Stratosphere Temperature Watch 2013/2014

[chionomaniac]

What does that mean? 

 

Karyo

It effectively means that even though the vortex is stretched by the wave 2 activity, it never really loses its strength. So when the wave activity reduces the stretching reduces with it and the vortex is likely to retire back to the pole. The warming never really penetrates through the surf zone and into the core of the vortex and this is critical for those hoping to see the strength reduce significantly. That isn't to say that that won't happen in future runs - it's just not being forecast presently.

[feb1991blizzard]

It effectively means that even though the vortex is stretched by the wave 2 activity, it never really loses its strength. So when the wave activity reduces the stretching reduces with it and the vortex is likely to retire back to the pole. The warming never really penetrates through the surf zone and into the core of the vortex and this is critical for those hoping to see the strength reduce significantly. That isn't to say that that won't happen in future runs - it's just not being forecast presently.

 

Is the surf zone the area on the boundary between the vortex and high heights?

[chionomaniac]

Is the surf zone the area on the boundary between the vortex and high heights?

Yes - as described by:

 

McIntyre, M. E., and T. N. Palmer (1984), The ‘surf zone’ in the

stratosphere, J. Atmos. Terr. Phys., 46, 825–849.

[Recretos]

Chionomaniac you beat me to the explanation, but since I have put time in it, I will post it anyway and for anyone else that might not be so familiar with the concept of "heights".

 

What does that mean? 

 

Chionomaniac is referring to the geopotential height. I am not sure how familiar you are with that, so I will make a quick explanation (at least I will try to). 

 

Geopotential height is represented by the white lines (contours) that you can see on this chart, or on the "instant weather maps" geopotential height charts. Basically it s a parameter that tells us at what geometric height (elevation) is a certain pressure at a certain time. As an example, on this chart, we have 30mb geopotential height lines in DM (dekameter = 10 meters). If you look at one of the labels, it says 2224, which means that at that layer, 30mb pressure is at 22.240 meters.

 

 

 

Now about the statement from Chiono: if you have lower geopotential height (or GPH, gph, height, heights, etc,.. as we call it), that corresponds with lower pressure. And this goes for our tropospheric cyclones just as much as for the polar vortex. Lower heights-lower pressure-stronger cyclone. That is why the lowest heights are associated with the "core" of the vortex. Over time, if you see heights decreasing (lowering) that means the cyclone is intensifying. If you see the heights rising (increasing), that corresponds with weakening of the cyclone or the vortex. (And opposite for anticyclones/ridges).

Now the closer these height lines are to each other (or the faster the height changes perpendicular to the height lines), the stronger the wind, because of the pressure gradients. The faster the pressure changes through a specific distance, the stronger the wind (that is the general rule of thumb, but it has its variations, which are not so important at this moment).

 

So to sum it up, the lower the heights are in the polar vortex, the stronger it is (or its core, depending on the overall picture), and if you would see the heights rising in the center of the vortex, that would mean that the polar vortex is weakening. And it also implies that the overall pressure gradients would decrease and the "jet stream" (polar night jet) around the vortex would begin to weaken, basically reducing the momentum of the polar vortex and making the warmer air intrusions (might there be any) more viable to penetrate the surf zone. And the vortex might even split if there is decent wave activity pressure being applied on the vortex itself. Of course this is just a general "flow of events" that you have to keep in mind, because it mostly varies from situation to situation and it depends on "why" and "how intense" the height rises actually are. There are usually some normal fluctuations of heights in the core of the vortex, so you want to see more intense or prolonged height rises. 

 

It is not easy to explain this, since there are so many variations, and I haven't even mentioned how the temperature comes into play. But for the general understanding, I hope I got the point over and now you might understand why the heights are just as important to monitor as the temperature.

 

Best regards.

Edited December 22, 2013 by Recretos

[aginob]

good evening in the late hours

 

Pressure Altitude Calculator ( converter )

example = 10mb ( millibars ... hpa ) => 25907.5 m ( or feet => ft )

example = 850mb => ~1500 m

 

 

source: http://www.csgnetwork.com/pressurealtcalc.html

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northern hemisphere

stratosphere diagnostics

temperature at 30 mb

ecmwf

 

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northern hemisphere

stratosphere diagnostics

geopotential hight ( dam ) at 2 PVU

ecmwf

 

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Polar Vortex Frcst

animation ( +00 h - +96 h )

 

Edited December 22, 2013 by aginob

[karyo]

Thank you for the explanation to Recretos and chiono.

 

Karyo

[AWD]

Increasingly noteworthy wave 2 activity forecast for the turn of the year now;

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_ha2_f240.gif

This is likely to make NWP output rather volatile in FI.

Edited December 23, 2013 by AWD

[aginob]

good morning

 

freie universität berlin D

stratosphere diagnostics ecmwf via dwd

again online http://www.geo.fu-berlin.de

===

community forum team and user netweather UK

I wish you all merry christmas 2013 and a happy new year 2014

Edited December 23, 2013 by aginob

[Duane S.]

