Stratosphere Temperature Watch

[tundra]

I suspect the impact of the stratospheric warming has not yet materialised, the delay being due to a lack of downward propogation of the warming. I'll be looking out for things to start happening around March 5th or so.

Quite agree, and i am more than hopefull that we will start to see a positive trend develope in the models during the coming week for high latitude blocking to show itself. Although i doubt you will see this on the UKMO model as it only goes out six days ahead.

[johnholmes]

not totally true ba

they have verified on some occasions but obviously not for the very large temperature rise and wind changes on or around 20 January.

Prior to that they gave reasonably accurate indications of blocking. As several regular posters on here have tried to explain, no one ever promised it was the forecasters dream. All of us, me included, did feel that they did offer another bow to the forecasters arsenal in trying to predict several weeks down the line what might happen. Again those with more knowledge than I have did indicate that no one yet has any certainty even if the warming transfers into the height we all live at that the location can be predicted. Other drivers, such as those quoted on the thread by GP, Brick and others also need to be understood and 'married' if that is the right word, with what the Stratosphere shows.

Its all highly complex but very interesting. If you are expecting a quick answer to the warming theories then best not to wait too expectantly I suggest.

[chionomaniac]

I personally was having a day off!

Truth is there is not much change form the last couple of days. There is still no major propagation forecast and if anything there is a slight burst of westerly winds forecast in the troposphere which is not particularly conducive to northern blocking.

Furthermore the 100 hPa level forecasts are suggesting that the Siberian polar vortex is set to move back over the North Pole.

The zonal winds are set to return to westerly at the 10 hPa level over the next day or so. However even if the winds aren't easterly they will still be weaker than would be expected and this may still effect the troposphere.

Even though we haven't seen the northern blocking that we may have expected so far, the zonal winds have been significantly below average since the start of the MMW, at the top of the troposphere/ tropopause level, as the following chart shows.

I think this has mainly translated here as weaker westerlies rather than significant blocking. So the slack weather pattern we are in at the moment looks like it is a by product of the MMW. It will be interesting to see if this pattern continues through March.

c

Edited February 22, 2009 by chionomaniac

[Guest North Sea Snow Convection]

I too have other things to do! lol!

I would agree that the current non descript and very unwintry pattern is probably a by product of the MMW. A response that certainly was not one that was previously anticipated and is in acute contrast to the nature of the beast itself.

Edited February 22, 2009 by North Sea Snow Convection

[tundra]

The weak piece of the vortex that drifted east lowering heights across the Greenland area when the models flipped over to a milder regime a couple of weeks ago pushed our anticipated cold, very cold weather into central and eastern Europe where it has been very cold and snowy with a large blocking high to the north, and much further east than we and the models originally thought it would be.

It was because of this that our cold and potentially snowy February went down the pan. As a appropriate quote from Nick Sussex would be " in this country what can go wrong for cold and snow usually does".

Because the warming was very strong and of a long duration i believe there will be further northern latitude blocking potential as we go through March and as the last of the negative zonal winds and warming propagate down to the surface.

[Gray-Wolf]

Are we at a point yet where we may be suspecting that this event was not only a 'record' warming event (without parrellel since our measurements of such things began) but that it may also prove to be the earliest FW that we have measured/seen?

[shuggee]

I've been wondering whether or not the MWW has actually scuppered what might have been. The pattern locked-in for the first 10 days of Feb was of a type not seen for twenty years - and had it not been for the MWW it might have stuck? As others have ably alluded to above, the remnant of the vortex and its position couldn't have been predicted but has turned out to be the least favourable possible in the circumstances. The synoptics of the last 18 months or so - had they been left to carry merry along might have produced more wintry weather - until along came the Stratos warming and the knock on effect on our day to day weather we are now seeing. Talk about ironic.

Pure conjecture on my part mind

[chionomaniac]

Are we at a point yet where we may be suspecting that this event was not only a 'record' warming event (without parrellel since our measurements of such things began) but that it may also prove to be the earliest FW that we have measured/seen?

With the zonal winds set to return to westerly (and may have already done so today at the 10 hPa level) it is now looking that we are not going to get the earliest FW, (which would have resulted if the winds had kept easterly - the default summer pattern).

