Possible Stratospheric Demolition & Final Winter Thoughts…

27 Nov

With just a few days of autumn left and an autumn which has produce quite a few extremes, the attention now turns towards winter.  I’ll add at this junction that (time willing) I’ll produce a blog looking specifically at December in the next few days. In this blog I wanted to directly focus my attention and information on the state of the stratosphere as we now enter into winter.

Many may well have heard of the ‘stratosphere’ in recent months and also within the last year or so as this particular ‘variable’ has been given more and more scientific attention.  Some people believe that the stratospheric conditions aren’t the be all and end all when it comes to affecting the weather across the UK during the winter and in a way they are correct.  There are a large number of variables which come in to play, but equally I can disagree and argue that comment with substantial evidence, of which I have acknowledged myself over the last few years.  Without question, the conditions of the stratosphere do affect the weather across the UK and the northern hemisphere during the winter and early spring period.

In one of my previous blogs, which explains the two primary different states of the stratosphere (https://matthugo.wordpress.com/2012/10/01/stratospheric-conditions-winter-weather-analysis-information/) I give a perfect example of how the stratosphere can directly affect the weather within the troposphere and a perfect example of that was last December.  Now without going over those details, I wanted to take a look at the state of the stratosphere up to present day and what is forecast to happen in the coming days;

Initially, through this autumn, the stratosphere has cooled (as it should) at quite a significant rate to say the least and generally this progression would often lead to a pattern as evident last December.  However, for a number of factors, including the likes of the QBO (Quasi-biennial Oscillation) these particularly potent stratospheric conditions haven’t been able to filter down into the troposphere this autumn and are now highly unlikely to do so.  The rapid drop in temperatures across the polar stratospheric region can be seen on the below 2 images;

As can be clearly seen on the first image in particular the temperatures have now dropped below -80C which is pretty much as low as they can go. Within the second image you can see that at this time last year the temperatures were very similar, but perhaps slightly warmer.  However, there are clear differences, of which I highlighted earlier, this year the stratospheric conditions have been unable to penetrate down into the troposphere and aid the development of a significant polar vortex (http://en.wikipedia.org/wiki/Polar_vortex). To give an example of what the stratospheric vortex looks like at the moment, the below image shows this;

What this image is essentially showing is the temperatures within the stratosphere and also the overall ‘shape’ of the stratospheric vortex.  At the moment, whilst rather elongated, it remains a noteworthy feature and as can be seen within the bottom left of the image the lowest temperature on that chart is -83c (82.5N 2.5W) essentially near the center of the vortex over the polar region.

So what is expected in the coming 7 to 14 days to change this setup?…

Well, without going into the details too much, of which even I am still attempting to get a grasp of, the stratospheric vortex through the winter period can often be at risk of under-going ‘attacks’ from various sources.  These ‘attacks’ help to distort and weaken the vortex and the so-called “holy grail” can be a complete split and relocation of the vortex as well, you may have heard of an SSW (Sudden Stratospheric Warming) event.  At this point don’t forget that a highly disorganised stratospheric vortex has been found (time after time) to aid in the development of northern latitude blocking and a heightened risk of colder weather across the UK and other areas of the northern hemisphere during the winter period than if the vortex is well organised.

So a few more charts of interest;
1)

2)

3)

1) The first image clearly shows a very different vortex within the next 7 or 8 days compared with the actual vortex of present day.  The vortex, as can be seen, has split and of significance is the major warming event taking place over Eastern Russian in association with a major region of higher pressure across Alaska and far eastern areas of Russia.  This is represented by the lighter blue colours and also the patch of pale yellow colour of which represents temperatures of -50C or above.  This may still seem cold but clearly compare that to temperatures of below -80C and that is a marked area of warming.

2) The second image shows the zonal wind speeds (m/s) up through the troposphere and more specific the stratosphere in relation to latitude.  Of significance here is the negative (blue) colours and contours above 70N across the right of the image.  This highlights a progression towards a highly disorganised and weak stratospheric vortex.

3) Finally the bottom image and more importantly the top 3 graphs show how the temperatures are forecast to rise into early December compared with at present to either near or even above average. Of significance, don’t forget that a warmer stratospheric vortex essentially equates to a weaker vortex and a greater likelihood of potential blocking (higher pressure) within the troposphere.

In conclusion;

Gathering the above information and more together the situation through this autumn has been quite unique.  The behavior of the vortex would (more often than not) have led to a likely period of zonal conditions across the UK as the autumn progressed, but clearly this hasn’t happened.  Despite the highly organised and very cold stratospheric vortex there are now a variety of variables which are forecast to “attack” the vortex within the next 7 to 14 days of which, if successful, may actually demolition the vortex almost completely.  For this to happen at this time of year would (combined with other factors) lead to a heightened risk of more meridional and blocking conditions developing.

So, and finally, combining this data and with other information I believe that the winter across the UK between December and February will end up being colder than average with a greater frequency of blocking patterns leading to cold outbreaks.  Clearly details are not possible, but particularly as we progress through the second half of December and also particularly into January if the stratosphere fails to recover from this potential “attack” then I wouldn’t be surprised to see at least one major and noteworthy cold outbreak across the UK.

It’s all to play for, but I certainly feel that compared with last winter, the coming winter will be markedly colder for the UK.

Time will tell as ever in meteorology and I look forward to looking back on this particular blog come next March to contrast and compare.

Regards to all,

M.

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3 Responses to “Possible Stratospheric Demolition & Final Winter Thoughts…”

  1. Doug November 27, 2012 at 9:03 pm #

    Great blog as always, much appreciated 🙂

  2. Sean Donoghue November 27, 2012 at 9:28 pm #

    Loved reading that report,,Amazing and so interesting Thank you ,Dublin ireland

  3. Col November 28, 2012 at 11:38 am #

    Thanks for sharing a very informative forecast and update. The more blocking the better!

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