Stratosphere Temperature Watch

[Guest North Sea Snow Convection]

hi all, this is my first post ever! I am new to netweather, although i have been following a few threads such as this one for most of the winter. anyway i have a few questions for the experts, particuarly NSSC or GP...if the current model outlooks of a slightly milder pattern are based on a downwelling of slight westerly zonal winds, when do you expect the subsequent easterlies to appear over the polar field? is it likely that model outputs will change dramatically, over a relatively short period of time, when these are picked up? in other words how long will this preceding westerly downwelling last before easterlies propagate right through the trophosphere? hope that makes sense and that my understanding isnt too flawed.

matt

Hello matt - welcome along. You have clearly picked things up well. <_<

I don't think at this stage there is much to add to what John H has already said. It is very much a waiting game now to see the polar field settle down following this westerly burst of energy. The current modelling seems to suggest amplification developing in the jet stream over the atlantic next week and high pressure pulling westwards to allow some further colder weather by the end of the week/next weekend. So cold weather might never go far away for very long by the looks of things.

In terms of MMW developments we wait to see height rises out of the arctic rather than an amplifying ridge northwards from the Azores, but there is grounds for optimism that eventually high pressure will become centred nr or just west of Greenland with low pressure over Scandinavia and Europe. And that arrangement will provide wintry weather for the UK

This an evolving picture against the background of a 'loaded gun' scenario and events could yet gather speed quite abruptly in the days ahead. Keep posted on the thread for developments and feel free to pitch in and also ask questions about anything you don't understand. There are plenty of experts around who I am sure will help

The above analysis from chionomaniac and tundra is a very valid one in term of the breakdown of the present cold spell which is imminent. My thoughts would be that the life span of this piece of disruptive energy is limited and the models will suddenly realise it is a spent force. That is one good reason to have justification for believing that a progressive improvement will be seen in the GIN area over the coming days, and rather like late Jan, atlantic cyclogenesis and the flatter pattern will downgrade and pave the way for pressure rises instead.

Edited February 12, 2009 by North Sea Snow Convection

[tundra]

I would have thought a partial vortex to the southwest of Greenland would have helped with height rises over Greenland what with waa going up the western side, but obviously not in this case.

[Rollo]

anyone interested in the blog I promised on looking at what has happened so far, try below

http://www.netweather.tv/forum/index.php?showtopic=53715

Many thanks for the blog John-even I can understand the majority of it and I would reccommend everybody to read it.

[chionomaniac]

I would have thought a partial vortex to the southwest of Greenland would have helped with height rises over Greenland what with waa going up the western side, but obviously not in this case.

Originally so did I and thought great but now I think probably not, considering the height?

[Guest North Sea Snow Convection]

I would have thought a partial vortex to the southwest of Greenland would have helped with height rises over Greenland what with waa going up the western side, but obviously not in this case.

Not with the energy disrupted and thrown west to east instead though. I think the reason why the ECM initially modelled height rises more favourably was because it progged the energy displacement south to north but the UKMO and GFS were keen to throw that energy and associated shortwaves eastwards towards Iceland.

As we now know, that unfortunately has turned out to be the outcome, and so we wait for the energy to dissipate in line with expectations of the negative anomaly cavalry eventually riding into town

[johnholmes]

Many thanks for the blog John-even I can understand the majority of it and I would reccommend everybody to read it.

thanks R

scientific training does tend to try and make one show reasons rather than hypothesise although that happens at times

[chionomaniac]

thanks R

scientific training does tend to try and make one show reasons rather than hypothesise although that happens at times

Thanks for the blog John. It's good to see those correlations from a pro and not just a bumbling amateur like myself!

Regarding the present warming I think the general consensus is more time needed. I reckon that you could pretty much split the effect of the present MMW into two possible effects though. For ease I will call them early and late. The present MMW started with a rather large wave number 2 breaking event that set off a chain of events causing the stratosphere to warm to record levels from the top down as the vortex started to split. As this occurred the mean zonal winds reversed layer by layer down the stratosphere as the vortex slowly split in two. Finally the split reaches the troposphere whereupon it can finally impact our weather. This split creates havoc which result in a pulse of energy traveling eastwards right across the UK into the west Atlantic. This occurs as an Easterly around the 2nd Feb and results in a foot of snow for Surrey and a cold pool being left across the UK that gives further snowfall that week. This could imo be described as an early MMW effect. Here is the Nasa link again showing the vortex split.

