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Was looking optimistic over the last few days but less so today.

 

Can't complain though since the E US has been quite cold and snowy. We wouldn't need a full SSW to keep it that way the rest of the winter. The PV has been entrenched into Canada for a while and another lower stratosphere split at some point in the next two weeks would most likely keep things cold. I like the wavebreaking we're seeing in the N. Atlantic. GFS showing warming events coming from that region and hopefully it'll be enough to knock the PV down some more. I've already convinced myself not to pay attention to the 6z forecasts...too much hope that gets dashed away in subsequent runs.

Yes but today even the 6z wasn't that great! The last hot run was last night's 18z.

 

Karyo

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Yes but today even the 6z wasn't that great! The last hot run was last night's 18z. Karyo

Deep breath then back to lurking and enjoying a very informative thread again this year :-) Overall pattern is promising rather than conclusive - dice in hand ready to roll - so let's just let it play out and enjoy whatever happens. Even if the UK misses out it will be instructive and fascinating for wherever in the Northern Hemisphere that benefits. I'm with the view a broad concensus of runs should be taken rather than hanging onto every run. Don't need the inter run drama of the mod thread here...please...this place is light relief by comparison ;-)
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hi gents.

I have been lurking in your forum for awhile.

I am starting to learn tids and bits through the vast array of posts in the website .

I see several dedicated and enthusiastic members posting here.

I have a few questions .

i have seen quite a bit of enthusiasm from yesterday's runs in regards to an SSW .

I noticed the following from Berlin (yesterday) ... see below

 

Posted Image

 

 

If an SSW was supposed to be pronouncing itself wouldn't we see an increase in temperature between 1-5 mb from 70N/90N?

forgive me for the lack of terminology capacity that u guys have.

I also do not see berlin ( again) showing anything that would actually give us more certainty from the following ...

 

Posted Image

 

-QBO is more pronounced but we see no drop in temps at 70N/90N at 10 hpa.

i would appreciate if someone would pitch in.

As recretos says ... he did not know much not too long ago.

I hope i can at least learn 10 % of what you guys know.

cheers

Edited by stratolearner
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Does anyone know the answer to the question as to what has gone wrong this winter - I mean even many milder than average winters during the 2000s produced some short cold spells at times - even the very mild 2006-07 season had around 3-4 days of colder weather in late Jan and a few days in the first half of Feb - this winter has been almost completely devoid of even a cold snap for most parts of the UK.  It may not come out quite as mild overall as 1988-89, but if February doesen't deliver something at some point it will still be on a par to 1988-89 for being completely devoid of anything remotely wintry.

 

History shows us that it is very rare to see a winter devoid of anything remotely wintry - even a winter like 1974-75 which more or less was, saw some decent cold in late March / early April.  2007-08 was devoid of anything wintry apart from cold Rex blocking but saw some decent cold setups in late March and in April.

 

What has gone wrong?  What bad building blocks have been in place to give us this absolutely dire winter, and it now almost looks set to join the 1988-89, 89-90, 97-98 horror show list now.  We have had a neutral ENSO in place, 88-89 Strong La Nina, 97-98 record Strong El Nino.  I know a neutral ENSO does not guarantee cold for the UK, but at least it generally means that a winter is unlikely to be very mild like this one has and looks to be.

 

It is often the case that very mild horror show winters occur close together - such as the very mild winter 89-90 came after the previous one - 74-75 occurred after a previous duff winter, 73-74.  A strong El Nino enhanced the 97-98 horror show - and La Ninas meant that the following two winters were pretty rubbish.  2006-07 came during the warmest 12 month period ever and a record warm second half of the year in 2006.  2007-08 was also a La Nina year and it followed on from the previous very mild winter in 2006-07.

 

We are of course not going to get a winter like 2009-10 or even 2012-13 every year, which due to the cold March, was effectively an extended cold winter with frequent cold spells from mid January up until early April, and looking at that period it was comparable to a decent cold winter.  Even in years close to colder winters milder winters do and have historically occurred - but no-one would have thought that winter 2013-14 would turn out in the "88-89 / 89-90, 97-98 horror show" territory.

