Stratosphere Temperature Watch

[bluearmy]

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)

not a shock ch but maybe with a p/v strengthening over siberia (not greenland), a jet which is south of the uk, coupled with what is likely to be a scandi surface cold high + embedded cold over the uk and the near continent could leave us in evolution whereby the slow undrecutting continues for a fair old while, sometimes edging north and then south. that sort of invisible blocking to our north which doesnt look strong enough to deflect the jet, but does so. i do hope this thread has a lot further to go this coming winter.

[Catacol]

CH - these long distance forefasts for the Stratosphere: how accurate are they? If they are accurate and are clear precursors to pressure changes lower down in the atmosphere, why do climate models have such difficulty predicting patters even out to 6 days or sometimes less? I hear your gloom, and perhaps the logic and the outcome will prove to be correct, but I cant help thinking it must be much more complex than this, otherwise weather forecasting in general would surely be much easier.

And while the Met Office are not always right, they have come out with quite a cold outlook right up to 19th December at present, so surely gloom need not be too great.

[cooling climate]

The record warming in the stratosphere in January 2009 coincided with a

large solar flare and very strong east Pacific ridge (+PNA). Did the flare

initiate a barotropic response in the stratosphere or was the warming the

result of rosby wave breaking caused by the PNA ridge or did the flare cause

both.

During +QBO's heightened solar activity is meant to be a precursor to stratospheric

warming from what I have read. How or why this works I don't know.

Chionomaniac I posted in the model output thread that the renewed heights in the

Arctic during the mid and latter stages of the 12z GFS run yesterday and even more so

on the 06z run today are very likely down to the mountain torque event over Asia.

This would in my opinion have the effect of bolstering the heights to our north over

Greenland and Svalbard prolonging the very cold weather such as the 06z run was

alluding to.

I think it could be quite possible because of the zonal westerly winds higher up in the

stratosphere where it is bitterly cold that the wave breaking of these torque events and

rosby waves is happening in the lower stratosphere where we are seeing the effects

almost straight away.

[knocker]

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:

For those of us without the in depth knowledge does this site which includes useful yearly info. on monthly sunspot numbers and the QBO help in the understanding or does it pose more questions than it answers. One could spend some time doing some correlations.

http://www.atmosp.ph...5_Labitzke.html

Also a useful article on the Brewer-Dobson circulation for the unitiated like myself.

http://www.atmosp.ph.../15_Norton.html

Edited November 21, 2010 by weather ship

[chionomaniac]

CH - these long distance forefasts for the Stratosphere: how accurate are they? If they are accurate and are clear precursors to pressure changes lower down in the atmosphere, why do climate models have such difficulty predicting patters even out to 6 days or sometimes less? I hear your gloom, and perhaps the logic and the outcome will prove to be correct, but I cant help thinking it must be much more complex than this, otherwise weather forecasting in general would surely be much easier.

And while the Met Office are not always right, they have come out with quite a cold outlook right up to 19th December at present, so surely gloom need not be too great.

All I can say is the stratosphere is just one driver of the weather patterns seen in the troposphere. Granted it is a very important driver but the other drivers will have their say in influencing the weather patterns seen. The strength and positioning of the stratospheric vortex can give us an idea of the major picture in the stratosphere but we need to have the tropospheric drivers to see the detail.

Longer term forecasts can be based on the fact that a cooler stratosphere leads to a stronger vortex and positive AO. In the time that I have been monitoring the stratosphere and the tropospheric coupling, I have found a good deal of correlation. Even when we have the curved ball of a SSW thrown at us this is also the case but less predictable to how it occurs.

And I agree that the cold pattern is likely to persist until early to mid December with the slow undercutting of a diminishing block. It is from then onwards that I think that the cold stratosphere will come into play.

The record warming in the stratosphere in January 2009 coincided with a

large solar flare and very strong east Pacific ridge (+PNA). Did the flare

initiate a barotropic response in the stratosphere or was the warming the

result of rosby wave breaking caused by the PNA ridge or did the flare cause

both.

During +QBO's heightened solar activity is meant to be a precursor to stratospheric

warming from what I have read. How or why this works I don't know.

Chionomaniac I posted in the model output thread that the renewed heights in the

Arctic during the mid and latter stages of the 12z GFS run yesterday and even more so

on the 06z run today are very likely down to the mountain torque event over Asia.

This would in my opinion have the effect of bolstering the heights to our north over

Greenland and Svalbard prolonging the very cold weather such as the 06z run was

alluding to.

