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You sound cautiously pessimistic this year Chio - but I'll draw some crumbs of comfort from the suggestion of a weak vortex early on and then a potential SSW later in the season that MIGHT bring more blocking. Enough to make sure that this is the best thread once again of the winter months... and maybe the atlantic cold pool can affect the jet enough to aid in the disruption of the atlantic weathertrain...

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You sound cautiously pessimistic this year Chio - but I'll draw some crumbs of comfort from the suggestion of a weak vortex early on and then a potential SSW later in the season that MIGHT bring more blocking. Enough to make sure that this is the best thread once again of the winter months... and maybe the atlantic cold pool can affect the jet enough to aid in the disruption of the atlantic weathertrain...

I think cautiously pessimistic at this point is a fair assessment. But I am not ruling out any surprises - especially early winter before the vortex cranks up. There are slightly conflicting signals which means that a straightforward El Nino winter forecast is anything but that!

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I think cautiously pessimistic at this point is a fair assessment. But I am not ruling out any surprises - especially early winter before the vortex cranks up. There are slightly conflicting signals which means that a straightforward El Nino winter forecast is anything but that!

 Not providing odds of any nature

 

This is an superb dissection of an atmospheric mode that was within last 7 years non existent. Vortex wins.

 

Any forecasts you see excluding the wintertime variations of the vortex you know will be wrong ( that includes Nino analogs and SSTs). Hint

 

:)

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Hi Chio, first of all many thanks for this wonderfull summary! I will give it some attention to the weather geeks in the Low Countries.

 

Two small things. In the first selection of years (december chart) I noticed 1962. I think you mean 1982?

 

And in Januar 1998 in stead of 1996?

Edited by sebastiaan1973
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http://www.terradaily.com/reports/Forecasters_look_higher_for_clues_to_winter_weather_999.html

 

According to this publication, stratospheric forecasting can double the accuracy of forecasts for 2-4 weeks ahead.

 

 

Fantastic summary there as usual Chiono. I've looked at 500 mb height composites for February under W QBO and a strong El Nino and found a signal for anomalously high pressure west of the UK with a trough over Scandinavia... but no signal for the high latitudes either way, despite that vicious looking 10 mb composite. Delays working down to the troposphere perhaps?.

 

The high heights west of the UK appear to be in large part a consequence of the Pacific jet barreling into the Atlantic from around Florida to The Azores Isles.

 

 

Having said that, there's an interesting progression when looking at 10 mb, 30 mb and 100 mb levels for February. I've used 1958 instead of 2003 (i.e. only strong El Nino + W QBO winters) but the theme is broadly similar:

 

FebStrat_10_30_100mb_GPH.PNG

 

Increasing signs of a ridge over Greenland, but more west-based in terms of the -ve NAO... which is in line with your concerns but could be adding to the strength of positive height anomalies west of the UK at the 500 mb level (which are around +10 dam).

Edited by Singularity
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http://onlinelibrary.wiley.com/doi/10.1002/2013JD021343/abstract

-> we are in a declining phase of the solar cycle.

Using 13 solar cycles (1869–2009), we study winter surface temperatures and North Atlantic oscillation (NAO) during four different phases of the sunspot cycle: minimum, ascending, maximum, and declining phase. We find significant differences in the temperature patterns between the four cycle phases, which indicates a solar cycle modulation of winter surface temperatures. However, the clearest pattern of the temperature anomalies is not found during sunspot maximum or minimum, but during the declining phase, when the temperature pattern closely resembles the pattern found during positive NAO. Moreover, we find the same pattern during the low sunspot activity cycles of 100 years ago, suggesting that the pattern is largely independent of the overall level of solar activity.

 

So the pattern described by Chio could be the right one.

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Thanks Chio for such a superb opening Post, started to follow

And try to understand this thread last year, and with such

Excellent posts from the knowledgeable posters in this thread

I am starting to understand (although still a long way to go) and

Learn this subject of the weather, thanks again and keep up

The good work.

C.S

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Ah.. The first proper sign of winter approaching, not the geese flying overhead, leaves falling from trees but Chiono opening the Strat thread! The second sign naturally is the Berlin strat charts fully opening for business on the 1st of November :-)

Fantastic summary, as always, Chiono, probably cementing most people's thoughts, which is much less (on occasion, wild!) optimism aka 14/15's E-QBO / high snow cover pre-winter frenzy and a more tempered W-QBO / declining solar cycle / dice generally less loaded on paper viewpoint. But as always a strong EL Nino will be the wild card here, plenty up for grabs. Sustained Wave1 activity looks a likely outcome and as we know displacement can be good for us but more often than not a thorn in our side as cold plunges down through Eastern Europe or away to our west down through the Mid Atlantic, possibly the form horse this time around. But better have wave activity than not, especially early winter as the vortex will be winding itself up and being fuelled from the W-QBO as well no doubt.