 

No-one ever suggested it was likely that this winter would be a good one up there with 2009-10 and even the one last year - even the laws of averages suggested that this winter would be milder than those two, but I do not think on the other hand anyone expected that this winter would turn out a real stiniker and devoid of anything remotely wintry.  We have still only relatively recently (within the last decade) seen two stinkers, 2006-07 and 2007-08 - both of these were equally as awful as this one has been so far.

 

What has gone wrong with this winter - why can't trough disruption allow cold air from the east to reach us - the Greenland High has been completely absent - cold zonality has been absent, at least apart from Scotland.  Just why can't and haven't any of these happened this winter?

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Referring to my post from a week or so go, it's getting to the 'throwing in the towel' time....

 

Latest EC32 maintains its consistency from recent weeks and maintains a zonal outlook throughout the 3 weeks of February. Granted final week isn't covered, but there isn't a hint from this model at all in recent weeks of a pattern change and the continued 'back and forth' in terms of conditions within the strat are now beginning to lead me to think that time really is running out. Clearly ENS data from GFS, ECM, NAEFS and the likes, including MOGREPS as well is now covering the half way point of February and if anything there is a trend for temps to rise back to nearer average with time and with little evidence of anything cold by mid-Feb.

 

Could well have been a post for the Model thread, but still relating to the strat, the lack of any real significant warmings actually coming in the 'here and now' time frame, to me look as though will combine with what remains an organised vortex to essentially get us to winters end now. Clearly weeks back there was meant to be a significant warming late January/early February but that has not materialised to the likes of which the GFS, in particular, was highlighting.

 

Still a month to go and obviously first half of March may provide a very late window of opportunity, but given actual model guidance and output now out to mid-February time is running out and it could well be a better idea to just forget about this horrific winter in terms of relentless unsettled conditions and hope the next is something far better. It really is and has been a bad one for cold synoptics and even in some of the pre-2008/2007 winters whilst they were often wet, windy and mild at least they did produce a week or two of cold weather over the winter as a whole.

 

Regards, Matt.

It starting to look like we may not quite get the 'biggie' strat event that looked possible a few weeks ago with the GFS pulling away now from that idea. That to me was most likely to be the winter saviour (before winter started).

 

Option 1 anyone for Feb?

 

February

February is the most difficult month to predict, as there are two likely outcomes. The first is another average to slightly above average month temperature wise, with again average precipitation. The second outcome is for a significantly colder month with below average temperatures and the risk of heavy snow and easterly winds. This very much depends on whether we see a SSW in the stratosphere. In the second scenario the ridge that has been building towards Scandinavia will dominate the UK, whereas in the first outcome the trough to the west would be likely to dominate the UK.

 

 

YUK!

Edited by chionomaniac
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So February doesn't look promising. Any thoughts about what March may bring?

Karyo

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Any idea what's been causing the awful accuracy in the GFS temperature charts? The SSW last year was modeled weeks ago and was pretty much spot on ever since the warming was picked up at 384. GFS underestimating the strength of the vortex?

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6z is a good run with a much better split but hard to have any faith given its erratic output.

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6z is a good run with a much better split but hard to have any faith given its erratic output.

 

Haha this is ridiculous. Best not to believe anything until it gets into the high res output.

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It may be the 6z showing a split but it is literally all we have to cling on to.

Having said that, the split starts at +204, on the edge of high res, so something to watch most certainly.

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No offense to the people in here, but if you live in UK and expect the winters to be overall snowy and cold you live in the wrong place

 

The UK weather during winter is most of the time mild and little to no snow( the north part has more winter) but still not enough if you want snow for more than 3-4 weeks at row. My tip for you is move to one of these countries below

 

east/middle Poland,  the baltic countries, west Russia, Scandinavia ( not Denmark included) or Germany. 

 

The chances of snow/frost would increase much more than now, since the cold arctic air has a hard time getting more south than this during normal winters

 

And again sorry if my comment did upset anyone, i just want to be realistic at this moment. 

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No offense to the people in here, but if you live in UK and expect the winters to be overall snowy and cold you live in the wrong place

 

The UK weather during winter is most of the time mild and little to no snow( the north part has more winter) but still not enough if you want snow for more than 3-4 weeks at row. My tip for you is move to one of these countries below

 

east/middle Poland,  the baltic countries, west Russia, Scandinavia ( not Denmark included) or Germany. 

 

The chances of snow/frost would increase much more than now, since the cold arctic air has a hard time getting more south than this during normal winters

 

And again sorry if my comment did upset anyone, i just want to be realistic at this moment. 

