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Stratosphere and Polar Vortex Watch 2020


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Posted
  • Location: Ludgershall, Wiltshire
  • Location: Ludgershall, Wiltshire
    4 minutes ago, General Cluster said:

    I wouldn't worry about it, Don... Sorry Crewe, but how many strat, ENSO, or any other winter forecasts (during October) have ever yielded fruit? I reckon I'll just wait and see.. or leave it up to Michael Fish!🤓

    True and we don’t know how strong this La Niña is going to get yet.  However, the awol QBO is a frustration and a concern in general.

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    It has been interesting to see ECM strat disruption undermodelled this season so far. The wave 1 warming we have been going through was upgraded at short range, and again we have an upgrade in wave 2

    This might be a good time to remind everyone that the Stratosphere charts on Meteociel will not show you whether there is a split in the polar vortex or not - the polar vortex is not just a chunk of c

    As always, a great animation of the SPV from Andrej.  

    Posted Images

    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT
    39 minutes ago, CreweCold said:

    Looking at the strat and trop forecast charts, it looks as though there will be an easy, early connect. Given the characteristics of the SPV at present I think we can begin to count out an outlandish start to the winter season (1995/1996 2010/2011 came up as analogues initially). 

    Whilst i'm relatively confident we'll see some cool/cold PM incursions from time to time (providing some snow to prone NW areas), I think the chances of a more deep seated nationwide cold spell has diminished somewhat for the early winter period. Though I'm willing to go along with the notion of perhaps some later season cold via a possible SSW?

     

    Making assumptions now for the entire winter based on the october strat is a risky business ( same as assuming a slower start means narnia )

    The current forecast gets the vortex to 30 M/S

    23650BD9-CE95-4197-9C3E-3C885484FDB3.thumb.jpeg.c6f501e94fd589ead31def2c12dd9d8f.jpeg

    The years you mention reached 40M/S in some cases although the theme of some sort of sharp reduction in November is apparent.

    3E9EBA15-C7DF-4BD8-8086-42ACF31FB985.thumb.jpeg.23cc5ad2958f6b81beb94fa4ee6f53fb.jpegC0CE6E0C-D96C-4E6B-9766-CF07921410C2.thumb.jpeg.80b8028d36958cf9e8c5e0b1abe14f32.jpeg296D4CD3-A892-4611-9860-A27DDAD50CD6.thumb.jpeg.28857dd7f495523041a8195b5ad32537.jpeg296D4CD3-A892-4611-9860-A27DDAD50CD6.thumb.jpeg.28857dd7f495523041a8195b5ad32537.jpeg

    90E69317-6E7E-432D-A99E-BB88C5F32D53.jpeg

     

    The key time for 2020/2021 Winter is the period post 05th Nov - Start of December as we dip off from that first 30M/S maxima...

    CE2B2E89-7965-4BE3-9025-CAF003816B22.thumb.jpeg.3acdeb9cccba87adefa88c7f187e73a3.jpeg

    Edited by Steve Murr
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    Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
    20 minutes ago, Don said:

    True and we don’t know how strong this La Niña is going to get yet.  However, the awol QBO is a frustration and a concern in general.

    It's more annoying that it's been the EQBO getting blocked both times!

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    Posted
  • Location: Ludgershall, Wiltshire
  • Location: Ludgershall, Wiltshire
    2 minutes ago, CreweCold said:

    It's more annoying that it's been the EQBO getting blocked both times!

    Absolutely and what’s concerning is it’s happened twice within 5 years.  Something is definitely up and I suspect it’s a symptom of climate change.

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    Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
    32 minutes ago, Steve Murr said:

     

     

    The years you mention reached 40M/S in some cases although the theme of some sort of sharp reduction in November is apparent.

    296D4CD3-A892-4611-9860-A27DDAD50CD6.thumb.jpeg.28857dd7f495523041a8195b5ad32537.jpeg

     

     

    The key time for 2020/2021 Winter is the period post 05th Nov - Start of December as we dip off from that first 30M/S maxima...