I've been wondering whether or not the MWW has actually scuppered what might have been. The pattern locked-in for the first 10 days of Feb was of a type not seen for twenty years - and had it not been for the MWW it might have stuck? As others have ably alluded to above, the remnant of the vortex and its position couldn't have been predicted but has turned out to be the least favourable possible in the circumstances. The synoptics of the last 18 months or so - had they been left to carry merry along might have produced more wintry weather - until along came the Stratos warming and the knock on effect on our day to day weather we are now seeing. Talk about ironic.

Pure conjecture on my part mind

The MMW set off the pattern for the first 10 days of Feb by causing the split in the vortex that subsequently brought the easterly. Ironically, as you say, it then scuppered the very pattern it created by the fact that a daughter vortex from the original split, hung around Greenland. The propagation has not occurred in the way we would liked and has had the effect of knocking the steam out of the jetstream (flights from Singapore have been arriving an hour early!). Unfortunately HL blocking has not occurred -maybe the Greenland daughter vortex was responsible because I would have thought that this area would have been prime for blocking otherwise.

c

Edited February 23, 2009 by chionomaniac

[johnholmes]

interesting posts from both Shuggee and ch

I had not thought about the 'daughter' being the cause of the non occurrence of cold for this area although it has been both cold and snowy over some parts of Europe.

lots to learn in this thread for sure, and quite fascintaing.

I wonder when the UK Met O will start putting a section in its forecasting courses, perhaps for the senior end, some ideas on this type of thing. I certainly had nothing of this kind at any stage of my career.

[chionomaniac]

With the zonal winds set to return to westerly (and may have already done so today at the 10 hPa level) it is now looking that we are not going to get the earliest FW, (which would have resulted if the winds had kept easterly - the default summer pattern).

c

I just thought that I would come back to GW's point about FWs. The information I have given above may be correct but I have done some further research on the exact classification of a Final Warming so as to avoid any ambiguity or confusion. It appears the accepted definition in the literature is from Black et al in 2006. The criterion that Black has used in the identification of the date of Stratospheric FWs is

"the final time that the running 5-day average of the zonal-mean zonal winds at 70N and 50 hPa drops below zero and it does not return to a value higher than 5m/s until subsequent autumn"

Black and B A Mc Daniel the dynamics of NH FW events. J. Atmos. Sci., 64, 2932-2946, 2007b.

So going by this GW could well be right regarding an earliest ever FW event this year but it is still too early to tell!

c

[BrickFielder]

My take is that the stratospheric vortex can cause a fixed pattern below it. In its normal configuration it starts over Northern Russia lat autumn and moves to the pole before moving back toward northern europe in spring where it finally collapses. A strong vortex towards the pole tends to give us an icelandic/greenland low which usually translates to wet atlantic weather. A split vortex will tend to create a much more fixed pattern having twin low pressure centers in the troposphere. A single displaced vortex will create a fixed pattern near to the vortex. We currently have a very weak vortex towards northern china giving a low pressure system there and a high pressure system towards the northern pacific. This however gives no real signal over the UK and normal winter patterns due to sea surface temperatures occur. That pattern is currently low angular momentum with the jet stream likely to be quite far south for periods of time. If the reminants of the vortex move round the globe as seems likely over the next 2 weeks then we may end up with a more fixed pattern with a risk of some colder weather.

In summary to assess the mid winter warmings impact you need to look at what happens and where to the stratospheric vortex and winds in the stratosphere as a result of the disturbance (MWW).

[summer blizzard]

Brickfielder, if this is indeed the early final warming event, then could it not indicate a higher chance of a warm late spring/early summer as the summer pattern takes hold earlier??

[Gray-Wolf]

I just thought that I would come back to GW's point about FWs. The information I have given above may be correct but I have done some further research on the exact classification of a Final Warming so as to avoid any ambiguity or confusion. It appears the accepted definition in the literature is from Black et al in 2006. The criterion that Black has used in the identification of the date of Stratospheric FWs is

"the final time that the running 5-day average of the zonal-mean zonal winds at 70N and 50 hPa drops below zero and it does not return to a value higher than 5m/s until subsequent autumn"

Black and B A Mc Daniel the dynamics of NH FW events. J. Atmos. Sci., 64, 2932-2946, 2007b.