I think it could be quite possible because of the zonal westerly winds higher up in the

stratosphere where it is bitterly cold that the wave breaking of these torque events and

rosby waves is happening in the lower stratosphere where we are seeing the effects

almost straight away.

Agree with that cc, though difficult to be very sure of the last bit as it appears that some warming has tried to break through higher up the stratosphere.

[Glacier Point]

<br />Longer term forecasts can be based on the fact that a cooler stratosphere leads to a stronger vortex and positive AO. quote]

This is key - we need to distinguish the difference between forecasting a suddden stratoshperic disruption (the clue is in the name) and the long term mode of the Arctic Oscillation.

Imagine yourself standing over a bucket of water. Take a stick, stir the upper layer in an anticlockwise motion. Continue to stir. Eventually the lower layers will become stirred if energy is continuing to be applied to a sealed system through the laws of energy conservation. The same is true of the atmosphere where energy is applied to the motion of the stratosphere through either long term disruption of the Brewer Dobson Circulation and or inhibition of Rossby Wave dispersal in the polar region through a La Nina like circulation. Cooling air generating ice clouds resulting in ozone destruction in the presence of NOx further drived the feedback loop causing a stronger pressure thermal and pressure gradient and the mean zonal westerly motion (the stratospheric jet) increases. Vorticity is passed down through the atmosphere through frictional torques until this imapacts the middle and lower troposphere lifting the surface pressure and causing the AO to persist in a positive state.

The other point to note is that stratospheric timescales are extremely slow - sometime even inter-seasonal (although fast propagating warmings have been documented). This implies that we should see changes to the vortex in a 21 - 30 day timescale and it should be noted that outside of the polar field there is still a very strong and persistent signal for blocking so expect to see mid latitude highs, as per all long term model guidance.

Edited November 21, 2010 by Glacier Point

[Gavin P]

GP, would you class Scandinavian Highs as mid latitude blocking or northern blocking? Because what I'm wondering for December is whether, whilst the PV is becoming active towards Greenland, the Scandi High might continue to rule the roost for most of Europe, all-be-it perhaps tending to become centered more towards Germany/UK later on the month, but still with that residual cold mass of air very much keeping us on the cold side for most of the month underneath that high?

If that kind of Scandi High/easterly trending towards mid latitude high later in the month type pattern is go'er, then I reakon December 2010 has the potential to be an exceptionally cold month! What do you think?

Edited November 21, 2010 by Gavin P

[Glacier Point]

I would say it would be a mid latitudinal feature, especially if its core is southern Scandinavia. However, that would require La Nina and falling angular momentum (more particularly the latter) to take a holiday in the next 2-3 months, not to mention tropical convection to shift its position.

At the moment, those tropospheric ridges over the North Pacific and now Greenland are going to cause some serious damage to ozone levels due to inhibited wave breaking. I suspect that we'll see a vortex developing just east of the North Pole and wamer / greater heights over Canada in December, which should faciliate ridge development in the Atlantic.

By the way Gav, hope you managed to get out and get that de-icer we were talking about some time ago.

Edited November 21, 2010 by Glacier Point

[Gavin P]

Thanks mate. So your thinking we continue basically with the ridge in the Atlantic and presumably the trough over Scandinavia for December?

Re. De-icer, Yep, got 4 cans a couple of weeks ago.

Edited November 21, 2010 by Gavin P

[cooling climate]

This is key - we need to distinguish the difference between forecasting a suddden stratoshperic disruption (the clue is in the name) and the long term mode of the Arctic Oscillation.

Imagine yourself standing over a bucket of water. Take a stick, stir the upper layer in an anticlockwise motion. Continue to stir. Eventually the lower layers will become stirred if energy is continuing to be applied to a sealed system through the laws of energy conservation. The same is true of the atmosphere where energy is applied to the motion of the stratosphere through either long term disruption of the Brewer Dobson Circulation and or inhibition of Rossby Wave dispersal in the polar region through a La Nina like circulation. Cooling air generating ice clouds resulting in ozone destruction in the presence of NOx further drived the feedback loop causing a stronger pressure thermal and pressure gradient and the mean zonal westerly motion (the stratospheric jet) increases. Vorticity is passed down through the atmosphere through frictional torques until this imapacts the middle and lower troposphere lifting the surface pressure and causing the AO to persist in a positive state.

The other point to note is that stratospheric timescales are extremely slow - sometime even inter-seasonal (although fast propagating warmings have been documented). This implies that we should see changes to the vortex in a 21 - 30 day timescale and it should be noted that outside of the polar field there is still a very strong and persistent signal for blocking so expect to see mid latitude highs, as per all long term model guidance.

