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chionomaniac

Stratosphere Temperature Watch

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Just a quick post to bring this up to the top of the page again. I've noticed that there seems to be a slight warming event over Greenland at the end of the month. Am I reading the chart correctly or is this just wishful thinking?

Hi mo63,

I am unsure of which chart it is that shows a stratospheric warming event over Greenland at the end of the month. Perhaps if you could post it then we could see what it shows.Thanks.

The latest NCEP forecasts only go out 10 days ahead and these are showing a cooling trend with no warm anomalies near Greenland:

post-4523-1229547477.gif

post-4523-1229547500.gif

The latest ECM forecasts also suggest that the stratosphere is going to cool down with a corresponding increase in westerly winds:

post-4523-1229548068_thumb.png

post-4523-1229548082_thumb.png

This could be the cooling down of the stratosphere that we have been reluctantly expecting. However all is not lost as the cooler winter stratosphere has still produced many MWWs in the last few years after a dearth in the mid 1990's.

http://www.geo.fu-berlin.de/en/met/ag/stra...pole/index.html

Perhaps the stratosphere is like a coiled spring -the more compressive force exerted, the more it is likely to want to release the pressure and spring out. We shall see.

c

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Guest zebra danio

There is just the possibility of another wave breaking/mountain torque event before probable cooling, as you say, in the next week or two.

However, this cooling may not necessarily have too much of a surface response - and also any conseqences may not be felt until later than previously believed due to the benign overall state of the stratosphere holding out longer than might have been anticipated. The polar vortex is relatively weaker than last winter. The +QBO though is being stubborn and is unlikely to weaken sufficiently in time to provide any opportunity for a MWW to assist prolonged high latitude blocking before the winter is out. But never say never of course!

A FW (final warming) is perhaps more probable once Spring arrives, and the stratospheric temps naturally rise at the same time as the west QBO is expected to change to the east phase, which as we know is more conduisive for more significant warmings.

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Latest Update.

At present if we look at the stratosphere temperatures we see that the bulk f the stratosphere is slightly below average but not significantly so:

post-4523-1229783991_thumb.png

When we look at a cross section of the zonal wind anomalies it is just possible to make out that these are about to return to positive at the upper level of the stratosphere.

post-4523-1229784474_thumb.png

However the zonal wind anomalies have been negative since the start of the month and these negative wind anomalies are propagating into the troposphere presently. This affects us by reducing the strength of the westerly airflow which normally bring us Atlantic based weather. If this continues then we may see that the next 3/4 weeks will hold are best chance for cold this winter.

The zonal wind anomalies are forecast to increase:

post-4523-1229784610_thumb.png

This will bring a corresponding drop in the stratospheric temperatures as we can see from the forecast.

post-4523-1229784719_thumb.png

This forecast seems to look worse every time I look at it. With the stratosphere more likely to cool with zonal wind enhancement from a westerly QBO there is a chance that we are unlikely to see any return above average any time soon unless something unexpected occurs. One line of thought from Jim Hughes across the pond is that a warming event may occur around mid January. A brave call.

Ultimately if the cooling occurs as predicted now, then it is likely come mid to late January that we will return to a strong tropospheric polar vortex situated where we least want it with a strongly positive AO bringing us mild SWesterlies.

Time will tell!

c

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Can someone do an update here - there's a few questions regarding the stratospheric temps in the Model Thread and I'm sure members would appreciate it :D

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I'll show the 30mb temp link but its best to pm GP and ask him or for chion who is keeping this going.

Its true to say the 30mb temperature does show a reasonable fall, the first such one below the average line for a while. This is partly why I made a comment, either this morning, more probably last evening, sorry I'm vague about the time, regarding this cold spell lasting into the 2nd/3rd week then a change occurring. GP suggested this morning, I think, that the indications were for a surface high to settle over the UK by 'month end' I believe was his quote, meaning January I assume. My own view, less well versed in this topic than GP is by the way, is that it could equally be a milder unsettled Atlantic interlude.