http://earthobservatory.nasa.gov/images/im...o_200901-02.mov

However we may not be finished with just the early effect and now is the time that late effects may begin to show. These occur some time after the vortex split has occurred when effectively the strong stratospheric vortex that was there previously has been 'switched off'. This results in an overall negative wind anomaly and potentially the if stratosphere can be compared to a hoover sucking up (hopefully the troposphere) it has now been put into reverse and is blowing out. the measure of any effects we may receive at the troposphere can be ascertained by how strong can the hoover blows out and can it permeate through the tropopause and into the troposphere. The effects we see of this are the propagated downwellings of negative zonal winds. If these negative zonal winds can effect the troposphere by creating high latitude blocking where once there was a strong vortex then we may receive a late effect of the MMW. The second late effect is probably the area that is in embryonic research as GP says and the one that can be hit or miss depending on the properties of the MMW. THe timings of these potential late effects follow a pattern but can differ depending upon the MMW.

With so much propagation of this record MMW I would be very surprised not to see a late effect however nothing is guaranteed as the present short term outlook has shown. I am sure that if the weak residual Canadian vortex segment that is situated west of Greenland at the 100 hPa level can disappear then we will be back in business for some strong northern blocking that may just be in the right area to affect us.

Finally, thanks to all the people who have contributed to this thread today, there have been some great posts and analysis.

c

Edited February 12, 2009 by chionomaniac

[bluearmy]

was there an MMW in jan/feb 1969? how far back does the data go?

[chionomaniac]

was there an MMW in jan/feb 1969? how far back does the data go?

No

[Mr Maunder]

was there an MMW in jan/feb 1969? how far back does the data go?

No

But there was a Canadian Warming in November 1968 and December 1968 was "Stratospherically Cold" (if that helps).

I have data that covers 1951 - 2000. I think there is additional new research that covers all or part of the 1940's.

Here is a link to the source data I use: http://www.atmosp.physics.utoronto.ca/SPAR...5_Labitzke.html

MM

Edited February 12, 2009 by Mr Maunder

[matt44myst]

thanks, JH and NSSC. It looks as though the models may just be starting to pick up on these signals. I think that wed/thurs next week is looking promising for the start of perhaps another wintry chapter. I hope so anyway.

Matt

[chionomaniac]

But there was a Canadian Warming in November 1968 and December 1968 was "Stratospherically Cold" (if that helps).

I have data that covers 1951 - 2000. I think there is additional new research that covers all or part of the 1940's.

Here is a link to the source data I use: http://www.atmosp.physics.utoronto.ca/SPAR...5_Labitzke.html

MM

Here is my source as that is slightly out of date now for recent years.

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

thanks, JH and NSSC. It looks as though the models may just be starting to pick up on these signals. I think that wed/thurs next week is looking promising for the start of perhaps another wintry chapter. I hope so anyway.

Matt

Welcome to the site Matt!

Hopefully we shall see something soon.

c

[Glacier Point]

One theory that we could make for the time lag for full impact of the MMW is that the speed of the main propagation is related to the development of cold air (positive zonal winds) above the warmed column.

Currently we see some limited development of positive zonal winds at 5 hPa and above:

http://www.cpc.ncep.noaa.gov/products/stra...JFM_NH_2009.gif

This warming event is notable for the scale of the warming and crucially its duration. Even now,the 10hPa layer has just returned to climatological norm. That's a 20 day duration. This might take some time to recover as we still have significant wavebreaking c/o strong recent mountain torques:

http://www.cdc.noaa.gov/map/images/reanaly...ltaum.90day.gif

In effect, do we need a 'push' from a downwelling positive eddy above the negative anomaly ?

To test this, we might look at Februarys which featured a strongly negative AO. These may not all be related to stratospheric warming events but the AO is generally correlated to 30 hPa temperature and pressure (reanalysis shows 0.6 correlation).

Reanalysis of these years with a recorded AO greater than -2 SD shows a 30 hPa temperature anomaly as follows:

A cold stratosphere. This might support the theory that we need a displacement to drive the propagation at expected timescales. Therefore, monitoring of any developing cold anomaly (westerly winds) at 10 hPa should also be on our agenda perhaps ?

[chionomaniac]

One theory that we could make for the time lag for full impact of the MMW is that the speed of the main propagation is related to the development of cold air (positive zonal winds) above the warmed column.

Currently we see some limited development of positive zonal winds at 5 hPa and above:

http://www.cpc.ncep.noaa.gov/products/stra...JFM_NH_2009.gif

This warming event is notable for the scale of the warming and crucially its duration. Even now,the 10hPa layer has just returned to climatological norm. That's a 20 day duration. This might take some time to recover as we still have significant wavebreaking c/o strong recent mountain torques:

http://www.cdc.noaa.gov/map/images/reanaly...ltaum.90day.gif

In effect, do we need a 'push' from a downwelling positive eddy above the negative anomaly ?

