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1 hour ago, northwestsnow said:

Wonder if this is something Exeter are looking at as their extended forecast now bears the hallmarks of  a big scandy anticyclone..

A little like the week 4 cfs z500 anomaly forecast :)

wk3.wk4_20181023.z500.gif

Edited by blizzard81
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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

Posted Images

Here is my updated plot with SSW markers included. The SSW markers on top are colour coded by their respective ENSO phase. 

screenshot20181024-20110.jpg

 

Edited by Recretos
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Incidentally, today sets another date record for vortex strength at 10hpa ............. taking on board that this is merely part of the ebb and flow of the developing strat vortex but this years strengthening is clearly pretty impressive......... as I said a page or so ago........big structures built on dodgy foundations .......... 

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Nice one @Interitus good detective work.. some great stuff on those links - the Ellipse plots page is really good, in particular as you can move easily up and down the layers of the vortex as it moves through the model run.

Where some of the levels are robust, you get a sense of vortex size and also the chaos at other levels. Neat rendering here to ID the vortices with the dots..

ellipse50_37.thumb.png.eaa2af03062fb0d23939d1962b139e45.png

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Just looking at the 12z gfs op and control at 10hpa,there looks to be some sort of elongation/displacement of the pv,they wasn't showing this until today.

ok it's not a warming but there is some greens showing up on the Siberian side.

gfsnh-10-384.thumb.png.19aea1c65e6b487c8b35e20f7e4b02c8.pnggensnh-0-7-384.thumb.png.38e4ac6a149d52b8f18d6750c0ce6d3a.png

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8 minutes ago, Allseasons-si said:

Just looking at the 12z gfs op and control at 10hpa,there looks to be some sort of elongation/displacement of the pv,they wasn't showing this until today.

ok it's not a warming but there is some greens showing up on the Siberian side.

gfsnh-10-384.thumb.png.19aea1c65e6b487c8b35e20f7e4b02c8.pnggensnh-0-7-384.thumb.png.38e4ac6a149d52b8f18d6750c0ce6d3a.png

The 10hpa level won't give us any clues yet, that'll come further down the line (if at all). Anything that slows down the zonal flow will be most welcomed though. As things stand, we don't need a technical early SSW, any warming/repeated minor warmings will suffice (as the trop and strat are decoupled) but by the same token we don't want a strong zonal flow in the strat when they do couple, one that will overwhelm the trop. 

We've seen over the past few years how a strong zonal strat flow can bulldoze the trop set up in a matter of days.

Edited by CreweCold
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10 minutes ago, CreweCold said:

The 10hpa level won't give us any clues yet, that'll come further down the line (if at all). Anything that slows down the zonal flow will be most welcomed though. As things stand, we don't need a technical early SSW, any warming/repeated minor warmings will suffice (as the trop and strat are decoupled) but by the same token we don't want a strong zonal flow in the strat when they do couple, one that will overwhelm the trop. 

Thanks Crewe although this malarky is way over my head in the thundametal/tech side but i do understand some of it

what impact would a CW have on a de-coupled strat/trop if there was one say next month as this is when they usually happen isn't it?

Edited by Allseasons-si
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7 minutes ago, Allseasons-si said:

Thanks Crew although this malarky is way over my head in the thundametal/tech side but i do understand some of it

what impact would a CW have on a de-coupled strat/trop if there was one say next month as this is when they usually happen isn't it?

I'm feeling my way into this strat malarky too! 

I think the upshot of a CW with a decoupled strat/trop would be a strat vortex which would be much less bullish and less likely to impose itself on the trop below...although I'm not 100% on this. This is to say, I believe the trop would remain more influential so thus less likely to see a sustained zonal onslaught for our fair islands. 

I believe (I'm sure I read this somewhere) that for maximum effect of any SSW, a coupled strat and trop is best as you'll often get blocking which is directly influenced by where the thrust of the warming is centred in the strat. As I understand it, for example, a CW is conducive to post warming Greenland blocking.

Someone will enter and put me straight soon enough I would imagine...:)

Edited by CreweCold
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For cold snow lovers who like a snowy cold build up week before christmas lasting well into the new year, I suppose the best time for a SSW is late Nov/early Dec- but events at that time of year are I believe very rare indeed. Most SSW events occur post New Year.

However, I think there was an early SSW in 2010 in November?

I've also read about canadian warmings being a good precursor to cold..

Alas - interesting developments in the strat going into the winter this year, current situation feels like 2009 and 2010.

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1 hour ago, damianslaw said:

For cold snow lovers who like a snowy cold build up week before christmas lasting well into the new year, I suppose the best time for a SSW is late Nov/early Dec- but events at that time of year are I believe very rare indeed. Most SSW events occur post New Year.

However, I think there was an early SSW in 2010 in November?

I've also read about canadian warmings being a good precursor to cold..

Alas - interesting developments in the strat going into the winter this year, current situation feels like 2009 and 2010.

2010 did not see a SSW. The trop came in extremely kind (early wave action and tropical assistance) and things slowly degenerated.

2009 did see the double warming early and late and so was strat led largely though the AO had gone record negative at times all year.

For all the obsession with canadian warmings history is not all kind for Nov/Dec warmings and the rest of winter. Often the strat reforms a few weeks later and winter is over.

What we really want is a warming right at the end of December/early Jan like 2012/2013.

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6 minutes ago, summer blizzard said:

2010 did not see a SSW. The trop came in extremely kind (early wave action and tropical assistance) and things slowly degenerated.

A stunning late Nov and Dec but such an annoying winter ultimately. All because of a strong Nina that ruined the early set up.

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10 hours ago, CreweCold said:

A stunning late Nov and Dec but such an annoying winter ultimately. All because of a strong Nina that ruined the early set up.

Not quite that simple in that as per 2016 and 2017 it is La Nina that often encourages a kinder trop/strat early on. Without that strong Nina, there is no guarantee we would have seen any cold at all. 

 

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gfs ops (and gefs to an extent) continue to build upper strat ridging on the western side of n America  as we reach the back end of week 2. the vortex displaced to Siberian side with trough extension towards east side of canada 

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21 hours ago, CreweCold said:

A stunning late Nov and Dec but such an annoying winter ultimately. All because of a strong Nina that ruined the early set up.

Depends where you live Crewe. even with two strat warmings winter 2009/10 was poor here in Dorset.

It was much colder and the heavy snowfall much deeper in the five weeks of cold Nov/Dec 2010 than in the entire winter of 2009/10 here. Not to mention the Red met office warning than didn't, produce a single flake of snow in early jan 2010.

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Yes its relative vorticity, but I am not sure about the value, I think around 18? Since it was done on the fly...

Tho for SSW reanalysis from ECMWF ERA data, I rather use absolute vorticity. Its much more clean and gives a better impression. But the new ERA-5 data only has relative vorticity for now, so I will try that out since it has really nice resolution for a reanalysis model.

Edited by Recretos
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