     

    Surprising 1995/96 - you wouldn't think the level of cold / snow of that winter would have happened with those statospheric zonal wind charts, above average pretty much right the way through.

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    2 hours ago, CreweCold said:

    Not worried about the sock as I don't think we'll be significantly milder than average overall!

    Just skip over the border to Wales and you have the excuse you won’t be able to buy a sock!

    Yes, I agree signals have got worse quite quickly from just a few days ago.  Not good if we’re putting all our chips on a SSW yet again.  

    Edited by Mike Poole
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    Posted
  • Location: Ludgershall, Wiltshire
  • Location: Ludgershall, Wiltshire
    10 minutes ago, Mike Poole said:

    Yes, I agree signals have got worse quite quickly from just a few days ago.  Not good if we’re putting all our chips on a SSW yet again.  

    Always seems to be the way in recent years.  Very disappointing but there is time for signals to revert back to looking favourable again do you think?

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    Just now, Don said:

    Always seems to be the way in recent years.  Very disappointing but there is time for signals to revert back to looking favourable again do you think?

    Yes, I do actually, Don.  The seasonal models, GloSea5, ECM and CFS don’t seem to have ruled out a cold winter so far for us, like sometimes they do (and when they do they are usually right).  But that is so far....the worry i have is that the La Niña will prove stronger.  The trend is your friend, it is often said in here, but at the moment the trend is not our friend, but plenty of time for that to change, I would say.  

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    Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
    Just now, Mike Poole said:

    Yes, I do actually, Don.  The seasonal models, GloSea5, ECM and CFS don’t seem to have ruled out a cold winter so far for us, like sometimes they do (and when they do they are usually right).  But that is so far....the worry i have is that the La Niña will prove stronger.  The trend is your friend, it is often said in here, but at the moment the trend is not our friend, but plenty of time for that to change, I would say.  

    Talking of the CFS, it's pretty hideous at the moment-

    image.thumb.png.698fee0d5c3484d186e22f03d1550e54.png

    image.thumb.png.7bc3814534ecdf92ba955a29f4e34fa3.png

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    Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
    11 minutes ago, CreweCold said:

    Talking of the CFS, it's pretty hideous at the moment-

    image.thumb.png.698fee0d5c3484d186e22f03d1550e54.png

    image.thumb.png.7bc3814534ecdf92ba955a29f4e34fa3.png

    I am not actually too disappointed about the vortex ramping up early - this happened in lots of cold Dec winters, lately we have had a disjointed, fragmented vortex early and its got us nowhere, the quicker it ramps up, the quicker it has nowhere to go, the quicker it explodes and sends cold air south, haven't had time to test this theory out for a while - looks like now is our chance.

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    Posted
  • Location: Ludgershall, Wiltshire
  • Location: Ludgershall, Wiltshire
    27 minutes ago, CreweCold said:

    Talking of the CFS, it's pretty hideous at the moment-

    image.thumb.png.698fee0d5c3484d186e22f03d1550e54.png

    image.thumb.png.7bc3814534ecdf92ba955a29f4e34fa3.png

    Probably because it is forecasting a super Nina.  Just hope it’s overdoing it.  However, it was the first model to pick up on the Nina signal earlier this year.

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    Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
    2 hours ago, feb1991blizzard said:

    Surprising 1995/96 - you wouldn't think the level of cold / snow of that winter would have happened with those statospheric zonal wind charts, above average pretty much right the way through.

    True. It shows perhaps that favourable wave breaking eddies are possible in any background state - as happened in early Feb 96. Ultimately we all know I think that we are involved in a game of probabilities when trying to forecast small scale synoptics for an island as small as the UK. An understanding of teleconnections allows us to give some degree of correct weighting to those probabilities - but in the end the 1 in 100 shot can and does come in at the head of the field every now and again. 5 x 100 to 1 winners of the Grand National in 179 years of the race...

