Stratosphere Temperature Watch

[knocker]

CC, I see that the AO and NAO are forecast to go strongly negative again later on this month... If this comes to pass, can you see them overiding the teleconnections again?

Is the NAO forecast to go stongly negative?

[bluearmy]

Is the NAO forecast to go stongly negative?

not according to the gfs ens means WS - no. however, as kevin says above, thats just a reflection of the gfs ens data. if they change, so does that output you posted. there are other models and also forecasts that are not straight reflections of nwp runs. however, it does, currently, look as though the NAO will go at least to neutral value week after next as some w - e mobility returns.

[brogdale]

not according to the gfs ens means WS - no. however, as kevin says above, thats just a reflection of the gfs ens data. if they change, so does that output you posted. there are other models and also forecasts that are not straight reflections of nwp runs. however, it does, currently, look as though the NAO will go at least to neutral value week after next as some w - e mobility returns.

Any links BA?

[phil nw.]

AO and NAO are just indices in the measurement of the intensity of a pressure pattern. Something has caused the blocking and the AO and NAO are just indices that measure how intense this is, they do not tell you what caused it, just the result of it.

Yes indeed Mr D.

I had this exchange with C.C. just prior to Winter.

It seems even experts like JH who also concurred that AO and NAO are simply measurements not drivers cannot convince him.

[TEITS]

I would be interested in hearing from the pundits taking into account of the state of the stratosphere over the last few weeks, La Nina etc, are you surprised that we had one of the coldest Decembers on record?

Also worth mentioning Mr D that it isn't just that we have seen the coldest Dec on record but the frequency of blocking over Greenland has been noticeable throughout 2010.

My own view is the state of the Stratosphere and the ENSO are nothing to do with it. Something else has caused this frequent blocking. I have my own idea why this has occured but I don't have any proof as of yet. I also believe there is a link between our recent poor summers and the recent cold winters. This change in our weather patterns began in 2007 with the jetstream moving further S. Interestingly there was a change in the position of the jetstream in the S hemisphere during 2007!!

I agree about the AO/NAO. These are wrongly used on this forum.

[weather eater]

Yes indeed Mr D.

I had this exchange with C.C. just prior to Winter.

It seems even experts like JH who also concurred that AO and NAO are simply measurements not drivers cannot convince him.

I think the confusion lies in the fact that once you have a -NAO pressure pattern in place, it alters where we get our weather from, so I can see where people get the idea that its some sort of driver. In its simplistic form a + NAO, is a persistent low over Greenland and Iceland and a persistent high off the coast of Portugal. Whereas a -NAO, is a persistent High over Greenland and Iceland and a persistent low off the coast of Portugal, the drivers are what got them there in the first place.

[knocker]

Does this not open pandoras box? Precisely what is the the driver and merely a teleconnecton when considering the major questions regarding lrfs. For example the lower stratosphere has cooled from about 1980 although slowing down lately and model calculations suggest that the observeved ozone loss is is the predominant cause of the cooling. (I could introduce CO2 increases here, but perhaps not). Thus cause and effect as Mr. D. suggests. I suspect I know the answers that some will give and I acknowledge they know far more about the subject than I do.

As a matter of interest the great teleconnection of the El Niño/La Niña-Southern Oscillation is not a driver but is it enhanced/effected by drivers such as record levels of CO2? Which of course also effect the stratosphere.

Edited January 2, 2011 by weather ship

[lorenzo]

Also worth mentioning Mr D that it isn't just that we have seen the coldest Dec on record but the frequency of blocking over Greenland has been noticeable throughout 2010.

My own view is the state of the Stratosphere and the ENSO are nothing to do with it. Something else has caused this frequent blocking. I have my own idea why this has occured but I don't have any proof as of yet. I also believe there is a link between our recent poor summers and the recent cold winters. This change in our weather patterns began in 2007 with the jetstream moving further S. Interestingly there was a change in the position of the jetstream in the S hemisphere during 2007!!

I agree about the AO/NAO. These are wrongly used on this forum.

TEITS - would appreciate if you expand on these comments for folks with less expertise than yourself and others on this thread, It would be good to see some charts or further illustration of what you are alluding to, especially if you are commenting on a pattern that is as recent as establishing over the last 3 years, this is an excellent development that everyone should be able to comment on.

