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chionomaniac

Stratosphere Temperature Watch

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Worth noting that we are seeing strong tropical supression right now with a big -ve mountain torque event:

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

Just to pick up on GP's post above from the Model Thread, am I right in thinking that chart shows a large mountain torque event over both Asia and North America?

GP has suggested before that strong mountain torque events can trigger SSW. Considering the current slightly above average stratospheric state with cooling weak and the forecast for average to continue would this event be large enough to possibly trigger a SSW? Or am I way off the mark?

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Just to pick up on GP's post above from the Model Thread, am I right in thinking that chart shows a large mountain torque event over both Asia and North America?

GP has suggested before that strong mountain torque events can trigger SSW. Considering the current slightly above average stratospheric state with cooling weak and the forecast for average to continue would this event be large enough to possibly trigger a SSW? Or am I way off the mark?

Hi fozi.

It seems from GP that the large negative mountain torque event in alliance with suppressed tropical convection is having a knock on effect at a tropospheric level. I am not sure how this is going to affect the stratosphere!

You are right to suggest that (planetary wave breaking from) strong mountain torques associated with increased storminess over the mountain ranges of the hemisphere can set off a SSW. The strength and location of the stratospheric vortex, direction of the QBO, strength of the torque event and other factors may effect whether a SSW occurs. This is an area that I am keen to look into further ie - the tropospheric triggers for SSWs but find it difficult to track down info on the causes. What we do know is that a SSW is unlikely as we are in a westerly QBO which is not favourable for SSWs to occur - but who knows with the stratosphere in a less cool state presently ( and with a SSW occurring in March 2000 with a westerly QBO) one can't 100% rule one out.

c

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The current state of the stratosphere is looking quite good! We are experiencing a considerable warming event: http://ds.data.jma.go.jp/tcc/tcc/products/...e/pole30_n.html

A look in the forecast shows that this warming will be followed by a a small cooling but temperatures should remain at just above average for the time of year: http://strat-www.met.fu-berlin.de/cgi-bin/...mps&alert=1

Certainly a lot better than the last 2 years when November and especially December were characterised by major cooling events.

Karyo

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Warming event now could mean blocking mid to late Jan, right?

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Warming event now could mean blocking mid to late Jan, right?

As long as it continues yes! But the forecast is showing flactuations in the stratospheric temperatures so i am not sure whether the curent warming will be enough to cause significant blocking in January.

Karyo

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Guest zebra danio
Hi fozi.

It seems from GP that the large negative mountain torque event in alliance with suppressed tropical convection is having a knock on effect at a tropospheric level. I am not sure how this is going to affect the stratosphere!

You are right to suggest that (planetary wave breaking from) strong mountain torques associated with increased storminess over the mountain ranges of the hemisphere can set off a SSW. The strength and location of the stratospheric vortex, direction of the QBO, strength of the torque event and other factors may effect whether a SSW occurs. This is an area that I am keen to look into further ie - the tropospheric triggers for SSWs but find it difficult to track down info on the causes. What we do know is that a SSW is unlikely as we are in a westerly QBO which is not favourable for SSWs to occur - but who knows with the stratosphere in a less cool state presently ( and with a SSW occurring in March 2000 with a westerly QBO) one can't 100% rule one out.

c

Some events which begin at the 10mb level don't always spread down to the troposphere and others do. Zonal wind anomalies play a part and also certain wave breaking events too. So it gets quite complicated because you can get propagating and non propagating warmings too

Early warmings like Canadian warmings in association with the Aleutian high occur with the +QBO but, as you say, generally not major warmings. However, when the west phase is weakening and ending then more notable warmings can occur (I think the March 2000 was such a case) so it is important to measure how quickly the westerly QBO weakens through the winter as this will in turn affect the stability of the PV. Easterly QBO's tend to produce the warm unstable polar vortex which can lead to the big height rises we look for in the model threads!

In terms of this winter, the trend continues for a very good case scenario for a west QBO with a stable pattern as might be expected, but without (so far) any depth of cold to worry about. Further mountain torque events are possible which could provide further minor rises in temp and as long as a significant cooling is kept deferred then any long lasting mild zonal spell with homogenously +AO should be avoided. I think that the JMA forecast lags a little behind the ECM. The latter shows a correction downwards but stabilises back close to the average in its freshly updated 8 day forecast.

http://strat27.met.fu-berlin.de/cgi-bin/ti...mps&alert=1

Apologies if you have already supplied this link, but there is lots of good info on the various types of warmings, their classifications, the impact of the west or east QBO,on this linked section of the Berlin site

http://strat-www.met.fu-berlin.de/products...m/html/section2

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As long as it continues yes! But the forecast is showing flactuations in the stratospheric temperatures so i am not sure whether the curent warming will be enough to cause significant blocking in January.

Karyo

by the way things look, perhaps just staying cool to average for the rest of december and early january, and then things may be interesting for mid jan on.

