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Stratosphere Temperature Watch 2012/2013


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the daily ones recretos !! i'm not for one minute suggesting there's anything solid to take from them but they do show big -AO setting up, beginning sometime between mid jan and early feb. that must surely be to do with the model processing the SSW. could well be a load of rubbish but it does show how the response varies run to run.

Oh the dailies. Yea I think they have some wild ideas for some time now. Dailies are basically just a time downscaled version of the monthlies if I'm not mistaken.

A little something about CFSv2 and stratosphere. I showed this CFSv2 generated blocking forecast some time ago. I will test it in our case, to see just how legitimate it is, and if it will pick up any possible tropospheric response and how far in advance.

Posted Image

But about CFSv2 and stratosphere in general, here are a few facts, by Shaw&Perlwitz:

- In CFSv2 polar vortex is too weak in early winter and too strong in late winter.

- Variability of stratospheric polar vortex is similar between CFSv2 and Reanalysis.

- Dynamic coupling between the stratosphere and troposphere is not well represented in the CFSv2.

- CFSv2 has a serious spin up problem that is mostly pronounced in the stratosphere but can also be seen in the troposphere - will degrade any assimilated stratospheric information with potential benefit for improved tropospheric forecast.

- Doesn't generate QBO very well and has a lower number of vertical levels, which will need to be upgraded.

I am not saying CFSv2 wont pick up any signals, but it has some known problems with stratosphere coupling. It will still be useful as a test, to see how good or bad it really is. Posted Image

P.s.: If I can add my personal thought on CFSv2 monthlies and the seasonal runs: I really really don't like it too much.

No offence to the great people of NCEP Posted Image, but I think that this CFSv2 operational system has to stop. Like right away. Posted Image The old CFS had an ensemble system, but this new one, has an operational system, meaning it has 4 daily operational runs. Like the GFS system for example. The old one also had 4 runs, but was more like the GEFS system. Basically it had much less variability or the "jumping around". CFSv2 has some great data assimilation systems, but this operational forecasting system has to go away. CFSv2 assimilation system and an ensemble forecast system would be the bomb if you ask me. Posted Image Of course I dont mean it would be as accurate as it gets, but it would pick up seasonal and sub-seasonal pattern changes much quicker.

For example, here are the last 25 runs from CFSv2, 500mb anomaly forecast for January. That is only one month lead time, where it should show some consistency, but it is basically allover the place.

Posted Image

P.s.2: Hello and welcome scellus. Posted Image

Edited by Recretos
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I read somewhere that the stratosphere-troposphere coupling is poor even in CFS v2. It might not have good idea of what happens after the SSW, then.

(Greetings from Finland, by the way. Posted Image)

in which case, its quite odd that it suddenly begins to show output, run after run, which develops a strong -AO signature. maybe the model is too crude to cope with the possible barriers to propogation and is therefore untrustworthy. we will know soon enough when mid jan comes within the radar of the gfs suite. if no ops or gefs members show a decent -AO then the CFS is indeed worthless.

thanks for that info recretos. oh, and welcome scellus. pardon my rudeness.

Edited by bluearmy
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in which case, its quite odd that it suddenly begins to show output, run after run, which develops a strong -AO signature

thanks for that info recretos. oh, and welcome scellus. pardon my rudeness.

No problem. Yes I'm an amateur in this stuff and in other kind of meteorology, but see http://www.cpc.ncep.noaa.gov/products/ctb/meetings/2012/CFSv2/Perlwitz.pdf slide 14 or so, and the conclusions at the end.

GFS ensemble is still quite +AOish, but mybe it doesn't reach far enough.

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I couldn't help but post this chart if nothing else because of the symmetry , can someone explain what the contours are showing on this, to my untrained eye it looks like a complete vortex split and a blob of High Pressure Over Iceland and with even higher temperatures looking to make their way right into the core of the N.Pole.

Edit ..I know that blob isn't High pressure over Iceland on this image below, but what IS it ?? never gotten my head around what the contours are representing if not the same as the pressure charts on a normal GFS / ECM etc ?

