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Stratosphere and Polar Vortex Watch


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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

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1 hour ago, sebastiaan1973 said:

Is someone able to record these presentations? 

https://events.ecmwf.int/event/129/timetable/

They will record them almost certainly. For example see the "Workshop on Predictability, dynamics and applications research using the TIGGE and S2S ensembles" from April 2019 - https://www.ecmwf.int/en/learning/workshops/workshop-predictability-dynamics-and-applications-research-using-tigge-and-s2s-ensembles

Scroll down to 'Presentations and recordings'.

Lots of interesting presentations on subseasonal to seasonal forecasting (MJO, QBO, sea ice etc) including one on forecasting the 2018 SSW from Alexey Karpechko.

Some of the previous events have simple videos and PDF files of the presentations but this TIGGE/S2S one uses Adobe Connect which neatly combines the video of the speaker with the slides they're presenting (as well as having separate PDFs).

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In 2018 NAO tightened ahead of SSW, this is something I thought was linked  as an artefact of all vortex events ahead of an SSW, given strong anecdotal model watching. No one was wrong, we were possibly observing other things simultaneously, trough disruption, MJO/AAM Imprints

Dr Butler confirmed it is not analogous, ergo cannot be a confirmed regime watch out on NWP... More stuff to observe lays ahead and - no comfort from NAO heralding an SSW..

Although it did last year ?

From Dr Amy Butler

image.thumb.png.650fe39a3f2c236f4a37d971a08feb94.png

https://twitter.com/DrAHButler

Lady is the boss folks - ? privilege to get insight like this

 

 

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6 minutes ago, lorenzo said:

In 2018 NAO tightened ahead of SSW, this is something I thought was linked  as an artefact of all vortex events ahead of an SSW, given strong anecdotal model watching. No one was wrong, we were possibly observing other things simultaneously, trough disruption, MJO/AAM Imprints

Dr Butler confirmed it is not analogous, ergo cannot be a confirmed regime watch out on NWP... More stuff to observe lays ahead and - no comfort from NAO heralding an SSW..

Although it did last year ?

From Dr Amy Butler

image.thumb.png.650fe39a3f2c236f4a37d971a08feb94.png

https://twitter.com/DrAHButler

Lady is the boss folks - ? privilege to get insight like this

 

 

Hey, @lorenzo please could you put some meat on those bones, as per implications for this year? Thanks 

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1 minute ago, feb1991blizzard said:

Strongest forecast warming yet.

image.thumb.png.a0d1aaacc687e8e48b696825be1529bd.pngimage.thumb.png.afe4710315714b812ea6e7f41ba0629e.png

Just beat me to it feb, I am interested this winter to see how the GFS (now FV3) handles the strat side of things as last winter (in the lead up to / and when we got the ssw) it was on and off quite a bit with the warming whilst overall the GEFS stayed pretty firm.

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1 minute ago, Kirkcaldy Weather said:

Just beat me to it feb, I am interested this winter to see how the GFS (now FV3) handles the strat side of things as last winter (in the lead up to / and when we got the ssw) it was on and off quite a bit with the warming whilst overall the GEFS stayed pretty firm.

That;s actually a concern of mine, c\annot remember exactly but did it not overdo the troposheric blocking last year?

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1 minute ago, feb1991blizzard said:

That;s actually a concern of mine, c\annot remember exactly but did it not overdo the troposheric blocking last year?

cant remember that side of things but it was back and forth whether we would see a split and overall I would say the ensembles handled it better.

 

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17 minutes ago, Kirkcaldy Weather said:

Just beat me to it feb, I am interested this winter to see how the GFS (now FV3) handles the strat side of things as last winter (in the lead up to / and when we got the ssw) it was on and off quite a bit with the warming whilst overall the GEFS stayed pretty firm.

It really struggled with the down welling of the stratosphere especially but so did most models so it will be interesting to see what this one does as each warming is unique!

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Good points folks ^^^ the documentation about the FV3 prior to it going live did suggest some deficiencies re the strat, good time for us to start to check that out?....

Edited by Mike Poole
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16 minutes ago, Mike Poole said:

Good points folks ^^^ the documentation about the FV3 prior to it going live did suggest some deficiencies re the strat, good time for us to start to check that out?....

And see if it come's to fruition ?

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8 hours ago, lorenzo said:

In 2018 NAO tightened ahead of SSW, this is something I thought was linked  as an artefact of all vortex events ahead of an SSW, given strong anecdotal model watching. No one was wrong, we were possibly observing other things simultaneously, trough disruption, MJO/AAM Imprints

(SNIPPED)

There's a very good paper written by Simon Lee and Jason Furtado et al detailing the 2018 SSW:

Abrupt Stratospheric Vortex Weakening Associated With North Atlantic Anticyclonic Wave Breaking

The sudden stratospheric warming (SSW) of 12 February 2018 was not forecast by any extended-range model beyond 12 days. From early February, all forecast models that comprise the subseasonal-to-seasonal (S2S) database abruptly transitioned from indicating a strong stratospheric polar vortex (SPV) to a high likelihood of a major SSW. We demonstrate that this forecast evolution was associated with the track and intensity of a cyclone in the northeast Atlantic, with an associated anticyclonic Rossby wave break, which was not well forecast. The wave break played a pivotal role in building the Ural high, which existing literature has shown was a precursor of the 2018 SSW. The track of the cyclone built an anomalously strong sea level pressure dipole between Scandinavia and Greenland (termed the S-G dipole), which we use as a diagnostic of the wave break. Forecasts that did not capture the magnitude of this event had the largest errors in the SPV strength and did not show enhanced vertical wave activity.

Full paper: http://ifurtado.org/wp-content/uploads/Publications/LeeCharltonFurtadoWoolnough.pdf

And there's many. more papers in the Netweather Research Library:

 

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1 minute ago, mushymanrob said:

what are the implications at surface level for a warmin in that location?  (novice here)

Assuming it verifies, unknown rob ...... last winters ssw didn’t propagate effectively ....

 and would this evolve into a ssw?  Would it be a displacement?  Or would it become a split ?  And if it did propagate, how would the shattered tpv be left ?  Most strat warming’s seem to become notable in that particular part of Asia. 

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Just now, bluearmy said:

Assuming it verifies, unknown rob ...... last winters ssw didn’t propagate effectively ....

 and would this evolve into a ssw?  Would it be a displacement?  Or would it become a split ?  And if it did propagate, how would the shattered tpv be left ?  Most strat warming’s seem to become notable in that particular part of Asia. 

cheers ? so an indication as to what might evolve as opposed to a more certain path of consequences...

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8 minutes ago, bluearmy said:

Assuming it verifies, unknown rob ...... last winters ssw didn’t propagate effectively ....

 and would this evolve into a ssw?  Would it be a displacement?  Or would it become a split ?  And if it did propagate, how would the shattered tpv be left ?  Most strat warming’s seem to become notable in that particular part of Asia. 

Hehe - so many possibilities. I’m going to plump for a split, and I’m also going to suggest residual energy will end up over Canada and East Asia. Surface impacts will be different to last year with favourable QBO context by January smoothing a path to a better downwelling. It’s all in my forecast over on the speculation thread (though I don’t discuss the QBO shape in that write up in an attempt to keep it from being mammothly long) - but a short spell of Canadian vortex induced weather leading to a definitely blocked pattern by the latter half, maybe final third, of January.

This winter is really “hotting” up.

Edited by Catacol
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