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Stratosphere Temperature Watch 2012/2013


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A few points on the excellent bit of research by Interitus:

1) many of the Cohen events are, I believe, late season or even final warmings warmings which have quite different dynamics for us due in part to the lack of cold pooling in the NH. However, I suspect having tried to do something similar that it may not make a huge difference to exclude these. It does show that an SSW is no guarantee of cold for the British isles and we should certainly bear that in mind.

2) I think the analogues aren't strictly relating to the occurrence of an SSW but rather the stratospheric temperature signature for January. That there is a secondary warming into Greenland forecast followed by a further warming and zonal wind reversal is quite a bit more favourable for helpful blocking to develop than a typical SSW, and I think if it was the latter there would be far less of a buzz around the possibilities from mid month onwards.

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Ok, having combined the Cohen list with Martineau's to give a total of 54 SSW events compared with 1940-2012 CET anomalies -

1-20 days following SSW is 0.038°C warmer than the 20 days preceding SSW.

7-28 days following SSW is 0.116°C warmer

15-45 days following SSW is 0.089°C warmer.

Essentially, there is little difference.

There are trends however - 7 day running means show that there is on average a cooling response in the 2nd week after SSW, followed by a milder interlude, before a second period of cold about 5 weeks after SSW. Not easy to be precise because there is some variation in the dates used by Cohen and Martineau, and the years obviously don't always follow the same pattern. The first cooling on the graph looks smaller but is often the more dramatic and the anomaly is reduced by the strong positive temperature swings that can occur in some instances.

post-2779-0-23245700-1357295550_thumb.jp

It's interesting seeing certain years being used as analogues - the Januaries 1979, 1982, 1987 have been used regularly. Is it being said that the atmosphere now or in the near future is genuinely like those months, or is it because they featured cold weather and SSWs?

The thing is, in each of those years, the CET was significantly WARMER after the SSW than the preceding spell.

1987 SSW was between 23-26 of January and followed by prolonged cold weather with 15-45 day anomaly of -1.07°C but this was over 3 degrees warmer than the very cold spell beforehand.

1982 is complicated by the fact that there was also an SSW in December 1981 which was followed by a extremely cold spell of weather. Between the two SSWs on 4/12/81 and 27/1/82 the CET anomaly was -3.53°C but in the 20 days following the January SSW there was an immediate upswing in temperature of over six degrees to 2.55°C above average. Days 15-45 were an average +0.03.

1979 is a peculiar choice because the SSW was near the end of February, around 22nd-27th. After an initial warming, this was followed by cold weather throughout March and into April, 15-45 day anomaly of -2.48. But this was relatively much warmer than the bitter spell that left a January CET of -0.37°C, over 4 degrees below normal.

Thanks for that - can you provide a link for the Martineau list of warmings please. With regard to winter 78 - 79, there was a Canadian warming in December 1978 - that may be a reason for the cold prior to the SSW at the end February

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I think that it shows that each strat warming should be taken on it's own merits. All along it has been stated that SSW's do not guarantee cold over the UK. However for the purpose of research - the scientists often include the period prior to a strat warming as part of the event due to the increase in blocking precursers - that is why the precursor can be better than the main course.

For the purpose of research, I would like to see the SSW's divided into propagating and non propagating. Immediately a number of SSW's would be discounted from the CET results. After this then the frequency of HLB's should be analised and how many of these then are in the rioght position for cold to the UK. This should then be split up into sections prior and post SSW's to determine the effects. That is an awful lot of research!

I have some links to research papers on file at home that show the 'cold' episodes following SSW's into the mid latitudes and these show hemispherically the significance of SSW's.

Chiono I think also a look at the initial state of the NAM or AO would be very important because some of the research suggests propogation and effect on the AO is correlated with that.

That paper I linked a few days back shows much more impact on the troposphere with a background positive or neutral AO at the initial stage, that might seem logical, the interest however would be for CET post SSW with either background negative, neutral, positive AO.

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I think that it shows that each strat warming should be taken on it's own merits. All along it has been stated that SSW's do not guarantee cold over the UK. However for the purpose of research - the scientists often include the period prior to a strat warming as part of the event due to the increase in blocking precursers - that is why the precursor can be better than the main course.

For the purpose of research, I would like to see the SSW's divided into propagating and non propagating. Immediately a number of SSW's would be discounted from the CET results. After this then the frequency of HLB's should be analised and how many of these then are in the rioght position for cold to the UK. This should then be split up into sections prior and post SSW's to determine the effects. That is an awful lot of research!

