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chionomaniac

Stratosphere Temperature Watch

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Hi Tamara,

I agree with you here about it now looking more than likely that we are going to have a delayed Final Warming.

ftp://hyperion.gsfc.nasa.gov/pub/ftpmet/n...60n_10_2008.gif

Looking at the zonal mean winds they are indeed climbing when the usual trend at this time of year is the exact opposite. However they are not yet above the average for this time of year.

With the stratospheric vortex regaining strength, will that lead to a more Atlantic based Spring once the final effects of the MMW have worn off?

Earlier in this thread we wondered whether the westerly QBO would prevent a MMW from ocurring, as the timeframe clashed with the solar minimum, and that it had never occurred before when the two coincided. We now know that that wasn't to be the case but after further reading of the GWO thread it does make perfect sense that even though the westerly QBO didn't prevent the MMW from occurring, it may have instrumental in preventing the anticipated propagation. This has only served in reducing angular momentum, with corresponding weakening of the jetstream (also keeping it south) and combined with the weak La Nina state, no amplication in the flow, ultimately we have seen the net result being no northern blocking.

For those who have wondered (including myself) why this MMW has not delivered as anticipated it is good finally to have a credible reason why this is so. It also shows us how all tropospheric factors need to be pointing in the right direction as well, to obtain maximum benefit form a MMW.

I for one feel that I have learned loads from this last winter!

c

There was northern blocking but it got pushed east over Scandinavia and western Russia by a segment of the daughter vortex moving into Greenland. If it wasn't for this small piece of vortex energy i am positive we would have had a very prolonged very cold spell in February.

Admittedly we did not see anything like the amount of blocking we thought we would see and this i think was down to very slow propagation of the warming after the initial burst, due in part to the strength of the warming and the very relaxed state the stratosphere was left in.

Had we been in a easterly QBO instead of west would things have been different i do not know.

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Guest North Sea Snow Convection
Hi Tamara,

I agree with you here about it now looking more than likely that we are going to have a delayed Final Warming.

ftp://hyperion.gsfc.nasa.gov/pub/ftpmet/n...60n_10_2008.gif

Looking at the zonal mean winds they are indeed climbing when the usual trend at this time of year is the exact opposite. However they are not yet above the average for this time of year.

With the stratospheric vortex regaining strength, will that lead to a more Atlantic based Spring once the final effects of the MMW have worn off?

Earlier in this thread we wondered whether the westerly QBO would prevent a MMW from ocurring, as the timeframe clashed with the solar minimum, and that it had never occurred before when the two coincided. We now know that that wasn't to be the case but after further reading of the GWO thread it does make perfect sense that even though the westerly QBO didn't prevent the MMW from occurring, it may have instrumental in preventing the anticipated propagation. This has only served in reducing angular momentum, with corresponding weakening of the jetstream (also keeping it south) and combined with the weak La Nina state, no amplication in the flow, ultimately we have seen the net result being no northern blocking.

For those who have wondered (including myself) why this MMW has not delivered as anticipated it is good finally to have a credible reason why this is so. It also shows us how all tropospheric factors need to be pointing in the right direction as well, to obtain maximum benefit form a MMW.

I for one feel that I have learned loads from this last winter!

c

Hi :lol:

Yes I have learned loads too. It seemed too good to be true that we had an unprecedented MMW with a +QBO and solar min. In the end the 'diffuse' solution as described has been the most logical one in heinsight even though it is not the desired one.

The westerly QBO has had the final say, but we can only dream about what may well have happened under an easterly QBO!

If the present stratospheric trend continues, then Spring may evolve into an average westerly atlantic pattern after some blocking (which I still think will occur this Month and into April). The other alternative is evolvement into the blocking sinking into mid latitude high pressure belts across UK from the atlantic and into Europe. So a nice cold start to the Spring but becoming wamer and sunnier later as high pressure sinks south and the jet stream returns over the top.

However I still think that following the FW lag, long term we are looking at high latitude blocking again towards Summer - especially with the east QBO starting up.