    I'm still looking at an SSW dice roll for this season. I agree with Crewe that whatever happens to December it wont be a mild month - and its what happens after that which holds interest. We are again seeing early November well setup for longer term strat disruption. ECM anomaly at 240.

    image.thumb.png.e61e2ac46770bf66a9a7bb024f2e5c43.png

    Looking further ahead same basic spread on the ECM extended through that first week

    image.thumb.png.16dffc42d28bf2e1b1f7e905d102ec97.png

    Beyond that we will wait and see - but regardless of the early speed of the vortex these are quite good charts for the time being. It is still early...........

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    Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl
    1 hour ago, Catacol said:

    True. It shows perhaps that favourable wave breaking eddies are possible in any background state - as happened in early Feb 96. Ultimately we all know I think that we are involved in a game of probabilities when trying to forecast small scale synoptics for an island as small as the UK. An understanding of teleconnections allows us to give some degree of correct weighting to those probabilities - but in the end the 1 in 100 shot can and does come in at the head of the field every now and again. 5 x 100 to 1 winners of the Grand National in 179 years of the race...

    I'm still looking at an SSW dice roll for this season. I agree with Crewe that whatever happens to December it wont be a mild month - and its what happens after that which holds interest. We are again seeing early November well setup for longer term strat disruption. ECM anomaly at 240.

    image.thumb.png.e61e2ac46770bf66a9a7bb024f2e5c43.png

    Looking further ahead same basic spread on the ECM extended through that first week

    image.thumb.png.16dffc42d28bf2e1b1f7e905d102ec97.png

    Beyond that we will wait and see - but regardless of the early speed of the vortex these are quite good charts for the time being. It is still early...........

    Just a hunch and that's all, we may see more in the way of polar maritime air early season, and some quite cold air with it,  not writing off December at all. Might be one of those months with alternating cold and milder spells. This is not a forecast, but early cold to our NW if it comes our way will have some potency to it given it will have had a head start in light of current and upcoming synoptics.

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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    npst30.png

    ...and so the chase begins for another winter 🤪.

    Serious hat on - I think that given the active MJO propagation across the Pacific coupled with La Nina base state enhancing the wave-2 pattern featuring N Pacific and N Atlantic ridges prodding poleward, this is a fairer representation of the potential polar vortex state by mid-November than the runs we've been seeing with a rampant circulation.

    General sense that we've got Nov to mid-Dec to try for anything of much interest cold weather wise, before the classic +NAO response to a moderate/strong La Nina kicks in. Pot of gold would be a rare December SSW... looks a tall order but you never know.

    Late winter SSWs are relatively common during a La Nina winter, but its a coin-toss as to whether the resulting highly amplified pattern is aligned in favour of cold or warm conditions. Contrast, for example, Feb 1998 and Feb/Mar 2018.

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    Posted
  • Location: Netherlands
  • Location: Netherlands

    Predictability of European Winters 2017/2018 and 2018/2019: Contrasting influences from the Tropics and stratosphere
    https://rmets.onlinelibrary.wiley.com/doi/10.1002/asl.1009
    The European winters of 2017–18 and 2018–19 were not climatically extreme, but both winters had a major sudden stratospheric warming (SSW). In February 2018, an SSW led to an intense cold outbreak across Europe and further spells of cold weather in March. The SSW of January 2019, although well predicted and expected to increase the chance of a cold end to winter, apparently produced little impact. In this study, we examine the performance of the Met Office seasonal prediction system in these winters, and the influences that led to these outcomes. To achieve this latter objective, sets of numerical experiments are performed in which the tropical troposphere and the extratropical stratosphere are relaxed towards their observed state, allowing the influence of each on the North Atlantic‐European atmospheric circulation to be identified. Using these experiments, we show that the SSWs had similar impacts in each case, creating a signal of easterly surface wind anomalies in the weeks following the event. In contrast, tropical influences were opposite in the two winters, acting to strengthen the easterly signal at the end of February 2018 and opposing it in January 2019. The different apparent responses to the two events therefore came about largely through tropical tropospheric variability. Furthermore, we highlight the importance of a very strong cycle of the Madden‐Julian Oscillation (MJO) in late January and early February 2018 as an important driver for the February 2018 SSW. MJO teleconnections appear to have been critical in creating the large mid‐latitude wave 2 amplitude that has been identified as the immediate cause of this event.