This thread is to discuss/learn about the Stratosphere and its potential effect on weather patterns.... there is a nice introduction on the first page,  your comments would be better in here....Posted Image 78680-model-banter-moans-and-ramps-winter-201314

 

Its my first post in here after following this thread for last few years. Thanks to all, it is nice to see that the knowledge in here really seems to progess....one day I may even be able to understand some of It Posted Image

 

I do have a quick question for some more knowledgeable members.....I understood the strat and SSW are easier to model...is this correct and if so what is the typical FI mark in comparison to lower down.

Edited by beatpete

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It may be the 6z showing a split but it is literally all we have to cling on to.

 

I think to sum that up -  the models have been on the wind up all Winter.. Really had us chasing ghosts. Glad that fergieweather updated  to confirm about Glosea5 seeing an SSW earlier in Jan, and wasn't just imagining things.  If only that had come to fruition, we wouldn't even need to be chasing a 06z run, which whilst worthy of a ramp, as Recretos pointed out ran the other day with some data excluded, hence not to be trusted only matched by I think one 12z or 18z run, and as Matt writes it is fairly late in the day for meaningful impact. Brings new meaning to the phrase 'warm outlier'..

post-7292-0-54276800-1390922219_thumb.gipost-7292-0-85770100-1390921988_thumb.pn

post-7292-0-68526000-1390922307_thumb.gipost-7292-0-33865300-1390922329_thumb.gi

 

What has already impacted the vortex between December and the degradation of Vortex strength has created a loss of cold from the Arctic. Just not where we want it, as below.  

post-7292-0-43643700-1390921527_thumb.pn

 

Bottom line is that the Greenland Vortex is a thorn in the side for UK Winter and perhaps some re-analysis of jet activity in that region would be a good investigation, particularly with December in mind. Also read that the previous trend with splits modelled in this fashion have positioned the remaining vortex right in the same very location.

 

The Berlin charts are full of splits at different levels today, however not sure how these will filter through into what we will see in the output, time to relax and watch it all unfold and enjoy some snow on Friday !

post-7292-0-00774500-1390922049_thumb.gipost-7292-0-13704100-1390922056_thumb.gi

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Just looking through some of the other models, there is some support for the GFS evolution and in an earlier timeframe on some models, always baring in mind of course that there isn't the level of data as there is with the GFS, namely heights charts.

 

Posted Image

 

Posted Image

 

 

 

Posted Image

 

 

Posted Image

 

 

 

 

 

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No offense to the people in here, but if you live in UK and expect the winters to be overall snowy and cold you live in the wrong place

 

The UK weather during winter is most of the time mild and little to no snow( the north part has more winter) but still not enough if you want snow for more than 3-4 weeks at row. My tip for you is move to one of these countries below

 

east/middle Poland,  the baltic countries, west Russia, Scandinavia ( not Denmark included) or Germany. 

 

The chances of snow/frost would increase much more than now, since the cold arctic air has a hard time getting more south than this during normal winters

 

And again sorry if my comment did upset anyone, i just want to be realistic at this moment. 

This winter is far from the norm, as evidenced by 2 much warmer than average months.

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Just looking through some of the other models, there is some support for the GFS evolution and in an earlier timeframe on some models, always baring in mind of course that there isn't the level of data as there is with the GFS, namely heights charts.

 

 

And the key point lies more in those height charts than the by far "favoured" 10mb temperature. :)

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And the key point lies more in those height charts than the by far "favoured" 10mb temperature. Posted Image

 

Cant help thinking the NAVGEM heights chart would be decent though and maybe the CMA.

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NAVGEM reduces the stratospheric vortex (at least temperature-wise) to zero every run in app. 120 hrs time. It's been that way for the entire season. Either the data uploaded to meteociel are corrupted, or the model just does not make sense. 

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Cant help thinking the NAVGEM heights chart would be decent though and maybe the CMA.

 

Here it is, tho you should consider what Ruben is saying. Posted Image

 

Posted Image

 

In the meanwhile, 12z GFS comes out with a sobering thought. :)

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NAVGEM reduces the stratospheric vortex (at least temperature-wise) to zero every run in app. 120 hrs time. It's been that way for the entire season. Either the data uploaded to meteociel are corrupted, or the model just does not make sense. 

