Stratosphere Temperature Watch 2012/2013

[bluearmy]

Did anyone note my post on the MTD re the ecm ens. Apparently the top of the model is 5hpa. That may explain its lack of cold members in a fortnights time? Also, it only started throwing up some clusters of cold runs a coule of days ago when the onset of warming would have been evident at 5hpa at initialisation.

[snowking]

Did anyone note my post on the MTD re the ecm ens. Apparently the top of the model is 5hpa. That may explain its lack of cold members in a fortnights time? Also, it only started throwing up some clusters of cold runs a coule of days ago when the onset of warming would have been evident at 5hpa at initialisation.

I'm not entirely convinced that's accurate BA, I know it probably came from the ECMWF website, but then how would you explain this:

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=1&forecast=all&lng=eng

Which assumes that either that's an outdated article, or that the main tropospheric operational run for some reason isn't coupled with the uppermost Strat......but that would seem a little suspect to me when the data is there

SK

[BrickFielder]

Please can you tell me something about situation for south europe, specialy Portugal and Spain? Thank you so much.

It is too far out to be able to tell, but the outlook might be for a cooler spell. It seems possible that spain and portugal could have atlantic maritime air circulating via the UK or possibly scandinavia (see charts below). I guess temperatures might just dip below freezing over night, but charts are not at the moment suggesting anything exceptional for Portugal and Spain. Now if you were looking at Greece, Italy or North Africa then you might expect an unusually cold spell.

See wind directions on the charts below.

These charts are at the limit of model forecasting and will most likely be substantially wrong. At the moment the best we can honestly say is that there is potential for some cooler weather.

[bluearmy]

I'm not entirely convinced that's accurate BA, I know it probably came from the ECMWF website, but then how would you explain this:

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=1&forecast=all&lng=eng

Which assumes that either that's an outdated article, or that the main tropospheric operational run for some reason isn't coupled with the uppermost Strat......but that would seem a little suspect to me when the data is there

SK

The operational runs at 29 more layers than the ens and i believe goes into the mesosphere. The berlin data is from the op. i know shuttler came on here and quoted the extended ecm strat ens data. Maybe he can let us know what level that data goes up to.

[snowking]

The operational runs at 29 more layers than the ens and i believe goes into the mesosphere. The berlin data is from the op. i know shuttler came on here and quoted the extended ecm strat ens data. Maybe he can let us know what level that data goes up to.

Sorry, I had missed the crucial word 'ens' in there!

In which case I guess it makes more sense in terms of limitations of data processing (bearing in mind its a 51 member ensemble suite). Still not ideal but then I guess even in a top-down situation, the change will have to come through 5mb regardless before it can get to the troposphere, and this may be the thinking behind such a move? It might mean a delay in picking up such a warming though as you suggest, though having said that, I'm still reasonably pleased with the london ensembles this morning:

More members sub 5c than above, and actually on the face of it slightly cooler than De Bilt (which would suggest to me tendency more towards a northerly initially as we see the remaining chunks of the PV heading south)

SK

Edited December 31, 2012 by snowking

[snowking]

The other thing to be noted is the strong decline in the temperature of the tropical stratosphere at present too:

Running cooler than average down to 50 and 70mb too, though I would be more encouraged to see a further decline here too

The net result is an even weaker polar vortex in the medium term (as if it didn't have enough on its plate already)

SK

[cooling climate]

The trouble is the 380k potential vorticity charts do not accurately portray the H5 synoptic

charts.

Also this is a top down warming that is taking place which has only just begun to

effect the 10mb level around 60n let along the Arctic.

If I am wrong please correct me.

I must admit the more I look into this to try to analyze what may happen down the

road the more unsure I become I will give you an example why.

When looking at the lower strat 100mb temperatures this is how things look at the

moment

Here is the H5 synoptics for the same time

They are completely disconnected with little correlation between warmer/cooler

stratosphere zones and higher/lower pressure.

This will obviously make it very difficult to second guess what lies ahead.

Maybe all we can do is see where the vortices split and take a stab from there.

With the past warmings that we have seen in the last few years I have found it

more beneficial to look more closely at what is happening at the 10 and 30mb

levels as this had greater impact on the synoptic pattern than what was

happening lower down in the stratosphere.

It would be nice to see the changes that take place between 100mb and 500mb

so we could have a better understanding of what is going on.

[feb1991blizzard]

The trouble is the 380k potential vorticity charts do not accurately portray the H5 synoptic

charts.

Also this is a top down warming that is taking place which has only just begun to

effect the 10mb level around 60n let along the Arctic.

If I am wrong please correct me.

I must admit the more I look into this to try to analyze what may happen down the

road the more unsure I become I will give you an example why.

When looking at the lower strat 100mb temperatures this is how things look at the

moment

Here is the H5 synoptics for the same time

They are completely disconnected with little correlation between warmer/cooler

stratosphere zones and higher/lower pressure.

This will obviously make it very difficult to second guess what lies ahead.