Less proper sustained blocking but with a bit of luck thrown in, I can see a couple of real cold snowy spells coming about in the way 1981 produced. Now that sounds like wild optimism! :-)

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Hi Chio, first of all many thanks for this wonderfull summary! I will give it some attention to the weather geeks in the Low Countries.

 

Two small things. In the first selection of years (december chart) I noticed 1962. I think you mean 1982?

 

And in Januar 1998 in stead of 1996?

The reanalysis data isn't that clear. I used yr's 82/83, 87/88, 97/98, 02/03 - perhaps I should have included 57/58 as well and if I had have done then DEC and Jan would have been the same, but Feb would have had a completely different look to it because of the Feb 58 SSW.

 

post-4523-0-13764900-1445171212_thumb.pn

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While not Nino's, those strat charts do remind one a little of winters 09 and 11. They were both +QBO winters.

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http://www.terradaily.com/reports/Forecasters_look_higher_for_clues_to_winter_weather_999.html

 

According to this publication, stratospheric forecasting can double the accuracy of forecasts for 2-4 weeks ahead.

 

 

Fantastic summary there as usual Chiono. I've looked at 500 mb height composites for February under W QBO and a strong El Nino and found a signal for anomalously high pressure west of the UK with a trough over Scandinavia... but no signal for the high latitudes either way, despite that vicious looking 10 mb composite. Delays working down to the troposphere perhaps?.

 

The high heights west of the UK appear to be in large part a consequence of the Pacific jet barreling into the Atlantic from around Florida to The Azores Isles.

 

 

Having said that, there's an interesting progression when looking at 10 mb, 30 mb and 100 mb levels for February. I've used 1958 instead of 2003 (i.e. only strong El Nino + W QBO winters) but the theme is broadly similar:

 

FebStrat_10_30_100mb_GPH.PNG

 

Increasing signs of a ridge over Greenland, but more west-based in terms of the -ve NAO... which is in line with your concerns but could be adding to the strength of positive height anomalies west of the UK at the 500 mb level (which are around +10 dam).

Hi thanks singularity. The publication that you quote is based from the paper linked to by Tripathia and Charlton et al in the first post (http://iopscience.iop.org/article/10.1088/1748-9326/10/10/104007 ) and also in the last thread - the forecasting by the ECM improves in both Vortex Intensification periods and SSW's.

 

We can see in VI strong events that if anything over the UK the increased temperature anomaly observed is slightly underestimated by the model through weeks 1-4 but overall the accuracy if very good

 

post-4523-0-39699500-1445177063_thumb.pn

 

Whereas typically in weak vortex events the observed overall model accuracy is again improved compared to average but week 4 there is an overestimation of negative anomalies over northern Eurasia - but fairly accurate for the UK

 

post-4523-0-05923800-1445177435_thumb.pn

 

Your findings regarding anomalies towards the troposphere are accurate and with a 'ridgy' Atlantic there may be periods where this exteneds towards us leaving benign 'warm' high pressure episodes this winter.

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I thought a strong El Nino typically brings a mild first half of winter and cooler 2nd half. Interesting that the analogues are going for the opposite. So many mixed signals this year.

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Hi thanks singularity. The publication that you quote is based from the paper linked to by Tripathia and Charlton et al in the first post (http://iopscience.iop.org/article/10.1088/1748-9326/10/10/104007 ) and also in the last thread - the forecasting by the ECM improves in both Vortex Intensification periods and SSW's.

 

We can see in VI strong events that if anything over the UK the increased temperature anomaly observed is slightly underestimated by the model through weeks 1-4 but overall the accuracy if very good

 

attachicon.gifScreen Shot 2015-10-18 at 14.56.25.png

 

Whereas typically in weak vortex events the observed overall model accuracy is again improved compared to average but week 4 there is an overestimation of negative anomalies over northern Eurasia - but fairly accurate for the UK

 

attachicon.gifScreen Shot 2015-10-18 at 14.56.59.png

 

Your findings regarding anomalies towards the troposphere are accurate and with a 'ridgy' Atlantic there may be periods where this exteneds towards us leaving benign 'warm' high pressure episodes this winter.