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Good morning,

I have seen over the winter numerous references made to set time periods that a MMW could/should affect us. What the January MMW hopefully has demonstrated is that there are no set time frames that a MMW will exert its influence upon the troposphere. The strength, duration and propagation of the MMW are far more important when looking at the potential tropospheric effects of an MMW. It is therefore very important to monitor the MMW as it progresses ( as it is so far impossible to predict intensity) to see how these possible may be seen on the tropospheric level.

The MMW that arrived on the 23rd Jan is still having some effect on the lower stratosphere and this has not returned to normal just yet. This can be demonstrated by the temperature anomaly chart which quite clearly shows how the propagated increased temperatures may have a final influence before returning to normal.

post-4523-1236412370_thumb.png

I have mentioned before that it is quite common to get early and late cold spells from some MMWs. One MMW that was similar to the present one was seen in January 1985. This too was a vortex split and there followed many days when the -10ºC 850 isotherm covered the UK. THe MMW struck on the 1st Jan and the cold filtered through within a week. As can be seen from the temperature anomaly chart the duration of the event as similar to the existing MMW.

post-4523-1236413112_thumb.png

Furthermore there was also a widespread cold outbreak 14-15 Feb, at the time of final propagation some time after the start of the MMW.

This leads the to the question can the final propagation of this MMW lead to a similar cold outbreak. Well the signs are certainly there if recent tropospheric model outputs are anything to go by, with firm suggestions that pressure may rise over Greenland. And are these supported by stratospheric conditions? Well, tentatively yes they are. Looking at the mean zonal wind forecasts for 5 days ahead we can see that there is a significant area of negative (blue easterly) winds from 70-90N.

post-4523-1236413826_thumb.png

This is conducive to strong northern blocking and almost into reliable timeframe as well.

The potential vorticity chart forecast shows very little in the way of strong vorticity and I can well imagine where BF would circle where the High pressure is likely to form- right over Greenland!

post-4523-1236414078_thumb.png

The forecast 100hPa vortex patterns for the GFS and ECM support this:

post-4523-1236414158_thumb.pngpost-4523-1236414179.gif

One can only watch and see what does develop, but I certainly for one wouldn't mind a final fling from winter before spring arrives.

c

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Guest North Sea Snow Convection
Good morning,

I have seen over the winter numerous references made to set time periods that a MMW could/should affect us. What the January MMW hopefully has demonstrated is that there are no set time frames that a MMW will exert its influence upon the troposphere. The strength, duration and propagation of the MMW are far more important when looking at the potential tropospheric effects of an MMW. It is therefore very important to monitor the MMW as it progresses ( as it is so far impossible to predict intensity) to see how these possible may be seen on the tropospheric level.

The MMW that arrived on the 23rd Jan is still having some effect on the lower stratosphere and this has not returned to normal just yet. This can be demonstrated by the temperature anomaly chart which quite clearly shows how the propagated increased temperatures may have a final influence before returning to normal.

I have mentioned before that it is quite common to get early and late cold spells from some MMWs. One MMW that was similar to the present one was seen in January 1985. This too was a vortex split and there followed many days when the -10ºC 850 isotherm covered the UK. THe MMW struck on the 1st Jan and the cold filtered through within a week. As can be seen from the temperature anomaly chart the duration of the event as similar to the existing MMW.

Furthermore there was also a widespread cold outbreak 14-15 Feb, at the time of final propagation some time after the start of the MMW.

This leads the to the question can the final propagation of this MMW lead to a similar cold outbreak. Well the signs are certainly there if recent tropospheric model outputs are anything to go by, with firm suggestions that pressure may rise over Greenland. And are these supported by stratospheric conditions? Well, tentatively yes they are. Looking at the mean zonal wind forecasts for 5 days ahead we can see that there is a significant area of negative (blue easterly) winds from 70-90N.

This is conducive to strong northern blocking and almost into reliable timeframe as well.

The potential vorticity chart forecast shows very little in the way of strong vorticity and I can well imagine where BF would circle where the High pressure is likely to form- right over Greenland!