Decent reduction in zonal winds at the the top of the strat being forecast

 

 

A vortex under pressure, strong wave 2 signature very graphic here...

Edited December 23, 2013 by s4lancia

[snowking]

Interesting end to the latest ECMWF stratosphere forecast:

 

 

Concurrent wave 1 and wave 2 attacks at the top of the stratosphere. As Chio has already said nothing yet breaking the surf zone, with the E-P Flux facing away from the pole at the moment:

 

 

We ideally could do with some poleward flux in to January, but should the wave 1 attack continue to ramp up following the wave 2 attack then with more and more pressure being piled on to the vortex eventually something has to give. We saw something similar last year (though in reverse if I recall correctly - wave 1 followed by wave 2).

 

Most forecasts for the winter as a whole currently look right on track.

 

SK

[chionomaniac]

That is quite a big wave.... and could really do some damage to the vortex, sk. Highly promising this forecast for (comparatively) early in the New Year. I know I did suggest strong wave 2 activity in Jan to overwhelm the vortex by Feb - but I am even surprised by this forecast.

[Severe Siberian icy blast]

That is quite a big wave.... and could really do some damage to the vortex, sk. Highly promising this forecast for (comparatively) early in the New Year. I know I did suggest strong wave 2 activity in Jan to overwhelm the vortex by Feb - but I am even surprised by this forecast.

The irony of it is , if these forecasts go as planned we may actually have a fantastic jan , considering how poor things looked until recently , my first snow fall last year was 19th jan , so still plenty of time to have a good winter . . . Good to see such strong wave activity in the pipe line .

[aginob]

22.12.2013 00 UTC - 23.12.2013 00 UTC - 23.12.2013 12 UTC

northern hemisphere

surface chart

hights vorticity mslp

animation

 

[Recretos]

I have noticed that ECMWF is perhaps slightly too optimistic in the 10 day range for the upper strat, being a bit too warm and having the vortex slightly too weak. I cant say if it is a bias or not, because I dont have enough observations. But it probably all originates from the over optimistic wave activity in the 10 day range, which I have noticed on more occasions this year and last year. I am not saying that the last run is unrealistic, but just trying to point out a possible bias. 

 

 

 

 

 

All that, while the GFS has a negative bias for height and temperature, growing with time. basically meaning that it has a slightly too strong vortex at 10mb in the FI. There is a notable difference after the resolution decrease (204-384).

 

 

 

The same goes for ensemble means, while they have no obvious bias for temperature. 

 

 

Best regards.

 

[feb1991blizzard]

That is quite a big wave.... and could really do some damage to the vortex, sk. Highly promising this forecast for (comparatively) early in the New Year. I know I did suggest strong wave 2 activity in Jan to overwhelm the vortex by Feb - but I am even surprised by this forecast.

 

Do you think the ECM forecast is overdoing the wave forecasts as per Rectretos post or is some sort of decent even possible earlier than first thought?

[stodge]

Hope the stratosphere/vortex experts don't mind me asking a couple of historic questions in here.

 

1) Has the PV always been around Greenland/Canada/Siberia ? I gather it tends in winter to be around 80-90N though could be anywhere within that area. That said, there seems to be a preponderance toward Greenland rather than say north of Scandinavia. I wonder where the PV was and what it looked like in the LIA or in the last Ice Age ? 

 

2) Similar question re: stratosphere temps. We talk about a cold stratosphere in winter and I understand it's warmer in summer etc, etc but what were strat temperatures like during the LIA or the last Ice Age ? Historical accounts of winters in the LIA talk about cold and frost rather than snow which makes me think the prevailing synoptics were an easterly flow from HP over Scandinavia or to the North of the UK. That synoptic would suggest a warmer stratosphere and a much less vigorous PV but is there any scientific evidence for that assumption ?

 

Presumably when the last Ice Age ended, there was a gradual (rapid in geological terms) re-distribution of the atmosphere from what prevailed in the colder epoch to the current interglacial but what triggered that - solar activity ?

[bluearmy]

Note the end of the 12z gfs op shows the vortex repositioning towards the pole having survived the Asian warming. This is what ed expected.

As far as the ECM forecasts are concerned, the wave 2 stuff is consistent and the wave 1 has been showing for a few days. Looking back at sat/sun, the day 9/10 forecasts tend to be a bit overdone.

at least there's something to look at in the mornings!

Edited December 23, 2013 by bluearmy

[mpkio2]

Note the end of the 12z gfs op shows the vortex repositioning towards the pole having survived the Asian warming. This is what ed expected.

As far as the ECM forecasts are concerned, the wave 2 stuff is consistent and the wave 1 has been showing for a few days. Looking back at sat/sun, the day 9/10 forecasts tend to be a bit overdone.

at least there's something to look at in the mornings!