 

You're very welcome  :hi:

 

Taking the two very strong El Nino events from the past half-century in isolation (82/83 and 97/98) does produce 500 mb anomalies that feature a band of positive height anomalies extending right across the North Atlantic and just about into the UK. Given how the surface patterns relate to this, I am keen to make sure I have other things to occupy my mind in the face of 'limpet highs' sat in undesirable locations. Let alone combinations of that with high pressure over Europe which seems likely to happen at times given how the extended Pacific jet displaces the Azores High to the east (or so it appears from those analogue years).

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Congrats on a new season and a great new intro post! :)

 

I have nothing major to share, just some forecast anomalies, showing the GEFS and GFS going for a bit less organised vortex going into November, as expected.

 

geopotentialheightisobar.png geopotentialheightisobar.png

 

temperatureisobaric-in-1.png temperatureisobaricens-i.png temperatureisobaricunwei.png

 

The zonal wind zonal mean forecast from GFS does show a less organised vorex, also compared to this time last year. Of course its just a forecast. 

 

u-componentofwindisobari.png u-componentofwindisobari.png

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Sorry guys, I am looking for the archived first Strat thread or the earliest one available. Can't seem to find it, although I am on a phone - which probably doesn't help- can anyone link it for me please ?

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All the previous strat threads are linked to in the first post....

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Sorry guys, I am looking for the archived first Strat thread or the earliest one available. Can't seem to find it, although I am on a phone - which probably doesn't help- can anyone link it for me please ?

Is this what you are looking for? :)https://forum.netweather.tv/topic/50299-stratosphere-temperature-watch/

You should have seen it rooted at the bottom of the post.

Edit: it is great to see this thread up and running but I'll remain as bystander it is quite a complicated subject.

Edited by Daniel*
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Top quality intro, as always. :good:

 

I had posted the sessions for the international conference on sun -climate relations in the climate thread but there was a lot of interesting new research (particularly on Wednesday)  that relates to the stratosphere.

 

Conference topics with abstracts.

 

http://scc.geomar.de/frontend/index.php?page_id=506&v=List&do=0&day=121

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Top quality intro, as always. :good:

 

I had posted the sessions for the international conference on sun -climate relations in the climate thread but there was a lot of interesting new research (particularly on Wednesday)  that relates to the stratosphere.

 

Conference topics with abstracts.

 

http://scc.geomar.de/frontend/index.php?page_id=506&v=List&do=0&day=121

 

 

Thanks Nouska - looks like some quality topics in there. Do you subscribe to the strat list?

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Excellent introduction

 

It will be interesting to see how the strong Nino matches up with the +QBO. I'd place bets that the strong Nino with wave breaking events in the N. Pacific and perhaps N. Atlantic that will eventually win out but I think it will be rather difficult. As you've stated, the chances of a SSW are heightened with a Nino. Should be a fun battle. 

 

Cheers from across the pond on another insightful thread. There is much to be learned about the troposphere-stratosphere dynamic. 

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As ever Chiono a superb summary of the runners and riders in this winters weather stakes.

 

Have followed the start thread for a few years now since the days of the late lamented Glacier Point.  it is clear that trying to make prognostications for the coming winter

without taking into account the potential state of the vortex and strat connections is really just p*****g in the wind.

 

Look forward to your future updates Chiono  and also posts from other knowledgable guys like Lorenzo, Recreteos etc.

 

Thanks for all your hard work and the time you put in.

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As ever Chiono a superb summary of the runners and riders in this winters weather stakes.

 

Have followed the start thread for a few years now since the days of the late lamented Glacier Point.  it is clear that trying to make prognostications for the coming winter

without taking into account the potential state of the vortex and strat connections is really just Tut**g in the wind.

 

Look forward to your future updates Chiono  and also posts from other knowledgable guys like Lorenzo, Recreteos etc.

 

Thanks for all your hard work and the time you put in.

The late lamented GP is back with us. Happy days  :)

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    • By chionomaniac
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      The ozone content in the polar stratosphere has been shown to be destroyed by CFC's permeating to the stratosphere from the troposphere but there can be other influences as well. Ozone is important because it absorbs UV radiation which creates warming of the stratosphere. The Ozone is formed in the tropical stratosphere and transported to the polar stratosphere by a system known as the Brewer-Dobson –Circulation (the BDC). The strength of this circulation varies from year to year and can in turn be dictated by other influences.
       