Posted Image

Edited by EML Network
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I couldn't help but post this chart if nothing else because of the symmetry , can someone explain what the contours are showing on this, to my untrained eye it looks like a complete vortex split and a blob of High Pressure Over Iceland and with even higher temperatures looking to make their way right into the core of the N.Pole.

Edit ..I know that blob isn't High pressure over Iceland on this image below, but what IS it ?? never gotten my head around what the contours are representing if not the same as the pressure charts on a normal GFS / ECM etc ?

Posted Image

It is a complete vortex split to my untrained eye (at mid strat level though), the contours showing the height of 30mb, just as the black line shows 552 dam height on 500mb charts, however, probagation is not guaranteed, if it was guaranteed and this chart was representative of every level all the way down then we would be looking at very cold weather from a N/NE direction at surface level.

Edited by feb1991blizzard
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@EML: Basically you should treat this chart the same way as any ECM/GFS geopotential height chart. The contours represent the height of the 30mb pressure level in Dam (Dekameter). So if you see a contour having a 2352 label for example, that would translate to roughly 23.520m height.

About the "blob" over Iceland. I drew streamlines on you chart, for a better idea of the flow. Basically a complete split yes. I wouldn't put much focus on that blob in this range, but the way I see it, its just a small negative vorticity center, on the edge of two bigger positive vortices. Might have a future within next runs. Posted Image

Posted Image

edit: And as always, I was beaten to it by someone else. I need to speed up. Posted Image

Edited by Recretos
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Just wondering if someone could help me out please, most gratefull if they could, i understand what a 2 wave pattern is at 500mb level and what that brings but i am confused slightly as to this stratospheric chart, i am confused as to the 3d meaning of it.

Posted Image

I understand the chart posted below as the mean wind speed at various levels.

Posted Image

however, not sure exactly what the 3rd dimension of the first chart represents.

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Just wondering if someone could help me out please, most gratefull if they could, i understand what a 2 wave pattern is at 500mb level and what that brings but i am confused slightly as to this stratospheric chart, i am confused as to the 3d meaning of it.

Posted Image

I understand the chart posted below as the mean wind speed at various levels.

Posted Image

however, not sure exactly what the 3rd dimension of the first chart represents.

The first chart simply measures the intensity of wave amplitude at various levels of the atmosphere and at certain longitudes. Basically what we see today from the ECM between hour 0 and hour 240 of its forecast period is much stronger wave 1 activity at the top of the stratosphere centered around 70N.

The biggest question we have right now is not if we see a SSW but when and how do the subsequent displacement and fragmentation lead to colder/stormier pattern. It looks to be case of various levels of the stratosphere doing different things as the GFS/ECM show variations in what happens to the polar vortex as you make your way from 1mb to 100mb, which is to be expected when the PV becomes significantly weakened.

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Oh boy, you could spend the next 50 years of your life trying to make a case for any one of those teleconnections being more critical than the other for UK during winter. You would also have to take ENSO into consideration.

A topic for another thread I suppose Posted Image

Well I was only trying to answer him. Posted Image And you just made me look like I don't realize what at least the main global drivers are. Thanks for that. Posted Image

If I would want to show him correlations for every important piece of the puzzle, there is not enough space in the post. And I event cant make correlations for all, and the problem is that some if not almost all are successive "through" each other. But ok. Posted Image

Cheers.

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The least enthusing gfs strat run for some time. The split vortices never far apart and subsequently the ridge between not nearly as impressive. the ep flux on ecm starting to switch direction at the very end of the forecast bit a fair way to go from there.

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I read somewhere that the stratosphere-troposphere coupling is poor even in CFS v2. It might not have good idea of what happens after the SSW, then.

(Greetings from Finland, by the way. Posted Image)

Hi scellus. Can you you pop your location into your profile please??

Great to have more overseas members!Posted Image

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Hi, which of these forecast graphs should I track to spot a SSW?