Here it is, tho you should consider what Ruben is saying. Posted Image

 

Posted Image

 

In the meanwhile, 12z GFS comes out with a sobering thought. Posted Image

 

 

Cheers, renders it useless then, oh well!

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This winter is far from the norm, as evidenced by 2 much warmer than average months.

 Do you have any maps to show? From December and January?

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 Do you have any maps to show? From December and January?

Here's January's from the MetOffice

 

http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_mean.html

 

December:

 

http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_mean2013.html

 

1.7c and 2.1c above average. That's as far from the norm as a 1 month constant cold spell is.

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 Do you have any maps to show? From December and January?

 

I know we don't live in Poland or Russia lol, but a few days/a week, of snow and frost is a reasonable goal in a UK winter. Hence the interest in the this thread, we all know the UK is rather unfortunately placed for a prolonged wintry spell, but more often than not a SSW will be beneficial to the general synoptic pattern than can deliver such a spell. So far this winter many have yet to see a flake of snow let alone a proper continental type freeze up. So although moving to your specified countries would no doubt give us what we seek, I think we will just have to continue our hunt for snow in the UK. And for longer term predations this thread, and the science behind Stratospheric forecasting, has been a very useful tool in winters past. And is proving to be so in this winter, though not with the results many many desire.

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      As ever, I will supply links to various stratospheric websites were forecasts and data can be retrieved and hope for another fascinating year of monitoring the stratosphere.
      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: https://www.netweather.tv/charts-and-data/stratosphere
      Instant weather maps: http://www.instantweathermaps.com/GFS-php/strat.php
       NASA Merra site: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
      Previous stratosphere monitoring threads:
      2016/17 https://www.netweather.tv/forum/topic/86485-stratosphere-temperature-watch-201617/
      2015/16 https://www.netweather.tv/forum/topic/84231-stratosphere-temperature-watch-20152016/
      2014/2015 https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/
      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/
      2010/2012 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/
    • By iapennell
      As promised I have piece together macroscale developments of sea-surface temperature and regional wind/pressure anomalies to provide a preliminary forecast for the coming winter.During October the global winds, pressure and temperature-patterns across the Northern Hemisphere gravitate towards their winter states, which they will tend to retain until late March.
      First thing though we need to list what we know so far:
      1) Sea surface temperatures are, in general well above normal across the North Atlantic with anomalies close to 4C for early October in the European Arctic section with anomalies of +6C off the eastern coast of the USA and in the Baltic. The section is part of the mid-North Atlantic about 45 to 55N and 20 to 40W where sea surface temperatures are up to 2C colder than usual. Such warmer than usual waters around the UK would directly warm any winds blowing over them more and would tend to support milder weather and more evaporation from the warmer seas would support increased rainfall. The cool patch in the North Atlantic is sufficiently far west for it to cause the southern part of the strong upper Westerlies to re-curve south over it and just to the east whilst the upper air would be encouraged to "re-curve" northwards having crossed the warmer waters around Britain: This would place an upper trough near to the UK and enhance wet, windy weather.  
      2) The North Pacific north of 20N is substantially warmer than normal with sea surface temperature anomalies generally 3 to 4C warmer than normal for early October. However the Equatorial central and eastern Pacific is colder than usual with anomalies up to 2C below normal. The development of La Nina with cool equatorial waters would promote weaker north-easterly Trade Winds over the Pacific between the Equator and a weaker subtropical high-pressure belt centred over warmer than usual waters of the North Pacific around 30 to 35N: Weaker NE Trade Winds impart less westerly atmospheric angular momentum (AAM) to the Northern Hemisphere's atmospheric circulation through frictional interaction with the sea-surface- particularly as less wind means a calmer sea-surface with very low coefficient of friction. There is correspondingly need for less of a sink for accumulated westerly momentum in higher latitudes which implies weaker westerlies reaching Britain with a correspondingly higher chance of cold-air outbreaks from Russia or the Arctic. 