So going by this GW could well be right regarding an earliest ever FW event this year but it is still too early to tell!

c

Kudos to you Chionomaniac!!

Though I probably am wrong in my wondering (and it was just a thought as I am very new to all of this) thank you so much for the time and effort in telling me 'your truth'!!

[Guest North Sea Snow Convection]

I'm not too sure regarding the FW. I still think that a temporary cool-off and increase in zonal winds will occur before an FW. The underlying west QBO has been very relisient and that may also be having its last hurrah here as well in terms of a last burst of poalr westerlies before the seasonal changes kick in.

Regarding the MMW, it is again too early to be sure, but I am wondering if we are seeing the first tropospheric indications predicted in the next 10 days of changes over the polar field and those overdue negative anomalies finally showing their hand? The coming days may prove more interesting to see.

[chionomaniac]

I'm not too sure regarding the FW. I still think that a temporary cool-off and increase in zonal winds will occur before an FW. The underlying west QBO has been very resilient and that may also be having its last hurrah here as well in terms of a last burst of polar westerlies before the seasonal changes kick in.

Regarding the MMW, it is again too early to be sure, but I am wondering if we are seeing the first tropospheric indications predicted in the next 10 days of changes over the polar field and those overdue negative anomalies finally showing their hand? The coming days may prove more interesting to see.

Yes, looking at the 50 hPa level forecasts today the present easterly negative mean zonal winds are forecast to return westerly and rise above 5m/s.

Reading BF's post from yesterday, I can see that the slack stratospheric pattern that we are in does lead us to have no strong upper signal, and in the absence of that, the local tropospheric influences such as SST's have a great bearing on the resultant weather that we recieve. I am left wondering that if the tropospheric pattern had had greater wave amplitudes in the last couple of weeks would this have been the trigger necessary for meridional flow and greater blocking to our north. Instead we have been left with an extremely weak but flatter jet pattern . 'What ifs', heh?

Looking at the 100 hPa forecasts with regard to vortex position, both the ECM and GFS suggest that a more regular spherical vortex is set to strengthen in the Pacific /Siberian area with the Canadian now totally absorbed / dissipated by its stronger Siberian sister. If this reformed vortex can stay weak and keep away from Greenland, then there will be the chance that if a more amplified jet pattern occurs, heights could rise in areas that may lead to a colder pattern down the line. That is still a long way off, but we are still in February and March has had potent cold snaps in the past.

Finally the ECM is suggesting that the negative mean zonal wind anomalies may be leaving the middle stratosphere. Will they propagate downwards finally? Worth watching as it has been suggested all along that there may need to be a forcing from above to encourage propagation.

c

[Guest North Sea Snow Convection]

Yes, looking at the 50 hPa level forecasts today the present easterly negative mean zonal winds are forecast to return westerly and rise above 5m/s.

Reading BF's post from yesterday, I can see that the slack stratospheric pattern that we are in does lead us to have no strong upper signal, and in the absence of that, the local tropospheric influences such as SST's have a great bearing on the resultant weather that we recieve. I am left wondering that if the tropospheric pattern had had greater wave amplitudes in the last couple of weeks would this have been the trigger necessary for meridional flow and greater blocking to our north. Instead we have been left with an extremely weak but flatter jet pattern . 'What ifs', heh?

Looking at the 100 hPa forecasts with regard to vortex position, both the ECM and GFS suggest that a more regular spherical vortex is set to strengthen in the Pacific /Siberian area with the Canadian now totally absorbed / dissipated by its stronger Siberian sister. If this reformed vortex can stay weak and keep away from Greenland, then there will be the chance that if a more amplified jet pattern occurs, heights could rise in areas that may lead to a colder pattern down the line. That is still a long way off, but we are still in February and March has had potent cold snaps in the past.

Finally the ECM is suggesting that the negative mean zonal wind anomalies may be leaving the middle stratosphere. Will they propagate downwards finally? Worth watching as it has been suggested all along that there may need to be a forcing from above to encourage propagation.

c

Hiya - agreed, these were/are my thoughts too

I think the more amplified pattern holds the key - it has flattered to deceive a few times recently with the downgraded northerlies but it is only a matter of time before it does finally happen. I think that will be the trigger for the pattern we are wating for with the downwelling negative mean anomalies. I enjoy winter type spells as long as they are able to occur 'out of season' and if last April gave snow that lasted through into another day then there is time yet for some bigger interest than that in March, albeit there is the ever growing solar power issue.

