Stratosphere Temperature Watch

[Guest North Sea Snow Convection]

Also looking at the possible downwelling of positive zonal mean wind anomalies, one would expect these to hit the troposphere around the start of January. This would be in possible conflict with the -NAO signal that GP has indicated that could be possible around that time. Hopefully they won't be that strong by the time they reach the troposphere.

Yes, this is the thing that I am concerned about and why I have banged on about the need for a follow up full blown warming event to occur. Although I suggested on the model thread that a -NAO is likely to dominate the winter - the large caveat is that the stratosphere behaves as many experts have widely predicted. Otherwise this will be overriden.

We need to see signs of a significant warm up asap - the present trend is not good for the New Year as there is a danger that the disrupted vortex is being given every chance to regroup and prevent another reload of cold air, the longer that this cooling remains. GP suggests that the cold tropical stratosphere should offset this - hopefully that will be the case, in the absence of any warming signal atm

Edited December 20, 2009 by North Sea Snow Convection

[cooling climate]

MJO in phase 7-8, another kelvin wave over Indonesia moving east over the coming days with convection

already near the date line.

hopefully This will intergrate with the polar westerlies building another strong +pna signal (strong rosby

wave breaking in the stratosphere) and the NWP models will pick up on this in the coming days, also of

course the GFS and ECM stratosphere charts.

http://www.cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/OLR/m.3d.html

[chionomaniac]

Still no signs of a major warming of the stratosphere on the horizon.

However, it is worth noting how cool the tropical stratosphere is at the moment. The differential between the tropical stratosphere and polar stratosphere is bound to have an effect on the vortex strength and positioning.

Tropical stratosphere 30 hPA temps:

Polar stratosphere 30 hPa temps:

The differential between them is only around 6 Kelvin. Now imagine previous or worst case scenarios where the tropical stratosphere is as warm as can be and the polar stratosphere is as cold as can be - the differential could be in the region of 30 Kelvin!

c

[Guest North Sea Snow Convection]

Hi good you please tell me what that would mean for us please!!! Thanks

Basically the net difference between the polar and tropical stratosphere levels being as minimal as possible mitigates the strength of the polar vortex, which in turns means that it is harder for it to organise itself over the North Pole with low heights over Greenland than is the case when the polar stratosphere is cool but the the tropical stratosphere is significantly warmer.

As you may know, when the polar vortex is strong and resident in that position it leads to a mild zonal set-up for the UK with corresponding pressure high over the Azores and into europe. The present situation is a much better one in terms of reducing the chances of that happening to any extent.

[SteveB]

I know the fear is the Polar vortex reforming, but what's to say it will reform in a disadvantage place for us. It could easily reform and set up shop in a place that could help with our Winter prospects couldn't it?

[Guest North Sea Snow Convection]

I know the fear is the Polar vortex reforming, but what's to say it will reform in a disadvantage place for us. It could easily reform and set up shop in a place that could help with our Winter prospects couldn't it?

Yes it could, and as per the discussion on the model thread, it very well might.

The background evidence points to an eventual (probable major) warming of the stratosphere, but in the meantime, we are watching to see what happens to the profiles of the warmer lower layers of the stratosphere and troposphere boundary that is at this time supporting a continued disrupted vortex, and the cooler upper layers. It could be that the vortex locates over Scandinavia/western russia and a colder weather pattern is maintained rather than any return to traditional atlantic zonality.

Edited December 22, 2009 by North Sea Snow Convection

[SteveB]

Thanks Tamara,

All to play for, and I still have to pinch myself that it only December.

[johnholmes]

Still no signs of a major warming of the stratosphere on the horizon.

However, it is worth noting how cool the tropical stratosphere is at the moment. The differential between the tropical stratosphere and polar stratosphere is bound to have an effect on the vortex strength and positioning.

Tropical stratosphere 30 hPA temps:

Polar stratosphere 30 hPa temps:

The differential between them is only around 6 Kelvin. Now imagine previous or worst case scenarios where the tropical stratosphere is as warm as can be and the polar stratosphere is as cold as can be - the differential could be in the region of 30 Kelvin!

c

hi c

I suspect its this relatively small difference that is creating some of the building blocks for blocking even though the supposed classic blocking signal is not that coherent?