Anyway I'll post the 30mb link asap

here now

http://ds.data.jma.go.jp/tcc/tcc/products/...e/pole30_n.html

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Can someone do an update here - there's a few questions regarding the stratospheric temps in the Model Thread and I'm sure members would appreciate it :D

More than happy to oblige now that Christmas commitments have reduced.

The state of play so far as we finish the first third of winter is that the stratosphere has not cooled as it has done so in recent years leaving us with less strong westerly winds filtering down to the troposphere as one would have expected.

This has helped create the tantalising prospects of real cold in the new year. However it looks like things are all about to change in the stratosphere with some dramatic cooling now forecast and starting to occur:

post-4523-1230497484_thumb.png

Forecast not looking too rosy:

post-4523-1230497553_thumb.png

Now thats the bad news. However before the affects of these lower temps come into play we have a lot to look forward to. If we look at the zonal wind anomalies presently we see that down in the troposphere 100hPa to 100hPa we are still experiencing average zonal westerly winds which are just showing signs of dipping below average again:

post-4523-1230497852_thumb.png

These average to below average winds are likely to last between 2-3 weeks. Looking further up in the stratosphere right at the top it is reading above average zonal winds. These are forecast to increase and eventually filter down to the troposphere (in line with the westerly QBO).

post-4523-1230498217_thumb.png

At this time I expect the tropospheric polar vortex to restart and probably sit over Greenland sucking the Jetstream northwards and normal January service with mild wet Atlantic based weather that we have become accustomed to, resume. The question is how long will we have to wait for this to occur, and will the Atlantic need several bites of the cherry, with possible snowy battle scenarios before it wins out?

c

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Guest North Sea Snow Convection

Upper zonal wind anomalies have increased and the stratosphere has/is entering a cooling phase.

However, there should be a lag time into the second half of Jan before the effects in the stratosphere start to be felt at the surface. The hope is that we may still retain a mid latitude ridge by this time as an inversion high to suppress temperatures and provide some continued seasonality once the northern arm of the jetstream kicks back into work as a symptom of this polar stratospheric cooling. Much better obviously than the other alternative of high pressure well to the south and mild flat zonal westerlies prevailing.

However, not withstanding all that, in the meantime there should be a two to three week window for the present cold spell not to be threatened.The present and upcoming cold spell is, in part, with other factors of course, the reward for some negative zonal wind anomalies that have downwelled from the stratosphere during the first half of December

For the longer term it is a case of watching those positive upper zonal wind anomalies over the coming days and see how much they increase, and in turn stir up the polar westerlies and polar vortex for the second half of winter.

I have also seen a well respected view expressed though that a warming wave may follow the present cooling trend and appear by mid January or thereafter - this might help with providing some interest for the end of season, but all that is speculation and a long way off.

Whatever happens though, overall a far better situation than the last couple of years, and whatever the last third of Jan holds, there could well be quite some temperature deficit to turn round :D

Edit: snap!

a very good reply above from chinomaniac which has saved me pasting the links!!

It will be interesting to see how much the +QBO continues to weaken during Jan - a return to cold conditions is quite possible to end the winter and provide some interest for March/April.

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I have also seen a well respected view expressed though that a warming wave may follow the present cooling trend and appear by mid January or thereafter - this might help with providing some interest for the end of season, but all that is speculation and a long way off.

Whatever happens though, overall a far better sitaution than the last couple of years, and whatever the last third of Jan holds, there could well be quite some temperature deficit to turn round :D

Edit: snap!

a very good reply above from chinomaniac which has saved me pasting the links!!

Good to see that we have the same thoughts NSSC!

Looking back at previous years, dramatic coolings have quite often been followed by equally dramatic warmings. However as you say that is a long way off, but I still wouldn't dismiss another possibility of a colder spell late winter as well.

Time will tell.

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Good to see that we have the same thoughts NSSC!

Looking back at previous years, dramatic coolings have quite often been followed by equally dramatic warmings. However as you say that is a long way off, but I still wouldn't dismiss another possibility of a colder spell late winter as well.