 Actually, bluearmy, I see the exact opposite.

 

Forgive me if I'm wrong but the chart below of the t384 12z op run shows a weak PV with the artic high sitting more or less in centre (Notice the yellows over Alaska). Also the PV is strectched in the t384 chart, with two warmings on either side. I'm not saying it will happen; I'm just saying what I'm seeing, unless I'm seeing it all wrong?

 

[cooling climate]

 

Note the end of the 12z gfs op shows the vortex repositioning towards the pole having survived the Asian warming. This is what ed expected.As far as the ECM forecasts are concerned, the wave 2 stuff is consistent and the wave 1 has been showing for a few days. Looking back at sat/sun, the day 9/10 forecasts tend to be a bit overdone.at least there's something to look at in the mornings!

I would not have thought that the warming would have had much affect in thetroposphere at that range. The warming is still up around the 10-30mb level.The GPH maps show a possible split taking place in the mid levels (30mb)andas this downwells in to the lower levels and hopefully troposphere in the daysto come we should see a split taking place.I have a question which has been nagging me. How do you know what is wave 1activity and what is wave 2.Cheers. Edited December 23, 2013 by cooling climate

[bluearmy]

i'm afraid the two charts are not comparable. the first being the troposphere at 500hpa whilst the second is the upper strat at 10hpa.  they are a long way apart (or as ed might say, there are a hell of a lot of spinning plates between them).

also, that meteociel chart is only showing the temperature and doesnt show the heights so we dont see the exact vortex placement and shape>

[aginob]

good evening

i hope is correct

see animation

red color ( 60°N )

 

northern hemisphere

wave 2

 

 

pressure level: 10mb 30mb 50mb 70mb 100mb 150mb

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northern hemisphere

surface

 

Edited December 23, 2013 by aginob

[chionomaniac]

I have a question which has been nagging me. How do you know what is wave 1activity and what is wave 2.Cheers.

Without the help of the ECM wave amplitude charts, the shape of the vortex is a dead giveaway. With wave 1 type events the large scale wave presses onto the vortex from one side and the vortex will look like a big comma shape. With wave 2 type events the vortex will look elongated - like a sausage, with 2 sources of warming evident on opposite sides of the hemisphere.

[Recretos]

i'm afraid the two charts are not comparable. the first being the troposphere at 500hpa whilst the second is the upper strat at 10hpa.  they are a long way apart (or as ed might say, there are a hell of a lot of spinning plates between them).

also, that meteociel chart is only showing the temperature and doesnt show the heights so we dont see the exact vortex placement and shape>

 

Well, basically the elongation from the strat is reflected in the trop with each basically having its own "elongation" mechanism. The "filter zone" seems to be around 100mb.

 

   

 

 

 I have a question which has been nagging me. How do you know what is wave 1

activity and what is wave 2.Cheers.

 

To put Chionos words into a graphical perspective with 10mb height examples : Wave 1 on the left, and wave 2 on the right. The wave 1 lat/lon chart is actually an analysis from 28/02/1871. Not the perfect example, but It gets the point over. The wave 1 perspective from above, is the analysis on my birthday in 2012.  It is quite a vigorous wave 1 at that point, but again its a good example.

And the wave 2 charts are the 12z GFS 384h forecast.

 

 

 

 

 

 

 

1) Has the PV always been around Greenland/Canada/Siberia ? I gather it tends in winter to be around 80-90N though could be anywhere within that area. That said, there seems to be a preponderance toward Greenland rather than say north of Scandinavia. I wonder where the PV was and what it looked like in the LIA or in the last Ice Age ? 

 

2) Similar question re: stratosphere temps. We talk about a cold stratosphere in winter and I understand it's warmer in summer etc, etc but what were strat temperatures like during the LIA or the last Ice Age ? Historical accounts of winters in the LIA talk about cold and frost rather than snow which makes me think the prevailing synoptics were an easterly flow from HP over Scandinavia or to the North of the UK. That synoptic would suggest a warmer stratosphere and a much less vigorous PV but is there any scientific evidence for that assumption ?

 

 

I think that the stratospheric analysis that far back is way beyond our abilities. It is just too far back and there is hardly any data to do reconstructions. There was more data towards the end of 1800's, but event that is not really enough data to do an in depth analysis of the stratosphere. We can just speculate about it. At least that is my take on it.  

As for the LIA itself, I think there are plenty of technical and less technical publications on its possible/likely causes.

Best regards.

Edited December 23, 2013 by Recretos

[Snowman.]

18z offering a Greenland warming!

 

[Snowy L]

18z offering a Greenland warming!

 

 

Wow that's a big improvement to the earlier charts today. That second warming is back (makes sense seeing as we have both wave-1 and wave-2 breaking going on) and that is very close to becoming a decent minor warming at least.