Also - why are AO and NAO wrongly used - I dont understand, the indices predict patterns of whether, are they wrongly used because we are not seeing what is expected of them in a La Nina state?

In regards to JS - why has this occurred are there any factors which have invoked this change? Interested to hear your thoughts. TY

[cooling climate]

Yes indeed Mr D.

I had this exchange with C.C. just prior to Winter.

It seems even experts like JH who also concurred that AO and NAO are simply measurements not drivers cannot convince him.

I am probably not explaining what I mean correctly, they are as you say measurements and not

drivers as such. Lets try this when you get certain enso states, GWO, AAM or whatever and

the composites say the atmospheric pattern should be such and such if then a strongly negative

or strongly positive AO and NAO occurs it can completely skew the predicted pattern.

This was the case last year and again this December and will almost certainly be the case again

during January.

As for the question do I think the AO will tank this month then yes and with a more easterly based

- NAO in other words a very good chance of seeing the real deal from the east, -15c uppers etc, etc.

[BLAST FROM THE PAST]

As regards to the change in Feb 2007 then it is IMO no coincidence that the perturbation cycle [solar controlled] flipped to La Nina dominance which correlates strongly with a -ve NAO period. This cycle is about 36 years long. Superimposed are the longterm solar and lunar cycles that suggest that we are going to see a shift equatorwards of jetstreams in both hemispheres and a shrinking/narrowing of the ITCZ which has been 'fattening since the 19th century [matching the observed overall warming of this period?].

I replied to Mr D in my LRF thread...I am not surprised by how cold it has got.

I agree with TEITS but for probably different reasons but Stratospheric warming doesn't drive blocking but is a response to the solar/lunar phasing as is the blocking patterns...they co-incide.

I don't think we will see this month as a major freeze up, cold but not the coldest....... :smiliz19:

BFTP

Edited January 2, 2011 by BLAST FROM THE PAST

[knocker]

As regards to the change in Feb 2007 then it is IMO no coincidence that the perturbation cycle [solar controlled] flipped to La Nina dominance which correlates strongly with a -ve NAO period.

BFTP

I wonder if you could explain this in more detail. Flipped to La Nina dominance? How do do know it was solar controlled? You are playing a guessing game.

[lorenzo]

As regards to the change in Feb 2007 then it is IMO no coincidence that the perturbation cycle [solar controlled] flipped to La Nina dominance which correlates strongly with a -ve NAO period. This cycle is about 36 years long. Superimposed are the longterm solar and lunar cycles that suggest that we are going to see a shift equatorwards of jetstreams in both hemispheres and a shrinking/narrowing of the ITCZ which has been 'fattening since the 19th century [matching the observed overall warming of this period?].

I replied to Mr D in my LRF thread...I am not surprised by how cold it has got.

I agree with TEITS but for probably different reasons but Stratospheric warming doesn't drive blocking but is a response to the solar/lunar phasing as is the blocking patterns...they co-incide.

I don't think we will see this month as a major freeze up, cold but not the coldest....... :smiliz19:

BFTP

BFTP that is way technical ! am immediately confused as presumably the el nino to la nina base state is not 36 yrs ?

[Kentish Kiwi]

As regards to the change in Feb 2007 then it is IMO no coincidence that the perturbation cycle [solar controlled] flipped to La Nina dominance which correlates strongly with a -ve NAO period. This cycle is about 36 years long. Superimposed are the longterm solar and lunar cycles that suggest that we are going to see a shift equatorwards of jetstreams in both hemispheres and a shrinking/narrowing of the ITCZ which has been 'fattening since the 19th century [matching the observed overall warming of this period?].

I replied to Mr D in my LRF thread...I am not surprised by how cold it has got.

I agree with TEITS but for probably different reasons but Stratospheric warming doesn't drive blocking but is a response to the solar/lunar phasing as is the blocking patterns...they co-incide.

I don't think we will see this month as a major freeze up, cold but not the coldest....... :smiliz19:

BFTP

Do you still think February will be the coldest month out of the three this winter ala your forecast? Or at least do you still see it being notably colder than January?

[Alan Robinson]

The -AO and NAO dominated the pattern, over riding the enso signals.

In fact this is what I was talking about in the fall I think it was when I

argued the point that the AO and NAO can drive the weather regardless of

other variables or teleconnects.

