Stratosphere Temperature Watch

[Guest North Sea Snow Convection]

Hi Tamara

I hope you had a good Christmas.

I confess to still not knowing enough about the tropical convective signals to which ones are more likely to set off a warming event. I tend to look at the mountain torques to try and judge the possibilities and then look at the wave 1 and 2 forecasts.

With this renewed split I can see the ECM being on the mark up to T+168 and then the northern trough dropping into Scandi. Then with possible renewed easterly zonal winds a NEly develops with extreme cold a possibility being sucked our way - but this will all depend on how quickly the GH migrates west - it may just hold up enough with the renewed split. Still a good cold pattern though.

ok - thanks for that

I agree with your assessment re a possible timetable for the pattern regarding the predicted new split. You and I and others down here very much need that cold easterly I think. In terms of just the southerly tracking lows alone, we are indeed closest to the marginal/wrong side of marginal ppn zone for the time being

[Mark Bayley]

I have noticed that Stratosphere is predicted to go even more below average. From what i have read it seems it may not be as bad as it looks. Wouldn't a below average stratosphere for a prolonged period of time lead to the polar vortex gaining strength leading to a the AO which is currently very negative trending up towards positive? Or will we see the it disrupted with continued height rises over Greenland (negative NAO) with colder air over Scandinavia? It seems some of models are keen on losing the heights over Greenland with high pressure dropping over us. The GFS 12z for example. Or is it being to progressive? I am very much new to all this however i find it all very interesting

I was also wondering what zonal winds are, i keep seeing them mentioned every now and again?

[azores92]

well the ecm tonight supports the idea of the vortex gaining strength deep in fi, with the once prominent greenland high toppling into the atlantic, and the AO tending positive. could this be the cool stratosphere showing its hand, and could this spell the end for the cold? or will a scandi high save the day?

Edited December 30, 2009 by azores92

[Fozfoster]

well the ecm tonight supports the idea of the vortex gaining strength deep in fi, with the once prominent greenland high toppling into the atlantic, and the AO tending positive. could this be the cool stratosphere showing its hand, and could this spell the end for the cold? or will a scandi high save the day?

Bugger! was thinking on the same lines.good one azores92

[chionomaniac]

Happy New Year to all.

I am just seeing the first signs of some sort of warming at the 10 hPa level on the GFS forecasts.

Currently the stratosphere is very cold at this level as can be seen from the following chart:

However the 10 day forecasts are showing a warming over Eastern Siberia:

This is still a minor warming, but any warming could be a bonus and it could grow to something more significant. The ECM and GFS forecasts will need careful monitoring over the coming days.

c

[Guest North Sea Snow Convection]

Happy New Year to all.

I am just seeing the first signs of some sort of warming at the 10 hPa level on the GFS forecasts.

Currently the stratosphere is very cold at this level as can be seen from the following chart:

However the 10 day forecasts are showing a warming over Eastern Siberia:

This is still a minor warming, but any warming could be a bonus and it could grow to something more significant. The ECM and GFS forecasts will need careful monitoring over the coming days.

c

Happy New Year Ed!

Might seem inappropriate but that is going to get a from me. Even if it is premature!

I really can't see the cold stratosphere being sustained when taking into account the background factors present this winter

[geoffw]

exactly - any warming is great news and if there is warming could this mean more cold in February?

[chionomaniac]

Happy New Year Ed!

Might seem inappropriate but that is going to get a from me. Even if it is premature!

I really can't see the cold stratosphere being sustained when taking into account the background factors present this winter

It's a bit early to get me shouting out just yet ,T! However, it will be good if the ECM picks up on this tomorrow

exactly - any warming is great news and if there is warming could this mean more cold in February?