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Some events which begin at the 10mb level don't always spread down to the troposphere and others do. Zonal wind anomalies play a part and also certain wave breaking events too. So it gets quite complicated because you can get propagating and non propagating warmings too

I think we had such a case earlier this year:

Only in the March warming did propagation occur to a worthy level and I saw snow on 6th April.

Regarding the ECM forecast, this seems to have changed to be slightly more favourable in the last few days. Also the zonal winds were forecast to rise as well and this is now less pronounced:

So all in all things not looking too bad for the next few weeks and perhaps the positive AO situation that most of us dread will not be as pronounced come January if the present forecasts hold true.

Thanks ZB for the final link some extra reading for this evening methinks!

c

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As long as it continues yes! But the forecast is showing flactuations in the stratospheric temperatures so i am not sure whether the curent warming will be enough to cause significant blocking in January.

Karyo

Thanks. :D

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Guest zebra danio
I think we had such a case earlier this year:

Only in the March warming did propagation occur to a worthy level and I saw snow on 6th April.

Regarding the ECM forecast, this seems to have changed to be slightly more favourable in the last few days. Also the zonal winds were forecast to rise as well and this is now less pronounced:

So all in all things not looking too bad for the next few weeks and perhaps the positive AO situation that most of us dread will not be as pronounced come January if the present forecasts hold true.

Thanks ZB for the final link some extra reading for this evening methinks!

c

Hi

Those zonal wind flux anomalies are very important. As long as they don't stir up too much then the worst of the polar westerlies can be kept at bay. Taking into account lag times, every day the current sq holds means every day during Jan the worst of this threat is possibly postponed.

Re last Spring - yes, those series of warmings finally kicked in for the start of Spring lol! The April 6 event was fantastic for me too! :)

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Quite warm at the moment!

http://ds.data.jma.go.jp/tcc/tcc/products/...e/pole30_n.html

The stratospheric temperature over the North Pole is way above normal at present. The forecast is still expecting this to be the peak with a small cooling in the next few days and then another small rise. Overall things are currently looking fine.

Karyo

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Guest zebra danio

http://strat27.met.fu-berlin.de/cgi-bin/ti...mps&alert=1

Small peaks and troughs continue around the average level in the stratospheric forecast. The JMA forecast and observed line is pretty well mirroring the ECM with a slight lag time of a day or so. The peak shown on the former forecast indicator should show a slight drop over the next day or so from the moderate warming peak. The forecasted period now takes us right up to mid month with no substantial cooling having occured, nor predicted yet.

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Sorry guys but as I see it the polar stratosphere remains anomolously cool...

10hpa

gfs_t10_nh_f00.gif

50hpa

gfs_t50_nh_f00.gif

Combined

time_pres_TEMP_ANOM_OND_NH_2008.gif

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Guest zebra danio

Relative to the time of year the temps are not unduly low as the Berlin site average shows and are oscillating either side of the average.

There is not an expectation of any major warming this winter due to the westerly QBO. But on the other hand, thus far, with zonal wind flux being reduced to stir up any cooler anomalies and, moreover, no appreciable sustained cooling as yet of the sort already seen at the very start of last winter (or the winter prior to that) then as long as this remains the case the Polar vortex should not attain the intensity of strength seen on those occasions.

It is also worth bearing in mind the movement of the PV and the background global weather patterns in terms of how we are affected by the westerly circulation of upper cold around the stratosphere. Even with a fairly strong vortex so far this season we have been seeing a marked difference in winter weather and patterns with heights over the atlantic sustained by very high SST's off Newfoundland as well as correspondingly lower heights than normal over Europe. So in this sense, even without any real warmth to play with to make the PV more unstable, we have been doing pretty well out of it so far - early as it is in the season.

So an 'averagely cool' stratosphere does not necessarily = flat jet mild zonality.

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is karyo right about a warm stratosphere atm, or are things looking fairly average?

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I'd say it's slightly warmer than average but nothing to get excited about. It's likely to cool off a little in the short term but at the moment the general trend seems to be about average.

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I'd say it's slightly warmer than average but nothing to get excited about. It's likely to cool off a little in the short term but at the moment the general trend seems to be about average.

well, in reality if it stays average or above, its really all to play for, and i believe the models reflect this.

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well, in reality if it stays average or above, its really all to play for, and i believe the models reflect this.

In terms of the North Pole, the stratosphere is well above average, as the link i posted earlier indicates. For the Northern hemisphere as a whole it is slightly above.

As for Jack Wales's post, it shows where exactly the warm and cold anomalies exist. That's how i read them anyway.

Karyo

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I know the stratospheric temps have been all over the place for the last couple of weeks but look at this:

http://ds.data.jma.go.jp/tcc/tcc/products/...e/pole30_n.html

That surely cannot be bad news!!