The forecast 100hPa vortex patterns for the GFS and ECM support this:

One can only watch and see what does develop, but I certainly for one wouldn't mind a final fling from winter before spring arrives.

c

Excellent post :)

It has always been a matter of timing in terms of when this final tropospheric effect might occur. And we well know that these effects have been longer than might have been anticipated or hoped for- which backs up well your initial point about there not being a set time period for these events to knock onwards.

I'm always happy for spring time flings (of the winter weather variety of course! :o )

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I think one item we have to take account next autumn/winter is, IF there are warmings shown, is to see how/where that might impact in terms of the main polar vortex. Its position is crucial as to which part of the northern hemisphere receives the cold.

It may be that the two earlier shortish warming spells did coincide with two anticipated cold spells for the UK; I have no idea, but is it possible that 'minor warmings are more conducive to subsequent cold spells for the Uk rather than the dramatic warming we later saw. Like I say I have no idea, its just a theory for one of you to shoot down - I won't feel offended if that happens.

As others have said this is a first class discussion thread with all of us learning from it.

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This leads the to the question can the final propagation of this MMW lead to a similar cold outbreak. Well the signs are certainly there if recent tropospheric model outputs are anything to go by, with firm suggestions that pressure may rise over Greenland. And are these supported by stratospheric conditions? Well, tentatively yes they are. Looking at the mean zonal wind forecasts for 5 days ahead we can see that there is a significant area of negative (blue easterly) winds from 70-90N.

This is conducive to strong northern blocking and almost into reliable timeframe as well.

The potential vorticity chart forecast shows very little in the way of strong vorticity and I can well imagine where BF would circle where the High pressure is likely to form- right over Greenland!

Chionomaniac,

I'm trying to get a handle on why short wave formation around Newfoundland appears to overwhelm any teleconnections predications, and as you highlighted above that a 2nd MMW was about to break possibly giving Greenland heights as well.

Do you have an idea as to why this short wave formation appears to be unpredictable in model output and appears to over-ride any teleconnection predictions and MMW propogation signals?

Also, can be assume that a 2nd propogation is further delayed?

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[Chionomaniac,

I'm trying to get a handle on why short wave formation around Newfoundland appears to overwhelm any teleconnections predications, and as you highlighted above that a 2nd MMW was about to break possibly giving Greenland heights as well.

Do you have an idea as to why this short wave formation appears to be unpredictable in model output and appears to over-ride any teleconnection predictions and MMW propogation signals?

Also, can be assume that a 2nd propogation is further delayed?

Hi MS,

What we are seeing is different models offering different solutions to the scenarios as they think it will occur. Firstly we are not about to see a 2nd MMW. What is looking probable is that negative zonal winds from the Jan MMW are propagating down into the troposphere in a final push -evident here:

post-4523-1236553326_thumb.pngpost-4523-1236553206_thumb.png

Now that kind of downwelling if forecast correctly (presently upto a weeks worth) is bound to have an effect on the Northern latitudes. Looking at the ECM Northern Hemisphere charts there is a distinct lack of polar vortex with an almost split in the vortex and an Arctic High pressure.

post-4523-1236553506_thumb.png

The GFS is suggesting height rises in this area as well but the last few runs show far less amplification in the 100 hPa flow pattern as can be seen below than previously, preventing the distinct pressure rises over Greenland suggested earlier:

post-4523-1236553715.gif

The short waves are forming because of the lack of northern height rises due to the flatter flow.

As there is still some variance between the GFS and ECM it is worth watching what occurs. I wouldn't bet against a split lower stratospheric vortex again with two distinct daughter vortices again. Where these may set up will influence the weather we receive. The ECM is suggesting that a daughter vortex will set up at the southern tip of Greenland which could potentially give us a repeat of the second half of February.

post-4523-1236554391_thumb.png

When there is a complex vortex and considerable negative wind propagation then it will be a time for considerable chopping and changing from the models so it could all change tomorrow. The lower stratosphere forecasts are no way set in stone and can change as much as the tropospheric ones.

c

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a very large link there and will take some time to read let alone digest it and feel able to comment on it.

so much for not using spell check!