Maybe all we can do is see where the vortices split and take a stab from there.

With the past warmings that we have seen in the last few years I have found it

more beneficial to look more closely at what is happening at the 10 and 30mb

levels as this had greater impact on the synoptic pattern than what was

happening lower down in the stratosphere.

It would be nice to see the changes that take place between 100mb and 500mb

so we could have a better understanding of what is going on.

Yes, your post is sobering but realistic, i just hope we can get the right response down the line tropospherically, i wonder if it just might take more time and that second warming to probagate down, that would tie in with monthly forecasts although they are quite vague and show uncertainty which one would expect.

[Interitus]

There's a lot of speculation here as to the outcome of an SSW, but what is the actual impact on the UK?

Taking the list of 35 SSW episodes highlighted in this paper http://web.mit.edu/jlcohen/www/papers/CohenandJones_JC12.pdf and comparing the CET for the 20 days before and after each event with the mean daily CET since 1940 to the present day, we find that on average the CET is actually marginally WARMER after an SSW (0.059°C).

Of the 35 events, 13 were followed by a fall in temperature but 22 followed by warming - the nature of the stratospheric vortex change doesn't seem to matter - splitting = 6 coolings, 10 warmings and displacement = 7 coolings, 12 warmings.

So on the face of it, a warming CET is more likely than cooling, but this doesn't quite tell the whole story, more significant perhaps is the likelihood of temperature change with on average 1.98°C difference between CET before and after the SSW. Cooling averages -2.59°C whilst warming averages 1.62°C with the greater number of warmings giving the slight average increase overall. The difference between magnitude of coolings vs warmings is one might expect due to the decrease/increase of maritime air which is already a main determinating factor for our temperature.

The average CET anomaly after a cooling is -1.67°C; after a warming it is 0.84°C.

Of the 9 coolings from a +ve CET position, 7 were followed by a -ve anomaly with an average of -1.56°C with the largest swing being December 1981 from 1.31°C above average to -6.00°C below.

[Polar Maritime]

Very interesting, does this take into account where the warmings are taking place ?

[Recretos]

They are completely disconnected with little correlation between warmer/cooler

stratosphere zones and higher/lower pressure.

You also have to realize, that 100mb level is in between the tropospheric and stratospheric forcing (leaning almost more toward the stratosphere), while H500 is much more "in tune" with the tropospheric forcings. And besides that, I think you will find much better correlation between H500 and GPH100, than the 100mb temperature.

[Interitus]

Very interesting, does this take into account where the warmings are taking place ?

No, could look at that next, the only suspicion being that with such a small sample size it may be hard to draw any firm conclusions.

[nick sussex]

Interesting post Interitus.

Just to add in some of the research I read there was suggestions that propogation to the troposphere is closely correlated with the NAM or AO at the initial onset of the SSW.

The result being that propogation was more likely to occur with a background neutral/positive NAM. The effects with a background negative NAM were difficult to ascertain and not statistically significant.

Another thing that perhaps ties in with CC's post, mention also that even with a strong negative zonal wind after SSW this was not always likely to lead to propogation.

That perhaps too much attention is paid to the 10hPa level when the suggestion was the troposphere was more effected by events in the lower stratosphere.

Edited December 31, 2012 by nick sussex

[sebastiaan1973]

Nice research. What are the results when you take in account that the effects of the SSW are felt in the trophosphere around 7-28 days, so not 1-20 days, after the SSW.

There's a lot of speculation here as to the outcome of an SSW, but what is the actual impact on the UK?

Taking the list of 35 SSW episodes highlighted in this paper http://web.mit.edu/j...dJones_JC12.pdf and comparing the CET for the 20 days before and after each event with the mean daily CET since 1940 to the present day, we find that on average the CET is actually marginally WARMER after an SSW (0.059°C).

Of the 35 events, 13 were followed by a fall in temperature but 22 followed by warming - the nature of the stratospheric vortex change doesn't seem to matter - splitting = 6 coolings, 10 warmings and displacement = 7 coolings, 12 warmings.

So on the face of it, a warming CET is more likely than cooling, but this doesn't quite tell the whole story, more significant perhaps is the likelihood of temperature change with on average 1.98°C difference between CET before and after the SSW. Cooling averages -2.59°C whilst warming averages 1.62°C with the greater number of warmings giving the slight average increase overall. The difference between magnitude of coolings vs warmings is one might expect due to the decrease/increase of maritime air which is already a main determinating factor for our temperature.

The average CET anomaly after a cooling is -1.67°C; after a warming it is 0.84°C.

Of the 9 coolings from a +ve CET position, 7 were followed by a -ve anomaly with an average of -1.56°C with the largest swing being December 1981 from 1.31°C above average to -6.00°C below.

[Shuttler]

The operational runs at 29 more layers than the ens and i believe goes into the mesosphere. The berlin data is from the op. i know shuttler came on here and quoted the extended ecm strat ens data. Maybe he can let us know what level that data goes up to.