Yes it's good to see but is forecast to drop as the temp at the 10hPa level is doing so:

What we also want to see is the zonal wind mean anomalies not rise. These have dropped at the moment and as can be seen from GP's excellent post (in the model discussion thread) that if and when these make their way down to the troposphere they can reduce the strength of the blowtorch westerly flow - and all this despite the QBO being against us. Forecasts for the 10hPa and 30 hPa zonal wind speeds at 60N are set to stay around where they are which suggests a weaker polar vortex than what we have been accustomed to in recent winters. Forecast:

The NCEP/GFS forecast for 10 days ahead have been quite close so far this season. Pretty impressive as I thought that they would be as accurate as the AO/NAO forecasts. So here are the stratospheric forecasts for 10 days ahead from the GFS. There seems nothing too much to get excited about as overall the temperatures look to be sliding slightly below average.

I'll try and compare on the 19th December which is two days before the winter solstice - the stratosphere should think about getting warmer pretty soon after.

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Guest zebra danio
What we also want to see is the zonal wind mean anomalies not rise. These have dropped at the moment and as can be seen from GP's excellent post (in the model discussion thread) that if and when these make their way down to the troposphere they can reduce the strength of the blowtorch westerly flow - and all this despite the QBO being against us. Forecasts for the 10hPa and 30 hPa zonal wind speeds at 60N are set to stay around where they are which suggests a weaker polar vortex than what we have been accustomed to in recent winters.

The NCEP/GFS forecast for 10 days ahead have been quite close so far this season. Pretty impressive as I thought that they would be as accurate as the AO/NAO forecasts. So here are the stratospheric forecasts for 10 days ahead from the GFS. There seems nothing too much to get excited about as overall the temperatures look to be sliding slightly below average.

I'll try and compare on the 19th December which is two days before the winter solstice - the stratosphere should think about getting warmer pretty soon after.

Yes very much agree, that's exactly what I tried to say earlier today. And also the fact that everyday this continues, another day is chalked off the anomalous warmth threat for January. Bearing in mind Jan is supposed to represent the deepest part of winter, it is ironic that this is the month that we have seen the least wintry weather over recent years. In that respect, although December is certainly paying its way for seasonal cold, the next couple of weeks or so are becoming increasingly important in terms of limiting the strength of the polar westerlies for the peak of winter when the AO is most connected to the overall state of the stratosphere.

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Latest update;

The temperature at the 30hPa level has dropped as expected and is now below average:

This is still expected to fluctuate as can be seen by the Berlin forecast:

post-4523-1229171740_thumb.png

The weaker stratospheric winds that have been filtering down to the troposphere are showing signs of returning to normal:

post-4523-1229172248_thumb.png

The forecast for the zonal winds is for them to increase again in a westerly direction at the 10hPa level which will have the net effect of strengthening the stratospheric vortex if it verifies.

post-4523-1229192921_thumb.png

The warm sector east of Alaska has decreased in size and intensity:

post-4523-1229193100.gif

But there are signs that it could increase again:

post-4523-1229193156.gif

All in all there are signs that the stratosphere may be showing signs that it is cooling, but so far this is not like the start of winter that we have seen in recent years. With the tropospheric vortex hinting that it may be about to start up and take residence NW of us, this is not necessarily in agreement with the findings of last 6 weeks of the stratosphere, so hopefully any mild weather we experience won't be prolonged.

c

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Latest update;

The temperature at the 30hPa level has dropped as expected and is now below average:

This is still expected to fluctuate as can be seen by the Berlin forecast:

post-4523-1229171740_thumb.png

The weaker stratospheric winds that have been filtering down to the troposphere are showing signs of returning to normal:

post-4523-1229172248_thumb.png

The forecast for the zonal winds is for them to increase again in a westerly direction at the 10hPa level which will have the net effect of strengthening the stratospheric vortex if it verifies.

post-4523-1229192921_thumb.png

The warm sector east of Alaska has decreased in size and intensity:

post-4523-1229193100.gif

But there are signs that it could increase again:

post-4523-1229193156.gif

All in all there are signs that the stratosphere may be showing signs that it is cooling, but so far this is not like the start of winter that we have seen in recent years. With the tropospheric vortex hinting that it may be about to start up and take residence NW of us, this is not necessarily in agreement with the findings of last 6 weeks of the stratosphere, so hopefully any mild weather we experience won't be prolonged.

c

chiono, may i ask, do you mean cooling as in returning to normal, or below, either way it would be late jan/early feb before the effects really took hold.

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chiono, may i ask, do you mean cooling as in returning to normal, or below, either way it would be late jan/early feb before the effects really took hold.

Below average, though there appears to be a small rise forecast first. And what actually happens compared to what is forecast may be two different things! I agree that we are now looking into late Jan before regular winter arrives.

c

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Just a quick post to bring this up to the top of the page again. I've noticed that there seems to be a slight warming event over Greenland at the end of the month. Am I reading the chart correctly or is this just wishful thinking?

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