      One of these influences is the QBO. This is a tropical stratospheric wind that descends in an easterly then westerly direction over a period of around 28 months. This can have a direct influence on the strength of the polar vortex in itself. The easterly (negative ) phase is though to contribute to a weakening of the stratospheric polar vortex, whilst a westerly (positive) phase is thought to increase the strength of the stratospheric vortex. However, in reality the exact timing and positioning of the QBO is not precise and the timing of the descending wave is critical throughout the winter.
       
      The direction of the QBO when combined with the level of solar flux has been shown to influence the BDC. When the QBO is in a west phase during solar maximum there are more warming events (increased strength BDC) in the stratosphere as there is also during an easterly phase QBO during solar minimum.( http://strat-www.met...-et-al-2006.pdf) (http://onlinelibrary....50424/abstract)
       
      The QBO is measured at 30 hPa and has entered an easterly phase for this winter. As mentioned warming events are more likely during solar minimum – solar flux below 110 units. Currently, we have just experienced a weak solar maximum and the solar flux heading into winter is slightly above 110 units. This doesn’t rule out warming events, but they will not be as likely unless the solar flux continues to drop prior to winter.
       

       
       
       
      One warming event that can occur in the stratospheric winter is a Sudden Stratospheric Warming (SSW) or also known as a Major Midwinter Warming (MMW). This as the name suggests is a rather dramatic event. Normally the polar night jet at the boundary of the polar vortex demarcates the boundary between warmer tropical and cooler polar stratospheric air (and ozone levels) and is very difficult to penetrate. SSWs can be caused by large-scale planetary waves being deflected up into the stratosphere and towards the North Pole, often after a strong mountain torque event. These waves can introduce warmer temperatures into the polar stratosphere and can seriously disrupt the stratospheric vortex, leading to a slowing or even reversal of the vortex. This year if the solar flux drops below 110 units then the chances of a SSW increase - as can be seen by the following chart.
       

       
      Any SSW will be triggered by the preceding tropospheric pattern - in fact the preceding troposheric pattern is important in disturbing the stratospheric vortex even without creating a SSW.  Consider a tropospheric pattern where the flow is very zonal - rather like the positive AO phase in the diagram above. There has to be a mechanism to achieve a more negative AO or meridional pattern from this scenario and there is but it is not straightforward.  It just doesn't occur without some type of driving mechanism. Yes, we need to look at the stratosphere - but if the stratosphere is already cold and a strong polar vortex established, then we need to look back into the troposphere. In some years the stratosphere will be more receptive to tropospheric interactions than others (such as the eQBO this year) but we will still need a kickstart from the troposphere to feedback into the stratosphere. This kickstart will often come from the tropics in the form of pulses of convection interacting with long wave undulations in the polar vortex which influence the positions of the sub tropical jet stream and polar jet streams respectively. The exact positioning of the large scale undulations (or Rossby waves) will be influenced by (amongst other things) the pulses of tropical convection (aka the phase of the MJO) and that is why we monitor that so closely. These waves will interact with land masses and mountain ranges which can absorb or deflect the Rossby waves disrupting the wave pattern further - and this interaction and feedback between the tropical and polar systems is the basis of how the Global Wind Oscillation influences the global patterns. The ENSO state will influence the GWO base state
       
      If the deflection of the Rossby Wave is great enough then the wave can be deflected into the stratosphere. This occurs a number of times during a typical winter and is more pronounced in the Northern Hemisphere due to the greater land mass area. Most wave deflections into the stratosphere do change the stratospheric vortex flow pattern - this will be greater if the stratosphere is more receptive to these wave breaks (and if they are substantial enough, then a SSW can occur). The change in the stratospheric flow pattern can then start to feedback into the troposphere - changing the zonal flow pattern into something with more undulations and perhaps ultimately to a very meridional flow pattern especially if a SSW occurs - but not always. If the wave breaking occurs in one place then we see a wave 1 type displacement of the stratospheric vortex, and if the wave breaking occurs in two place then we will see a wave 2 type disturbance of the vortex which could ultimately squeeze the vortex on half and split it – a split vortex SSW. The SSW is defined by a reversal of mean zonal winds from westerly to easterly at 60ºN and 10hPa. This definition is under review as there have been suggestions that other warmings of the stratosphere that cause severe disruption to the vortex could and should be included.  http://birner.atmos.colostate.edu/papers/Butleretal_BAMS2014_submit.pdf
       
      The effects of a SSW can be transmitted into the troposphere as the propagation of the SSW occurs and this can have a number of consequences. There is a higher incidence of northern blocking after SSW’s but we are all aware that not every SSW leads to northern blocking. Any northern blocking can lead to cold air from the tropospheric Arctic flooding south and colder conditions to latitudes further south can ensue. There is often thought to be a time lag between a SSW and northern blocking from any downward propagation of negative mean zonal winds from the stratosphere. This has been quoted as up to 6 weeks though it can be a lot quicker if the polar vortex is ripped in two following a split SSW.
       