      3) Arctic sea-ice extent has recovered remarkably during September and it's extent is close to the seasonal norm east of Greenland but the sea-ice extent remains some 500 km north of its normal October extent north of Alaska and the extreme east of Siberia. Open waters in the Arctic Ocean surrounding the sea-ice remains substantially (i.e. widely up to 4C warmer than normal for October however): This is likely to encourage the Circumpolar Vortex to be contracted as well as displaced towards the UK by up to 200 km, however the warmth of Arctic seas would encourage the strong baroclinic gradients to be shifted towards the Arctic. This lends support to deeper depressions encircling the Arctic close to 70N, particularly in the North Atlantic sector and the warmth of the oceans just to the south of them means rather more moisture latent-heat potential to fuel these storms. The northwards displacement of the Westerlies is likely to encourage them to be strong in any case because they have to blow harder closer to the axis of the Earth's rotation to offset the tropical, subtropical and polar easterlies as required by Conservation of Angular Momentum laws.
      4) Also supportive of a mild wet and windy winter is the fact that the Quasi Biennial Oscillation (QBO) at 30mb high above the Equator remains in Westerly phase. During August these stratospheric Equatorial Winds averaged just over 10 metres per second (23 mph) from the west. These stratospheric winds feed down into the general circulation and reach the mid-latitude jet-streams and Westerlies over three or four months. This suggests (strongly) that the coming winter will be mild wet and stormy.
      5) The Sun is now entering the quiet phase towards the end of Schwabe cycle 24: Indications are that the Sun is indeed going quieter than it has been for a few years. An active Sun produces Solar Flares which interact with the atmospheric circulation to increase the strength of the Circumpolar Vortex. Instead few (if any) magnetic storms from the Sun will be interacting with the Earth's atmosphere and instead (if anything) that just leaves tidal friction due to the Sun and Moon which affects the atmosphere as well as the oceans. The tidal effects on the atmosphere are very weak but these act to reduce the Earth's rotation by very mall amounts (these are significant over time, which is why Leap Seconds are added at the end of each year). The net effect of all this (weak phase of Solar Cycle, atmospheric tidal friction) would be to weaken the Westerlies a little.
      6) At least until mid November, the fact that sea-surface temperatures in the tropical Atlantic and Pacific just north of the Equator is likely to enhance tropical storm activity. More hurricanes and typhoons with strong easterlies on their northern flanks that enter the Northern Hemisphere circulation add Westerly AAM to the global atmospheric circulation. This increases the need for stronger Westerlies in higher latitudes to counter-balance them: This strongly hints to late autumn/early winter being wet, mild and stormy. However, from late January onwards the Intertropical Convergence Zone (ITCZ) will be south of the Equator and the fact that sea-surface temperatures in tropical waters just south of the Equator are also warmer than normal now suggests more tropical storms will occur there; Southern Hemisphere tropical depressions (sliding westwards along the ITCZ) have strong westerlies on their northern flank and it is these that will affect the Angular Momentum Budget of the Northern Hemisphere circulation by removing Westerly AAM through frictional impact with the underlying surface: This points to weaker Westerlies coming across the North Atlantic in January/February which would, other things being equal, increase the chances of much colder, drier spells reaching Britain from the east.  
      We can now put all this together to get some sort of prediction for Winter 2016/17:
      (Continued below)
    • By chionomaniac
      Welcome to the latest stratospheric temperature watch thread.
       
      A bit later this year with a new thread – but better late than never! It is now the 7th winter stratospheric temperature watch thread on netweather, and how much have we learnt in the past years!
       
      As ever, the first post will become both a reference thread and basic learning thread for those wanting to understand how the stratosphere may affect the winter tropospheric pattern, so forgive me for some repeat from previous years, but it is important that those new to the stratosphere have a place that they can be directed to in order to achieve a basic grasp of the subject.
       
      The stratosphere is the layer of the atmosphere situated between 10km and 50km above the earth. It is situated directly above the troposphere, the first layer of the atmosphere and the layer that is directly responsible for the weather that we receive at the surface. The boundary between the stratosphere and the troposphere is known as the tropopause. The air pressure ranges from around 100hPa at the lower levels of the stratosphere to below 1hPa at the upper levels. The middle stratosphere is often considered to be around the 10-30hPa level.
       

       
      Every winter the stratosphere cools down dramatically as less solar UV radiation is absorbed by the ozone content in the stratosphere. The increasing difference in the temperature between the North Pole and the latitudes further south creates a strong vortex – the wintertime stratospheric polar vortex. The colder the polar stratosphere in relation to that at mid latitudes, the stronger this vortex becomes. The stratospheric vortex has a strong relationship with the tropospheric vortex below. A strong stratospheric vortex will lead to a strong tropospheric vortex. This relationship is interdependent; conditions in the stratosphere will influence the troposphere whilst tropospheric atmospheric and wave conditions will influence the stratospheric state.
       