The ice clouds created by the bitter cold do not really cause a problem until the sun returns

to the polar stratosphere in spring similar to what happens at the south pole, although not as

extreme due to the south pole being so much colder.

[chionomaniac]

Interesting developments in the stratospheric forecasts today. Report later.

[KTtom]

Interesting developments in the stratospheric forecasts today. Report later.

You tease! :lol:

[chionomaniac]

Firstly there is no great change in the output at 100hPa for the coming week. By 10 days the vortex is regaining some of its shape and is mainly centered over Siberia.

I am sure that this will lead to a slow reduction in blocking.

Higher up the stratosphere we are seeing a cooling of temperatures and strengthening of the polar vortex. We need to see some kind of wave activity breaking into the stratosphere and a warming to result, otherwise we may find that the stratosphere will power us to a +ve AO later on this winter.

And, right on cue, it looks like an increase in wave 1 activity may just cause another warming to disrupt the stratospheric vortex again. It is very early days but I am already impressed with the 5hPa forecast warming at T+240.

This is already forecast to be propagating down to the 10 hPa level

Encouraging. Let's see if anything develops.

c

[Glacier Point]

Interesting, however those 5hPa and 10hPa forecasts are also increasing temperatures outside of polar region which might decrease the opportunity for any sustained wave breaking into the future.

Current mountain torque contributions to angular momentum budget are low.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltaum.90day.gif

Not overly impressive although consider the significant totals of outgoing longwave radiation (thunderstorm activity) in the Indian Ocean which is usually a precursor to a positive Asian mountain torque.

http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/OLR/m.3d.html

Within 5-10 days we should see the torques switch round and, with a large persistent +ve wind component present across 30N, allied to any residual westerly winds off the back of tropical convection, another spike in relative angular momentum seems very plausible.

http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltend.sig.90day.gif

What impact this will have on the stratosphere will be worth monitoring as I suspect the previous spikes have driven both the mid October and now November patterns.

However, the global circulation is setting out its stall to sink back into strong Nina territory which is likely to drive down stratospheric temperatures in December I think.

[azores92]

Well its good to see that theres perhaps a hint of some hope in the stratosphere of a renewed warming, all tentative i guess though.

[greybing]

ok,for us laymen what is the current state of the stratosphere in the pole etc and how does the general picture look with relation to cold spells and blocking events.Apparently this current omega blocking event looks to break down a week and a half from now ,so reallly i am wondering beyond this..thankyou.

[chionomaniac]

ok,for us laymen what is the current state of the stratosphere in the pole etc and how does the general picture look with relation to cold spells and blocking events.Apparently this current omega blocking event looks to break down a week and a half from now ,so reallly i am wondering beyond this..thankyou.

A bit of a confusing picture still.

Firstly looking at the 100 hPa charts we still see a pattern at T+240 that looks to hold troughing to the east and weak pressure rises to the west. We may get some kind of Northerly (with a hint of westerly) in this airflow as the cold spell will only slowly relinquish its grip. I do not see any quick smash through of the Atlantic.

Further up the stratosphere we are seeing a moderate warming episode that may or may not break into the vortex.

As can be seen from these charts on the following link a squeeze is put on the stratospheric vortex but normally a stronger and more concerted warming is needed to displace the vortex off the pole. A Canadian warming perhaps.

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=10&forecast=all&lng=eng

When we trace this type of squeeze down to the troposphere, we often will see a Siberian placed vortex which is in a better position to allow northerly out breaks. And so, when the easterly airflow relinquishes its grip, I think that we will be under a northerly influence for a little time, keeping temperatures below average.

[greybing]

ahh,ok...,thanks for the info

[chionomaniac]

Quick update.

There are still signs that the stratosphere may not be cooling down quite as expected with another disruption forecast by the GFS at the 10 hPa level. A good warming this one following some wavenumber 1 disruption:

The best way to describe the upper stratospheric vortex is strong but squeezed so it will be worth seeing if this warming will have an effect on it.

Oh and one other thing - The lower strat ECM 100hPa forecast looks to be suggesting another split in the vortex (we know what follows that). Worth seeing if the GFS picks up on this!

Otherwise a mid Atlantic high not a bad bet.

Edited November 30, 2010 by chionomaniac

[jonboy]

Quick update.

There are still signs that the stratosphere may not be cooling down quite as expected with another disruption forecast by the GFS at the 10 hPa level. A good warming this one following some wavenumber 1 disruption:

The best way to describe the upper stratospheric vortex is strong but squeezed so it will be worth seeing if this warming will have an effect on it.