      One noticeable aspect of the recent previous winters is how the stratosphere has been susceptible to wave breaking from the troposphere through the lower reaches of the polar stratosphere - not over the top as seen in the SSWs. This has led to periods of sustained tropospheric high latitude blocking and repeated lower disruption of the stratospheric polar vortex. This has coincided with a warmer stratosphere where the mean zonal winds have been reduced and has led to some of the most potent winter spells witnessed in recent years.
       
      We have also seen in recent years following Cohen's work the importance of the rate of Eurasian snow gain and coverage during October at latitudes below 60ºN. If this is above average then there is enhanced feedback from the troposphere into the stratosphere through the Rossby wave breaking pattern described above and diagrammatically below.
       

       
       
      And it appears that the reduction in Arctic sea ice may be contributing to this mechanism and this should be factored in to any forecast.  http://web.mit.edu/jlcohen/www/papers/Cohenetal_NGeo14.pdf
       
       
      So that leaves us to the try and forecast what will happen in the stratosphere this year. Out of the many variables what we do know at the moment is that the QBO is descending easterly and that we are probably entering El Nino conditions – although weak presently. And as mentioned earlier, the level of solar flux is slightly above conditions that are favourable for SSW’s. Despite this, conditions are favourable enough to suggest that we will see a warmer than average stratosphere this year. Evidence of this may already be suggested by an enhanced BDC in the Southern Hemisphere leading to a possible early final warming.
       
       If we look at 500hPa analogue composites for comparable easterly QBO/ El Nino 'lite' years (holding off on solar flux analogues just yet) then we see that the suggestions are that the polar vortex will have positive anomalies in December and January, before the vortex gains strength later in the winter. I would put the likelihood of an SSW at around 80% with the peak time for this to occur around early January. http://www.columbia.edu/~lmp/paps/butler+polvani+deser-ERL-2014.pdf
       
      December
       

       
      January
       

       
      February
       

       
       
      It’s a little too early to suggest how exactly this will effect the troposphere until we see other data - including the updated solar flux and ENSO as well as the SAI, SCE values. But all in all, if the stratosphere behaves as we expect at this point, then tropospheric northern blocking would be favoured during the winter leading to a negative AO index and mid latitude polar episodes being experienced.
       
      But after last year, when the stratosphere cooled dramatically, it is best that we remain cautious and wait to see how cold the stratosphere becomes over the next 6 weeks prior to winter, and how this may subsequently affect the strength of the polar vortex.
       
      As ever the best sites to monitor the stratosphere and forecasts are listed below:
       
      GFS: http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/
       
      ECM/Berlin Site: http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html
       
      Netweather: http://www.netweather.tv/index.cgi?action=stratosphere;sess=75784a98eafe97c5977e66aa65ae7d28
       
      Instant weather maps: http://www.instantweathermaps.com/GFS-php/strat.php
       
      Analysis can be found here: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
       
      http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/
       
       
       
       
      Previous NW stratosphere monitoring threads:
       
      2013/2014 https://forum.netweather.tv/topic/78161-stratosphere-temperature-watch-20132014/
       
      2012/2013 https://forum.netweather.tv/topic/74587-stratosphere-temperature-watch-20122013/
       
      2011/2012 https://forum.netweather.tv/topic/71340-stratosphere-temperature-watch-20112012/
       
      2010/2011 https://forum.netweather.tv/topic/64621-stratosphere-temperature-watch/?hl=%20stratosphere%20%20temperature%20%20watch
       
      2009/2010 https://forum.netweather.tv/topic/57364-stratosphere-temperature-watch/
       
      2008/2009 https://forum.netweather.tv/topic/50299-stratosphere-temperature-watch/
       
      Here's hoping for another exciting and intriguing season.
       
      Ed
       
      PS I look forward to all the contributers on this thread. It has grown from strength to strength over the years which has helped increase our knowledge of this fascinating and important subject - and there have been a core of extremely knowledgeable contributers from both national and international quarters and I thank them all and ask them to keep the discussion coming!
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