      At the surface the strength and position of the tropospheric vortex influences the type of weather that we are likely to experience. A strong polar vortex is more likely to herald a positive AO with the resultant jet stream track bringing warmer and wet southwesterly winds. A weaker polar vortex can contribute to a negative AO with the resultant mild wet weather tracking further south and a more blocked pattern the result. A negative AO will lead to a greater chance of colder air spreading to latitudes further south such as the UK.
       
       AO chart
       

       
      The stratosphere is a far more stable environment then the troposphere below it.
      However, the state of the stratosphere can be influenced by numerous factors – the current solar state, the Quasi Biennial Oscillation (QBO), the ozone content and distribution and transport mechanism, the snow cover and extent indices and the ENSO state to name the most significant. These factors can influence whether large tropospheric waves that can be deflected into the stratosphere can disrupt the stratospheric polar vortex to such an extent that it feeds back into the troposphere.
       
      Ozone Content in the stratosphere
       
       Ozone is important because it absorbs UV radiation in a process that warms 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. The ozone content in the polar stratosphere has been shown to be destroyed by CFC's permeating to the stratosphere from the troposphere. The overall ozone content in the polar stratosphere will help determine the underlying polar stratospheric temperature, with higher contents of ozone leading to a warmer polar stratosphere. The ozone levels can be monitored here: 
       
      http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/index.shtml
       
      One of the main influences on the stratospheric state 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 thought 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 can be critical throughout the winter.
       
      Diagram of the descending phases of the QBO: (with thanks from http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/qbo/index.html )
       

       
       
      The QBO has been shown to influence the strength of the BDC, depending upon what phase it is in. The tropical upward momentum of ozone is stronger in the eQBO , whereas in the wQBO ozone transport is stronger into the lower mid latitudes, so less ozone will enter the upper tropical stratosphere to be transported to the polar stratosphere as can be seen in the following diagram.
       

       
      http://www.atmos-chem-phys.net/13/4563/2013/acp-13-4563-2013.pdf
       
      However, the direction of the QBO when combined with the level of solar flux has also been shown to influence the BDC. When the QBO is in a west phase during solar maximum there are more warming events in the stratosphere, as there is also during an easterly phase QBO during solar minimum, so the strength of the BDC is also affected by this – also known as the Holton Tan effect .
       
      http://strat-www.met.fu-berlin.de/labitzke/moreqbo/MZ-Labitzke-et-al-2006.pdf
      http://onlinelibrary.wiley.com/doi/10.1002/jgrd.50424/abstract  
      http://onlinelibrary.wiley.com/doi/10.1002/2013JD021352/abstract
       
       
      The QBO is measured at 30 hPa and has entered a westerly phase for this winter. As mentioned warming events are more likely during solar maximum when in this westerly phase – with the solar flux below 110 units. Currently, we have just experienced a weak solar maximum and the solar flux heading into winter is still around this mark. This doesn’t rule out warming events, but they will not be as likely – perhaps if the solar flux surges then the chance will increase.
       
      Latest solar flux F10.7cm:
       

       
      http://www.swpc.noaa.gov/products/solar-cycle-progression
       
       
      Sudden Stratospheric Warmings:
       
      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 mid latitude and colder polar stratospheric air (and ozone levels) and this is very difficult to penetrate. SSWs can be caused by large-scale planetary tropospheric (Rossby) 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 which can seriously disrupt the stratospheric vortex, leading to a slowing or even reversal of the vortex.
       
       
      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 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 and patterns of convection. These can help determine the position and amplitude of the long wave undulations – Rossby waves - that are formed at the barrier between the tropospheric polar and Ferrel cells. The exact positioning of the Rossby waves will be influenced by (amongst other things) the pulses of tropical convection – such as the phase of the Madden Jullian Oscillation and the background ENSO state 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.
       