[Gray-Wolf]

But ,as we stand now, (and not at the mercy of either our hopes or the models) this was the last SSW of the 'winter' (so far)?

Edited February 24, 2009 by Gray-Wolf

[chionomaniac]

But ,as we stand now (and not at the mercy of either our hopes or the models) this was the last SSW of the 'winter' (so far)?

Technically, one can't have a MMW within 20 days of the central date of a previous one. That time has now elapsed and winds are again westerly at 10 hPa and 60N. When Mr Pulvani et al set the criteria for MMWs, I don't think there had been one before that had started in Jan that had maintained negative mean zonal winds for the greater than the 20 days that they had originally set as the benchmark.

I think in light of the present MMW that there needs further thought and perhaps rewriting of definitions to avoid further confusions. I reckon the FW criteria should be based upon the same hPa level as the MMW.

If we have another wave breaking event causing another vortex split now would it be a new MMW or classified as a continuance of the present one or part of a final warming (as winds are still negative at the 50 hPa level)???

It is probably unlikely anyway as (I think) the vortex has to be quite strong before a MMW which it isn't.

So probably the last MMW of winter but not technically!

c

[Gray-Wolf]

Technically, one can't have a MMW within 20 days of the central date of a previous one. That time has now elapsed and winds are again westerly at 10 hPa and 60N. When Mr Pulvani et al set the criteria for MMWs, I don't think there had been one before that had started in Jan that had maintained negative mean zonal winds for the greater than the 20 days that they had originally set as the benchmark.

I think in light of the present MMW that there needs further thought and perhaps rewriting of definitions to avoid further confusions. I reckon the FW criteria should be based upon the same hPa level as the MMW.

If we have another wave breaking event causing another vortex split now would it be a new MMW or classified as a continuance of the present one or part of a final warming (as winds are still negative at the 50 hPa level)???

It is probably unlikely anyway as (I think) the vortex has to be quite strong before a MMW which it isn't.

So probably the last MMW of winter but not technically!

c

Thanks C.

Of all the 'new' ways folk would like to see weather and climate influenced to me ,the impact of the Strat. on the trop. ,and it's impacts on climate and weather there, rings most true.

My 'angle' is (as you have probably guessed) the possible interaction between solar wind and strat/Trop.

If Cycle 24 is to be a big and disruptive one then we will have lots of opportunity to explore my ruminations!

[Erl Happ]

Gray Wolf

"My 'angle' is (as you have probably guessed) the possible interaction between solar wind and strat/Trop."

In my view you are on pretty firm ground. The geomagnetic indices that reflect the solar wind also reflect the incidence of energetic particle precipitation events that produce nitrogen compounds in the mesosphere that are carried down into the polar stratosphere where they erode ozone.

The ozone content of the stratosphere and upper troposphere drives temperature in the ozone rich areas and the mid latitude high pressure cells are ozone rich. For this reason 200hPa temperature in these regions varies independently of surface temperature. This directly affects vorticity and surface wind strength together with ice cloud cover and has knock on effects in terms of the strength of the Hadley circulation and the location of the jet streams.

There is evidence in the recent cooling of the equatorial stratosphere conjunctional with warming of the Arctic stratosphere that the solar wind is capable of shifting the atmosphere and thereby changing the density of the optical path that the suns rays must traverse to reach the surface. I can not think of any other way that the equatorial stratosphere is forced to cool as the mid latitude and polar stratosphere warms. What do you think?

[Guest North Sea Snow Convection]

I am very interested in the solar/stratosphere relationship -perhaps the discusssion on those lines can be made separately on the climate threads?

Wrt to this MMW to have led to an FW, then as suggested above it would require no intervening return to polar westerlies. Any new wave breaking now constitutes another event in its on right, and due to being on the cusp of the Spring season would/will surely be counted as the FW.

[Gray-Wolf]

Gray Wolf

In my view you are on pretty firm ground. The geomagnetic indices that reflect the solar wind also reflect the incidence of energetic particle precipitation events that produce nitrogen compounds in the mesosphere that are carried down into the polar stratosphere where they erode ozone.

