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Posted
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
  • Weather Preferences: continental climate
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
    1 hour ago, Steve Murr said:

    Updated QBO chart for mid August sees negative ( Easterly ) Winds down to about 5HPA..

    The increments of negativity are in 5M/S so we can see 10HPA is just tipping into negative, 5HPA is about -5M/S which quickly traverses to ~-30 M/S at 3 HPA.

    The start of December is 14 weeks away which is just enough time to see some stronger values downwell ...

    Perhaps for once some good news....

    06DE6082-119A-42F2-8F5E-6B4E46E6A90B.thumb.png.ed66a8537d556e8ef857a2d89378d6c3.png

    Looks like westerlies are going to take over in upper levels and easterlies could descend lower by autumn,early winter. What impact that is going to make is anyone's guess. I would disregard QBO as a factor hence and perhaps try and focus on the SST in the north Atlantic which now support more +NAO, I would swap relatively unfavorable QBO for favorable SST myself

    ecmwfzm_u_f240.png

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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

    Posted Images

    Posted
  • Location: Scunthorpe
  • Location: Scunthorpe
    27 minutes ago, jules216 said:

    Looks like westerlies are going to take over in upper levels and easterlies could descend lower by autumn,early winter. What impact that is going to make is anyone's guess. I would disregard QBO as a factor hence and perhaps try and focus on the SST in the north Atlantic which now support more +NAO, I would swap relatively unfavorable QBO for favorable SST myself

    ecmwfzm_u_f240.png

    I would probably agree with that based on December 2010

    We had a strong polar vortex in December 2010 and no sign of a SSW

    The QBO was in a strong WQBO phase by December 2010

    What we did have however was a tripole in the N Atlantic and that overrode both of the above signals

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    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT
    7 hours ago, SqueakheartLW said:

    I would probably agree with that based on December 2010

    We had a strong polar vortex in December 2010 and no sign of a SSW

    The QBO was in a strong WQBO phase by December 2010

    What we did have however was a tripole in the N Atlantic and that overrode both of the above signals

    I doubt that was the overriding factor - maybe a contributer- Look at the polar cap heights from October.

    The whole of the troposphere disconnected from the Strat so the -AO was huge

    6921D9F1-7300-4232-82ED-EA186C9C17AB.thumb.jpeg.e258ea625d2775e655f6ea283985b842.jpeg

    Edited by Steve Murr
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    Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire

    We want the Ely's to be descended to a lower level for winter. The QBO state closest to the troposheric level seems to be the bigger player on our weather...so basically whatever is being flushed down.

    I presume it is because the E'ly layer creates a buffer which allows the trop to be completely disconnected from the strong westerlies at the top of the strat. With this in mind, suggestion of a front-loaded winter may not be too far off the mark.

    Edited by CreweCold
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    Posted
  • Location: Ludgershall, Wiltshire
  • Location: Ludgershall, Wiltshire
    22 hours ago, CreweCold said:

    We want the Ely's to be descended to a lower level for winter. The QBO state closest to the troposheric level seems to be the bigger player on our weather...so basically whatever is being flushed down.

    I presume it is because the E'ly layer creates a buffer which allows the trop to be completely disconnected from the strong westerlies at the top of the strat. With this in mind, suggestion of a front-loaded winter may not be too far off the mark.

    Remember you will have to eat a sock if winter 2020/2021 is very mild!

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    Posted
  • Location: Exile from Argyll
  • Location: Exile from Argyll
    22 hours ago, chionomaniac said:

    December 2010 was unique in the fact that tropospheric wave 2 breaks into the strat occurred in the perfect position to reinforce a Greenland high. The split of the vortex was high into the stratosphere. At the time I called this an ‘internal wave break’, ie very much tropospheric led and not one that leads to a traditional SSW. These are far more beneficial to the UK than the more easily recognised over the top type wave 2 break from negative EAMT scenarios that force pressure up and from the surf zone of the strat vortex before leading to a collapse of the SPV from top to bottom. 

    As you say ... perfect alignment ....and up she goes!

          500mb psnh_pen_hist_z500_201066.gif   100mb  psnh_pen_hist_z100_201066.gif   30 mb  psnh_pen_hist_z30_201066.gif

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    Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
    39 minutes ago, Don said:

    Remember you will have to eat a sock if winter 2020/2021 is very mild!