The warm November stratosphere has helped set up the pattern for winter so far,but this is likely to come to an end unless we get another warm push from the stratosphere. So far we have seen 'upwelling' stratosphere disturbances originating from the troposphere. The December cold spell and the projected one now have both come from vortex splits that have originated from the troposphere, so it would be interesting to see what would occur from an upper stratosphere led disturbance. Of course it is too early to say where this warming is heading but it is a good sign to see.

c

[geoffw]

well lets hope this warming comes true, i agree any warming will be interesting

[weatherjunkie]

It's a bit early to get me shouting out just yet ,T! However, it will be good if the ECM picks up on this tomorrow

The warm November stratosphere has helped set up the pattern for winter so far,but this is likely to come to an end unless we get another warm push from the stratosphere. So far we have seen 'upwelling' stratosphere disturbances originating from the troposphere. The December cold spell and the projected one now have both come from vortex splits that have originated from the troposphere, so it would be interesting to see what would occur from an upper stratosphere led disturbance. Of course it is too early to say where this warming is heading but it is a good sign to see.

c

I wish a happy, healthy, and wealthy new year to all.

In reference to the bolded, is the stratosphere likely to play an important role down the road given how significantly low the -AO is? To me it appears that the troposphere will not be seriously affected by the potential strengthening stratospheric vortex in the next 1 to 2 weeks. There are signs that both the -NAO and -AO will lose their grip a bit, but would you expect a pattern reversal come the latter half of January?

I've seen Don Sutherland's post on Eastern which had the mean composite chart for when the AO reached -6 SD, but I'm curious to know how the stratosphere looked in year's with a similar -AO, and whether or not the stratosphere will be much of a factor.

Here in the US, the active subtropical jet and combined forces of strong -AO and -NAO has many people in the eastern third of the country in love with the pattern and reflecting back to how it compares to the 70s. I would love for this to continue and to hear some good news related to the stratosphere.

I guess it's a mostly wait and see situation.

Edited January 2, 2010 by weatherjunkie

[chionomaniac]

I wish a happy, healthy, and wealthy new year to all.

In reference to the bolded, is the stratosphere likely to play an important role down the road given how significantly low the -AO is? To me it appears that the troposphere will not be seriously affected by the potential strengthening stratospheric vortex in the next 1 to 2 weeks. There are signs that both the -NAO and -AO will lose their grip a bit, but would you expect a pattern reversal come the latter half of January?

I've seen Don Sutherland's post on Eastern which had the mean composite chart for when the AO reached -6 SD, but I'm curious to know how the stratosphere looked in year's with a similar -AO, and whether or not the stratosphere will be much of a factor.

Here in the US, the active subtropical jet and combined forces of strong -AO and -NAO has many people in the eastern third of the country in love with the pattern and reflecting back to how it compares to the 70s. I would love for this to continue and to hear some good news related to the stratosphere.

I guess it's a mostly wait and see situation.

Hi weatherjunkie,

I agree with you that the strengthening stratospheric vortex is likely to affect the troposphere but probably not until the end of January unless we see some kind of warming in the meantime.

I highlighted yesterday that the GFS was showing the first signs of warming at the 10 hPa level and have checked the Berlin site today for evidence that this may be backed up. What I am looking for is evidence of a strong warming that could be classified as a MMW but it may take some time for this to become apparent.

There is the first signs that something may be occurring when one looks at the zonal winds at the 1 hPa level. There is the first signs of a dramatic reduction.

When one compares this reduction to last year's MMW then one can see that a similar thing occurred then.

So now it is time to see what is happening at the 1 hPa level at T+240 to cause this drop in zonal winds.

And lo behold we see a 20ºC rise in temperature within a couple of days. Furthermore there is evidence that this is forecast at the 5 hPa level. Encouraging signs but that is all at present.

So what could be causing this upper level warming? Perhaps it is an increase in wave 1 activity which is consistent with an Atlantic blocking based precursor.

My own thoughts all along have been with something like this occurring so I will be watching with interest.

c

[azores92]

better news for late jan/early feb then, or back to business?

Edited January 2, 2010 by azores92

[chionomaniac]

The forecast warming is still present on the latest GFS outputs.