    Edited by sebastiaan1973
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    Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
    16 hours ago, Singularity said:

    npst30.png

    ...and so the chase begins for another winter 🤪.

    Serious hat on - I think that given the active MJO propagation across the Pacific coupled with La Nina base state enhancing the wave-2 pattern featuring N Pacific and N Atlantic ridges prodding poleward, this is a fairer representation of the potential polar vortex state by mid-November than the runs we've been seeing with a rampant circulation.

    General sense that we've got Nov to mid-Dec to try for anything of much interest cold weather wise, before the classic +NAO response to a moderate/strong La Nina kicks in. Pot of gold would be a rare December SSW... looks a tall order but you never know.

    Late winter SSWs are relatively common during a La Nina winter, but its a coin-toss as to whether the resulting highly amplified pattern is aligned in favour of cold or warm conditions. Contrast, for example, Feb 1998 and Feb/Mar 2018.

    Yes - it would be a surprise if the wave 2 forcing pattern that looks to be a feature for November knocked the vortex out in one blow...but we’ve been surprised by weather before and these days surprising extremes are becoming more commonplace.

    Later SSW more likely, and given possible MJO timings I’d punt at late January, perhaps very early February. Beyond that a lottery as to any downwelling impacts vv speed/extent...but at least a chance.

    So a sandwich style winter. Chances of cold early and late. Niña ridge and SSW downwell the 2 sources respectively. January cold less likely.

    Cue now the coldest January in 100 years. Haha! Let’s hope so...👍🏻

    Edited by Catacol
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    Posted
  • Location: Netherlands
  • Location: Netherlands

    What will the MJO do this winter? This is an intresting read. Can the MJO be powerful this winter?

    WWW.CLIMATE.GOV

    How this winter's temperature swings may have been partially driven by the Madden...

    And we need a MJO 7 with La Nina

     

    USJyNwM.png

    Edited by sebastiaan1973
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    Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl
    21 minutes ago, Steve Murr said:

    If only.....

    3AFB6934-E5C5-46E5-9864-FE655C1FBF08.thumb.jpeg.fc4c953d9d9274ab5543e71a4625cb61.jpeg

    Wouldn't surprise me if it came off, given the craziness of 2020..

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    Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK
    8 hours ago, Steve Murr said:

    If only.....

    3AFB6934-E5C5-46E5-9864-FE655C1FBF08.thumb.jpeg.fc4c953d9d9274ab5543e71a4625cb61.jpeg

    They should just bin the extended CFS runs completely. With so much known weak vortex bias, they aren't really much use at all! I just follow the bias corrected runs instead.

    Edited by mb018538
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    Posted
  • Location: Broadmayne a few miles north of Weymouth in Dorset
  • Weather Preferences: Snowfall
  • Location: Broadmayne a few miles north of Weymouth in Dorset
    8 hours ago, Steve Murr said:

    If only.....