Oh and one other thing - The lower strat ECM 100hPa forecast looks to be suggesting another split in the vortex (we know what follows that). Worth seeing if the GFS picks up on this!

Otherwise a mid Atlantic high not a bad bet.

Hi C

What do you think is causeing this warming as GP didn't forsee this in his lastest comments in the technical thread

[Cheshire Freeze]

Good to see this warming, or at least not cooling to what was expected. I suspect we aren't going to see that stratosphere behave in a signature way to a nina pattern. Could bode well.

[Glacier Point]

Hi C

What do you think is causeing this warming as GP didn't forsee this in his lastest comments in the technical thread

There's a very interesting profile to the upper layers right now across the low, middle and high latitudes which are reflecting downwelling waves overlain with our La Nina signal pervading the troposphere.

http://www.cpc.noaa.gov/products/stratosphere/temperature/

Across the 10hPa layer, we're seeing some record low temperatures over the tropics and above average values in the mid latitudes and rising values above the pole.

At the 30hPa, a similar but less well developed pattern with temperatures over the pole crucially continuing below average.

At 50hPa and 70hPa this 'registration' is less well defined but could potentially be starting to show similar trait, especially in terms of falling values over the tropics and rising over the middle latitudes.

I suspect that the reluctance of the 30hPa to follow the 10hPa lead is a clear manifestation of the QBO / Nina combo effectively cancelling out the signal from the upper layers of the stratoshpere.

So what do we take away from these trends ? Bottom line is that these are suggesting support for mid latitude blocking structures in time. Be worth monitoring how these propagate downwards and whether any of these blocks can get far enough north to pull out some polar air.

[heavysnow05]

There's a very interesting profile to the upper layers right now across the low, middle and high latitudes which are reflecting downwelling waves overlain with our La Nina signal pervading the troposphere.

http://www.cpc.noaa....re/temperature/

At the 30hPa, a similar but less well developed pattern with temperatures over the pole crucially continuing below average.

Why is that crucial GP?

Thanks

[Glacier Point]

If the atmosphere above the high latitudes is anomalously colder and the airmass below it in the middle latitudes amolously warm, you create a stronger thermal gradient and increase in the mean zonal winds at 30hPa. Exactly the same as the 200-300hPa layer for the jet stream in the troposphere.

This has two implications:

1) Interference with any favourable warmings of the layers above preventing any downwelling of mean easterly zonal wind anomaly (blocking signal);

2) if sustained, increase in vorticity in the lower layers resulting in the Arctic Oscillation being driven positive.

Edited December 1, 2010 by Glacier Point

[phil nw.]

Hi Stewart(GP),

Thanks for your last post regarding your views on the latest state of the Straatosphere.

I was just wondering, even if there`s no dramatic warming over the Pole whether we could get still continue to get cold here this Winter.

I am speculating that Polar heights will likely fall if we don`t get a warming event so the vortex will deepen with time,at least that`s the common conception.

However even with say a neutral AO if other factors play in our favour could the UK still have cold periods as Winter develops?

.

The scenarios i imagine are a split jet with periods of meridonality around a ridging Atlantic High in conjuction with a Scandi Trough-similar to the current pattern.

Another possibility for a cold setup is a Scandi High if the main Vortex becomes centered towards Canada along with a Southerly tracking Jet.

Here in 1979

http://www.wetterzentrale.de/archive/ra/1979/Rrea00119790119.gif

The severe Winter of 62/63 had cold spells where the Upper Heights were not always at high latitudes but had periods of blocking in Mid-latitudes with a split vortex or a Scandi High with a balanced jet.

http://www.wetterzentrale.de/archive/ra/1963/Rrea00119630104.gif

http://www.wetterzentrale.de/archive/ra/1963/Rrea00119630116.gif

http://www.wetterzentrale.de/archive/ra/1963/Rrea00119630124.gif

http://www.wetterzentrale.de/archive/ra/1963/Rrea00119630210.gif

http://www.wetterzentrale.de/archive/ra/1963/Rrea00119630213.gif

There are a number of other examples where the setup for cold wasn`t classic but stil delivered.

The common theme was that we were North of the jet and we had deeply embeded surface cold--even in modestly cold uppers.

Now maybe this seasons ENSO state, ie La Nina, overides my ideas of continued cold spells as this Winter goes on so i would be very interested in your views and/or those of others who are more knowlegable in the teleconnections.

As you suggest a milder Jan and Feb in your LRF do you believe that the scenarios i have outlined above are unlikely?