    I'll get some HP sauce in just in case ;)

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    Posted
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
  • Weather Preferences: continental climate
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
    10 hours ago, CreweCold said:

    I'll get some HP sauce in just in case ;)

    More blues over eastern Conus @CreweCold over next few months and you may not need that HP sauce when the HP will be around Greenland not your shopping basket😀

    cdas-sflux_ssta7diff_global_1.png

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    Posted
  • Location: Scunthorpe
  • Location: Scunthorpe

    Noticed this SSTA map in the above post

    cdas-sflux_ssta7diff_global_1.thumb.jpg.d79de3007001c6e9a62fe586e0aa92bd.jpg

    Have to hope these trends continue with further cooling in the NE Pacific

    Also couldn't help but notice the most rapid cooling in the N Atlantic is following a possible re-emergence of a tripole with the deepest blues generally between the two red lines

    It also looks like the EQBO is gathering some pace at 10hpa now when looking on nullschool.net

    1886060216_eqIndian.thumb.jpg.101a9a9c7a4d9cd852faf8e247b2e8eb.jpgIndian Ocean Region

    When looking above the Indian Ocean Region there are no obvious easterlies above the equator itself but they are raging strong just north of the equator and this area is the most average still westerly region, especially near Indonesia and Singapore which could explain the westerly element still present on the NASA Singapore charts at 10hpa

    However when looking at other equatorial regions a different pattern is emerging

    569545328_eqSAmeriaEPac.thumb.jpg.bf95f9e4d0f60d81b58df8db2dd9f7c7.jpgS America and E Pacific Region

    Although still rather disorganised there is generally a more easterly element to the QBO above the S America and E Pacific Regions. This lot has in general gathered some momentum recently and very few if any westerlies regions are still showing up. Hope this continues the trend and possible EQBO return.

    The best region for easterlies is the final one

    347865823_eqWPacific.thumb.jpg.28a91317ecb3b6daea8a19992c685b13.jpgW Pacific Region

    The W Pacific region was the first to show limited easterly bursts of QBO a week or two ago and each new burst has started in this region but now it appears to be becoming a bit more permanent and the easterlies here appear to be squeezing that small region of westerlies out of existence. A few days ago there was a distinct westerly jet from the Indian Ocean through to the W Pacific. Now there's only that small patch of westerlies left now.

    Even if the EQBO does make a comeback at 10hpa it is still highly unlikely that it will descend down to 30hpa in time for this winter but could at least give us a chance of better news for winter 2021/22 if the EQBO hangs around long enough to become a factor for that winter instead.

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    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT

    Todays stratospheric zonal wind site at -0.3 M/S meaning that the birth of the 2020/21 vortex arrives tomorrow or the 26th ....

    The climatic ave for the vortex is the 26th so thus far nothing out of the ordinary...

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    Posted
  • Location: Scunthorpe
  • Location: Scunthorpe
    7 hours ago, Steve Murr said:

    Todays stratospheric zonal wind site at -0.3 M/S meaning that the birth of the 2020/21 vortex arrives tomorrow or the 26th ....

    The climatic ave for the vortex is the 26th so thus far nothing out of the ordinary...

    It would be much better if we got the vortex in Summer to keep all the cool air locked away over the pole so we could have a decent dry and warm summer every year then have the summer pattern in winter so we had a decent chance of cold weather in every winter with no polar vortex to give us the usual bore fest of mild and zonal nearly every single winter

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

    Todays stratospheric zonal wind site at -0.3 M/S meaning that the birth of the 2020/21 vortex arrives tomorrow or the 26th ....

    The climatic ave for the vortex is the 26th so thus far nothing out of the ordinary...

    Up to +0.4m/s today....everyone say welcome to the 2020/21 PV! All hoping for an exciting season 🙏🏻 

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    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT
    12 hours ago, SqueakheartLW said:

    It would be much better if we got the vortex in Summer to keep all the cool air locked away over the pole so we could have a decent dry and warm summer every year then have the summer pattern in winter so we had a decent chance of cold weather in every winter with no polar vortex to give us the usual bore fest of mild and zonal nearly every single winter

    That would be interesting- typically though anything that usually helps us ie the EQBO is the only thing that will fail...

    Lets see how we get on in Oct / Nov this year !

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    Posted
  • Location: Purley, Surrey - 246 Ft ASL
  • Weather Preferences: January 1987 / July 2006
  • Location: Purley, Surrey - 246 Ft ASL
    1 hour ago, mb018538 said:

    Up to +0.4m/s today....everyone say welcome to the 2020/21 PV! All hoping for an exciting season 🙏🏻 

    Kill it, kill it now!

    😆

    Hopefully this one will have a mid life crisis and withdraw from public view during December. 

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    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

    l6WmYoSfV_5HXNs6QkzXpaBLNPAxK9gvSA2abLcV

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    Posted
  • Location: Netherlands
  • Location: Netherlands

    Thanks to Karel.

