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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: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
    1 minute ago, Interitus said:

    What big reversal is this?

    The displacements of 23/1/87, 15/12/98 and 21/1/6 all got below -20 m/s.

    Aha, I wondered if there might a a few. Good to see '87 on that list, thanks! For some reason I only have records that list temp and GPH anomalies, not the peak reversal so I couldn't pick out the exact years reliably.

    Just realised I meant to put historical guidance for all displacements in my previous post - do'h! Using these strongest ones should prove much more informative ?.

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  • Location: Netherlands
  • Location: Netherlands

    Thanks for Karel for finding this research.

    https://pdfs.semanticscholar.org/12d5/f40389c3e38ca4be146450203a275d0ebd31.pdf 

    Abstract Sudden stratospheric warmings (SSWs) contribute to intraseasonal tropospheric forecasting skill due to their surface impacts. Recent studies suggest these impacts depend upon whether the polar vortex splits or is displaced during the SSW. We analyze the annular mode signatures of SSWs in a 1000 year IPSL-CM5A-LR simulation. Although small differences in the mean surface Northern Annular Mode (NAM) index following splits and displacements are found, the sign is not consistent for two independent SSW algorithms, and over 50 events are required to distinguish the responses. We use the wintertime correlation between extratropical lower stratospheric wind anomalies and the surface NAM index as a metric for two-way stratosphere-troposphere coupling and find that the differences between splits and displacements, and between classification methodologies, can be simply understood in terms of their mean stratospheric wind anomalies. Predictability studies should therefore focus on understanding the factors that determine the persistence of these anomalies following SSWs.

    From the discussion part

    Recent studies using reanalysis data have suggested that the tropospheric response to SSWs depends upon the type of event, categorized as either a vortex split or displacement [Mitchell et al., 2013; Seviour et al., 2013] (M13 and S13, respectively). These studies found that the surface anomalies following splits project more strongly onto the Northern Annular Mode (NAM) than for displacement events. This is in contrast withCharlton and Polvani [2007] (CP07) and Cohen and Jones [2011] who did not find a consistent difference in the impact of splits and displacements using a different method for identifying SSWs.

     

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  • Location: Netherlands
  • Location: Netherlands

    ""Predictability of downward propagation of major sudden stratospheric warmings Alexey Yu. Karpechko,et al

    Major sudden stratospheric warmings (SSWs) are striking phenomena of wintertime stratospheric circulation usually defined as a reversal of zonal mean circulation from
    westerlies to easterlies. SSWs often have significant impact on tropospheric circulation and cause anomalies in surface climate lasting for up to 2 months. For this reason, dynamics and predictability of SSW receive considerable attention. It is however well-known that not all SSWs cause significant, long-lasting impact on the troposphere. In order to explain differences in tropospheric impacts following SSWs, several reasons have been previously proposed, including differences in type of SSW (split or displacement), persistence of stratospheric anomalies, preconditioning of the tropospheric circulation, and whether or not SSW was accompanied by a planetary wave reflection in the stratosphere. Here we address the predictability of tropospheric impacts by SSWs by seeking early precursors of the impacts. We separate midwinter SSWs into two groups: those which are followed by significant, long-lasting impacts on the tropospheric circulation (defined in terms of anomalous Northern Annular Mode) and those not followed by significant anomalies in the annular mode. We show that SSWs characterised by a more negative Northern Annular Mode index in the lower stratosphere around 150 hPa and enhanced wave activity propagation to the stratosphere during the first few days following the central date have a larger probability of being followed by tropospheric impact, both in reanalyses and in climate model runs. These anomalies play a more important role in the subsequent downward propagation of the signal to the troposphere than the type of SSW: whether it is a split or a displacement, or absorptive or reflective SSW. We propose that using these anomalies as precursors of tropospheric impacts of SSW can enhance climate predictability.

    https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/qj.3017?purchase_referrer=scholar.google.nl&tracking_action=preview_click&r3_referer=wol&show_checkout=1

    Edited by sebastiaan1973
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  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    1 hour ago, Summer Sun said:

     

    Interesting, does anyone know what that phase space, if that is what it is, represents?  I'm familiar with the MJO and GWO ones, but this one is entirely new to me, and, annoyingly the axes are not labelled!

    Edited by Mike Poole
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  • Location: Dublin, Ireland
  • Weather Preferences: Cold, snowy winters and warm, sunny summers
  • Location: Dublin, Ireland
    24 minutes ago, Mike Poole said:

    Interesting, does anyone know what that phase space, if that is what it is, represents?  I'm familiar with the MJO and GWO ones, but this one is entirely new to me, and, annoyingly the axes are not labelled!

    That's Met Set's so-called "stratospheric index" which divides into 8, nothing to do with MJO. See the below tweet from the same people:

    Here's how the 2012-13 major warming evolved at 10hPa to compare with the 2018-19 one since the Glosea5 is picking up on it being similar to that of 2012-13.

    1155313146_2012-13majorSSW.thumb.gif.b63c26a588c8b790364c8d7364eab7ab.gif

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  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl
    3 minutes ago, BruenSryan said:

    That's Met Set's so-called "stratospheric index" which divides into 8, nothing to do with MJO. See the below tweet from the same people:

    Here's how the 2012-13 major warming evolved at 10hPa to compare with the 2018-19 one since the Glosea5 is picking up on it being similar to that of 2012-13.