Time will tell.

potentially, come mid-month( when the pattern change may take place), we could be looking at a colder scenario with the stratospheric cooling, as GP suggested, a surface high over the uk, leading to dry, frosty, and foggy conditions. its a 50/50 between that and zonality.

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Cheers lads and lasses - we're all now fully appraised! :D

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So perhaps a mild end to January and a mild February, followed by a classic chilly La Nina type spring? ;)

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Guest North Sea Snow Convection
potentially, come mid-month( when the pattern change may take place), we could be looking at a colder scenario with the stratospheric cooling, as GP suggested, a surface high over the uk, leading to dry, frosty, and foggy conditions. its a 50/50 between that and zonality.

I still believe that is possible - much is down to those upper zonal winds. The effect of the current negative zonal anomalies that have worked their way down to the troposphere is to temporarily weaken and spilt the polar vortex. That is why we are seeing a core of upper cold over Scandinavia at this time, which we hope to tap into in the next week or two.

But remember, in the same way as the current negative upper zonal wind anomalies are allowing those height rises towards Iceland and Southern Greenland, the converse is true when the positive upper zonal wind anomalies increase (ie the speed of the spinning of the polar vortex westerlies) and this makes its way down to the troposphere, This will determine the latitude that any mid zone high pressure belt can hold at without being flattened by the northern jetsteam that is very likely to return by midmonth. That high pressure belt remember, is our current friend that is driving the colder weather from a more northerly latitude atm. It will stay relatively friendly as long as it can keep the tropical maritime south westerlies from our door without slipping too far south under pressure from a re-invigorated polar vortex to the north.

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I have a rather basic question. If the stratospheric cooling event happens, are we talking about a localised event around Greenland. or a more general event around the polar region?

If it is a general event, how can you be sure that this would lead to a deep PV setting up over Greenland & not Alaska or Siberia?

Excuse my ignorance here, just trying to learn a little more everyday :crazy:

Dave

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Guest North Sea Snow Convection
I have a rather basic question. If the stratospheric cooling event happens, are we talking about a localised event around Greenland. or a more general event around the polar region?

If it is a general event, how can you be sure that this would lead to a deep PV setting up over Greenland & not Alaska or Siberia?

Excuse my ignorance here, just trying to learn a little more everyday :crazy:

Dave

Hi Dave

The effect of a polar stratospheric cooling and increase in the upper zonal wind anomalies will be to tighten the 'ribbon' of coriolis winds W-E across the polar stratosphere with the result that pressure falls there and as it does so then the low pressure vortex strenghtens and regroups as an 'entity' if you like. This means that heights over Greenland are very suppressed with this upper cold pool and the troughing and jetstream is sucked northwards as the cold air is bottled up into the arctic circle.

The Polar vortex tends to migrate anyway in mid winter towards the North Pole unless there is a significant warming event to disrupt and split it, and we get a situation not too unlike the present whereby part of it resides over Canada/alaska and the other over Siberia. It is this that has allowed the pressure rises towards Greenland we are currently seeing and agitating on in the model thread! In this scenario pressure is higher towards the pole, and because the vortex is split, it means that pressure can rise in between and cold air is displaced away from the pole. With a main part of the vortex over NE Europe and Siberia it means that we have the opportunity to tap into that cold pool (with luck!)

However, just to complicate things further, there are different kinds of warming events and the current situation has not arisen through a significant mid winter warming event but a type of early warming event associated with wave breaking of the stratosphere. This is a more temporary type of warming that disrups the PV and splits it sufficiently to allow the current cold opportunities we are looking at. The negative zonal anomalies associated with that wave breaking through mountain torque into the stratosphere have alligned in the troposphere in such a way that thet have allowed the height rises aroung Scandinavia, Iceland and Scotland. Because of the westerly QBO which inhibits significant warming events, we are actaully doing very well this winter - bear in mind the last westerly QBO winter was 2006/07 and that featured record high AO index figures and the winter was the first in a row of bad-uns.