    An excellent read by Robert Lee.

    http://blogs.reading.ac.uk/weather-and-climate-at-reading/2020/from-indonesia-to-the-british-isles-using-el-nino-and-weather-patterns-in-the-tropics-to-help-predict-north-atlantic-and-european-weather/

    The winter weather in the UK and Europe can be split into different patterns based on the large-scale flow in the atmosphere. A commonly used method is to use a type of machine learning algorithm – a clustering algorithm – to partition the weather into distinct categories, known as ‘regimes’. Weather regimes can persist for a number of days or even weeks, before transitioning to another regime. Using large-scale weather regimes such as these are useful when considering the ‘subseasonal’ forecasting period, approximately 10–20 days ahead since they give an approximate indication about the average weather covering many countries for many days, without focusing on precise differences on a local and hour-by-hour scale, which cannot be forecasted well due to the inherent chaos.

    For the combined North Atlantic and European region, it turns out that the optimal number of large-scale weather regimes is four [1]. These regimes are often called the (1) NAO− (a.k.a. Greenland Blocking), (2) NAO+ (a.k.a. Zonal), (3) Atlantic Ridge, and (4) Scandinavian Blocking. As a side note, the NAO− and NAO+ weather regimes are similar, but not identical, to the North Atlantic Oscillation index. 

    Subseasonal forecasts of weather regimes can help authorities and businesses to plan ahead in sectors such as agriculture, energy, health, aviation and transportation, water, and retail. In the energy sector, for example, if NAO− weather is forecasted, then the energy industry can plan for a ‘shortfall’ in electricity. A shortfall is caused when the demand exceeds the supply, due to increased electricity used for heating in the colder weather. A (growing) proportion of the electricity supply comes from wind generation: during NAO− days the winds are much calmer. Similarly in the health sector, a heads-up about an upcoming period of NAO− can aid preparations for an increase in average and peak (extreme 5-year return interval) hospital admissions and mortality in the UK, associated with the colder conditions.

    Remote atmospheric links from other regions, known as ‘teleconnections’, provide a way of getting an advanced warning for upcoming weather, thereby improving the potential for predictions on subseasonal timescales. For over 30 years there has been a known link between weather in the tropics and weather in the North Atlantic and European region that exists on these subseasonal timescales. These links are primarily driven by a weather phenomenon in the tropics known as the Madden-Julian Oscillation (MJO), which is an eastward moving ‘pulse’ of suppressed and enhanced cloud and rainfall near the equator which typically recurs every 30 to 60 days during the boreal winter (although the MJO is not active about one third of the time). An important study in 2008 [5] showed how these teleconnections from the MJO in the tropics influence the weather regimes in the North Atlantic and European region. The study also showed how packets of energy, known as ‘Rossby waves’, can travel eastwards from the Pacific to the North Atlantic in the jet streams of the atmosphere, revealing some of the physics involved in these teleconnections.  

    At the inception of our study, the El Niño–Southern Oscillation (ENSO) was hypothesised to also play a role in altering these teleconnections. ENSO characterises the periodic variation of sea surface temperatures and accompanying atmospheric circulation over the tropical Pacific Ocean. The warm phase is known as ‘El Niño’, and the cool phase as ‘La Niña’, reaching peak intensity during boreal winter. 

    This ENSO modification of the MJO then has a consequence on the type of teleconnection that is triggered and the path that it takes. Our study [6] shows that during El Niño winters the teleconnection from MJO phases 1–3 makes the NAO+ regime occur twice as often as the full climatology, with the signal travelling along the jet streams (Figure 4). Whereas during La Niña this MJO phases 1–3 teleconnection is absent and there is no increase in NAO+ regime occurrence. During La Niña years we also find the teleconnection from the MJO phases 6–8 makes the NAO– regime occur up to 2.5 times as often as the full climatology – this signal travels via the stratosphere, warming it and slowing the stratospheric polar vortex (Figure 4), with the total pathway taking around 20 days. There is a strong subseasonal link between the stratospheric polar vortex and the weather regimes throughout all winters [7], however, it is during La Niña years when there is the strongest subseasonal link between the MJO and the stratosphere.

     

    plaatje.PNG

    Edited by sebastiaan1973
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    Posted
  • Location: Netherlands
  • Location: Netherlands

    https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL084683 

    Abstract The teleconnection from the MaddenJulian Oscillation (MJO) provides a source of subseasonal variability and predictability to the North AtlanticEuropean (NAE) region. The

    El NiñoSouthern Oscillation (ENSO) modulates the seasonal mean state, through which the MJO and its teleconnection pattern propagates; however, its impact on this teleconnection to the NAE region has not been investigated. Here we nd a robust dependence of the teleconnections from the MJO to NAE weather regimes on the phase of ENSO. We show that the MJO to NAO+ regime tropospheric teleconnection is strongly enhanced during El Niño years, via enhanced Rossby wave activity, and suppressed during La Niña.

    Conversely, the MJO to NAO− regime stratospheric teleconnection is enhanced during La Niña years and suppressed during El Niño. This dependence on the background state has strong implications for subseasonal predictability, including interannual variations in subseasonal predictive skill.

