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

[Catacol]

Posting the obvious - significantly below average vortex strength for an extended period, regardless of SSW or no SSW.

To my casual eye the number of members dropping into that significantly below average bracket is increasing.

Edited December 4, 2023 by Catacol

[andy989]

Come out come out wherever you are @chionomaniac

[bluearmy]

49 minutes ago, andy989 said:

Come out come out wherever you are @chionomaniac

He’s too busy laughing at Man U’s woes …..

[lorenzo]

An easier way perhaps of viewing the ensembles courtesy of some excellent additions to Tomer Burg's site. Also has a rather long lead heat flux plot which will be good to keep an eye on too.

The cluster around Boxing day within the u10 plot caught my attention with a group displaying a notable peak before crashing.

The clusters which were around Boxing day, now moving toward New year,  within the u10 plot caught my attention with a couple of groups displaying peaks before deceleration. Timelines moving outward for this over the last 24-48 hrs. Also below the CFS 45 day view with 0 > -8 creeping in on the edges of model reality c19th Jan, way to far out to be in anyway reliable but have seen the CFS catch an early glimpse of SSW previously so always worth having a look in on.

GFS view  / GEFS view - both with clear split in Ensembles and routes ahead beyond Xmas..

 

 

Edited December 5, 2023 by lorenzo

[Andy8472]

https://www.climate.gov/news-features/blogs/polar-vortex-blog/welcome-polar-vortex-blog

Interesting new Polar Vortex blog by Amy Butler & Laura Ciasto

[DOdo]

On X Judah Cohen is reporting that early January that a Stratosheric Warming event is going to take place over the Poles.Is this correct?

[Andy8472]

16 minutes ago, DOdo said:

On X Judah Cohen is reporting that early January that a Stratosheric Warming event is going to take place over the Poles.Is this correct?

Possibly, atm 23% chance of a SSW by early jan with a general weaking although nothing showing up on the GFS runs atm

 

[knocker]

How do different pathways connect the stratospheric polar vortex to its tropospheric precursors?

Abstract

Processes involving troposphere–stratosphere coupling have been identified as important contributors to an improved subseasonal to seasonal prediction in the mid-latitudes. However, atmosphere models still struggle to accurately predict stratospheric extreme events. Based on a novel approach in this study, we use ERA5 reanalysis data and ensemble simulations with the ICOsahedral Non-hydrostatic atmospheric model (ICON) to investigate tropospheric precursor patterns, localised troposphere–stratosphere coupling mechanisms, and the involved timescales of these processes in the Northern Hemisphere extended winter. We identify two precursor regions: mean sea level pressure in the Ural region is negatively correlated with the strength of the stratospheric polar vortex for the following 5–55 d with a maximum at 25–45 d, and the pressure in the extended Aleutian region is positively correlated with the strength of the stratospheric polar vortex the following 10–50 d with a maximum at 20–30 d. A simple precursor index based on the mean pressure difference of these two regions is very strongly linked to the strength of the stratospheric polar vortex in the following month. The pathways connecting these two regions to the strength of the stratospheric polar vortex, however, differ from one another. Whereas a vortex weakening can be connected to prior increased vertical planetary wave forcing due to high-pressure anomalies in the Ural region, the pathway for the extended Aleutian region is less straightforward. A low-pressure anomaly in this region can trigger a Pacific–North American-related (PNA-related) pattern, leading to geopotential anomalies of the opposite sign in the mid-troposphere over central North America. This positive geopotential anomaly travels upward and westward in time, directly penetrating into the stratosphere and thereby strengthening the stratospheric Aleutian High, a pattern linked to the displacement towards Eurasia and subsequent weakening of the stratospheric polar vortex. Overall, this study emphasises the importance of the time-resolved and zonally resolved picture for an in-depth understanding of troposphere–stratosphere coupling mechanisms. Additionally, it demonstrates that these coupling mechanisms are realistically reproduced by the global atmosphere model ICON.

https://wcd.copernicus.org/articles/4/1071/2023/

[bluearmy]

2 hours ago, DOdo said:

On X Judah Cohen is reporting that early January that a Stratosheric Warming event is going to take place over the Poles.Is this correct?

A stratospheric warming event is not necessarily a full reversal ssw 

The word event reflects that he expects it will be a notable warming though - as shown on the EC46 anomoly charts 

[summer blizzard]

50% of Euro ensemble members today went for a SSW after 27th December. The mean has also dropped to +12 on Jan 11th.

