Stratosphere Temperature Watch

[Nick B]

Possibly the warmer air being cooled more at the surface level and 850 due to the entrenched cold over the land of Greenland itself but is allowed to have more of a warming effect over the relatively mild sea to the east? Hence the warm pool popping up on the east coast as it 'leap-frogs' the land from the west...

Sounds entirely reasonable to me. I'd go with that as an explanation.

[chionomaniac]

I will leave things another day before doing another full report on the stratosphere (mainly time restraints though I have been watching the charts).

Everything looks good for cold lovers for 10 days or so. My forecast for another stratospheric disturbance looks off the mark wrt an asian mountain torque but I may still come lucky (and that's what it will be) wrt a Canadian negative MT. Update tomorrow.

[Glacier Point]

Temperatures now below average and forecast to continue to drop:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

Zonal wind anomalies lagging behind little and the colder than normal mid latitude belt in the stratosphere should inhibit the impact for the time being but I'm wondering here just how low these 10hPa and 30hPa values could get in the next 40-50 days given a strengthening atmospheric Nina signal.

[azores92]

Temperatures now below average and forecast to continue to drop:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

Zonal wind anomalies lagging behind little and the colder than normal mid latitude belt in the stratosphere should inhibit the impact for the time being but I'm wondering here just how low these 10hPa and 30hPa values could get in the next 40-50 days given a strengthening atmospheric Nina signal.

Gah, never a good sign , do you still believe in a coldish december GP or do you think the atlantic will return for good following this potential cold spell?

[karyo]

Temperatures now below average and forecast to continue to drop:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

Zonal wind anomalies lagging behind little and the colder than normal mid latitude belt in the stratosphere should inhibit the impact for the time being but I'm wondering here just how low these 10hPa and 30hPa values could get in the next 40-50 days given a strengthening atmospheric Nina signal.

That's not what I wanted to hear but hardly surprising given the developing La Nina. High Pressure may be our best chance for cold surface conditions this winter, especially once December is out of the way.

Karyo

[knocker]

Came across this recent paper whilst browsing. Fatal. I have a copy but can't post because of © restrictions.

Cooling of the wintertime Arctic stratosphere induced by the western Pacific teleconnection pattern.

Abstract.

A composite analysis for extreme positive events of the Western Pacific (WP) teleconnection pattern with blocking flow configurations observed over the subpolar Far East shows that such an event in winter can trigger a persistent cold period in the polar stratosphere and, if it occurs in fall or early winter, it augments the possibility of the formation of polar stratospheric clouds. The stratospheric cooling occurs in conjunction with the weakening of upper-tropospheric planetary waves and their upward propagation into the stratosphere soon after the peak time of the WP pattern. Synoptically, this weakening of the upper-tropospheric planetary waves is manifested as westward evolution of a developing blocking high into the climatological-mean pressure trough over the subpolar Far East. This study thus presents a unique case where a blocking high can induce cooling in the polar stratosphere rather than warming.

http://www.agu.org/pubs/crossref/2010/2010GL043551.shtml

[Don]

That's not what I wanted to hear but hardly surprising given the developing La Nina. High Pressure may be our best chance for cold surface conditions this winter, especially once December is out of the way.

Karyo

Indeed. Joe B's latest video Winter outlook doesn't look too promising for us either. I think it's looking very likely now that our best chance of cold will occur in December with January and February possibly looking like mediocre months at best. Lets hope next week's cold spell delivers because I think it's certainly a case of make the most of it this year. One crumb of comfort is that the CFS charts are pointing towards a cold Winter and if I remember correctly, it did rather well last year.

Edited November 19, 2010 by Don

[karyo]

Indeed. Joe B's latest video Winter outlook doesn't look too promising for us either. I think it's looking very likely now that our best chance of cold will occur in December with January and February possibly looking like mediocre months at best. Lets hope next week's cold spell delivers because I think it's certainly a case of make the most of it this year. One crumb of comfort is that the CFS charts are pointing towards a cold Winter and if I remember correctly, it did rather well last year.

To be honest, I don't rate Joe B's forecasts much. I think he was lucky last winter!

However, I agree that not having the stratosphere on our side is a major problem.

Yes, CFS did rather well. I wonder why it predicts a cold winter?