I have some links to research papers on file at home that show the 'cold' episodes following SSW's into the mid latitudes and these show hemispherically the significance of SSW's.

I suppose it just boils down to whether it affects our little part of the world.

Thanks for explaining Chio

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At this stage in the game, is it possible for the predicted SSW to vaporise and not come to fruition? Is there a point at which it will inevitably happen, if so how/what guarantees this? Is there any history of anticipated SSW's not coming to fruition? Could all this vanish, like the hugely anticipated easterly a few weeks ago?

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At this stage in the game, is it possible for the predicted SSW to vaporise and not come to fruition? Is there a point at which it will inevitably happen, if so how/what guarantees this? Is there any history of anticipated SSW's not coming to fruition? Could all this vanish, like the hugely anticipated easterly a few weeks ago?

The SSW has already started. The technical SSW will 99.999999999% happen over the next couple of days.

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And we are also 99.999999999% uncertain as to how the strat warming(s) will influence the weather patterns in our little part of the world, and we will remain uncertain for several more days or even weeks. Always worth pointing this out before folk hang all their winter hopes & dreams on this event, as tantalising as it looks.

Bish

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At this stage in the game, is it possible for the predicted SSW to vaporise and not come to fruition? Is there a point at which it will inevitably happen, if so how/what guarantees this? Is there any history of anticipated SSW's not coming to fruition? Could all this vanish, like the hugely anticipated easterly a few weeks ago?

I think that we can be pretty ceratin that a displacement SSW is going to happen. What occurs after this stratospherically is probable but less certain. The most probable next phase is for a secondary warming and split to affect the displcaed vortex - this will affect the mid strat right down to the troposphere. It is the vortex positioning and tropospheric response at this point where most uncertainty lies.

Edited by chionomaniac
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That 2nd warming over Greenland/Canada keeps disappearing and reappearing, with the latest run showing a very weak warming. I never thought there would be so much uncertainty in a stratosphere forecast for something that's just 7-8 days away. At least the pressure charts at 10hpa still show that the weak warming will push that fragment of vortex away from East Canada/Greenland.

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Arctic Trifecta Could Lead To Brutal January-February

By

Andrew at

8:22 AM http://theweathercen...-to-brutal.html

I think he is trying to bamboozle his readers with catchy phrases like trifecta.

In reality, the cross polar flow and -ve AO are from a direct result of the splitting stratospheric vortex. To try and give them their own identity as if they would have occurred without the split is a nonsense. If he had suggested that the projected forecasts of the MJO were an important factor then his blog would be better set. I hope he is not a pro!

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I think that it shows that each strat warming should be taken on it's own merits. All along it has been stated that SSW's do not guarantee cold over the UK. However for the purpose of research - the scientists often include the period prior to a strat warming as part of the event due to the increase in blocking precursers - that is why the precursor can be better than the main course.

For the purpose of research, I would like to see the SSW's divided into propagating and non propagating. Immediately a number of SSW's would be discounted from the CET results. After this then the frequency of HLB's should be analised and how many of these then are in the rioght position for cold to the UK. This should then be split up into sections prior and post SSW's to determine the effects. That is an awful lot of research!

I have some links to research papers on file at home that show the 'cold' episodes following SSW's into the mid latitudes and these show hemispherically the significance of SSW's.

Here is a peer review paper on the subject of stratospheric wintertime responses - a few years since it was published but still valid.

http://www.nwra.com/resumes/baldwin/pubs/Thompsonetal_2002.pdf

Note Table 2

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A question for CC.

Out of interest, where did you start your interest in analysis of the stratosphere and potential effects downwards? I have followed all of the discussions since mid Dec and find it incredible over the accuracy that yourself, GP and Recreatos manage to find here.

I appreciate that the Meto and other professional organisations might well have seen the same information or more likely a lot more regarding any potential warmings but your ability to demonstrate many many weeks before the actual event with some accuracy is incredible.

A little off topic and without any specific information but I am truly impressed with the knowledge of you lot !

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@chio hey chio i c u gave the strat bug to p.coben seen some of his w.action tweets and he was "a cold blast is on it's way due to ssw sudden stratospheric warming".

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@chio hey chio i c u gave the strat bug to p.coben seen some of his w.action tweets and he was "a cold blast is on it's way due to ssw sudden stratospheric warming".

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