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Interesting research and theory from Erl which certainly warrants further investigation.

Back to this year the lower stratospheric vortex at the 100 hPa level is showing signs of fragmenting after a brief reformation. Further up the vortex has recovered strength since the MMW but is yet to be above average.

ftp://hyperion.gsfc.nasa.gov/pub/ftpmet/n...60n_30_2008.gif

I can see a slight further strengthening before weakening and a FW occurs.

Presently weak negative mean zonal winds are propagating into the troposphere as part of the final propagative effects of the MMW as can be seen from the zonal mean wind anomaly chart.

These are forecast to continue for the immediate future.

http://strat-www.met.fu-berlin.de/cgi-bin/...t=all&var=u

These are translating through in the troposphere as a forecast weak Arctic High pressure. I think when these finish that will be the final effects of the MMW as the stratosphere returns to normal (probably around the start of April).

The stratospheric winter lasts from November through to tha start of April and I will continue monitoring until then. At that point I will ask for the thread to be archived.

c

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Weekly update.

The 30 hPa mean zonal winds have now returned back up to average following Jan's MMW.

ftp://hyperion.gsfc.nasa.gov/pub/ftpmet/n...60n_30_2008.gif

This has taken a substantial period of time due to the unprecedented strength and duration of the MMW. These average zonal winds are beginning to filter down to the troposphere and it may not be long before the mid latitude blocking that we are experiencing is replaced by more Atlantic based weather with possibly a slightly stronger jet stream leading into April.

The present zonal wind situation suggests that the effects of the MMW are wearing out

post-4523-1237291441_thumb.png

Stronger mid latitude lower tropospheric zonal winds are entering the forecast period and I don't think it will be long before these are felt on the ground:

post-4523-1237291992_thumb.png

Furthermore when looks at the extent of the warming in the stratosphere since the MMW one can see how considerable it has been. But also look how considerable a corresponding cooling has been. This has occurred at the upper stratospheric levels after the warming has propagated through and has probably helped prevent a FW from occurring.

post-4523-1237291921_thumb.png

The lower stratospheric forecasts do not support a northerly outbreak presently but these are unreliable and can change.

c

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Furthermore when looks at the extent of the warming in the stratosphere since the MMW one can see how considerable it has been. But also look how considerable a corresponding cooling has been. This has occurred at the upper stratospheric levels after the warming has propagated through and has probably helped prevent a FW from occurring.

c

How is it that all that very cold air can sit up there on top of the warm air. Surely it has to be related to low density and lack of backup in the mesosphere. It's hanging back due to lack of reinforcements.

Best comparison I can see is with 1987, also shortly after solar minimum. See http://www.cpc.ncep.noaa.gov/products/stra...ALL_NH_1987.gif

But there is a similar pattern in the La Nina years 1985, 2004 and 2006. In the case of 1987 it led straight into the El Nino of 1988.

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Guest North Sea Snow Convection
Weekly update.

The 30 hPa mean zonal winds have now returned back up to average following Jan's MMW.

This has taken a substantial period of time due to the unprecedented strength and duration of the MMW. These average zonal winds are beginning to filter down to the troposphere and it may not be long before the mid latitude blocking that we are experiencing is replaced by more Atlantic based weather with possibly a slightly stronger jet stream leading into April.

The present zonal wind situation suggests that the effects of the MMW are wearing out

Stronger mid latitude lower tropospheric zonal winds are entering the forecast period and I don't think it will be long before these are felt on the ground:

Furthermore when looks at the extent of the warming in the stratosphere since the MMW one can see how considerable it has been. But also look how considerable a corresponding cooling has been. This has occurred at the upper stratospheric levels after the warming has propagated through and has probably helped prevent a FW from occurring.

