds play a central role in the formation of the ozone hole in the Antarctic and Arctic.

Not seen any r correlation to SSW - if anything my gut says opposite, this speaks to a very cold vortex in our locale which is the wrong locale for known trop pre-cursors.

[bluearmy]

9 hours ago, lorenzo said:

Now then... stunning EC progression and a 'Sudden' jump in and of itself.

Am completely intrigued by this one as looking at 'LOTS' of different charts it feels nearly there in terms of the warmings moving from a

1 perhaps technical SSW with u reversal but main vortex remains robust and just a minor visit to negative u, to, 

2 full SSW with the warmings over-whelming the vortex and full blows SSW...

Still right now for me the vortex looks concentric, yes tilted via the W1 but core is stable and heat flux is flying around the surf zone, so much so filaments are echoing off to create a PV incursion for North America c end of first week Jan. Yet, you cannot ignore such a consolidated forecast from our best wx model..

1 Last night's runs at 70hPa saw infiltration of this pulse into core of vortex, tonight it has eased off a little, the SSW solution is firmly in the mix though.

2 10hPa from GEOS at the edge of the modelling out to the 30th shows the next pulse - right on a cliffhanger - will the vortex swallow the red pill? 

3 From CPC the much maligned CFS - which happens to have a nose for technical SSWs into the left side of it's legend after 1st week in Jan. It's going to be a close run thing.

Technical reversal perhaps for now is maybe 65 / 35 on that EC U - but the caveat is the mean and how quickly it recovers, could be a function of a really strong displacement. It still feels to me like a robust vortex based on image 2..

 

The mean eps displaced spv is just off n Scandinavia at the end of the latest run. Looking at the spv circulation, it has almost cleared the North Pole so the mean U wind will likely be in low single figures. That does make me think (like you) that the reversal shown on the ec46 is displacement. That’s not to say we won’t then see another wave then split it but that’s currently in lala land 

[sebastiaan1973]

Tweet by World Climate Service.

 

[Andy8472]

CFS has it faster, too progressive i think but changes so much from run to run who can believe it?

[bluearmy]

8 minutes ago, Andy8472 said:

CFS has it faster, too progressive i think but changes so much from run to run who can believe it?

That’s a mad run with three further drops drops to follow the initial reversal and then another in feb - a coupled vortex would be fun if that verified! 

[CoventryWeather]

2 hours ago, Andy8472 said:

CFS has it faster, too progressive i think but changes so much from run to run who can believe it?

If that's the 00z run then that'll be fun to see when it comes out later. 

[Andy8472]

GFS op still doesn't want to know with decrease in zonal winds, new trend or just a blip? 

Edited December 21, 2023 by Andy8472

[Mike Poole]

19 minutes ago, Andy8472 said:

GFS op still doesn't want to know with decrease in zonal winds, new trend or just a blip? 

Seems to be modelling the same hump the other models and most of the ensembles see happening 5 days earlier.  Weird!

[sebastiaan1973]

45 minutes ago, Andy8472 said:

GFS op still doesn't want to know with decrease in zonal winds, new trend or just a blip? 

http://arctic.som.ou.edu/tburg/products/realtime/strat/100mb_vortex.php
The representation of the stratosphere and stratosphere–troposphere coupling processes is evaluated in the subseasonal Global Ensemble Forecast System, version 12 (GEFSv12), hindcasts. The GEFSv12 hindcasts develop systematic stratospheric biases with increasing lead time, including a too strong boreal wintertime stratospheric polar vortex. In the tropical stratosphere, the GEFSv12 winds and temperatures associated with the quasi-biennial oscillation (QBO) tend to decay with lead time such that they underestimate the observed amplitudes; consistently, the QBO-associated mean meridional circulation is too weak. The hindcasts predict extreme polar vortex events (including sudden stratospheric warmings and vortex intensifications) about 13–14 days in advance, and extreme lower-stratospheric eddy heat flux events about 6–10 days in advance. However, GEFSv12’s ability to predict these events is likely affected by its zonal-mean circulation biases, which increases the rates of false alarms and missed detections. Nevertheless, GEFSv12 shows stratosphere–troposphere coupling relationships that agree well with reanalysis and other subseasonal forecast systems. For instance, GEFSv12 reproduces reanalysis relationships between polar vortex strength and the Northern Annular Mode in the troposphere. It also exhibits enhanced weeks 3–5 prediction skill of the North Atlantic Oscillation index when initialized during strong and weak polar vortex states compared to neutral states. Furthermore, GEFSv12 shows significant differences in Madden–Julian oscillation (MJO) amplitudes and enhanced MJO predictive skill in week 4 during easterly versus westerly QBO phases, though these results are sensitive to the level used to define the QBO. Our results provide a baseline from which future GEFS updates may be measured.