I only see data for a couple of fixed levels from the ECM Ens, namely 10 and 50mb. I can't answer your query, but have quizzed my sources and will come back if/when I have an answer.

For information, the ECM Ens at the 10 and 50mb levels between 240 and 360h maintains a split PV in pretty much the same locations as the op at T240 i.e. Hudson Bay and Siberia, with no great re-location in this time frame. We therefore see the Polar High extending through from the Aleutians to Greenland/Iceland throughout.

[mountain shadow]

And to further complicate things we may well be looking at a multiple warming due to different waves.

Not simple this strat warming by any means.

[bluearmy]

I only see data for a couple of fixed levels from the ECM Ens, namely 10 and 50mb. I can't answer your query, but have quizzed my sources and will come back if/when I have an answer.

For information, the ECM Ens at the 10 and 50mb levels between 240 and 360h maintains a split PV in pretty much the same locations as the op at T240 i.e. Hudson Bay and Siberia, with no great re-location in this time frame. We therefore see the Polar High extending through from the Aleutians to Greenland/Iceland throughout.

Ed will be pleased to read that.

[chionomaniac]

Ed will be pleased to read that.

Yep, that was a concern.

[lorenzo]

Okay, some Polvani business to end 2012 here the composites for Vortex displacement and splits are analysed for trends, and some further questions posed around the lead factors outwith the wave activity. Interesting mention of a paper by Esler in the conclusion that cites a Stratospheric Internal mode within the Vortex itself - might go digging for that one.

Again very relevant as we are looking at both scenarios playing out over the next 14 days.

http://www.columbia.edu/~lmp/paps/matthewman+etal-JCLIM-2009.pdf

Some images attached of the Polar Vortex in 3d for displacement vs analogs and also split vs analogs.

The olympic rings are composites of 13 split events marked individually, some of the years discussed in the above paper are coloured. The Black shading and rings detail the composite and other split events.

Moving to the end of the paper the proposed benchmarks for all SSW events make interesting reading.

Enjoy !

[chionomaniac]

Yes,cc.

I am going to predict an early New Year displacement SSW, now on the back of what I have seen so far. One that not only displaces the vortex, but then follows the complete disintergration of the vortex. Around the first 10 days in January.

So one bust with the CW and one possible strike with the upcoming forecast SSW. Hopefully we will see some kind of tropospheric disturbance out of this!

Happy New Year to all!

Lorenzo, what is forecast is quite unusual. A displacement followed by a split - that would be my designer SSW!

Edited December 31, 2012 by chionomaniac

[lorenzo]

It makes for fantastic viewing C. Thinking out loud it is a Brillant way to kick off 2013, to be honest with so much going on across the hpa levels it has been difficult to track the various warming entering the circulation, right now would need better definition of the chunks of atmosphere between 10 and 70 to see more effects.

We have already had a rapidly cooling Vortex to kick off the season and this thread did kick off earlier than usual, then the Canadian Warming filtering through the background, before eventually migrating the vortex to Siberia in the longest drawn out model impact ever coinciding with that ECM. Also the Met lifted the lid on their model to include the strat and published on their blog recognition of the impact. Important steps.

The 1 hpa level seems to have been under constant attack all season and continues to torch, some crazy high temps up there and within that I sense some scope for mesosphere papers may be forthcoming by Winter 13 or perhaps the BDC is responsible coming on-line after being drained by the Southern Hemisphere.

The ruskie high eventually delivering a la Cohen has also been a good watch in real time, although some lateral viewing of output has been required to see through what can be some frustrating NWP output.

That background Canadian warming I think although leaving us a nasty parting gift as it departed in the shape of a daughter vortice determined to marry the resurgent Atlantic Jet - may be about to pay off in relation to it weakening the Vortex on that side of the hemisphere, once displaced and the elongation begins then the warming can potentially punch through that , especially with an added boost of the MJO pattern kicking energy into that area.

Certainly agree , displacement and then split, couldn't ask for more to be viewing in January, looking at the composites above we are looking at an obliterated Vortex, not quite sure if it could recover to anything prominent after that either... One could say It's all over bar the Blocking.. C'mon Greenland - you know you want a nosebleed high up there.

[Luisport]

[SMU]

DTWrisk ^ is an excellent forecaster!!- pity he doesnt do more on the strat...

S

[Isolated Frost]

Interesting he touches up on an east based -NAO pattern emerging, and that his week 3/4 composites seemed pretty conclusive on heights over Greenland and Iceland, with troughing over Britain and Scandinavia.

[LomondSnowstorm]

Interesting he touches up on an east based -NAO pattern emerging, and that his week 3/4 composites seemed pretty conclusive on heights over Greenland and Iceland, with troughing over Britain and Scandinavia.

I think given the position of the secondary warming, the current modelling of the stratospheric vortex position (including the ECM extended ens) and the MJO movement that's quite a strong signal given the timescale involved. It's also where I'd place the block when I used to doodle pressure charts on the map of Europe in my diary planner.