The lower stratospheric forecasts do not support a northerly outbreak presently but these are unreliable and can change.

c

As I suggested a short while ago it looks as though the FW may even end up later than usual based on the sustained cooling since the MMW. I think we can see now that the underlying strength of the west QBO and relative strength of the vortex was enough to override even the exceptionality of the MMW and the associated vortex split. That it could regroup so quickly is symbolic of this and I think that if we had been under an east QBO, that fragmented vortex that occured following the spitting would have disintegrated fully and not sat near Greenland back in mid Feb and scuppered the height rises that were anticiapted at the time to prolong (and further intensify)the Feb cold spell as was anticiapted for atime back then.

Long wave patterns will shorten due to seasonal factors so we won't neccessarily get a zonal and unsettled westerly flow from the return of westerly winds at 30mb level. It is one option of course, but we may equally get extensive Azores ridges and a downstream UK/euro High with a north west/south east split in the weather.

Not my kind of weather pattern at all, at any time of year, but may be the way things pan out.

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Are we any closer (yet) to discerning whether or not we have had our final warming yet?. <_<

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Guest North Sea Snow Convection
Are we any closer (yet) to discerning whether or not we have had our final warming yet?. <_<

No - as per my above post. Upper stratosphere temps continue well below and I think 30mb temps will continue to drop following their slow descent from the MMW to reflect this. Taking into account lag times it looks like westerly zonal winds will persist for some while throughout the Spring.

The change of the westerly QBO phase to easterly is due in the next month or so and that should precipitate the final warming - but there has been a steady steep drop since the MMW and so the benefits of this won't be felt till the summer at least IMO

So a late final break up of the polar vortex on the cards which might, perhaps, have implications for a delayed start to the ice melt season. That is a possible flip side to this.

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What is the latest ever date that a final warming event has occured in the Stratosphere?

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Guest North Sea Snow Convection
What is the latest ever date that a final warming event has occured in the Stratosphere?

Good question. I don't know that, maybe some else does.

Might be worth a look up to find out.

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Good question. I don't know that, maybe some else does.

Might be worth a look up to find out.

I have had a look up and am finding it difficult to pin down an actual date. FWs tend to occur between mid March to Mid May so at a guess the latest would be around late May. There is a lot of new research in this field I notice wrt the timing of final warmings and the influence of the arrival of Spring.

The majority of recent FWs have been late with the exception of last year and 2005. This follows a period of early FWs in the 80's.

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

c

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Here is the final update as the stratospheric NH winter comes to an end. We have not yet seen a Final warming. This now looks like it is going to be delayed after threatening to be the earliest ever following the unprecedented MMW. As one can see the temperature anomalies associated with the MMW at the lower levels have only just returned to normal over 2 months after the start of the MMW.

post-4523-1238531487_thumb.png

Higher up in the stratosphere the temperature is well below average. This is associated with the reformation of the polar vortex since the MMW.

post-4523-1238532023.gif

The 10 hPa and 30 hPa westerly winds are forecast to slowly weaken with no sign of summer reversal just yet.

post-4523-1238532141_thumb.png

These increased westerly winds are responsible for the delay in the FW and are likely to have a tropospheric effect, that being an increase in westerly winds until the FW occurs. With the tropospheric polar temperature gradient reducing at this time of year these increased westerly winds may translate with lower pressure towards the north of the UK and higher pressure towards the south.

Looking higher up in the stratosphere the temperature at the 1 hPa and 5 hPa level is rising and forecast to rise further. This is to be expected ay this time of year and is the precurser to the FW and subsequent summer reversal to easterly zonal winds.

post-4523-1238532436_thumb.png

All in all this winter has been a very interesting one stratospherically, starting with a warming over Alaska, a deep cooling over the pole at the start of the year, followed by the record breaking MMW and subsequent slow vortex recovery. We have seen the stratosphere having a delayed influence on the troposphere throughout this time. Unfortunately after the early February cold spell the MMW did not not create the high latitude blocking that we may have hoped for. The propagation seems to have had a more diffuse effect weakening the westerlies without the blocking and this has been discussed in more detail earlier in the thread.

That is all for this season which has been a great educational exercise. I look forward to the start of the next stratospheric winter and I will start a new watch on 1st November when we should have an easterly QBO and perhaps a different stratospheric season to report on.

c

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