'scuse my ignorance CC, but I thought the NAO is simply defined as the difference in surface pressure between Reykjavik and Lisbon, or is it Gibraltar still? What causes the NAO is a very different matter. I can grasp the concept of cause-and-effect, and so the observed pressure difference must play its part, but what is causing the pressure difference?

Just out of interest, by the way, I first became interested in the NAO in November 2009, when my kitchen garden froze over and snow buried my spring cabbages and garlic. I read somewhere that the NAO was the cause. Consequently, I downloaded a whole cartload of stuff about the NAO, including a graphical representation of the index going back to the 1950s, when I gather records first began. I very crudely analysed the positive and negative durations and found quite a decent probability curve, which made me so bold as to predict the negative phase that began November 2009 would end perhaps May or June 2010, and certainly no later than September 2010. I also predicted that November 2010 to February 2011 would be under maritime influences, and therefore comparitively mild.

What happened? Well, here in Denmark we've just had the coldest December on record, only paralleled by December 1981, and December 2010 was the sunniest December on record here. My spring cabbages, garlic, spinach and mini polutunnels over the Winter Density lettuce have only just emerged from the deep snow, and I've got egg all over my face and people calling me seer. And how right! My forecast was as wrong as it could be, and I dare say that experts in the field will confirm that this present NAO phase is totally unprecedented. The question is why? What has caused surface pressure to be unusually high near Iceland for an extraordinarily long time, while the Azores high seems to have beaten a retreat towards the equator? The NAO is a symptom of something else going on, and I'd like to know what, so I don't have to pull up withered cabbages every spring.

EDIT; cabbages, not acbbages

Edited January 3, 2011 by Alan Robinson

[Kentish Kiwi]

'scuse my ignorance CC, but I thought the NAO is simply defined as the difference in surface pressure between Reykjavik and Lisbon, or is it Gibraltar still? What causes the NAO is a very different matter. I can grasp the concept of cause-and-effect, and so the observed pressure difference must play its part, but what is causing the pressure difference?

Yes, the AO and NAO are simply indexes, measurements or representations of pressures patterns. They are certainly not atmospheric 'drivers'. Its almost as though saying that the CET is a driver of the temperatures we experience in the UK. Although that said the values the AO and NAO display and the pressure patterns that are reflected by this are particularly important as to what weather this part of the world sees.

As to what is causing these negative values and the associated northerly blocking they relfect, no one knows for sure and this has been particularly obvious this winter, especially when compared to last winter where there were some clear-cut variables/drivers that we expected would prove favorable to produce northerly blocking, and these delivered. However, there are certainly many many factors that affect this and it has become clear during the last month or so that the temperature of the polar stratosphere and what we normally expect from such temperatures can be 'over-ridden' by other variables to produce blocking at northerly latitudes, as the stratosphere has been overwhelming below negative for at least the last month yet we have still seen a disrupted vortex. I get the feeling, though, that the consistently cool temperatures experienced over the polar stratosphere will begin to show their hand much more obviously throughout January (as can be seen by some of the zonal outputs from the models in the medium term), unless an SSW is able to break this down before the vortex really gets going.

[BLAST FROM THE PAST]

Do you still think February will be the coldest month out of the three this winter ala your forecast? Or at least do you still see it being notably colder than January?

Yes, In scheme of things Jan will be disappointing but that would be rather picky. The storm that MB predicts...that looks like an arctic pattern reset period and will set up Feb for potential brutal cold.

Re answering other questions I will do this but I am at work and have been last few days so give me a couple of days and I will either on thread or by PM.

BFTP

[knocker]

Regarding the NAO something that may be of historical interest during the Little Ice Age. Luterbacher et al. have produced a 25 year smoothed mean of the NAO from 1350 and from 1500 a Winter Severity Index (WSI) has been indicated by Van Engelen et al. The WSI values are expressed as departures from the 1501-1900 mean.

When plotted there is quite a good correlation between the negative indices of the two graphs regarding the severe winters. This does not of course mean that the NAO was the driver. In fact, depending on what years you take for the Little Ice Age, the driver(s) were almost certainly the Wolf, Spörer and Maunder Minima.

[chionomaniac]

Also worth mentioning Mr D that it isn't just that we have seen the coldest Dec on record but the frequency of blocking over Greenland has been noticeable throughout 2010.