Karyo

[Guest mycroft]

To be honest, I don't rate Joe B's forecasts much. I think he was lucky last winter!

However, I agree that not having the stratosphere on our side is a major problem.

Yes, CFS did rather well. I wonder why it predicts a cold winter?

Karyo

If you define lucky by forcasting a cold winter in september when the met was predicting a warm winter yes?

but he also predicted a good ice recovery in winter and a big melt this summer!!

might pay to ask him to pick 6 numbers for the lottery with this much luck??

[chionomaniac]

Latest update.

Firstly, it looks like my assessment that a strong Asian mountain torque event leading to another stratospheric warming event may have busted. There is still a chance that that a negative MT event over North America could feedback stratospherically but we would need to see something occur in the next day or two.

Having said that there is still an increase in wave number 2 activity throughout the stratospheric profile but I think that this could be related to the current split vortex forecasts.

GP mentioned earlier that the stratosphere is cooling down now following earlier slight warmings that may have contributed to the current vortex disruption.. There is always some time lag between a warming or cooling event and the polar vortex weakening or strengthening, even at the level that such event may occur, never-mind the time it takes for any change to be felt in the troposphere.

The 5 day forecast at the 10 hPa level shows that the vortex is well and truly split despite the colder than average temperatures at this level.

By T+216 it appears that the PV looks to lose that split with the main vortex centered over Siberia. Note that there appears to be an area of warming towards the Canadian periphery of the vortex - perhaps this is caused by the -VE MT wave deflection in NA.

The GFS is a little slower with the idea of reformation of the vortex.

As we get nearer the troposphere we can see how the models are predicting exactly how the PV is likely to shape out in the next 10 days.

It appears that both the GFS and the ECM will suggest the slow decline of the GH. However pressure rises may be maintained a little while longer at the 500hPa level.

For me, I think that it is highly likely that by the middle of December the Atlantic will be having a far greater influence on our weather. We would need to quick changes in the cooling stratosphere for this not to be the case imo. Once the Atlantic gets in, it may be difficult to get deep cold air moving south of the pole as the strength of the PV may prevent further northern blocking.

In the shorter term it is good to look at the profile of the mean zonal winds in the coming days and watch the negative (blue) winds increase around 60-90ºN in the coming days.

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

However when the PV reforms it is likely to gain strength especially if the temperature of the tropical stratosphere at 10 hPa follows that of the 30hPa profile.

c

[ZONE 51]

I had read something interesting about the solar minimum,low sunspots and its effects on the stratosphere and troposphere, it pulls the jet stream south due to effects from the sun, its said that the jet stream is playing unusual patterns from these effects and higher chance of blocking as jet continues south this winter.

Update thanks for that at least we have something for next wk of interest, maybe some suprises are to be had with the upper atmosphere and pv..(:

[Don]

For me, I think that it is highly likely that by the middle of December the Atlantic will be having a far greater influence on our weather. We would need to quick changes in the cooling stratosphere for this not to be the case imo. Once the Atlantic gets in, it may be difficult to get deep cold air moving south of the pole as the strength of the PV may prevent further northern blocking.

c

I did have high hopes for a cold December but these are now waning somewhat. It may look good for the next ten days but it's still November. It's all well and good to have a cold spell at this time of the year but it's not going to deliver like it would in late December, January or February. If we revert back to an Atlantic driven pattern in December this could potentially hang around for a long time. As I said earlier make the most of next week because it could be the coldest spell of Winter before it's even started! I just hope things improve soon for the longer term.

[Glacier Point]

Here's why the temperature of the stratosphere matters going into the depth of the polar winter.

For years with a cold 30mb temperature in December - January period:

The proceeding January - February 500mb geoptential height anomaly:

Note the unusually high proportion of Nina winters there and absence of blocking (although the +ve height anomaly in the Atlantic is interesting).

Now, the inverted test. Years with a warm 30mb temperature December - January period:

The proceeding January - February 500mb geopotential height anomaly:

Edited November 19, 2010 by Glacier Point

[johnholmes]

hi Stewart

I know its a lot of work but could you give the years when mid November had similar synoptic patterns to what we have now (not what the models are predicting in 3 or 13 days time), what was the ENSO position, El Nino, La Nina, increasing/decreasing, and what was happening in the Stratosphere?

