Stratosphere and Polar Vortex Watch

[Gael_Force]

15 hours ago, Gael_Force said:

Does anybody remember the paper that mentioned higher incidences of neg NAO and winter blocking in uneven numbered solar cycles?  .... 62-63 and 78-79 were cycles 19 and 21.

From the Tokyo video up the page; she was touching on the subject of two cycles being part of the complete process but different result in each one depending on whether negative or positive rotation.  Sadly, she was difficult to understand and I would like to see their findings in print.

Just to add .... the well known Hale cycle which was noted by meteorologists of the past and the occurrence of severe winter weather in circa 20 year cycles. If this theory is correct, there should be some great winters to look forward to as we go into the next decade but what of warming oceans and melting ice ... will that be a spanner in the works?

[Interitus]

17 hours ago, chionomaniac said:

Probably is arbitrary and academic.

Interestingly Amy Butler doesn't include Feb 17 and she says in the last few days on Twitter that the last SSW was in 2013

https://www.esrl.noaa.gov/csd/groups/csd8/sswcompendium/majorevents.html

https://twitter.com/DrAHButler/status/954103368988770304

Thing is, the March 2016 warming was the second strongest wind reversal only just behind Jan 2009, and probably because of this it ended up being a final warming. Dynamically however, it was a wave forced SSW, not a final warming induced by the returning insolation. Someone (might've been Judah Cohen) argued this exact point on twitter, but Amy Butler wasn't having it. Ridiculous that a weak SSW would count, but this one doesn't.

Anyway, therein lies the point, classification really depends on the individual and why they want to know. For example, if studying the initial forcing and development of SSW, it isn't the best idea to include second in season SSW as they typically require less WAF - whereas the March 2016 would be a good candidate....unless looking for the effects on our winter when maybe all March SSW should be ignored. Then for strat-trop coupling there's the typical classification by split/displacement and minor/major warmings etc. Amy Butler mentioned in a tweet that the wind reversal is important so only considers major warmings. However, only at 60°N? The debatable one mentioned above from 1st Feb 2017 was a reversal from 62.5°N northwards in the NCEP reanalysis so counts for other people using 65°N. The various reanalyses in the SSW compendium don't match exactly in any case (and if using MERRA2 data the 2017 one should count). And then is having a 60°N mean of -0.01 m/s more significant than one at 0.0 m/s?

Might be better to follow the example of Coughlin & Gray http://journals.ametsoc.org/doi/abs/10.1175/2008JAS2792.1 who instead suggest that the stratosphere exists in a cold state ~90% of the time and warm state ~10%, within which there is no differentiation between major/minor but instead a continuum of warmings. This approach has also been applied to the classification of warmings by vortex geometry (eg Hannachi et al http://journals.ametsoc.org/doi/abs/10.1175/2010JAS3585.1)

[zdlawrence]

9 hours ago, Interitus said:

Thing is, the March 2016 warming was the second strongest wind reversal only just behind Jan 2009, and probably because of this it ended up being a final warming. Dynamically however, it was a wave forced SSW, not a final warming induced by the returning insolation. Someone (might've been Judah Cohen) argued this exact point on twitter, but Amy Butler wasn't having it. Ridiculous that a weak SSW would count, but this one doesn't.

Anyway, therein lies the point, classification really depends on the individual and why they want to know. For example, if studying the initial forcing and development of SSW, it isn't the best idea to include second in season SSW as they typically require less WAF - whereas the March 2016 would be a good candidate....unless looking for the effects on our winter when maybe all March SSW should be ignored. Then for strat-trop coupling there's the typical classification by split/displacement and minor/major warmings etc. Amy Butler mentioned in a tweet that the wind reversal is important so only considers major warmings. However, only at 60°N? The debatable one mentioned above from 1st Feb 2017 was a reversal from 62.5°N northwards in the NCEP reanalysis so counts for other people using 65°N. The various reanalyses in the SSW compendium don't match exactly in any case (and if using MERRA2 data the 2017 one should count). And then is having a 60°N mean of -0.01 m/s more significant than one at 0.0 m/s?