When I look at the 1 hPa level it is pretty obvious to see when comparing now with 10 days:

What we need to watch for is that the warming filters down throughout all levels of the stratosphere. We are certainly getting down to the 10 hPa level:

And to monitor what happens with the shape of the vortex and mean zonal mean winds particularly at the 10 hPa level where MMWs are classified. Here is the difference between now and 10 days time:

My early thoughts are that we could see a displacement type MMW as everything ( Atlantic blocking, wave type 1 activity, eQBO) would fit in with this but I will have to wait to see whether or not this will occur.

Displacement type MMW's do not proffer the same extent of propagation to the troposphere as splitting type of events, but there is certainly the chance that the forecast for a warmer February could be disrupted somewhat if a MMW was to occur. I am sure GP would have to have a rethink!

Still early days.

c

[snow showers]

So chionomaniac, does mean that what happens in the stratosphere and troposphere has the big effect, as well as the AO, on our winter weather, ie the main driver?

Thanks

[chionomaniac]

So chionomaniac, does mean that what happens in the stratosphere and troposphere has the big effect, as well as the AO, on our winter weather, ie the main driver?

Thanks

The stratosphere and troposphere are strongly interconnected. The state of the stratosphere during the early winter has helped create a troposphere where northern blocking has thrived creating the strongly negative AO. Remember that the AO and the NAO are not drivers of the weather but are more a product of the NH polar atmospheric pressure differences. The stratosphere, SST state, NH snow cover may be the drivers that help achieve this.

[Mark Bayley]

Interesting thoughts Wouldn't the cooler stratosphere now mean that a milder spell could be likely for at least a time before the effects of the potential warming could be felt? Then again the AO is currently negative and looks to remain so despite a rise. My understanding was a cooler stratosphere like were seeing now meant that polar vortex gained strength over the pole meaning a positive AO occurring? This doesn't seem to be happening. This is one of the most interesting threads on the forum. I'm learning quite a bit from your posts chionomanica

[chionomaniac]

Interesting thoughts Wouldn't the cooler stratosphere now mean that a milder spell could be likely for at least a time before the effects of the potential warming could be felt? Then again the AO is currently negative and looks to remain so despite a rise. My understanding was a cooler stratosphere like were seeing now meant that polar vortex gained strength over the pole meaning a positive AO occurring? This doesn't seem to be happening. This is one of the most interesting threads on the forum. I'm learning quite a bit from your posts chionomanica

We seem to be in an upwelling phase from the troposphere where any propagation down from the upper parts of the stratosphere seems to be somewhat delayed. When we look at the profile of the zonal winds the positive anomalies have not yet filtered down past the middle stratosphere.

This may yet occur by the end of January I suspect when we may enter a downwelling phase. However if the downwelling phase also coincided with a MMW then this could actually assist with the propagation of negative zonal wind anomalies!

[Mark Bayley]

We seem to be in an upwelling phase from the troposphere where any propagation down from the upper parts of the stratosphere seems to be somewhat delayed. When we look at the profile of the zonal winds the positive anomalies have not yet filtered down past the middle stratosphere.

This may yet occur by the end of January I suspect when we may enter a downwelling phase. However if the downwelling phase also coincided with a MMW then this could actually assist with the propagation of negative zonal wind anomalies!

Thanks will have to keep an eye out for signs of warming event starting to occur. I'm still unsure what zonal winds are? Positive and negative

[chionomaniac]

Thanks will have to keep an eye out for signs of warming event starting to occur. I'm still unsure what zonal winds are? Positive and negative

Zonal winds are the expected averaged out winds for a particular area. In the case of the winter polar stratosphere the expected trade zonal winds would be westerly or positive. If the were to reverse they would become easterly or negative. Any easterly winds that filter through to the troposphere would increase the likelihood of blocking which is exactly what has occurred with the two recent tropospheric led vortex splits.