To test this, we might look at Februarys which featured a strongly negative AO. These may not all be related to stratospheric warming events but the AO is generally correlated to 30 hPa temperature and pressure (reanalysis shows 0.6 correlation).

Reanalysis of these years with a recorded AO greater than -2 SD shows a 30 hPa temperature anomaly as follows:

A cold stratosphere. This might support the theory that we need a displacement to drive the propagation at expected timescales. Therefore, monitoring of any developing cold anomaly (westerly winds) at 10 hPa should also be on our agenda perhaps ?

Ah yes that does make sense. An increased westerly upper stratosphere will drive the easterly lower stratospheric winds down into the troposphere? Now that does make sense GP and adds a new dimension. So in fact the strong record breaking MMW may ultimately be the undoing of the tropospheric propagation if there is no upper driver to push the easterly winds down, So presently then, wanting a FW and weak upper strat may work against us?

c

[cheeky_monkey]

its interesting to see from the links to historic records that none of our severe spells of cold wintry weather was proceded by major warming...not feb 1956..winter 62/63..feb 69...feb78..winter 78-79..winter 81/82...jan 85...feb1986..jan 1987..feb91..even 95/96 had no significant warming..only jan 85 and feb 91 occured at the same time a warming occured.

note thats assuming i have read the tables right..or im missing something???..im guessing that warming does encourage colder synoptics but it is readily over ridden by other more important factors and vice versa. so if a winter is set up to be cold or mild warming or cooling of the stratosphere will only enchance the backround pattern or be steamrolled by the backround pattern?

[Guest North Sea Snow Convection]

Ah yes that does make sense. An increased westerly upper stratosphere will drive the easterly lower stratospheric winds down into the troposphere? Now that does make sense GP and adds a new dimension. So in fact the strong record breaking MMW may ultimately be the undoing of the tropospheric propagation if there is no upper driver to push the easterly winds down, So presently then, wanting a FW and weak upper strat may work against us?

c

I made the point earlier today about the suggested return of polar westerly winds at 10 and 30hPa may be the mechansim to push the 'backlog' of polar easterlies to the surface. It is true that the longer the dealy, the longer the effects might be, but winter is fast ticking on now and we don't want any undue delay.

I e=will have a look at JH latest work when I get chance

[johnholmes]

thanks Ch for that analysis which seems sound to me as a complete beginner, just one query, the result of endless proof reading when I was at work

traveling eastwards right across the UK into the west Atlantic

I assume you mean westwards not eastwards?

[chionomaniac]

its interesting to see from the links to historic records that none of our severe spells of cold wintry weather was proceded by major warming...not feb 1956..winter 62/63..feb 69...feb78..winter 78-79..winter 81/82...jan 85...feb1986..jan 1987..feb91..even 95/96 had no significant warming..only jan 85 and feb 91 occured at the same time a warming occured.

note thats assuming i have read the tables right..or im missing something???..im guessing that warming does encourage colder synoptics but it is readily over ridden by other more important factors and vice versa. so if a winter is set up to be cold or mild warming or cooling of the stratosphere will only enchance the backround pattern or be steamrolled by the backround pattern?

Feb56 No event

62/63 CW and MWW

Feb 69 CW

Feb 78 CW

78-79 CW and MWW

81/82 CW

Jan85 MWW

Feb 86 No event

Jan 87 MMW

Feb 91 MMW

95/96 No event

The majority of those winters either had Canadian Warmings to start those winters or MMWs in those winters. No one has ever said that MMWs are a prerequesite to cold winters but raise the chances of HLBs that can increase the chances of cold. We all know that there are many other factors that influence cold weather so unless you look in detail at the exact stratospheric conditions of those winters ( we know that you have better things to do with your time-post 646) then the exact correlation may still go unmissed!

c

thanks Ch for that analysis which seems sound to me as a complete beginner, just one query, the result of endless proof reading when I was at work

traveling eastwards right across the UK into the west Atlantic

I assume you mean westwards not eastwards?

YES sorry

[Methuselah]

From what I've read here, I believe that this stratospheric warming thing could be another part in an enormous jigsaw puzzle...And the more parts we have, the better???

PS: I never use cliche!