Thanks

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng

None of them. Sebastian posted the chart above. Note the mean wind speed is negative 0.6 m/s. also, you could check the zonal wind speed chart. Lookmfor the point at which the blue shade covers 10hpa 60N. That means zonal winds are forecast to reverse at that level/latitude. A technical SSW.

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The least enthusing gfs strat run for some time. The split vortices never far apart and subsequently the ridge between not nearly as impressive. the ep flux on ecm starting to switch direction at the very end of the forecast bit a fair way to go from there.

I think that the latest GFS run highlights the difficulty that we will have getting some kind of polar flow from this particular type of forecast SSW - certainly in the short term (first 20 days). We see the displacement push the vortex towards the Atlantic - not great positioning - followed by a split that could possibly leave a daughter vortex still too close to our west, thus preventing heights to build to our NW. What I would like to see is the ridge at 10 hPa completely push through from the Pacific side to the Atlantic side, rather than being held on the Pacific side. If we see this modelled then it will be far more favourable in the short term. Longer term -15 days plus - the opportunities remain for this type of scenario as we do not know what will occur after this.

The latest MJO forecasts do suggest that we have to get through phases 4 and 5 before reaching safer more favourable territory, so this all fits in with the strat vortex positioning.

Edited by chionomaniac
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Here you are. Where the arrow points at; 10hpa, 60N

Superb thanks seb and blue army.

Where can I get access to charts like these? (And a range of days?)

Thanks. I find this thread fascinating, informative and friendly.

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I think that the latest GFS run highlights the difficulty that we will have getting some kind of polar flow from this particular type of forecast SSW - certainly in the short term (first 20 days). We see the displacement push the vortex towards the Atlantic - not great positioning - followed by a split that could possibly leave a daughter vortex still too close to our west, thus preventing heights to build to our NW. What I would like to see is the ridge at 10 hPa completely push through from the Pacific side to the Atlantic side, rather than being held on the Pacific side. If we see this modelled then it will be far more favourable in the short term. Longer term -15 days plus - the opportunities remain for this type of scenario as we do not know what will occur after this.

The latest MJO forecasts do suggest that we have to get through phases 4 and 5 before reaching safer more favourable territory, so this all fits in with the strat vortex positioning.

Having viewed the runs yesterday, i thought we had some consistency showing the split to be wide and the pacific ridge pushing through in the upper strat. to see the 00z run was rather a let down and reminds us that whilst the temp forecasts in the strat seem quite consistent, the heights ones can vary quite considerably beyond T240. ( though not as much as trop ones)

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All I am doing is putting a realistic slant on it- Most have been discussing some sort of warming since the start of Dec-

On Average the propergation time is circa 21 days from top to bottom-

With that in mind the discussion of this event will span from ~ 5th of december- to the event ~ 5th of Jan- through the propgation wave ~ 15th- 25th jan--

That spans ~40-50 days building an expectation from something that is only just greater than say 50% of delivering something for us.

Something MAY happen sooner for the UK- then that begs the question was it related to the strat or not..

Possibly but because of the rest of the lower trop influences we cannot be sure.

S

Edited by Paul
All previous comments removed now, so have got rid of related items
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Trying to guess where the blocking and vortices are positioned can be fraught with danger.

I just made a post in the model thread suggesting that the profile of the 06z strat run was

far less favorable than what we have been seeing.

This was a little hasty for example when looking at the 100hpa temperature profile for the

present time you could be forgiven for thinking that we should be in quite a potent northerly

airflow with higher pressure over Greenland and the western side of the Arctic where the warming

is and lower pressure and vortices over to the east.

post-10506-0-81519100-1356694565_thumb.g

Just trying to highlight how difficult it is to second guess what type of weather patterns we can

expect down the road.

Edited by cooling climate
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As brick alludes above, we really need to see where this warming is headed to get an idea of how the odds might be stacking up for nw Europe. I am a little encouraged to see gfs now struggling, run to run, with the placement and shape of the upper strat pattern post warming. I am less encouraged to see two runs which appear to make the longevity of any upper strat disruption seem on the short

side. Lets hope for some clarity from ecm's extended modelling or exeter's which may be visible on the updated 30 dayer due shortly.

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