    Plain Language Summary The MaddenJulian Oscillation (MJO) is the dominant source of differing weather conditions in the tropics on timescales within a season. The remote linkage (teleconnection) from the MJO to the North AtlanticEuropean (NAE) region provides a source to modify or persist weather conditions and add predictive power to weather forecasts on 10 to 30 day timescales. The El NiñoSouthern Oscillation (ENSO) has an influence on the seasonal climate state, through which the waves and linkages from the MJO to the NAE region travel. Here we and a robust dependence of these teleconnections from the MJO to NAE weather regime patterns on the ENSO state, such that under certain states of the MJO, certain regimes occur more than twice as often. The different sources and pathways also become clearer, with the teleconnections travelling via the troposphere and the stratosphere. This dependence on ENSO state has signicant implications for predictions on 10 to 30day timescales.

    Edited by sebastiaan1973
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    Posted
  • Location: Netherlands
  • Location: Netherlands

    Northern Europe and the UK experienced an exceptionally warm and wet winter in 2019/20, driven by an anomalously positive North Atlantic Oscillation (NAO). This positive NAO was well forecast by several seasonal forecast systems, suggesting that this winter the NAO was highly predictable at seasonal lead times. A very strong positive Indian Ocean dipole (IOD) event was also observed at the start of winter. Here we use composite analysis and model experiments, to show that the IOD was a key driver of the observed positive NAO. Using model experiments that perturb the Indian Ocean initial conditions, two teleconnection pathways of the IOD to the north Atlantic emerge: a tropospheric teleconnection pathway via a Rossby wave train travelling from the Indian Ocean over the Pacific and Atlantic, and a stratospheric teleconnection pathway via the Aleutian region and the stratospheric polar vortex. These pathways are similar to those for the El Niño Southern Oscillation link to the north Atlantic which are already well documented. The anomalies in the north Atlantic jet stream location and strength, and the associated precipitation anomalies over the UK and northern Europe, as simulated by the model IOD experiments, show remarkable agreement with those forecast and observed.

    https://rmets.onlinelibrary.wiley.com/doi/10.1002/asl.1005

    open access.

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    Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL
    6 minutes ago, sebastiaan1973 said:

    Northern Europe and the UK experienced an exceptionally warm and wet winter in 2019/20, driven by an anomalously positive North Atlantic Oscillation (NAO). This positive NAO was well forecast by several seasonal forecast systems, suggesting that this winter the NAO was highly predictable at seasonal lead times. A very strong positive Indian Ocean dipole (IOD) event was also observed at the start of winter. Here we use composite analysis and model experiments, to show that the IOD was a key driver of the observed positive NAO. Using model experiments that perturb the Indian Ocean initial conditions, two teleconnection pathways of the IOD to the north Atlantic emerge: a tropospheric teleconnection pathway via a Rossby wave train travelling from the Indian Ocean over the Pacific and Atlantic, and a stratospheric teleconnection pathway via the Aleutian region and the stratospheric polar vortex. These pathways are similar to those for the El Niño Southern Oscillation link to the north Atlantic which are already well documented. The anomalies in the north Atlantic jet stream location and strength, and the associated precipitation anomalies over the UK and northern Europe, as simulated by the model IOD experiments, show remarkable agreement with those forecast and observed.

    https://rmets.onlinelibrary.wiley.com/doi/10.1002/asl.1005

    open access.

    Thanks Sebastian. These metrics would point already then to a colder and drier Winter for North Western Europe with both a La Nina and -IOD forecast, factor in low solar activity,slightly favorable QBO and potentially favourable North Atlantic ssts, then what can go wrong! 

    Edited by mountain shadow
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    Posted
  • Location: Tyrone
  • Location: Tyrone
    1 minute ago, mountain shadow said:

    Thanks Sebastian. These metrics would point already then to a colder and drier Winter for North Western Europe with both a La Nina and -IOD forecast, factor in low solar activity,slightly favorable QBO and potentially favourable North Atlantic ssts, then what can go wrong! 

    Everything 😅😅

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    Posted
  • Location: Clacton-on-Sea, Essex
  • Location: Clacton-on-Sea, Essex
    8 minutes ago, mountain shadow said:

    what can go wrong! 

    Anyone for a 'spoiler shortwave' 🙂

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

    @sebastiaan1973 Interesting coincident with the articles you have linked here with my post from yesterday in the autumn banter thread. Perhaps I could have written that post in this section. Here is the link.

     

    I have discovered something interesting and that in years where ENSO switched to La Nina in autumn in all seven related years we have seen MJO in November in phases 5-8 also combined height anomaly suggested NAO blocking, almost exactly what your linked article suggests.

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