My own view is the state of the Stratosphere and the ENSO are nothing to do with it. Something else has caused this frequent blocking. I have my own idea why this has occured but I don't have any proof as of yet. I also believe there is a link between our recent poor summers and the recent cold winters. This change in our weather patterns began in 2007 with the jetstream moving further S. Interestingly there was a change in the position of the jetstream in the S hemisphere during 2007!!

I agree about the AO/NAO. These are wrongly used on this forum.

After studying the stratosphere for a few years now, I wouldn't say that the state of the stratosphere has nothing to do with the frequent blocking that we have seen, but I would agree with you TEITS that there must be other forces come into play that we do not understand yet. Whereas we haven't had an extraordinary cold stratosphere in the polar regions in this time, the amount of blocking does seem to be above expectations. From what I have observed in this time, is that there have been two types of disruption seen on the polar vortex. One such disruption seen, are the well researched SSWs. Even though these may initially be created by tropospheric led wave breaking occurrences, there seems to be a more hit and miss type of effect regarding successful re-propagation back down to the troposphere. Quite often there seems to be an invisible barrier at the 30 hPa level. Even the smaller type of warming being witnessed presently looks like losing its power as the propagation occurs.

This brings me on to a point that GP often highlights regarding the slow upward and downward waves that propagate over the polar stratosphere over many months. The following paper illustrates this type of wave. http://journals.ametsoc.org/doi/full/10.1175/1520-0442%282002%29015%3C0781%3ADPTAIT%3E2.0.CO%3B2

So this bring me on to the other type of disturbance seen in the polar vortex. These tend to be tropospherically led creating PV splits and have helped create the dramatic negative AO values seen over the last couple of winters and also led to us receiving copious amounts of cold and snow. These splits extend some way upward into the stratosphere (upto the 10 hPa level) and tend to coincide with upper stratospheric disturbances in the slow downward propagating phase that GP highlights. Could these slow propagating waves hold a little more power in low solar conditions? Could this be the reason why even though the 30 hPa temps are below average at 60ºN, the corresponding mean zonal wind speed has stayed below average ;

http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/u60n_30_2010.pdf

We also have witnessed a colder tropical stratosphere in that time as illustrated here which will help reduce the strength of the polar vortex..

So back to the latest update.

As I have mentioned we are currently seeing the top of the stratosphere warming. This has reached the 10 and 30 hPa level and is creating some pressure on the polar vortex. This looked at one stage that a SSW could occur, but that looks less so now. At this time though the forecast for northern blocking sees it occurring over Alaska and not near Greenland. In fact, it looks like any residual strength in the polar vortex is kept firmly in the Atlantic sector, which is giving a more zonal look in the outputs, but rest assured the underlying pattern is far from that.

The reason is that there does seem to be a resurgence of warming over the coming week or so that will affect the vortex further. Looking at the following 3 charts it looks like the warming will wane before increasing again at the 10 hPa level.

The ECM shows a similar story. The long and short of this is that we are likely to see more Atlantic influence for a period before the next Atlantic sector block shows its hand. Currently it does not look like this will be over the Scandinavian segment unless there is a complete turnaround in both the stratospheric and tropospheric models.

I will be keeping a keen eye on the stratospheric temperature profile over the coming days. The following chart shows a significant warming at 60ºN at 10 hPa . Will this travel nearer the pole?

c

[ZONE 51]

Very interesting, and it is of course building up to our next widespread very cold period, we can't see at this stage how severe the cold/snow would become but it is likely, and while were waiting its atlantic time but this would bring snow first anyway! so all an interesting month ahead...

something for everyone in their.

[Alan Robinson]

We also have witnessed a colder tropical stratosphere in that time as illustrated here which will help reduce the strength of the polar vortex..

I notice that there appears to be a slightly assymetric annual cycle in tropical stratospheric temperatures. There seems to me a minumum occurring about a month following both solstices in any one year, a lag in time that resembles our surface temperatures following the sun's declination in winter, though admittedly in the northern summer one would expect a peak, not a trough. It also looks as though the minumum following the December solstice is slightly lower than the one following that in June, though over a longer period that might not be the case. The pattern does though repeat itself no matter the temperature level relative to mean values, and the amplitude is always something like 15 degrees. Is there an explanation what causes this pattern, and why should the northern winter minimum be lower than the other? Isn't Earth closer to the sun in January than late July and August?