I'm not over enthusiastic about looking for comparisons but it would be interesting to see what I've asked for IF its not too much hassle?

[Glacier Point]

Not something I would want to do John as this would undermine the importance of looking at variables in isolation and how these might work together.

The question relevant to this thread is this - what will the impact be of stratsopheric cooling some 30 days down the line be in terms of the tropospheric response ?

Based upon quite a large analogue sample for both variations (anomalously warm and cold), the clear inference is that cooling stratsopheric temperatures lead a strengthening of the thermal gradient with the mid and lower latitudes and resulting strengthening of the stratospheric jet which influences the height of the tropopause reducing the tropospeheric heights and probably causing further feedbacks through increased ice cloud formation (catalyst for ozone destruction in the presence of NOx) and inhibition of wave breaking resulting in further cooling.

What I would offer in terms of where we are and where we might be, looking at the position of highest ozone concentration in the north Pacific, we look to have a displaced polar vortex towards Siberia and enhanced Nina type signal. Also worth noting from those analogs that the banding of warm and cold is not as well defined this year so far in the mid latitudes which I think will inhibit the mean zonal winds stirring too much too early.

This signal also seems to support a tropsopheric response to La Nina so we will likely have both stratosphere and trosphere working for an Aleutian ridge in the Pacific. The Atlantic signal is up for grabs. I suspect that a mean solution is ridge not trough, particularly given the underlying SSTA and other tropospheric signals (mainly angular momentum). But that's for another thread.

[johnholmes]

Not something I would want to do John as this would undermine the importance of looking at variables in isolation and how these might work together.

The question relevant to this thread is this - what will the impact be of stratsopheric cooling some 30 days down the line be in terms of the tropospheric response ?

Based upon quite a large analogue sample for both variations (anomalously warm and cold), the clear inference is that cooling stratsopheric temperatures lead a strengthening of the thermal gradient with the mid and lower latitudes and resulting strengthening of the stratospheric jet which influences the height of the tropopause reducing the tropospeheric heights and probably causing further feedbacks through increased ice cloud formation (catalyst for ozone destruction in the presence of NOx) and inhibition of wave breaking resulting in further cooling.

What I would offer in terms of where we are and where we might be, looking at the position of highest ozone concentration in the north Pacific, we look to have a displaced polar vortex towards Siberia and enhanced Nina type signal. Also worth noting from those analogs that the banding of warm and cold is not as well defined this year so far in the mid latitudes which I think will inhibit the mean zonal winds stirring too much too early.

This signal also seems to support a tropsopheric response to La Nina so we will likely have both stratosphere and trosphere working for an Aleutian ridge in the Pacific. The Atlantic signal is up for grabs. I suspect that a mean solution is ridge not trough, particularly given the underlying SSTA and other tropospheric signals (mainly angular momentum). But that's for another thread.

cheers Stewart

I somehow felt it was asking rather a lot.

To the para re the Stratospheric cooling. The simple answer would be, for our part of the world, a more mobile Atlantic. However, its not that simple as you point out. The current position of the Polar vortex, unless it simply shifts further east would not really support that, at least not within 30 days I would have thought. As to what happens sort of Xmas and onwards then I suppose the form horse is for the Atlantic courtesy of the jet stream to begin to wind up, at least to some extent?

[AtlanticFlamethrower]

The Atlantic signal is up for grabs. I suspect that a mean solution is ridge not trough, particularly given the underlying SSTA and other tropospheric signals (mainly angular momentum). But that's for another thread.

This might also be for another thread but I notice the below image of seasonal model output and your analogue basket here are pretty similar. The set up doesn't rule out snowy cold snaps, but I'm getting the impression of a consensus from multiple sources that overall the UK winter should not be as cold as last year.

[sebastiaan1973]

Glacier Point, the fourth chart is not right, it is not a 500mb chart, instead a 30mb.

And I find it remarkable that in a year of cold 30mb temperature in December - January period we have a little +ve height anomaly in the Atlantic. I read such an anomaly too in the Netweather winter forecast and in the seasonal forcast of EC

And you wrote:

Note the unusually high proportion of Nina winters there.

Is this coincidence?