[cheeky_monkey]

The majority of those winters either had Canadian Warmings to start those winters or MMWs in those winters. No one has ever said that MMWs are a prerequesite to cold winters but raise the chances of HLBs that can increase the chances of cold. We all know that there are many other factors that influence cold weather so unless you look in detail at the exact stratospheric conditions of those winters ( we know that you have better things to do with your time-post 646) then the exact correlation may still go unmissed!

if it is the case that no one has ever said MMWs are a prerequesite to cold winters...why do many members seem to hold these events as the holy grail for cold outbreaks???..i mean this topic was hardly touched upon in previous winters...so this possible misconception must have come from somewhere???

also how would a canadian warming in november be a factor in a cold february for example?

[Guest North Sea Snow Convection]

if it is the case that no one has ever said MMWs are a prerequesite to cold winters...why do many members seem to hold these events as the holy grail for cold outbreaks???..i mean this topic was hardly touched upon in previous winters...so this possible misconception must have come from somewhere???

also how would a canadian warming in november be a factor in a cold february for example?

You keep asking the same questions and have received several answers now from various people, which you don't appear to understanding or be hearing. There is no denying the link for warmer stratospheres with an increased liklihood for cold outbreaks. Therefore the exercise of this thread was/is fully vaildated in terms of taking a case study of a SSW and monitoring its effects and progress.

I will repeat once more, there isn't a broadbrush outcome to every event. This has been stated so many times already, almost every day, but the tropospheric effects (if any) are dependant on the warmer layers propagating towards the troposphere. Not every event does this, but I would suggest that more often that not there is a response.

The lag times of these events also vary, according to the progress of the propagation and various other variables, including one's that exist outside of the stratosphere.

You keep suggesting that people are trying to fit cold events into time sequences to fit MMW's. I would actually put it to you, that what is being suggested instead, is that previous instances have been taken where there has been successful propagation, and the occurence and depth (potency) of subsequent surface effects has been compared with the nauture of the MMW event itself.

Therefore, on the basis that this event has shown every sign of responding in line (and more) with the most potent of previous events, there has been (still is) good reason to expect further surface impacts from this event. That isn't trying to make an event fit a cold spell at all, it is an on going monitored judgement that has been made, based on good analogue evidence and characteristic behaviour of this type of phenomenon.

The crux of all of this is that too many conclusions are being made by some people before the event is even finished! It might be too bad if the effects of this event come too late to provide the best wintry potential that has been hoped for, but that doesn't somehow diminish or scupper the whole purpose of this thread. Or diminish the significnace of the event just because it might not show its hand when everyone wants it to!

Edited February 13, 2009 by North Sea Snow Convection

[johnholmes]

if it is the case that no one has ever said MMWs are a prerequesite to cold winters...why do many members seem to hold these events as the holy grail for cold outbreaks???..i mean this topic was hardly touched upon in previous winters...so this possible misconception must have come from somewhere???

also how would a canadian warming in november be a factor in a cold february for example?

have you read my blog where I attempt to give the actual data as seen this autumn-winter?

[chionomaniac]

if it is the case that no one has ever said MMWs are a prerequesite to cold winters...why do many members seem to hold these events as the holy grail for cold outbreaks???..i mean this topic was hardly touched upon in previous winters...so this possible misconception must have come from somewhere???

also how would a canadian warming in november be a factor in a cold february for example?

Studies have shown that some MMWs will lead to Northern Europe having colder weather outbreaks. Dare I say that without the current MMW then a vast number of people who have had a lot of snow over the last week and a half wouldn't have had any at all. That is why I personally would rather see a MMW than not and will look out for them with slightly increased expectations. If the stratosphere had been cooler with a stronger vortex then it would be less likely to achieve cold weather (but not impossible).

I think all along we have stated that an MMW does not guarantee snow/cold. We have never once said that winter can't be cold without an MMW. However we have said that a colder stratosphere will lead to a stronger polar vortex which reduces the chance of protracted cold spells over these shores. Just because this topic hasn't been touched upon in previous winters doesn't mean that it isn't important, more so that the relationship between the troposphere and stratosphere is becoming better understood and needs further investigation and monitoring which is exactly what this thread was set up to do.

Personally I think this MMW has delivered but not necessarily as I expected it to do so but there is still time left for further impacts so it is too early to have a post mortem just yet.

Do you think it has delivered cold to the country CM?

c

[Guest North Sea Snow Convection]

Should add - In trying not to overplay the event, it is sometimes easy to forget to stress that whatever happens from now this MMW has already produced a cold outbreak. So much focus is always on future expectations and trying to answer those, the most obvious gets forgotten!

[Guest North Sea Snow Convection]

Based on latest available predictions still waiting for the negative anomalies to get their push from 10hPa perhaps