It makes for a fascinating time trying to decipher what may happen in 10-20 days let alone the rest of winter.

Edited December 22, 2009 by johnholmes

[V for Very Cold]

can I thank everyone for putting effort into explaining what SWEs are and how they effect us - it's an area I know little about, and I'm afraid I just tend to watch this trhead, but the help given to dunderheads like me is very welcome

Edited December 22, 2009 by V for Very Cold

[johnholmes]

We all learn on here V-no matter how long you have been involved with the weather-its also great to share our knowledge-there is always someone who has a greater understanding than each of us-true in my case for sure on this subject.

[chionomaniac]

Looking at the long range GFS stratospheric forecasts I am seeing signs that we could get another vortex split around New Year. If that occurred that would be fantastic news for New Year and would give us another chance of a reload of the current spell. Perhaps the tropospheric model outputs are picking up on this.

Here are the vortex charts for T+240 and they are very similar to the ones seen at the start of the month - the last split seemed to start from the troposphere and worked its way up into the middle stratosphere. If this does occur again I expect the AO to drop off the scale again.

100 hPa level

50 hPa level

30 hPa level

Very interesting and it will be very interesting to look at tomorrows outputs!

c

Edited December 23, 2009 by chionomaniac

[weatherjunkie]

MT spiking earlier this month to +4 SD. It has since come back down a bit to +2 SD and it appears to be continuing it's decline at a fairly decent pace. There is word on the street that would could see another spike. I would imagine that this would somehow play a role regarding the PV splitting, even if it's minimal.

Edited December 24, 2009 by weatherjunkie

[chionomaniac]

Looking at the long range GFS stratospheric forecasts I am seeing signs that we could get another vortex split around New Year. If that occurred that would be fantastic news for New Year and would give us another chance of a reload of the current spell. Perhaps the tropospheric model outputs are picking up on this.

Here are the vortex charts for T+240 and they are very similar to the ones seen at the start of the month - the last split seemed to start from the troposphere and worked its way up into the middle stratosphere. If this does occur again I expect the AO to drop off the scale again.

100 hPa level

50 hPa level

30 hPa level

Very interesting and it will be very interesting to look at tomorrows outputs!

c

The latest ECM Berlin forecast is not yet suggesting a split of the polar vortex into the stratosphere. However, we are seeing another favourable outcome with the vortex being forecast to become displaced over Scandinavia and Northern Russia. This will allow a door to open with height rises possible to the northwest and I believe that this scenario is being forecast on the ECM tropospheric modeling. So all very believeable and fits in with GP's thoughts.

MT spiking earlier this month to +4 SD. It has since come back down a bit to +2 SD and it appears to be continuing it's decline at a fairly decent pace. There is word on the street that would could see another spike. I would imagine that this would somehow play a role regarding the PV splitting, even if it's minimal.

The MT that holds most interest is the E Asia one which in itself is still a significant event. I believe that this one is most likely to affect us and could also be a precursor to a SSW. So another thing to look out for. However with the vortex disruption already seen this winter it is looking like we don't even need a SSW as the tropospheric negative mean zonal wind upwellings are doing a fine job of weakening the polar vortex.

c

[Guest North Sea Snow Convection]

You get the feeling that it will only take one more push in terms of further warming/ wave breaking to complete the disintegration of the polar vortex and secure long term NH northern blocking. That sounds like a bit of a ramp, but it is also totally credible. Very exciting days of watch are these - and last year was good, even if we didn't get thevery best outcome we wanted.

[chionomaniac]

You get the feeling that it will only take one more push in terms of further warming/ wave breaking to complete the disintegration of the polar vortex and secure long term NH northern blocking. That sounds like a bit of a ramp, but it is also totally credible. Very exciting days of watch are these - and last year was good, even if we didn't get thevery best outcome we wanted.