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Hi Dave

The effect of a polar stratospheric cooling and increase in the upper zonal wind anomalies will be to tighten the 'ribbon' of coriolis winds W-E across the polar stratosphere with the result that pressure falls there and as it does so then the low pressure vortex strenghtens and regroups as an 'entity' if you like. This means that heights over Greenland are very suppressed with this upper cold pool and the troughing and jetstream is sucked northwards as the cold air is bottled up into the arctic circle.

The Polar vortex tends to migrate anyway in mid winter towards the North Pole unless there is a significant warming event to disrupt and split it, and we get a situation not too unlike the present whereby part of it resides over Canada/alaska and the other over Siberia. It is this that has allowed the pressure rises towards Greenland we are currently seeing and agitating on in the model thread! In this scenario pressure is higher towards the pole, and because the vortex is split, it means that pressure can rise in between and cold air is displaced away from the pole. With a main part of the vortex over NE Europe and Siberia it means that we have the opportunity to tap into that cold pool (with luck!)

However, just to complicate things further, there are different kinds of warming events and the current situation has not arisen through a significant mid winter warming event but a type of early warming event associated with wave breaking of the stratosphere. This is a more temporary type of warming that disrups the PV and splits it sufficiently to allow the current cold opportunities we are looking at. The negative zonal anomalies associated with that wave breaking through mountain torque into the stratosphere have alligned in the troposphere in such a way that thet have allowed the height rises aroung Scandinavia, Iceland and Scotland. Because of the westerly QBO which inhibits significant warming events, we are actaully doing very well this winter - bear in mind the last westerly QBO winter was 2006/07 and that featured record high AO index figures and the winter was the first in a row of bad-uns.

Okeley Dokeley, so as Greenland is the closest piece of land to the pole, the vortex would have to be, at least in part overt it. Sometimes a little North, east or west but never far away?

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Okeley Dokeley, so as Greenland is the closest piece of land to the pole, the vortex would have to be, at least in part overt it. Sometimes a little North, east or west but never far away?

This is a good question Dave, and one that is well answered by NSSC. It was something that I meant to show the other day but didn't get round to.

Look below at the chart at the 10hPa level from 3rd Dec:

post-4523-1230610217.gif

The stratospheric vortex is displaced from the pole and is less strong than it is presently. The stratospheric high over Alaska shown there will have disrupted the vortex to some extent, weakening the westerly overall zonal wind flow. This disruption has the potential to eventually down well to the troposphere and we can tap into the disturbed cold pool as NSSC suggests.

Now look at the same height, to see what we have presently:

post-4523-1230610837.gif

Now the stratospheric vortex is deeper and almost perfectly aligned over the North Pole. The longer that this occurs then the greater time that the troposphere will be influenced. This is conducive to a more positive AO which as we all know doesn't bear well for our chances of sustained cold here. However it is likely that we may still have a window of opportunity for the next 2-3 weeks before the effects of the strengthening stratospheric vortex may become a major player in our weather.

One other thing is that the zonal wind forecasts still look none to promising, with zonal winds set to increase further:

post-4523-1230611504_thumb.png

Keep your eye on the 16th Jan though as thoughts as hinted by NSSC from a well respected view suggest a drop around this time. Not enough to cause a SSW but enough to have an affect.

Time will tell.

c

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Guest North Sea Snow Convection
This is a good question Dave, and one that is well answered by NSSC. It was something that I meant to show the other day but didn't get round to.

Look below at the chart at the 10hPa level from 3rd Dec:

post-4523-1230610217.gif

The stratospheric vortex is displaced from the pole and is less strong than it is presently. The stratospheric high over Alaska shown there will have disrupted the vortex to some extent, weakening the westerly overall zonal wind flow. This disruption has the potential to eventually down well to the troposphere and we can tap into the disturbed cold pool as NSSC suggests.

Now look at the same height, to see what we have presently:

post-4523-1230610837.gif

Now the stratospheric vortex is deeper and almost perfectly aligned over the North Pole. The longer that this occurs then the greater time that the troposphere will be influenced. This is conducive to a more positive AO which as we all know doesn't bear well for our chances of sustained cold here. However it is likely that we may still have a window of opportunity for the next 2-3 weeks before the effects of the strengthening stratospheric vortex may become a major player in our weather.