In the case of anomalies a positive anomaly would suggest increased westerlies and a negative anomaly would indicate decreased westerlies which may or may not have totally reversed to easterlies.

[Mark Bayley]

Zonal winds are the expected averaged out winds for a particular area. In the case of the winter polar stratosphere the expected trade zonal winds would be westerly or positive. If the were to reverse they would become easterly or negative. Any easterly winds that filter through to the troposphere would increase the likelihood of blocking which is exactly what has occurred with the two recent tropospheric led vortex splits.

In the case of anomalies a positive anomaly would suggest increased westerlies and a negative anomaly would indicate decreased westerlies which may or may not have totally reversed to easterlies.

Thanks, i shall hopefully get there in the end

[weatherjunkie]

Hi weatherjunkie,

I agree with you that the strengthening stratospheric vortex is likely to affect the troposphere but probably not until the end of January unless we see some kind of warming in the meantime.

I highlighted yesterday that the GFS was showing the first signs of warming at the 10 hPa level and have checked the Berlin site today for evidence that this may be backed up. What I am looking for is evidence of a strong warming that could be classified as a MMW but it may take some time for this to become apparent.

There is the first signs that something may be occurring when one looks at the zonal winds at the 1 hPa level. There is the first signs of a dramatic reduction.

When one compares this reduction to last year's MMW then one can see that a similar thing occurred then.

So now it is time to see what is happening at the 1 hPa level at T+240 to cause this drop in zonal winds.

And lo behold we see a 20ºC rise in temperature within a couple of days. Furthermore there is evidence that this is forecast at the 5 hPa level. Encouraging signs but that is all at present.

So what could be causing this upper level warming? Perhaps it is an increase in wave 1 activity which is consistent with an Atlantic blocking based precursor.

My own thoughts all along have been with something like this occurring so I will be watching with interest.

c

Thank you for the reply.

I also see heat fluxation at 30hPa that coincide with the slowing down of the winds. That appears to be a good sign as well, but it's probably expected given what's happening.

The ECM seems to want to weaken the wave 2 activity in the upper stratosphere and "downwell" it to the lower stratosphere as it propogates poleward, do you have any thoughts about this?

Your input is greatly appreciated and here's hoping the GFS hops onto the warming trend and hopefully the ECM will too.

[chionomaniac]

Thank you for the reply.

I also see heat fluxation at 30hPa that coincide with the slowing down of the winds. That appears to be a good sign as well, but it's probably expected given what's happening.

The ECM seems to want to weaken the wave 2 activity in the upper stratosphere and "downwell" it to the lower stratosphere as it propogates poleward, do you have any thoughts about this?

Your input is greatly appreciated and here's hoping the GFS hops onto the warming trend and hopefully the ECM will too.

We are still at the primordium stage of any warming development whether major or minor.

I think we are looking mainly at wave number 1 event here. With warmings we see the heat fluxed poleward at the top of the stratosphere and then downward propagation occurs. One can see the classic poleward heat flux being 'sucked' into the vortex at the 1hPa level if you follow the following link and trace it out to T+240. The next stage should be vortex strength reduction.

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/kiruna09/index.html

c

[kold weather]

I'd be interested to see what the 12z ECM stratosphere conditions look like by 240hrs because the PV seems to become very elongated yet again, almost to the point of splitting by 240hrs yet again...

[chionomaniac]

I'd be interested to see what the 12z ECM stratosphere conditions look like by 240hrs because the PV seems to become very elongated yet again, almost to the point of splitting by 240hrs yet again...

They only release data once a day with a days delay thrown in for good measure, KW!

[Glacier Point]

http://www.esrl.noaa.gov/psd/map/images/olr/olr.anom.png

Tropical convection is now centred over the Indian Ocean. I think this will have an impact on the polar stratosphere through planetary waves being refracted into the stratospheric jet.

The last tropical convection centred in this region was early to mid November. 10 days from this time we saw the stratosphere warm.