And looking at these cold 30mb years, I see some very cold months; 56, 86, 79, 96.

Edited November 19, 2010 by sebastiaan1973

[Glacier Point]

Glacier Point, the fourth chart is not right, it is not a 500mb chart, instead a 30mb.

And I find it remarkable that in a year of cold 30mb temperature in December - January period we have a little +ve height anomaly in the Atlantic. I read such an anomaly too in the Netweather winter forecast and in the seasonal forcast of EC

And you wrote:

Note the unusually high proportion of Nina winters there.

Is this coincidence?

And looking at these cold 30mb years, I see some very cold months; 56, 86, 79, 96.

Thanks, and fixed.

No coincidence that all of your cold selections were east QBO and all bar one were Ninos.

I think that it is very significant that there is a large weighting of Ninas on the cold list. Look at the 500mb plots for both cold and warm. They are typical patterns associated with La Nina (cold strat) and El Nino (warm strat) in the troposphere w/r/t pressure anomalies in the Pacific and Atlantic - Pacific and Atlantic ridges for La Nina, troughs for El Nino.

Edited November 20, 2010 by Glacier Point

[Catacol]

Thanks, and fixed.

No coincidence that all of your cold selections were east QBO and all bar one were Ninos.

I think that it is very significant that there is a large weighting of Ninas on the cold list. Look at the 500mb plots for both cold and warm. They are typical patterns associated with La Nina (cold strat) and El Nino (warm strat) in the troposphere w/r/t pressure anomalies in the Pacific and Atlantic - Pacific and Atlantic ridges for La Nina, troughs for El Nino.

First post here...

GP - a quick and punchy question on SSW. Do you believe it is the chicken or the egg? Doing some recent reading I have come across some strong arguments stating that SSW is caused by blocking patterns, and not, as would seem to be implied by much of what I am reading on NW, the creator of such patterns. I am sure the analogue data of La Nina to SSW does match either way - it would have to.. But in my attempt to increase my understanding of weather drivers surely the key is to try and get a handle of what causes blocking in the first place. I apologise if this is OT for this thread...

Are you of the belief that SSW warming is the key to blocked or unblocked patterns? How does it fit alongside other suggested drivers such as a weak sun? In our part of the world is it a more important factor than SSTs in the atlantic?

Curiously

Alastair

Edited November 20, 2010 by Catacol_Highlander

[Glacier Point]

First post here...

GP - a quick and punchy question on SSW. Do you believe it is the chicken or the egg? Doing some recent reading I have come across some strong arguments stating that SSW is caused by blocking patterns, and not, as would seem to be implied by much of what I am reading on NW, the creator of such patterns. I am sure the analogue data of La Nina to SSW does match either way - it would have to.. But in my attempt to increase my understanding of weather drivers surely the key is to try and get a handle of what causes blocking in the first place. I apologise if this is OT for this thread...

Are you of the belief that SSW warming is the key to blocked or unblocked patterns? How does it fit alongside other suggested drivers such as a weak sun? In our part of the world is it a more important factor than SSTs in the atlantic?

Curiously

Alastair

Welcome Alastair.

There are multiple factors associated with (1) warming events and (2) generally elevated stratospheric temperatures. What causes these is a continuing area of research, however, I would pick out a couple of drivers.

The fact that warming events tend to occur in Nino winters tells us that there is a relationship with the troposphere and the meridional circulation. During El Nino years, angular momentum is enhanced which favours tropical activity in parts of the Pacific which develop high pressure systems generating poleward dispersing Rossby Waves. El Ninos favour low pressure systems in the North Pacific and Atlantic so this probably does suggest that an absence of blocking around the edge of the Arctic does allow for penetration of Rossby Waves into the polar stratosphere deccelerating the polar jet and releasing energy.

Generally warm stratospheric years are also associated with west QBO phases during solar maxima and east QBO phases during solar minima. There is also a relationship between the northern and southern hemispheres. This suggests a second factor (via the Brewer Dobson Circulation) which makes a warming event much more likely.

Then there is 2008/9 polar winter. A low solar / west QBO / Nina winter but where we witnessed a massive mid winter warming event. What caused that ? I remember that there was a strong +ve mountain torque preceeding the event. Maybe the stratosphere got so cold it became unstable, maybe there was a solar influence through the Ionosphere ?