Might be better to follow the example of Coughlin & Gray http://journals.ametsoc.org/doi/abs/10.1175/2008JAS2792.1 who instead suggest that the stratosphere exists in a cold state ~90% of the time and warm state ~10%, within which there is no differentiation between major/minor but instead a continuum of warmings. This approach has also been applied to the classification of warmings by vortex geometry (eg Hannachi et al http://journals.ametsoc.org/doi/abs/10.1175/2010JAS3585.1)

 

Just want to address two points here:

Amy Butler agreed that the Mar 2016 "major final warming" was a wave-driven event, but since the circulation never recovered, it just cannot be included on her table of CP07 events. Amy Butler has never said that the CP07 definition for SSWs is the "best" or "standard" definition -- it's just one of many definitions, but it is commonly used in the literature (see her paper on defining SSWs, http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00173.1). I think her compendium of CP07 SSW dates is most helpful as a way to prevent errors in research & the literature; there are some small intricacies in the CP07 definition that do matter (see my next point below). I don't think her compendium was ever advertised as or intended to be the "definitive" list of events. 

Regarding the Feb 2017 event, I think the reason it's not an event in MERRA-2 is that the CP07 classification uses daily mean zonal mean zonal winds at 10mb 60N. They specifically say: "The first day on which the daily mean zonal mean zonal wind at 60°N and 10 hPa is easterly is defined as the central date of the warming." (see http://journals.ametsoc.org/doi/abs/10.1175/JCLI3996.1). If I wasn't on travel I would confirm, but since I can't, I would bet that averaging U1060 over the full 8 times per day of MERRA-2 would give a positive value. 

If anything, the above goes to show how any definition can be inadequate in specific situations, but that's just a side-effect of being consistent (i.e., true to the definition no matter what).

Edited January 21, 2018 by zdlawrence

[Interitus]

4 hours ago, zdlawrence said:

 

Just want to address two points here:

Amy Butler agreed that the Mar 2016 "major final warming" was a wave-driven event, but since the circulation never recovered, it just cannot be included on her table of CP07 events. Amy Butler has never said that the CP07 definition for SSWs is the "best" or "standard" definition -- it's just one of many definitions, but it is commonly used in the literature (see her paper on defining SSWs, http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00173.1). I think her compendium of CP07 SSW dates is most helpful as a way to prevent errors in research & the literature; there are some small intricacies in the CP07 definition that do matter (see my next point below). I don't think her compendium was ever advertised as or intended to be the "definitive" list of events. 

Regarding the Feb 2017 event, I think the reason it's not an event in MERRA-2 is that the CP07 classification uses daily mean zonal mean zonal winds at 10mb 60N. They specifically say: "The first day on which the daily mean zonal mean zonal wind at 60°N and 10 hPa is easterly is defined as the central date of the warming." (see http://journals.ametsoc.org/doi/abs/10.1175/JCLI3996.1). If I wasn't on travel I would confirm, but since I can't, I would bet that averaging U1060 over the full 8 times per day of MERRA-2 would give a positive value. 

If anything, the above goes to show how any definition can be inadequate in specific situations, but that's just a side-effect of being consistent (i.e., true to the definition no matter what).

Thank you for your input, welcome to the forum 

[Interitus]

Just for clarification, I didn't mean to imply that Dr Butler was unaware of the nature of the March 2016 warming but rather she was bound by consistency, as rightly pointed out.

Edited January 21, 2018 by Interitus

[Interitus]

GFS predicting perhaps another wave reflection event - compare with Shaw & Perlwitz composite sequence (Shaw & Perlwitz 2013 - http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00251.1)

GFS 0z day 1 corresponding to first image above -

GFS day 13 like composites 2/3 -

Charts weatheriscool.com - thanks @Mattias

 

Edited January 21, 2018 by Interitus

[bluearmy]

And Berlin chart shows some impressive wave 1 in week 2.  The zonal flow looks pretty weak but no sign of a reversal. patterns in the trop are likely to continue to be led by events in the trop. 

[Interitus]

2 hours ago, bluearmy said:

And Berlin chart shows some impressive wave 1 in week 2.  The zonal flow looks pretty weak but no sign of a reversal. patterns in the trop are likely to continue to be led by events in the trop. 