One other thing is that the zonal wind forecasts still look none to promising, with zonal winds set to increase further:

post-4523-1230611504_thumb.png

Keep your eye on the 16th Jan though as thoughts as hinted by NSSC from a well respected view suggest a drop around this time. Not enough to cause a SSW but enough to have an affect.

Time will tell.

c

Thanks for that c!

I was v tired last night and did not get round to replying again to Dave.

It is a pity that we are seeing this development now, but in a strange way the polar field may need re-loading wth cold air to provide some more ammunition later in the winter when the patterns improve a bit. I know that JH on eastern wx has suggested very much along the same lines. The +QBO is slow to weaken though and that prohibits, as we know, any major warming, but some more warming wave breaking events further down the line may then help turn things around for the latter part of the winter, and depending on how the QBO plays out (it should start to weaken significantly by Feb IMO?) we may then see a FW (final warning event) going in towards Spring time.

April snow events again?? :D

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I know that JH on eastern wx has suggested very much along the same lines

not this jh though!

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Guest North Sea Snow Convection
I know that JH on eastern wx has suggested very much along the same lines

not this jh though!

Maybe not John - I don't know what your longer term view is! :D

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don't post anywhere except on here so its not me whatever my lrf may say on Wednesday!

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Guest North Sea Snow Convection
don't post anywhere except on here so its not me whatever my lrf may say on Wednesday!

Someone called Jim Hughes, who knows a lot on this subject is the person I'm referring to

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ah, thanks, best contact him for my next lrf for his views maybe?

might start to drop in and view that site but not post that is for sure

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Stratospheric forecasting is very important in the short term, but understanding the mechanisms for stratospheric warmings can give an insight into weather patterns up to a month in advance especially during the UK winter.

I always picture the stratospheric vortex as like the little vortex than develops when you pull the plug out in the bath. Make some waves in the water and the vortex disrupts or wobbles. That wobbling or splitting is what happens when you get a warming, namely the cold air within the vortex moves away from the pole as the vortex wobbles away leaving warmer air of the pole.

What needs to looked out for is waves which can cause the vortex to wobble, split or disrupt. We know that rossby wave breaking plays a part, along with possible wave breaking at the tropopause over mountain regions. Having read some recent articles about how the energy associated with the forcing waves instead of analysing Eliassen-Palm fluxes may be important, I am going to propose perhaps a different mechanism by which those vortex wobbles can be created.

Wave Energy and the stratospheric Vortex.

What I propose is that rossby wave lengths (i.e. the number of rossby waves around the globe) along with the number of tropospheric polar vortexs cause wave excitations which can strengthen or weaken the stratospheric vortex. We know that vortex displacement type events are linked to rosby modes 1and 2 or planetary zonal wave 1 and split vortexs are linked to planetary zonal wave 2 events.

This suggest to me that the forecast twin tropospheric polar vortexes could lead to a warming which would affect weather patterns 3 weeks hence (colder period ?).

There are a lot of ifs and buts and I have taken a lot of liberties but it might prove an interesting hypothesis for somebody to chase up. This all links back into the theme of global angular momentum and tropical pacific thudnerstorm development and should be viewed within the context that a westerly QBO is not condusive for tropospheric events being trasnmitted up into the stratosphere.

This could perhaps be linked to the discussion I had in the sea ice thread and I will perhaps start a new thread about angular momentum and the GWO where I try to pull things together.

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An interesting hypothesis BF and thanks for the link to Portuguese paper, some good New year reading there.

I certainly think that a discussion thread encorporating GLAAM and GWO interlinking the stratosphere/tropospohere coupling interactions and associated planetary wave interactions would be a good thing. There are certainly a number of people on here who would like to increase their understanding in these areas to that of the likes of yourself and GP, and would welcome this type of thread.

c

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Guest North Sea Snow Convection

Yes, count me in on that too. The whole chain of factors all link up to decide what we see at the surface.

That hypothesis re twin troposphec vortexs may be interesting in light of a mid Jan wave breaking prediction that has been made elsewhere.

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