So chicken or egg is difficult to answer for SSW because all of the factors are so interrelated. For seasonally warmer stratospheres, definately egg.

[Catacol]

Welcome Alastair.

There are multiple factors associated with (1) warming events and (2) generally elevated stratospheric temperatures. What causes these is a continuing area of research, however, I would pick out a couple of drivers.

The fact that warming events tend to occur in Nino winters tells us that there is a relationship with the troposphere and the meridional circulation. During El Nino years, angular momentum is enhanced which favours tropical activity in parts of the Pacific which develop high pressure systems generating poleward dispersing Rossby Waves. El Ninos favour low pressure systems in the North Pacific and Atlantic so this probably does suggest that an absence of blocking around the edge of the Arctic does allow for penetration of Rossby Waves into the polar stratosphere deccelerating the polar jet and releasing energy.

Generally warm stratospheric years are also associated with west QBO phases during solar maxima and east QBO phases during solar minima. There is also a relationship between the northern and southern hemispheres. This suggests a second factor (via the Brewer Dobson Circulation) which makes a warming event much more likely.

Then there is 2008/9 polar winter. A low solar / west QBO / Nina winter but where we witnessed a massive mid winter warming event. What caused that ? I remember that there was a strong +ve mountain torque preceeding the event. Maybe the stratosphere got so cold it became unstable, maybe there was a solar influence through the Ionosphere ?

So chicken or egg is difficult to answer for SSW because all of the factors are so interrelated. For seasonally warmer stratospheres, definately egg.

Thanks GP - so uncertain. Do I get the impression from your post that the effects of a Nino in terms of low pressure development and eventual disruption of the PV are better understood generally than the impact of a Nina? I am relatively new to building up a knowlege base on this, but a number of forum threads I have been scanning seem to be really rather confused about any links between Ninas and "weather" as such, especially in our part of the world.

How far back does our data on such links go? I dont have anything bookmarked, but are we talking a very recent detailed dataset or have the QBO / Solar/ Nina / Nino links you mention above been catalogued for a fair while?

I'm going to need to go and read more about Brewer - Dobson. That's totally caught me unawares!

Many Thanks

Alastair

Edited November 20, 2010 by Catacol_Highlander

[knocker]

Welcome Alastair.

There are multiple factors associated with (1) warming events and (2) generally elevated stratospheric temperatures. What causes these is a continuing area of research, however, I would pick out a couple of drivers.

The fact that warming events tend to occur in Nino winters tells us that there is a relationship with the troposphere and the meridional circulation. During El Nino years, angular momentum is enhanced which favours tropical activity in parts of the Pacific which develop high pressure systems generating poleward dispersing Rossby Waves. El Ninos favour low pressure systems in the North Pacific and Atlantic so this probably does suggest that an absence of blocking around the edge of the Arctic does allow for penetration of Rossby Waves into the polar stratosphere deccelerating the polar jet and releasing energy.

Generally warm stratospheric years are also associated with west QBO phases during solar maxima and east QBO phases during solar minima. There is also a relationship between the northern and southern hemispheres. This suggests a second factor (via the Brewer Dobson Circulation) which makes a warming event much more likely.

Then there is 2008/9 polar winter. A low solar / west QBO / Nina winter but where we witnessed a massive mid winter warming event. What caused that ? I remember that there was a strong +ve mountain torque preceeding the event. Maybe the stratosphere got so cold it became unstable, maybe there was a solar influence through the Ionosphere ?

So chicken or egg is difficult to answer for SSW because all of the factors are so interrelated. For seasonally warmer stratospheres, definately egg.

Hi GP, I've also been attempting to come to grips with this along with the dreaded E-P flux ( I won't go there). Mainly through reading Stratosphere Troposphere Interactions by K. Mohanakumar. A very brief extract which unless I'm mistaken essentially agrees with your comments leaving aside the the Brewer-Dobson and one or two other of your points.

Major SSWs normally occur in the northern hemisphere because orography and land-sea temperature contrasts are responsible for the generation of long (wave number 1 or 2) Rossby waves in the troposphere. These waves travel upward to the stratosphere and are dissipated there, producing the warming by decelerating the mean flow (Matsuno 1971). Since the sudden warming is observed only in the northern hemisphere, it is logical to conclude that topographically forced waves are responsible for the vertical energy propagation.

