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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

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Posted
  • Location: Netherlands close to the coast
  • Location: Netherlands close to the coast
    On 16/11/2019 at 11:47, Northern Sky said:

    Apologies for what may be some obvious questions but just trying to learn a bit - 

    1. At the moment we have a very unorganised trop vortex that is not coupled to a strong strat vortex? 

    2. The strat vortex is forecast to become weaker so does that mean it is likely to become more or less coupled to the trop vortex?

    3. What would cause the trop vortex to gain strength as we move into Winter, would that be from forcing's in the trop, strat or both?

    4. In very basic terms I think I understand that a weak strat vortex induced by a warming can downwell to help to make a weak trop vortex which makes high latitude blocking in the trop more likely - although where that sets up may or may not be conducive for cold in the UK?

    5. Finally, given the current state of the trop vortex is there an optimum time for the potential influence of a warming to strike - ie would it be more effective if the trop vortex reorganises and following on from that would a strat warming be wasted on an unorganised trop vortex (if you see what I mean)?

    Thanks in advance.

    NS

    I suggest you watch the 3d vortex animations on https://www.stratobserve.com/misc_vort3d to sort of understands what happens, too bad you can't see last year's vortex split being modeled 

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

    A strat conundrum on the GFS 0z, here at T384:

    image.jpg.6af367ff596813c6f3d8cd54837b78da.jpg

    It was a bit toastier too on the 6z, but the following plot from stratobserve, which I believe is based on the same 0z run, doesn't seem to add up:

    image.thumb.jpg.a9a96170a29e445866bb3362a61bfbcf.jpg

    It puts the op run well behind most of the others including ensembles here.  Any ideas, anyone? 

    Looking at the GEFS at T384, it does seem that if any event is to happen, at the moment it looks like a displacement rather than a dismemberment...

    image.thumb.jpg.da5746f0b6fa2d1e8a37e3ded7a6b7de.jpg

    Edited by Mike Poole
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    Posted
  • Location: Kirkcaldy, Fife, Scotland 20m ASL
  • Weather Preferences: Snow, Thunderstorms
  • Location: Kirkcaldy, Fife, Scotland 20m ASL

    @Mike Poole not sure about your question regarding the differences with the GFS op compared to the ensembles but that may still suggest that it will be similar to last year with perhaps having more back and forth runs whilst the ensembles remain fairly steady, will certainly be an interesting watch as we progress. 

    And here is the solo ensemble member showing the reversal again from the CMC / GEM image.thumb.png.dbb4dcdac688d2f8ed37670a31a0e04a.pngimage.thumb.png.04d0e72f77099ab77b239b581e93253c.pngimage.thumb.png.361dc95f0e38bc56a18a0304f10dab93.png 

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    Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

    Not as good a mean as the last run.

    image.thumb.png.b84dcf676974303e124e74844524d8b6.png

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    Posted
  • Location: Live in central Gravesend work in NW Kent too now
  • Weather Preferences: Snowy November to March and Sunny and warm April to Early October
  • Location: Live in central Gravesend work in NW Kent too now

    And just like that were back to Weakened zonal winds except for one stray ensemble slightly above average come late January, February 

    20191117_212957.jpg

    Edited by Kentspur
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    Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

    Strat looks quite toast in deepest FI

    gfsnh-10-384.png

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    Posted
  • Location: Strathblane/Killearn nr Glasgow
  • Location: Strathblane/Killearn nr Glasgow

    https://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/gif_files/gfs_t30_nh_f240.png

    first decent warming of the season where we want to see it at 30hpa 

    will it be there consistently over the coming days and move into the more reliable timeframe? 

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  • Location: Royston , Herts
  • Weather Preferences: SNOW
  • Location: Royston , Herts

    The warming starting around day 12 on the gfs now and becoming very strong again . 
     

    @Recretos brilliant posts keep em coming . ?

    8C9833CE-9384-4053-8A09-485BD3FC3A53.png

    D00DB2B4-5FCC-45DC-A16A-1C2D3692C17E.png

    578EE26E-056C-4B8D-A0B6-CD35B9284031.png

    B2C333AE-5A49-43A6-B2B9-A0CB5DB25AC9.png

    5735DA15-E190-4865-9440-FDD0C402096E.png

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  • Location: st albans
  • Location: st albans
    14 minutes ago, Summer Sun said:

     

    The back end of the gfs op at 10hpa looks very suppressed at the very top of the strat - could be worth watching if it repeats as perhaps the start of a slowdown which could possibly stall the zonal flow at 10hpa 

     

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  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
    19 minutes ago, IDO said:

     

    So November continues with the wedges of heights to our north that are not conducive in UK cold. The UK remains at the end of the stalling Atlantic train as it slams into the Euro/Russian high and ATM signs that by the end of the month the Atlantic will slowly ease that Euro/Russia high east:

     

     

    I am sure i read somewhere that that is standard just prior to an SSW.

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  • Location: West Aberdeenshire
  • Location: West Aberdeenshire
    8 minutes ago, feb1991blizzard said:

    I am sure i read somewhere that that is standard just prior to an SSW.

    Any proof to back up that claim? Link?

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  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
    50 minutes ago, Sceptical said:

    Any proof to back up that claim? Link?

    I may have in a few weeks time.

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon

    Many thanks @Recretos for that great post, which categorically answers my question from yesterday re the warming vs the zonal winds.  ?

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  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
    Just now, Sceptical said:

    ?

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

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  • Location: Cambridge, UK
  • Weather Preferences: Anything out of the ordinary!
  • Location: Cambridge, UK
    4 minutes ago, feb1991blizzard said:

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

    I also think this is true - as one start area warms up intensely, the opposite side can actually go much colder. It's not until everything reaches tipping point and collapses at the top and hopefully trickles down that we get all the fun and games. It's certainly exciting to watch, and if it happens around the turn of the month, a certain date towards the end of December could be the best for years. Let's hope so!

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    Posted
  • Location: Strood, Kent, 19 feet above sea level
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Strood, Kent, 19 feet above sea level
    27 minutes ago, feb1991blizzard said:

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

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

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

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