So yes, it does appear that the stratosphere is forecast to experience significant distress. 

[bluearmy]

7 hours ago, summer blizzard said:

50% of Euro ensemble members today went for a SSW after 27th December. The mean has also dropped to +12 on Jan 11th.

So yes, it does appear that the stratosphere is forecast to experience significant distress. 

Impressive but for now, until we get a handle on what’s likely to happen to the zonal wind for the next two weeks it’s tough to be too confident in much.  I’d say that over the past few days, whilst the chances of a reversal in the new year have increased, the likelihood of a pretty average to weakish (30-40m/s) spv through the rest of December has increased aswell.  Most importantly still no signal for any real chance of a strong spv 

[JeffC]

 there is already a "warm" area showing at 10 hPa... 

earth :: a global map of wind, weather, and ocean conditions

EARTH.NULLSCHOOL.NET

---

See current wind, weather, ocean, and pollution conditions, as forecast by supercomputers, on an interactive animated map. Updated every three hours.

 

[summer blizzard]

7 hours ago, bluearmy said:

Impressive but for now, until we get a handle on what’s likely to happen to the zonal wind for the next two weeks it’s tough to be too confident in much.  I’d say that over the past few days, whilst the chances of a reversal in the new year have increased, the likelihood of a pretty average to weakish (30-40m/s) spv through the rest of December has increased aswell.  Most importantly still no signal for any real chance of a strong spv 

Yes. Always possible that we get screwed over however what makes me a little optimistic is that the 11th is not runs end which means it sees a genuine push from a cluster rather than just going through the trend motions. 

[Dennis]

SSW chart 9-12 

[bluearmy]

The ec46 10hpa zonal flow over the past week has extended the likelihood of December being weakly average out to the last few days of the month. I’d say that a week ago the average was dropping below 30m/s by the 22nd. Now that looks to be closer to the 29th.  This  does potentially mean that whilst the upper strat stays broadly weak, there isn’t much influence from it to affect what happens lower down and in the trop. The trop will continue to boogie away without the strat deciding what the dance is. 

[Andy8472]

Outer reaches of the GFS starting to pick up on a warming, subject to change of course 

The best ones....

[Mike Poole]

10 hours ago, Dennis said:

SSW chart 9-12 

 

3 hours ago, Andy8472 said:

Outer reaches of the GFS starting to pick up on a warming, subject to change of course 

The best ones....

Yes, looks like the SSW is now just in range of the GEFS, as well as the ECM 46.  

[summer blizzard]

The question is whether the 16 day GFS operations have greater resolution in the stratosphere than the Euro 32 day forecast. 

[Andy8472]

More warming on the 12z but the Operational still isn't showing anything noteworthy, maybe apart from a weaking core.

[bluearmy]

4 hours ago, Mike Poole said:

 

Yes, looks like the SSW is now just in range of the GEFS, as well as the ECM 46.  

There is no ssw due within 16 days though Mike?  
 

ec46 shows the odd run reversing into the new year. 

Edited December 9, 2023 by bluearmy

[Mike Poole]

3 minutes ago, bluearmy said:

There is no ssw due within 16 days though Mike?  

No, but there are some in the extended timescale of the GEFS:

[Andy8472]

This morning GEFS, most showing a initial warming from 24th/26th, Some would no doubt cause a SSW within 10 days later i would guess

Even the OP for the first time shows a warming although later & just getting going, Consistency is key & I've found the GFS is pretty good at zeroing in on to warmings over the years. 

As always watch this space 

 

[summer blizzard]

Perb 3 was best, placement > strength.

[bluearmy]

funnily enough the eps mean (which should be by far the best tool for the strat) has the warming at day 15 in a similar place to the gfs op 

Spv displaced to what should be a good place for European cold if we can get the zonal flow in the trop to relent. 

Edited December 10, 2023 by bluearmy

[northwestsnow]

5 minutes ago, bluearmy said:

funnily enough the eps mean (which should be by far the best tool for the strat) has the warming at day 15 in a similar place to the gfs op 

Spv displaced to what should be a good place for European cold if we can get the zonal flow in the trop to relent. 

" zonal flow to relent "

I wish it was easy !! 

Thank God we have you on here to provide level headed analysis while all around lose their heads !!

All eyes on mjo / zonal flow !!