    3AFB6934-E5C5-46E5-9864-FE655C1FBF08.thumb.jpeg.fc4c953d9d9274ab5543e71a4625cb61.jpeg

    Many people would call that an outlier Steve. I prefer the word trendsetter.😜

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    Posted
  • Location: Netherlands
  • Location: Netherlands

    http://wcd.copernicus.org/articles/1/657/2020/

    In the beginning of February 2018 a rapid deceleration of the westerly circulation in the polar Northern Hemisphere stratosphere took place, and on 12 February the zonal-mean zonal wind at 60∘ N and 10 hPa reversed to easterly in a sudden stratospheric warming (SSW) event. We investigate the role of the tropospheric forcing in the occurrence of the SSW, its predictability and teleconnection with the Madden–Julian oscillation (MJO) by analysing the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast. The SSW was preceded by significant synoptic wave activity over the Pacific and Atlantic basins, which led to the upward propagation of wave packets and resulted in the amplification of a stratospheric wavenumber 2 planetary wave. The dynamical and statistical analyses indicate that the main tropospheric forcing resulted from an anticyclonic Rossby wave breaking, subsequent blocking and upward wave propagation in the Ural Mountains region, in agreement with some previous studies. The ensemble members which predicted the wind reversal also reasonably reproduced this chain of events, from the horizontal propagation of individual wave packets to upward wave-activity fluxes and the amplification of wavenumber 2. On the other hand, the ensemble members which failed to predict the wind reversal also failed to properly capture the blocking event in the key region of the Urals and the associated intensification of upward-propagating wave activity. Finally, a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in late January 2018 likely played a role in triggering this SSW event.

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    Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
    22 minutes ago, sebastiaan1973 said:

    http://wcd.copernicus.org/articles/1/657/2020/

    In the beginning of February 2018 a rapid deceleration of the westerly circulation in the polar Northern Hemisphere stratosphere took place, and on 12 February the zonal-mean zonal wind at 60∘ N and 10 hPa reversed to easterly in a sudden stratospheric warming (SSW) event. We investigate the role of the tropospheric forcing in the occurrence of the SSW, its predictability and teleconnection with the Madden–Julian oscillation (MJO) by analysing the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast. The SSW was preceded by significant synoptic wave activity over the Pacific and Atlantic basins, which led to the upward propagation of wave packets and resulted in the amplification of a stratospheric wavenumber 2 planetary wave. The dynamical and statistical analyses indicate that the main tropospheric forcing resulted from an anticyclonic Rossby wave breaking, subsequent blocking and upward wave propagation in the Ural Mountains region, in agreement with some previous studies. The ensemble members which predicted the wind reversal also reasonably reproduced this chain of events, from the horizontal propagation of individual wave packets to upward wave-activity fluxes and the amplification of wavenumber 2. On the other hand, the ensemble members which failed to predict the wind reversal also failed to properly capture the blocking event in the key region of the Urals and the associated intensification of upward-propagating wave activity. Finally, a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in late January 2018 likely played a role in triggering this SSW event.

    A good article. The bit about tropospheric precursors is very interesting. To my amateur eye we have a good wave 2 precursor pattern coming into play in the first week of November with signs of a second pulse as we enter week 2. Wrong end of winter probably to create anything very significant - I know far too little of rare December SSWs to be able to comment on what has precipitated these in the past - but a slowing of the vortex after an above average start looks possible, and the extent to which any wave 2 forcing is able to distort/tilt it will be interesting to follow. If December cold is going to happen then this process might help assist the Niña ridge in getting to a higher latitude. Stratospheric events, especially given the short timeline of the shift in the forecasts as mapped out in 2018, remain our most interesting winter wild card.

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    Posted
  • Location: Ludgershall, Wiltshire
  • Location: Ludgershall, Wiltshire
    7 hours ago, mb018538 said:

    They should just bin the extended CFS runs completely. With so much known weak vortex bias, they aren't really much use at all! I just follow the bias corrected runs instead.

    Not sure why they don't just show the bias corrected runs only and remove the others?

    Edited by Don
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    Posted
  • Location: Brighton
  • Weather Preferences: Snow Storm That Lasts 3 Days
  • Location: Brighton

    I just noticed the following pattern by 18th of November. Is it a little beast from the east?

    image.thumb.png.f0077e974947b41689b8e1224d55ad21.png

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