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

[stodge]

Surprising not to see more comment on the stratospheric situation.

GFS 12Z OP has a clear 10 HPA split in far FI as has Control.

Many questions follow, none of which I'm able to answer with my limited knowledge of these things but I would suspect our old friend Mr N. Blocking and party will be paying us an extended visit from March to perhaps May (who knows?). Nothing terribly unusual in that and of course for every 2018 there's a 2020 so a late winter could just as easily be an early spring.

An early final warming? Again, too early to tell but looking at CFS monthly this evening, I'm drawn to the synoptic pattern which keeps trying to build heights to the north east and north with LP disrupting over or close to the British Isles. 

Snow for low ground? You'd bet against it. Snow for northern hills and mountains? You wouldn't bet against it.

[summer blizzard]

Yes, reasonable chance of a proper SSW in around ten days. Late Feb/early March most likely to feel the impact.

[summer blizzard]

 SqueakheartLW Do you have an updated U Wind anomoly chart so we can see how quickly the SSW is likely to downwell.

[damianslaw]

Updates on expected SSW would be greatly received.. conflicting messages at present.

[summer blizzard]

Euro is solid around the 19th albeit its downwelling we need. 

[Mike Poole]

 summer blizzard Big change on today’s plot compared to that:

Much increased cluster going for the second dip a week after the first, and a big reduction in the mean extending over several weeks.

[summer blizzard]

Final warming anybody.

[Don]

 summer blizzard A failed SSW?!

[summer blizzard]

To answer my own earlier question regarding the SSW currently occuring, it looks like almost no impact here with another reflective structure but even less kind. We actually see the tropospheric vortex strengthen around months end. 

Euro still goes for what is likely an early warming afterwards. 
 

[Rain All Night]

Suppose the zonal mean zonal winds at 10hPa did fall below zero again on (say) 6th March and never did recover back to above zero until next autumn - an "early final warming". What would be the expected consequences of this? Have there been any other recent years in which this has happened as early?

Edited February 18 by Rain All Night

[summer blizzard]

 Rain All Night 2016 saw the earliest final warning on record in mid February (also a strong Nino so It would be interesting to check dates).

So in theory the initial impact should be similar to a normal SSW and the duration should increase the chance of downwelling (so possibly bad for those wanting a warm March) but by April it will essentially encourage a weaker tropospheric response (be that blocking or westerlies) and the kind of more stagnant patterns that we normally see in spring and summer (good or bad).

So in short, you might not notice it all that much outside the initial impact but we probably see a less mobile pattern and one that for good or bad is increasingly stagnant, this just starts earlier than it would.

Edited February 19 by summer blizzard

[Rain All Night]

 summer blizzard Thanks, how was spring 2016? I don't recall it

[summer blizzard]

 Rain All Night

Standard Nino stereotype. 

Cool March, warm May.

[SqueakheartLW]

 summer blizzard

Looks like this run is going for yet another warming at the end. Maybe this one will end up a final warming

[summer blizzard]

SSW now looking much stronger. 

[Don]

 summer blizzard Too darn late if it does come off though!

[baddie]

 Don Doubt it will happen. Never had a winter turn up after the equinox due to an SSW after a mild and wet winter

Edited February 22 by baddie

[summer blizzard]

Does anybody have the NASA link to see each winter at each atmospheric level. 

[Don]

 baddie yes exactly!

[baddie]

 Don If anything, I can imagine a March/April 2021 type scenario, with an exceptional warm spell just after the equinox (25c on the 25th), then the Easter Weekend being cold and snowy, with a relatively cold and dry first week of April

[Don]

 baddie well, you never know these days!

[summer blizzard]

Better down welling as we head towards mid March on this one.

https://twitter.com/MetRyan96/status/1761082180615221332?t=6IU6Ui2A0UAqr3Bc4XD5ZQ&s=19

[Rain All Night]

@Mike Poole The mean minimum has crept back up from -18m/s to -12m/s, I don't suppose we could have a third disappearing SSW in a row could we? 

Edited February 29 by Rain All Night

[summer blizzard]

[Rain All Night]

 summer blizzard It's combed its hair today