Well, apart from the +NAO pattern which is encouraged if the wave reflection forecast comes off.

[bluearmy]

4 hours ago, Interitus said:

Well, apart from the +NAO pattern which is encouraged if the wave reflection forecast comes off.

Didn’t we see this upcoming pattern in December in the upper strat ? 

[bluearmy]

Expect a fair old temp spike on the Berlin charts tomorrow morning at 10hpa over the pole 

[Catacol]

On 19/01/2018 at 16:55, KyleHenry said:

Many, including myself have been scratching our heads as to why this winter, when the conditions have been so perfect for a loosening of the Polar jet and expansionism of cold air into the lower latitudes has not occurred. 

Signals consistantly showing via the models of HLB in Scandinavia & Greenland, yet failing to materialise each time in terms of predicted longevity. 

MJO entered sector 3 which is now culminating in EAMT event=Stratospheric wave 1 and yet as we approached finalisation point it has decreased in amplitude. 

 

No SSW, merely elongation of the PV which does show that even a weaker wave will create enough stress to contort vortex and allow intermissional cold break outs at the Tropispheric level. Just that unless sustained pulses/waves occurs, then it will return to default position.

 

Why so? 

That we are still on the decent to solar minimum. With that said the sun is continuing to emit bursts of protons/cm3. Negative NAOs struggle to develop in these conditions. Hence the failing of current wave to split PV.

 

Geomagnetic bursts charge the magnetosphere add expand it outwards. This permits all levels to elongate and acts as a dampener to wave pulses. The PV has additional upward momentum and hence becomes more taught adding strength.

Really interesting post. I have my summer research project now mapped out for me prior to next winter.....

[bluearmy]

Gefs are looking to lift the upper zonal flow again in week 2. Not overly convincing at the moment (not every run does so) but the fact that they do so at all is a bit of a surprise given the Berlin charts at day 10

[knocker]

 

[bluearmy]

the gefs continue to eek up the zonal flow week 2.  tbh, a reversal after mid feb without a QTR is not good for us. we could do with a warm early spring to help the economy, not a cold one like last year.

[Singularity]

I'm increasingly suspecting GEFS does not has a flying clue beyond a week's range at the mo, but we'll see. As per the JF tweet the Pacific uncertainty is large - and critical regarding how much happens and how soon.

[Don]

3 hours ago, bluearmy said:

the gefs continue to eek up the zonal flow week 2.  tbh, a reversal after mid feb without a QTR is not good for us. we could do with a warm early spring to help the economy, not a cold one like last year.

March last year had a CET of 8.7C!

[Paul_1978]

Any thoughts on this T+132 chart posted over the in the MOD thread?

https://www.netweather.tv/forum/topic/89199-model-output-discussion-mid-january/?do=findComment&comment=3727657

 

[feb1991blizzard]

57 minutes ago, Paul_1978 said:

Any thoughts on this T+132 chart posted over the in the MOD thread?

https://www.netweather.tv/forum/topic/89199-model-output-discussion-mid-january/?do=findComment&comment=3727657

 

Its just a slight displacement if you look at the charts showing the vortex, http://www.instantweathermaps.com/GFS-php/strat.php?run=2018012406&var=HGT&lev=10mb&hour=135 if you run the chart shown on the MOD thread through you will see the warming just fades away. its still better than not having the warming at all because it still slows the zonal flow down up top which makes it less likely to affect the trop meaning the trop can do what it wants, unfortunately though BA' posts above that there is an increase in zonal flow in the GEFS members in week 2 and even looking at the op there wont be a technical SSW anytime soon (reversal at 10mb), however, we may not need one though as some interesting output in the trop has been showing in week 2 lately anyway.

[comet]

26 minutes ago, feb1991blizzard said:

Its just a slight displacement if you look at the charts showing the vortex, http://www.instantweathermaps.com/GFS-php/strat.php?run=2018012406&var=HGT&lev=10mb&hour=135 if you run the chart shown on the MOD thread through you will see the warming just fades away. its still better than not having the warming at all because it still slows the zonal flow down up top which makes it less likely to affect the trop meaning the trop can do what it wants, unfortunately though BA' posts above that there is an increase in zonal flow in the GEFS members in week 2 and even looking at the op there wont be a technical SSW anytime soon (reversal at 10mb), however, we may not need one though as some interesting output in the trop has been showing in week 2 lately anyway.

