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Stratosphere and Polar Vortex Watch


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27 minutes ago, feb1991blizzard said:

Seriously though, there are a lot of times when a very zonal pattern suddenly becomes very blocked due to an SSW, more so than times where a blocked pattern becomes even more blocked, its a well known fact that the zonal flow increases just before an SSW although i cannot remember which layer of the atmosphere that most applies to.

There was a study in 2016 (can't remember for the life of me who by otherwise I'd link it, maybe someone can post it) that showed the UK/NW Europe was often colder prior to the SSW because the trop pattern which triggered an SSW was more favourable for UK/NW Europe cold than the pattern once the SSW had shaken things up. 

Zonal flow often increases because pressure against one side of the vortex tightens the pressure gradient, Recretos' post above makes for great reading. 

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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 minute ago, Met4Cast said:

There was a study in 2016 (can't remember for the life of me who by otherwise I'd link it, maybe someone can post it) that showed the UK/NW Europe was often colder prior to the SSW because the trop pattern which triggered an SSW was more favourable for UK/NW Europe cold than the pattern once the SSW had shaken things up. 

Zonal flow often increases because pressure against one side of the vortex tightens the pressure gradient, Recretos' post above makes for great reading. 

Yes read it since, but when you say zonal flow, what part of the atmosphere are you talking, that must have been what i was thinking of, you can often get just below average temps after the SSW but before the ensuing Easterly due to the undercutter / slider but that is after the SSW, 1991, 2012 good examples of that.

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1 minute ago, feb1991blizzard said:

Yes read it since, but when you say zonal flow, what part of the atmosphere are you talking, that must have been what i was thinking of, you can often get just below average temps after the SSW but before the ensuing Easterly due to the undercutter / slider but that is after the SSW, 1991, 2012 good examples of that.

I think it's probably different with each SSW and depends on the type/area of the trigger and whether it's a top down warming or bottom up warning I would presume 

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Indeed. Impressively high Wave 1 amplitude being predicted by the GFS as the month comes to a close just as wave 2 beings to subside. Continued pressure on the strat vortex is what we want to see!

gfs_nh-hgt-w1-60n_20191117.thumb.png.15a76f0d5fa6193c38f93e36ae02a4c1.png

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2 hours ago, Met4Cast said:

There was a study in 2016 (can't remember for the life of me who by otherwise I'd link it, maybe someone can post it) that showed the UK/NW Europe was often colder prior to the SSW because the trop pattern which triggered an SSW was more favourable for UK/NW Europe cold than the pattern once the SSW had shaken things up. 

Zonal flow often increases because pressure against one side of the vortex tightens the pressure gradient, Recretos' post above makes for great reading. 

I think it is better to look at things with GSDM in consideration to try and understand the whole atmospheric dynamics. Having had discussions with Tamara before, it is also important to have MJO passing Indian Ocean in high amplitude  to so called warm phases  and then for it to orbit through to cold phases 7,8 and 1. It allows for rise  +FT,+MT  and GLAAM which feedbacks in to GWO phases 5 to 8. You can see this by what happened in January 2018 prior to SSW on the MJO image attached.  What happened last winter was MJO even if it went to cold phases it didn't make the whole circle from Indian Ocean hence we only had a Nina like enhanced mid. Atlantic ridges.   When this happens in sync with SSW then its great, it appears that having initially hostile troposphere in warm MJO phases then rewards with better downwelling after SSW because GLAAM is supporting for later sustained tropospheric blocking. 

Capture.PNG

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21 hours ago, Blessed Weather said:

Anyone not doing anything over the next 4 days? ECMWF will be live-streaming their workshop on “Stratospheric predictability and impact on the troposphere” during 18th to 21st November 2019 and it's open to all with no registration or login required. There's some big names taking part including Amy Butler and Simon Lee.

"The topics will include understanding and diagnosing stratosphere-troposphere interactions, improved parametrizations and numerical schemes, the role of water vapour and ozone, observational evaluation and data assimilation."

Link to live-streaming: https://www.ecmwf.int/en/learning/workshops/workshop-stratospheric-predictability-impact-troposphere

 

I've been watching this. Ted Shepherd's presentation was very technical and difficult (for me, anyway) to follow. Amy Butler is on now, and her presentation is much more accessible to the layman. Hopefully, they'll put all the videos up later. 

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Just a side note: The GFS//GEFS suite is running without the Aura Ozone Monitoring Instrument (OMI) data in the inputs since 15th 06z run. I have seen a warm bias in the FI before when this dataset was not in the initials. Not saying that is why we are seeing the warming. The warming is likely legit, and already seems good on the 12z as well. I am just adding a note that there is a lack of ozone data in the initials for future reference.

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6 hours ago, Met4Cast said:

There was a study in 2016 (can't remember for the life of me who by otherwise I'd link it, maybe someone can post it) that showed the UK/NW Europe was often colder prior to the SSW because the trop pattern which triggered an SSW was more favourable for UK/NW Europe cold than the pattern once the SSW had shaken things up. 

Zonal flow often increases because pressure against one side of the vortex tightens the pressure gradient, Recretos' post above makes for great reading. 

A few years ago I checked the hellmann cold numbers for my location and more often than not the cold came before the ssw and usually after it became mild with a few exceptions. If cold is in place, I'd rather wouldn't get an ssw but if there is no cold it could help

 

here are the dates of ssw's until spring 2012 ( so only missing jan 1 2013 and february 2018)

 

JOURNALS.AMETSOC.ORG

ssi

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3 hours ago, jules216 said:

I think it is better to look at things with GSDM in consideration to try and understand the whole atmospheric dynamics. Having had discussions with Tamara before, it is also important to have MJO passing Indian Ocean in high amplitude  to so called warm phases  and then for it to orbit through to cold phases 7,8 and 1. It allows for rise  +FT,+MT  and GLAAM which feedbacks in to GWO phases 5 to 8. You can see this by what happened in January 2018 prior to SSW on the MJO image attached.  What happened last winter was MJO even if it went to cold phases it didn't make the whole circle from Indian Ocean hence we only had a Nina like enhanced mid. Atlantic ridges.   When this happens in sync with SSW then its great, it appears that having initially hostile troposphere in warm MJO phases then rewards with better downwelling after SSW because GLAAM is supporting for later sustained tropospheric blocking. 

Capture.PNG

I would absolutely love to, unfortunately the only website on the entire internet that hosts GSDM/AAM/GWO charts has decided to password protect it and be incredibly selective to who he allows access.

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5 minutes ago, Met4Cast said:

I would absolutely love to, unfortunately the only website on the entire internet that hosts GSDM/AAM/GWO charts has decided to password protect it and be incredibly selective to who he allows access.

I only know because I remember some of the musing of that SSW event by posters with access to the data,otherwise I rely on other feedback from GSDM experts from forums worldwide unfortunately

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5 minutes ago, bluearmy said:

Don’t forget that if there is a downwelling wave high up then it isn’t unusual for the stronger zonal flow from the mid/upper strat to be flushed down ahead of the wave towards the trop .....

Yes, agreed, good point, I'd missed that,  it does look like that is what we are seeing in the models now.

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8 minutes ago, Mike Poole said:

Yes, agreed, good point, I'd missed that,  it does look like that is what we are seeing in the models now.

Not sure the pre end November uptick is down to that but if we see a pos AO/NAO  period showing up in the nwp for first half Dec then that could be the reason 

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