       
      If the deflection of the Rossby Wave then a wave breaking event occurs – similar to a wave breaking on a beach – except this time the break is of atmospheric air masses. Rossby wave breaks that are directed poleward can have a greater influence on the stratosphere. The Rossby wave breaks in the troposphere can be demonstrated by this diagram below –
       
      RWB diagram:
       

       
      https://www.jstage.jst.go.jp/article/jmsj/86/5/86_5_613/_pdf
       
       
       
       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 places at once then we will see a wave 2 type disturbance of the vortex which could ultimately squeeze the vortex on half and split it – and if these are strong enough then we would see a displacement SSW and split SSW respectively. The SSW is defined by a reversal of mean zonal mean 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
       
      A demonstration of the late January 2009 SSW that was witnessed in the first strat thread has been brilliantly formulated by Andrej (recretos) and can be seen below:
       

       
       
      The effects of a SSW can be transmitted into the troposphere as the downward 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. A recent paper has shown how the modelling of SSW and strong vortex conditions have been modelled over a 4 week period. This has shown that there is an increase in accuracy following weak or strong vortex events – though the one area that the ECM overestimates blocking events following an SSW at week 4 is over Northwestern Eurasia.
       
      http://iopscience.iop.org/article/10.1088/1748-9326/10/10/104007
       
      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.
       
      Six stage Cohen Process:
       

       
       
      The effect of warming of the Arctic ocean leading to colder continents with anomalous wave activity penetrating the stratosphere has also been postulated
       
      http://www.tos.org/oceanography/archive/26-4_cohen.pdf
       
       
      Last year we saw a large snow gain but unfortunately tropospheric atmospheric patterns prevented the full potential of these being unleashed on the stratosphere – hence no SSW, but this winter could be different, but we will have to wait until the end of October.
       
       
       ENSO Influences
       
      One of the main influences in the global atmospheric state this winter will be the upcoming El Nino, and that is forecast to be the strongest since 1997. Studies have shown that SSW’s are more likely during strong ENSO events ( http://www.columbia.edu/~lmp/paps/butler+polvani-GRL-2011.pdf) 
       but also that there is a particular pattern of upward propagating waves. During El Nino events wave formation is suppressed over the Indian Ocean Basin whilst it is enhanced over the Pacific Ocean
       
      http://link.springer.com/article/10.1007%2Fs00382-015-2797-5
       
      The ENSO pathway taken may be all critical this year as can be demonstrated by this paper  http://www.columbia.edu/~lmp/paps/butler+polvani+deser-ERL-2014.pdf
       
      This can lead us to suggest that a rather distinctive wave 1 pattern is likely this winter with the trigger zone likely to be over the north Pacific in the form of a quasi stationary enhanced wave 1 – a traditional Aleutian low SSW trigger pattern is suggested by Garfinkel et al ( http://www.columbia.edu/~lmp/paps/garfinkel+etal-JGR-2012.pdf ) and this should be expected at some point this winter.
       
       
       

       
       
       
      The reported incidence of SSW in EL Nino years is roughly around 60%  - which is more than ENSO neutral years.  A big question remains however, whether the ENSO wave 1 pattern will override the negative HT effect that the wQBO with the reducing solar ouput link brings. And even if it does, and we do achieve a displacement SSW, the next question is how will this affect the Atlantic sector of the Northern Hemisphere? My suspicion is that even if we do achieve a SSW this winter it will be in the second half, and also any subsequent blocking may not be quite right for the UK and, that if we were to achieve a –ve NAO, any block will be nearer Canada than Iceland, leaving the Atlantic door ajar.  It is still too early this winter to be making any definitive forecasts – the next 6 weeks are very important stratospherically, determining in what vein winter will start. Already we are seeing a forecast of weak wave activity disrupting the growing vortex and it will be interesting to see if this is repeated during November.
       
      And it will be especially interesting to see what occurs in November and what is forecast for December before winter starts because typical strong El nino wQBO stratospheric composite analogues tell an opposite story. They suggest that the stratospheric vortex will be disrupted and weaker early in the winter before gaining in strength by February.
       
      December:
       

       
      January
       

       
      February
       

       
      The mean zonal winds are already forecast to be below average so perhaps an early disrupted vortex is more likely this year!
       

       
      As ever, I will supply links to various stratospheric websites were forecasts and data can be retrieved and hope for another fascinating year of monitoring the stratosphere.
       
       
       
      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
       
       NASA Merra site: http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html
       
       
      Previous stratosphere monitoring threads:
       
      2014/2015 https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/
       
      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/
       
      2010/2012 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/
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