The ozone content of the stratosphere and upper troposphere drives temperature in the ozone rich areas and the mid latitude high pressure cells are ozone rich. For this reason 200hPa temperature in these regions varies independently of surface temperature. This directly affects vorticity and surface wind strength together with ice cloud cover and has knock on effects in terms of the strength of the Hadley circulation and the location of the jet streams.

There is evidence in the recent cooling of the equatorial stratosphere conjunctional with warming of the Arctic stratosphere that the solar wind is capable of shifting the atmosphere and thereby changing the density of the optical path that the suns rays must traverse to reach the surface. I can not think of any other way that the equatorial stratosphere is forced to cool as the mid latitude and polar stratosphere warms. What do you think?

Thanks Erl!

Glad there are some who don't make me feel that I'm barking up the wrong tree...and you appear a lot better placed (to me) than most to understand such.

EDIT: When I've thought I'll let you know! promise.

EDIT,EDIT NSSC,

With the greatest of respect we are discussing that which you'd have us discuss on this thread.

I'm sure others will agree and , as such ,if you could make me see why this isn't so (in your understanding) and I can 'see sense' in your words I'll ask for the mods to remove such 'offenses' over to the thread I set up (on your behest).

Edited February 25, 2009 by Gray-Wolf

[Guest North Sea Snow Convection]

Thanks Erl!

Glad there are some who don't make me feel that I'm barking up the wrong tree...and you appear a lot better placed (to me) than most to understand such. :lol:

EDIT: When I've thought I'll let you know! promise.

EDIT,EDIT NSSC,

With the greatest of respect we are discussing that which you'd have us discuss on this thread.

I'm sure others will agree and , as such ,if you could make me see why this isn't so (in your understanding) and I can 'see sense' in your words I'll ask for the mods to remove such 'offenses' over to the thread I set up (on your behest).

No need to remove anything - it is obviously not my place nor my perogative anyway, as much as you will already know. Certainly no 'offenses'

Have already suggested how interesting the link is, but was emphasising the climactic link you referred to which is separate from the the seasonal temp watch. I would participate in such an extra thread - only umbly suggested by me as a way of not tangling up the temp watch associated with the MMW and the long terms influences on stratospheric behaviour. But ch and the mods are the one's to have any say in what happens or what goes where

[Gray-Wolf]

No need to remove anything - it is obviously not my place nor my perogative anyway, as much as you will already know. :lol: Certainly no 'offenses'

Have already suggested how interesting the link is, but was emphasising the climactic link you referred to which is separate from the the seasonal temp watch. I would participate in such an extra thread - only umbly suggested by me as a way of not tangling up the temp watch associated with the MMW and the long terms influences on stratospheric behaviour. But ch and the mods are the one's to have any say in what happens or what goes where

No worries NSSC, see over there sometime?

[chionomaniac]

I certainly would prefer this thread to be kept to the monitoring of the tropospheric/stratospheric interaction from this winter only. The interesting link of climatic stratospheric changes to solar wind and other non tropospheric influences certainly needs investigating but that is probably best left to its own thread, I agree.

Looking at the present state of the stratosphere I certainly don't believe that January's MMW has finished with its influence just yet.

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

Looking at the mean zonal wind forecasts we can see that the middle stratosphere has returned to a more positive westerly flow and this is set to increase further but is still way below average.

Interestingly this may trigger some propagation of negative winds to the troposphere as have been suggested in recent forecasts. In fact the forecast here for T+192 suggests quite strong negative mean zonal wind anomalies in the polar regions

Now these forecasts have fluctuated but a trend is certainly there. The next thing to do is to work out where these anomalies (if they verify) could transfer to, on the tropospheric surface. My guess would be away from the strongest area of polar vortex. This, looking at both the ECM and GFS/NCEP forecasts below appears to be centred above East Siberia and the East Siberian Sea in the Arctic Basin. Now, would this allow pressure to rise where there is evidence of a ridge over Greenland?

It looks like we are entering another pattern change with evidence of greater amplification. Hopefully this will help with the success of the propagation, in as much that not only do we see a weak jet, but also the right pattern to transfer the favourable stratospheric state to the troposphere and create favourable Northern Blocking. It is still not too late.

c