The warming is the reason for the strong Pacific ridge that moves into the Arctic. This could play a very important role in getting deep cold to the uk if we get strong support from the MJO. Think 12/13.

[knocker]

 

[KyleHenry]

 

Pleasantly surprised with the energy contained inside the two initial pulses from wave 1 at the 1hPa level.

 

 

GFS is predicting PV relocation towards Eastern Canada a non to common event if it does transpires. Patience is a virtue of stratospherics but all worth it when we arrive at this point.

 

 

 

 

 

[KyleHenry]

[bluearmy]

The mid/upper strat becomes a pretty benign environment on the ec op charts from Berlin. The gefs continue to show an uptick in the extended period 

[Amir Odeh]

Hello All, 

this is my 3rd year viewing this thread. 

at the moment something surprsing me about the strat warming at 10mb.

the PV Vortex displaced toward north america, something i didnt see for the past 5 years. 

still cant understand the effect of this behavior on 500mb Anomaly , nor in which years something like this happend. 

 

i will be happy for someone posting the years something like this happen in the past.

[Interitus]

On 1/2/2018 at 17:32, Interitus said:

Just to counter some of the positivity here, for the GEOS forecast 30mb 80°N temperature of 189.94K for 10/1/18, the earliest that an SSW has been achieved is 24 days (which would be Feb 3rd). Although Jan 2009 does feature as an analogue at the moment - principally because of the period of VI - the wave 2 heights that led to that split was a spell above 2000m at 10mb - nothing like that has been forecast at the moment, with the middle vortex looking cold and largely barotropic

 

On 1/3/2018 at 11:39, Interitus said:

There are 5 SSW (first of winter, since 1979) where wave 2 is dominant over wave 1 at 60°N 10mb on average for a full fortnight beforehand - 22/2/79 (preceding 11 days w2 dominant), 1/1/85 (12 days), 21/2/89 (17 days), 24/2/7 (11 days but 3 days of w1 >1000 just before SSW) and 24/1/9 (15 days and 23 out of 24). The first four all had some wave 1 height contribution >1000m in the fortnight. But 2009 is unique in having no wave 1 >450 metres in the three weeks before, and four weeks after last w1 >1000m.

To get an idea of of duration of wave 2 (arbitrary height >1000m) and when it might need to appear in forecast charts - 22/2/79 10 days before SSW, 1/1/85 11 days, 21/2/89 17 days, 24/2/7 14 days, 24/1/9 13 days (the last 7 >2000m) - the average is 14 days, conveniently close to long range forecast length.

But then large wave 2 values is no guarantee - for one day heights >2000m SSW in 1979, 1985, 1989, 2009; no SSW following the Januaries 1982, 1986, 2014.

For longer periods - at least 1 week >1500m - SSW as above 79, 85, 89, 09 plus 07; no SSW - Jan 80, Jan 82, Jan 86, Jan 91, Feb 94, Feb 96, Feb 97, Jan 03, Jan 08, Dec 09, Jan 14.

Although some things may enhance the chance of a split a little, eg. a Nina'ish background, it is unlikely there will be an SSW this month and though wave 2 may feature at some point, indeed maybe at the death, a period of wave 1 is most likely to do the damage to begin with.

It's safe to call this now......another accurate prediction 

Wave 1 has, is, and will continue to do some preconditioning of the vortex, but there are signs from both ECM and GFS that this will be on the wane (partly causing its own demise by wave reflection changing trop pattern?) and wave 2 will become dominant first in the troposphere -

then onwards to the strat -

Forecast wave 2 heights above 1000m - bearing in mind previous post above, "pure" wave 2 dominated SSW have all had 1000m+ for a continuous period of at least 10 days up to the date of reversal so can keep an eye on this.

However whether it will persist is another matter - a number of the GFS runs are showing weakening of the strat anticyclone on the Pacific side, as depicted very nicely in this geop. animation from Prof Lopez Lang - shows initial wave 1 on Pacific side, maybe weakening later on after being joined by wave on European side -