Winter 2012/2013 – Thoughts & Analysis

18 Sep

Of late there has been many discussions and pieces of information released with regards to the possible weather during the up coming winter.  This time of year is often the start as to when certain ‘variables’ can be used as to give an idea as to the potential broader synoptic patterns through the winter.

What I will add at this point is that this is NOT a winter forecast. I am using this particular blog to highlight features of interest that can give signs and indications as to the expected up-coming winter and discuss them so others know what to look for in the coming weeks and months.  As a scientist I put faith in forecast models and the analysis of these models and like many areas of science there are limitations and saying what the weather will be during the first or second half of January at this point, in my opinion is simply not possible.  Meteorology is not an exact science and the atmosphere can always bring about some unexpected surprises.

I was recently made aware of this publication and the information within this publication really is worth a read as it gives some clear thoughts and information regarding the longer term and how specific variables can be used;

One of the more recent documented features is the state of the sea-ice or lack of it across the polar regions at the end of this summer/start of the autumn.  There have been recent studies conducted, in conjunction with the severe winter of 2009/2010 that low Arctic sea ice can have a direct effect on the AO (Arctic Oscillation) through the winter in that low-level heating can aid to bring about a -ve AO pattern.  For those unsure about teleconnections, in a nut-shell a -ve AO pattern is directly associated with higher pressure across polar regions which thus aids to bring a more blocked pattern and hence a greater risk of colder weather affecting the UK, than compared with a more zonal (west to east) flow.

Clearly if there is any truth to this connection, then seeing the state of the Arctic sea ice is at its lowest ever recorded, then clearly this is one variable which  may well signal a more blocked pattern and higher pressure across places like Greenland and to the North of the UK, as per winter 09/10.

For any hardcore readers or analysts out there, then this is also another well constructed publication –

Another feature, which is highlighted in the above initial publication is the SST patterns across the North Atlantic and how these correlate to either a +NAO pattern (mild, wet, windy and zonal) or whether, as per 09/10 a -ve NAO pattern (blocked, colder and wintry).  At the present time the SST pattern is favorable for the latter to take place and develop.

The QBO (Quasi-Biennial Oscillation) is, without going into the details, also another feature that can affect the weather across the UK and the northern hemisphere during the winter.  The QBO has two phases, a westerly phase and also an easterly phase.  It is believed, again through various studies and publications, that the easterly phase of the QBO tends to be directly associated with a greater likelihood of blocking patterns and generally colder, less zonal/unsettled winters. The QBO phases of late can be seen on the below image for example;

The grey areas represent the westerly phase and the white areas represent the easterly phase.  Interestingly note how during last winter the general phase was westerly, but how if you extrapolate across through the rest of the year and into 2013, the pattern at the moment is for the phase to become easterly during this coming winter.  So again another variable which points towards a more blocked and potentially less zonal pattern.

Another important, but quite varied feature is ENSO.  The problem with this variable is that there has been numerous examples of colder weather affecting the UK both during El Nino and also La Nina events. At the moment there is still some uncertainty as to what state this will be in during the coming winter, but at the moment a weak or near neutral ENSO is expected, as highlighted on the below image from NOAA for example;

( )

Overall a near neutral ENSO through the winter period isn’t a bad thing and again when coupled with the other features continues to provide more speculation and reason for suggesting the coming winter could well be a rather cold and blocked one.

What can’t be discussed at this stage is how the stratosphere may affect the weather through the winter period, it is simply too early.  We have seen numerous examples of how a sudden warming of the stratosphere (SSW) can have direct and significant effects on the weather at surface levels in the following weeks and I believe that the stratosphere can over-ride the above variables at times.  Clearly a warmer stratosphere is directly related to a -ve AO and a greater risk of blocking across northern regions.  As a comparison, last December was clearly very mild, wet, windy and zonal.  This is due to the fact that the Arctic was particularly cold (+ve AO), this can be seen on the below image where the red line was below the average near Nov and Dec.  However, note that by mid-late January the red line suddenly became much warmer than average in association with a stratospheric warming event;

This warming event during the middle of January this year then resulted in a much colder start to February across the UK and also some bitterly cold and extreme conditions across other parts of Europe as the very mild and zonal pattern of December was left behind.  What this shows is that changes in the conditions of the stratosphere can have a direct and extreme effect on the weather across the UK and many other areas of the northern hemisphere during the winter period and for the time being it is too early to see what this is likely to be during the first half of the winter.

So, and in summary…

At the moment in time, combining the expected ENSO conditions with the expected QBO phase, the arctic sea ice state and SST’s the end result is a good one if you are looking for a colder and a more blocked winter.  Scientific studies, like I have highlighted earlier in this blog, have been carried out on these variables and they have to be acknowledged when looking at the expected longer term and seasonal trends.  As I highlighted at the start of this blog, this is not a winter forecast, I am simply highlighting the variables of interest which can give ideas and signs of the expected weather in the months ahead but again, at the present time, the current signs are leaning towards a colder, more blocked winter.

In relation to the stratosphere and how this may affect the weather during the early part of the winter, then this can start to be analysed approximately a month or so from now, so during the middle and latter half of October onwards.  Time willing  I will attempt to create a blog on this when the time comes.

Regards to all,



4 Responses to “Winter 2012/2013 – Thoughts & Analysis”

  1. matt September 18, 2012 at 11:06 am #

    Fantastic post.

  2. sturgeon220 September 18, 2012 at 8:23 pm #

    Excellent read Matt , Well constructed and balanced . I will be interested to see how things develop in a month or two .

  3. rickdangerous September 18, 2012 at 9:23 pm #

    Explained allot, without getting dragged into the ongoing “winter silly session” on some forums.

    Thanks again for the work and post.


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