He goes on to say:

During major SSW, the north pole warms dramatically with reversal of meridional temperature gradient, and breakdown of polar vortex occurs. The polar vortex is replaced by blocking high over this region. The westerlies in the Arctic at 10 hPa are replaced by easterlies so that the center of the vortex moves south of 60-65°N during the breakdown of polar vortex. The vortex is either displaced entirely or split into two.

He does appear to gloss over the part played by El Ninos.

Edit.

Although thinking about it perhaps the reasons behind generating poleward dispersing Rossby Waves was not part of his remit.

Regards

Fred

Edited November 20, 2010 by weather ship

[chionomaniac]

First post here...

GP - a quick and punchy question on SSW. Do you believe it is the chicken or the egg? Doing some recent reading I have come across some strong arguments stating that SSW is caused by blocking patterns, and not, as would seem to be implied by much of what I am reading on NW, the creator of such patterns. I am sure the analogue data of La Nina to SSW does match either way - it would have to.. But in my attempt to increase my understanding of weather drivers surely the key is to try and get a handle of what causes blocking in the first place. I apologise if this is OT for this thread...

Are you of the belief that SSW warming is the key to blocked or unblocked patterns? How does it fit alongside other suggested drivers such as a weak sun? In our part of the world is it a more important factor than SSTs in the atlantic?

Curiously

Alastair

Hi C_H and welcome to the forum.

We haven't really touched on this subject this year but did mention it in previous years.

As you correctly say, that prior to the majority of SSW events there appear to be some pre-conditioning of the troposphere and stratosphere in the form of blocking patterns. These blocks reside over the Pacific or Atlantic quarters and will influence the type of wave breaking seen in the stratosphere (numbers 1 or 2). This then helps determine the type of SSW that occurs - displacement or splitting. it appears that there are very few cases of SSW's without this type of pre-conditioning.

But there have been two. One in 1979 and the other in 2009 as GP has already mentioned. These are formed by resonant excitation of free modes within the stratosphere which create a barotropic mod.

To quote from this paper: http://www.columbia.edu/%7elmp/paps/waugh+polvani-PlumbFestVolume-2010.pdf

The focus of the above simulations, and analysis of

observations, has primarily been on the impact of upward

propagating Rossby waves. However, the recent study of

Esler and Scott [2005] revisited the idea of resonant exci-

tation of free modes considered earlier by Tung and Lindzen

[1979] and Plumb [1981]. Esler and Scott showed that in an

idealized 3-D quasi-geostrophic model, there are not only

upward and downward propagating Rossby waves, but there

is also a barotropic mode. This latter mode can be forced by

transient forcing and can dominate over the upward pro-

pagating waves. In fact, they showed that a “barotropicâ€

sudden warming occurs if this mode is resonantly excited.

Furthermore, some observed NH vortex-splitting major

sudden warmings, e.g., in 1979 and 2009, exhibit a very

similar structure to the modeled barotropic sudden warming.

I remember that there were suggestions at the time that this warming was solar influenced. It was the first ever recorded SSW, in the westerly QBO phase, combined with a solar minimum.

Which brings us neatly round to this year. Again we are experiencing a westerly QBO combined with low solar conditions. Up until two years ago, I would have ruled out a SSW this winter, but now I am not so sure. Whatever, I think it is highly unlikely this year, but worth monitoring nonetheless.

c

No real change in the outputs today. The main thing to note is that the GH and -VE NAO is likely to transfer to become more west based as time progresses. Both the GFS and ECM agree on this after both flirting with the idea of the high latitude block slowly sinking towards the UK.

[chionomaniac]

If ever we need to make the most of an early cold spell, now is it.

Luckily the lower 100 hPa charts are favourable for cold lovers for at least 10 days. However after that the stratosphere is forecast to cool rapidly. As it does so the vortex repositions itself on the Siberian side (not over Greenland!) I think that a slow undercutting of a waning block is the most likely breakdown scenario to this cold spell.

Temperature forecasts over the NH:

I don't like that one bit! (but not unexpected)