Edited January 4, 2011 by Alan Robinson

[chionomaniac]

I notice that there appears to be a slightly assymetric annual cycle in tropical stratospheric temperatures. There seems to me a minumum occurring about a month following both solstices in any one year, a lag in time that resembles our surface temperatures following the sun's declination in winter, though admittedly in the northern summer one would expect a peak, not a trough. It also looks as though the minumum following the December solstice is slightly lower than the one following that in June, though over a longer period that might not be the case. The pattern does though repeat itself no matter the temperature level relative to mean values, and the amplitude is always something like 15 degrees. Is there an explanation what causes this pattern, and why should the northern winter minimum be lower than the other? Isn't Earth closer to the sun in January than late July and August?

The respective polar stratospheric vortices of both hemispheric winters are completely different due to the effect of the land masses of the northern hemisphere feeding back into the stratosphere. I can only imagine that this feedback transfers right through to the tropical stratosphere causing the cooling affect.

Big developments today in the stratosphere forecasts - more later.

[BLAST FROM THE PAST]

BFTP that is way technical ! am immediately confused as presumably the el nino to la nina base state is not 36 yrs ?

Dr Theodore Landscheidt research. perturbation cycle is approx 36 year cycle driving ENSO.

http://www.john-daly.com/theodor/new-enso.htm

Re what lies ahead, big blocking signal for latter half of winter, wonder if the stratosphere will 'respond'

BFTP

Edited January 4, 2011 by BLAST FROM THE PAST

[chionomaniac]

Yesterday I suggested that the stratospheric forecasts were holding back from suggesting a SSW which I thought was likely last week. Well today, even though a SSW is not yet forecast the forecasts have taken a large step towards this. I commented that there was a second wave of warming forecast, and this looks like producing a dramatic effect on the polar vortex. Look at the temp forecast compared to yesterday :

A big improvement across the board.

And now for the major step towards a SSW - the mean zonal winds for the upper stratosphere for the first time have been forecast to reverse (from +80m/s) as seen here.

This is no mean feat and has occurred as the vortex gets displaced from the pole. This is not to say that reversal will occur throughout the whole stratosphere but we have to start somewhere.

Back down to the 100hPa layer and any displacement so far has firmly pushed the distorted vortex towards us with the blocking seen in the Pacific region, so not a whiff of an easterly on the cards until blocking can become established on our side of the hemisphere. We cannot rule out an Easterly longer term but for those wishing to base there forecasts on something more reliable than an odd ensemble member way out in FI, keep watching in here and I will be the first to let you know!

c

[beng]

Yesterday I suggested that the stratospheric forecasts were holding back from suggesting a SSW which I thought was likely last week. Well today, even though a SSW is not yet forecast the forecasts have taken a large step towards this. I commented that there was a second wave of warming forecast, and this looks like producing a dramatic effect on the polar vortex. Look at the temp forecast compared to yesterday :

A big improvement across the board.

And now for the major step towards a SSW - the mean zonal winds for the upper stratosphere for the first time have been forecast to reverse (from +80m/s) as seen here.

This is no mean feat and has occurred as the vortex gets displaced from the pole. This is not to say that reversal will occur throughout the whole stratosphere but we have to start somewhere.

Back down to the 100hPa layer and any displacement so far has firmly pushed the distorted vortex towards us with the blocking seen in the Pacific region, so not a whiff of an easterly on the cards until blocking can become established on our side of the hemisphere. We cannot rule out an Easterly longer term but for those wishing to base there forecasts on something more reliable than an odd ensemble member way out in FI, keep watching in here and I will be the first to let you know!

c

Great post as normal.

I guess the key thing will be for the warming stratosphere not to create blocking too far West as we are seeing at the moment. Do you see any signs that the new wave might create blocking further East (i.e. more focused towards Greenland than the Canadian Arctic) and for the vortex to displace further East - i.e. more towards Scandi? My concern at the moment is that if it's too far West then it will just lock in a mild pattern for W Europe.

Edited January 4, 2011 by beng

[Weather Boy]

I understand that warming of stratosphere doesn't equate to cold here in the UK (but it seems to be a good sign of that being likely). Maybe this is dealt with elsewhere in the thread (I haven't read it all) but can anyone explain for me please:

1. Why warming of the stratosphere tends to point to cold in the UK (in winter at least) and

2. What causes the stratosphere to warm or cool at this time of year when the sun is very weak.

Much obliged for the assistance and sorry if it involves going over old ground.