Yes these are very exciting model watching days. What fascinates me, in this second year of stratospheric monitoring, is how different things are compared to last year. Now, I knew that was to be expected but I am amazed at how weak the lower vortex has been. The reason that we want a SSW is so that the vortex is reversed right down to the troposphere - however we know that this doesn't successfully occur every time and there is some risk to it. To get the reversal of mean zonal winds at the tropospheric level without a SSW and for those negative winds held for some time at the lower level is truly remarkable and must be what would have occurred in years gone by. I thought that these reversed winds would have dissipated by now but they have held firm - this is in total contrast to what occurred after last winter's SSW where propagation occurred in bits and bobs but after the Feb easterly there was no sustained reversal at the tropospheric level. I keep thinking that these negative anomalies must come to an end soon, when taking into consideration the profile of the upper stratosphere, but hopefully not until we have seen a New Year renewed cold outbreak!

[chionomaniac]

Compare the difference with the dashed lines.

Jan- March 09

Oct - Dec 09

c

[Methuselah]

You get the feeling that it will only take one more push in terms of further warming/ wave breaking to complete the disintegration of the polar vortex and secure long term NH northern blocking. That sounds like a bit of a ramp, but it is also totally credible. Very exciting days of watch are these - and last year was good, even if we didn't get thevery best outcome we wanted.

I agree. And, I never ramp!!

We must (He hopes!) be getting towards the point where those who want mild weather need a cooling event to happen??

Ch, GP??

[chionomaniac]

I agree. And, I never ramp!!

We must (He hopes!) be getting towards the point where those who want mild weather need a cooling event to happen??

Ch, GP??

The upper stratosphere is cooling Pete, it is just that it is not as strong as recent years and hasn't propagated down.....yet!

[Methuselah]

The upper stratosphere is cooling Pete, it is just that it is not as strong as recent years and hasn't propagated down.....yet!

Cheers, mate...Let's just hope it doesn't then!

[chionomaniac]

The latest ECM Berlin forecast is not yet suggesting a split of the polar vortex into the stratosphere. However, we are seeing another favourable outcome with the vortex being forecast to become displaced over Scandinavia and Northern Russia. This will allow a door to open with height rises possible to the northwest and I believe that this scenario is being forecast on the ECM tropospheric modeling. So all very believeable and fits in with GP's thoughts.

c

Latest GFS output is still going with the idea of a split vortex right up to the 30 hPa level:

The lower vortex tends to keep more energy towards Canada but note this occurred with the split earlier this month before closer forecasts transferred the energy more towards the Siberian segment.

c

[kold weather]

The ECM seems to be more keen on the Scandinavian vortex getting the most energy, wil lbe interesting to see what happens.

I wonder how many severe prolonged cold spells have been undertaken via splitting of the PV...I know for a fact the 62/63 was kicked off with a PV split around xmas day, indeed its one of the most amazing things to see in the charts with the big PV just splitting in two and a huge Greenland high punching right through the middle of the gap.

[snowking]

I'm just wondering if somebody could point me in the direction of some analogues for the various phases of MJO and GWO?

I'm starting to get to grips with the stratospheric side of things rather well thanks to the tireless efforts of the likes of Ch and GP on here! It would just be useful to have some analogues for the more complex teleconnection outputs

Kind Regards

SK

[chionomaniac]

I'm just wondering if somebody could point me in the direction of some analogues for the various phases of MJO and GWO?

I'm starting to get to grips with the stratospheric side of things rather well thanks to the tireless efforts of the likes of Ch and GP on here! It would just be useful to have some analogues for the more complex teleconnection outputs

Kind Regards

SK

Hi SK try this link for MJO analogues http://raleighwx.easternuswx.com/MJO.html

Right, we are now starting to see some agreement again regarding the stratospheric outlook. Firstly, it has to be said that the upper layers of the stratosphere are cooler than average. This normally leads to a stronger stratospheric vortex but currently this does not tell the whole story. The shape and position of the vortex is not circular and is not sitting directly over the vortex.

Since the last vortex split earlier this month we have had around 2 weeks of negative mean zonal winds held in the troposhere. This is now coming to an end with an increase in westerly winds replacing the easterlies.

http://strat-www.met.fu-berlin.de/cgi-bin/ecmwfzm?alert=1&forecast=all&var=u

However, we now have agreement between the GFS and ECM for another split in the tropospheric vortex extending again into the lower stratosphere. This split does not seem to extend as far into the stratosphere as the previous one nor does it seem to be quite as vigorous. Once again that will leave us with two vortices with forecasts suggesting that the Candian vortex will once again lose intensity quite quickly with the Siberian daughter vortex becoming the dominant one.