    1155313146_2012-13majorSSW.thumb.gif.b63c26a588c8b790364c8d7364eab7ab.gif

    Thanks I admit I didn't spot that. Looks so similar to the MJO index at a glance. 

    My post removed. ☺️

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    Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    13 minutes ago, BruenSryan said:

    That's Met Set's so-called "stratospheric index" which divides into 8, nothing to do with MJO. See the below tweet from the same people:

    Here's how the 2012-13 major warming evolved at 10hPa to compare with the 2018-19 one since the Glosea5 is picking up on it being similar to that of 2012-13.

    Thanks for this, and the animation is really useful too.  I can see the similarities with the FV3 output up to day 16, really want to see the Wave 2 attack at the end that just destroys the thing...eyes glued to the FV3 runs at T384 for a while longer yet!

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

    Enough vertical energy transfer to make an event Jan 2019 the bigger brother of Jan 2013... though I seem to recall we were unlucky with the placement of one of the remnant vortexes that time such that the only benefits we saw were from the immediate response giving rise to a relatively small 'wedge' of high pressure against which Atlantic troughs disrupted effectively (in fact, too much so for residents of the southeast as the front largely or entirely fizzled out before getting there!).

    More luck needed this time with the orientation of the split. Historical precedent suggests we have about a 70% chance of that.

    First things first though - let's get that wave-2 attack into the reliable!

    Interestingly, it was already building in the upper layers days 7-10 of yesterday's ECM 12z.

    ecmwfzm_ha2_f240.gifecmwfzm_ta2_f240.gif

    Edited by Singularity
    ECM Charts
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  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
    50 minutes ago, knocker said:

     

    Anyone who wants to learn more about the mechanisms of heat flux associated with trop wave activity interacting with the strat would do well to read these series of tweets by Amy. Brilliant explanation.

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    Posted
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
  • Weather Preferences: continental climate
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow

    One interesting note. 

    The geop. height anomaly pattern indicated by recent numerical outputs resembles more precursor to split events rather then displacement.

    See Mitchell et al. 2013

    https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-12-00030.1

    I think we may see a split event come beginning of January if numerical models prove to be close to reality

    jcli-d-12-00030.1-f7.gif

    gfsnh-12-336.png

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  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
    1 hour ago, chionomaniac said:

    Anyone who wants to learn more about the mechanisms of heat flux associated with trop wave activity interacting with the strat would do well to read these series of tweets by Amy. Brilliant explanation.

    And shamelessly stealing a graphic from her final tweet:

    DuUT2klU0AACP4c.thumb.jpg.92a676b3787ce2ccb75c5c1635948dee.jpg

    Sustained warming on rolling 45 day averages now forecast to be +1SD and rising. Given the majority forecast for a reversal by 29th December with this signal demonstrating ongoing and sustained warmth being pumped from the tropics up to the pole we can expect to see further impacts. The precursor pattern is also more wave 2 now than wave 1 on EPS charts. Split in January looking possible. A split on top of a pacific pattern that looks conducive to high lat blocking in the medium term would be potentially significantly impactive.

    Edited by Catacol
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  • Location: Coniston, Cumbria 90m ASL
  • Weather Preferences: wintry
  • Location: Coniston, Cumbria 90m ASL

    Just the hint of it starting again? 

    Screenshot_20181214-055319.png

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    Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

    Yesterday's ECM T240hrs.data now picking up the start of the zonal winds reversal at the top.

    fluxes.thumb.gif.059ed12442afaa79841d3fdb05bc6cf9.gifecmwfzm_u_f240.thumb.gif.7f7dc0b974c69a58ff7a5f3463c14816.gif

    The H.Attard site continuing to show a post Christmas reversal from gefs suite.


    u_60N_10hpa_gefs.thumb.png.226c50653170ce7773484ce81c8dfc1a.png
     

    Now in range of both models so we can now monitor progress. 

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  • Location: County end Oldham 202 m Above sea level
  • Location: County end Oldham 202 m Above sea level
    30 minutes ago, ITSY said:

    A secondary displacement-type (severe) warming apparent at the far reaches of FI 

    gfsnh-10-384.png?12

    I noticed a double dip on the 00z run ?

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  • Location: North West of Ireland
  • Location: North West of Ireland
    2 hours ago, ITSY said:

    A secondary displacement-type (severe) warming apparent at the far reaches of FI 

    gfsnh-10-384.png?12

    Is this going to lead to the vortex eventually splitting? Is there any chance if there is blocking already in place due to the vortex displacement ,or, indeed, because of the pacific pattern being conducive to blocking, that a vortex split could actually turn out be more harmful than good to our chances of snowy cold?

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  • Location: London City ,Cobham Surrey , Hale Gtr Manchester
  • Weather Preferences: clear skies , hard frost , snow !
  • Location: London City ,Cobham Surrey , Hale Gtr Manchester
    On 05/12/2018 at 14:47, Glacier Point said:

    Strat warming looking like 26th December IMO.

    are we still expecting this to land as above ?

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  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
    56 minutes ago, Badgers01 said:

    are we still expecting this to land as above ?

    I think we're beyond that point.  That will happen somewhere around that date around Christmas. What is more interesting is whether we get the split that decimates the vortex later, and that has gone up a few tens of percent today for sure, given the model output, I'm going 80% chance vortex annihilation by 2 Jan!

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