Here we can see the present lower 100hPa stratospheric vortex today:

And the GFS and ECM forecasts for around 6 days time

And for around the same time further up the stratosphere at the 50 hPa level

The good thing about this is that we are likely to see a reset of the current pattern with negative zonal wind anomalies once again dominating the troposphere so we will need to keep an eye out for that. The positioning of the Siberian vortex will influence any likelihood of any blocking to our NE but currently I think this could be unlikely as is any Svalbard high, but forecasts can change. So all in all still a lot to look forward to and even with a cooling upper stratosphere.

c

[Guest North Sea Snow Convection]

Hi SK try this link for MJO analogues http://raleighwx.eas...wx.com/MJO.html

Right, we are now starting to see some agreement again regarding the stratospheric outlook. Firstly, it has to be said that the upper layers of the stratosphere are cooler than average. This normally leads to a stronger stratospheric vortex but currently this does not tell the whole story. The shape and position of the vortex is not circular and is not sitting directly over the vortex.

Since the last vortex split earlier this month we have had around 2 weeks of negative mean zonal winds held in the troposhere. This is now coming to an end with an increase in westerly winds replacing the easterlies.

http://strat-www.met...ecast=all&var=u

However, we now have agreement between the GFS and ECM for another split in the tropospheric vortex extending again into the lower stratosphere. This split does not seem to extend as far into the stratosphere as the previous one nor does it seem to be quite as vigorous. Once again that will leave us with two vortices with forecasts suggesting that the Candian vortex will once again lose intensity quite quickly with the Siberian daughter vortex becoming the dominant one.

Here we can see the present lower 100hPa stratospheric vortex today:

And the GFS and ECM forecasts for around 6 days time

And for around the same time further up the stratosphere at the 50 hPa level

The good thing about this is that we are likely to see a reset of the current pattern with negative zonal wind anomalies once again dominating the troposphere so we will need to keep an eye out for that. The positioning of the Siberian vortex will influence any likelihood of any blocking to our NE but currently I think this could be unlikely as is any Svalbard high, but forecasts can change. So all in all still a lot to look forward to and even with a cooling upper stratosphere.

c

Hi again Ed

Your own technical understanding of the mechanics is greater than mine, but I did think that another split was in the offing. I stand to be wrong, but in my own modest thinking I am becoming really very cautiously optimiastic about events to the north east. Traditionally we see the Siberian High try to come more into play as winter goes on and with each reload of this cold pattern, more and more cold air (colder each time) is being drawn/backed southwards and most importantly westwards. The main benefit of the heights over Greenland are being to allow the cold to back westwards.

This latest very probable reset is crucial in terms of giving a window of time for allowing the Siberian influence to come into play. That eurasian snow cover feedback that you discussed a lot back in the autumn is playing a big role here in terms of the -AO feedback.

Also, in your good opinion can I ask if a convective signal in the Indian Ocean is conduisive for priming another warming event, which provides further ammunition down the line to the probable upcoming vortex split?

I am not sure how this bit works!

Ta!

Tamara

[chionomaniac]

Hi again Ed

Your own technical understanding of the mechanics is greater than mine, but I did think that another split was in the offing. I stand to be wrong, but in my own modest thinking I am becoming really very cautiously optimiastic about events to the north east. Traditionally we see the Siberian High try to come more into play as winter goes on and with each reload of this cold pattern, more and more cold air (colder each time) is being drawn/backed southwards and most importantly westwards. The main benefit of the heights over Greenland are being to allow the cold to back westwards.

This latest very probable reset is crucial in terms of giving a window of time for allowing the Siberian influence to come into play. That eurasian snow cover feedback that you discussed a lot back in the autumn is playing a big role here in terms of the -AO feedback.

Also, in your good opinion can I ask if a convective signal in the Indian Ocean is conduisive for priming another warming event, which provides further ammunition down the line to the probable upcoming vortex split?

I am not sure how this bit works!

Ta!

Tamara

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.