Stratosphere Temperature Watch

[Glacier Point]

The temperature of the tropical stratosphere also continues to take the eye -

.. well below average conditions (yet again, another record low for the time of year) reinforcing the idea of continued blocking over the high latitudes for some considerable period yet.

[kold weather]

Yep thats very impressive it has to be said, I hope those cold tropical anomalies continue this could lead to a bit of an interesting hurricane season, esp if El Nino dies off quickly enough, so more then one reason I hope those anomalies stay that way for a while yet!

[BrickFielder]

In about 8 days time there will be the kind of warming signal over the UK in the stratosphere that I have been looking out for. Notice how the weak vortex is centered over northern canada with a further even weaker vortex out towards northern asia.

Looking at the 475k level I am seeing exactly what I would expect, with a signal for high pressure almost anywhere in the northern hemisphere.

Look at the 400k level and things look a little different and you can see the influence of the troposphere on the stratosphere. The question is will the 400k level begin to look more like the 475k level as time progresses.

One thing to be aware of is that sea ice extents are as close to the historical average as I have seen in a long while, which should help to keep the cold around. I also take this to be a sign that the thunderstorm season this year might be quite potent.

In summary I don't think this winter has seen the last of the heavy snow potential just yet.

[SteveB]

Hi BrickFielder,

As a big fan of thunderstorms, your comment regarding an active season caught my eye. I assume you mean for the UK, and if so what brings you to that conclusion?

[BrickFielder]

A weak stratospheric vortex, with a potential for early breakdown, with a big cold pool to our north.

[Glacier Point]

Snow cover is also becoming anomalously large:

http://moe.met.fsu.edu/snow/

With El Nino conditions very likely to persist into the summer, we could well be faced with a substantive surface albedo and by inference, anomalous ozone in the northern high latitudes (blocking signal). How that tees us up for next winter will be of interest, although with a west QBO developing, it will probably be more of a 'front-end' cold.

[Don]

Snow cover is also becoming anomalously large:

http://moe.met.fsu.edu/snow/

With El Nino conditions very likely to persist into the summer, we could well be faced with a substantive surface albedo and by inference, anomalous ozone in the northern high latitudes (blocking signal). How that tees us up for next winter will be of interest, although with a west QBO developing, it will probably be more of a 'front-end' cold.

Looking forward to Winter 2010/11 already! With this cold Winter we're experiencing, hopefully 2010 will continue to be a memorable year for weather.

[johnholmes]

Snow cover is also becoming anomalously large:

http://moe.met.fsu.edu/snow/

With El Nino conditions very likely to persist into the summer, we could well be faced with a substantive surface albedo and by inference, anomalous ozone in the northern high latitudes (blocking signal). How that tees us up for next winter will be of interest, although with a west QBO developing, it will probably be more of a 'front-end' cold.

What is 'front end cold' please Stuart?

Edited February 17, 2010 by johnholmes

[kold weather]

With El Nino conditions very likely to persist into the summer, we could well be faced with a substantive surface albedo and by inference, anomalous ozone in the northern high latitudes (blocking signal). How that tees us up for next winter will be of interest, although with a west QBO developing, it will probably be more of a 'front-end' cold.

Interestingly though GP the ENSO models are now trending towards a neutral phase by the summer so will be interesting to see whether that occurs, if it does go neutral like the latest models prog by early Autumn then what is likely the stratospheric response?

[Mark Bayley]

What is 'front end cold' please Stuart?

I was wondering that to. Interesting thoughts as ever GP I think most will concentrating on a warm summer for now

[bluearmy]

I was wondering that to. Interesting thoughts as ever GP I think most will concentrating on a warm summer for now :lol:

not complicated i dont think - first part=front end ???

[chionomaniac]

Snow cover is also becoming anomalously large:

http://moe.met.fsu.edu/snow/

With El Nino conditions very likely to persist into the summer, we could well be faced with a substantive surface albedo and by inference, anomalous ozone in the northern high latitudes (blocking signal). How that tees us up for next winter will be of interest, although with a west QBO developing, it will probably be more of a 'front-end' cold.

Worth pointing out I feel that it was mentioned (a lot by yourself GP) pre-winter about how the increased NH and Eurasion snow cover could initiate a stratospheric response during January and that this has occurred.

I think that BF raises a significant point regarding how tropospheric influences may interact with the stratospheric potential and counteract the blocking potential that is arising as a result of the MMW. It is certainly worth watching in the coming week or so.

[cooling climate]

Snow cover is also becoming anomalously large:

http://moe.met.fsu.edu/snow/

With El Nino conditions very likely to persist into the summer, we could well be faced with a substantive surface albedo and by inference, anomalous ozone in the northern high latitudes (blocking signal). How that tees us up for next winter will be of interest, although with a west QBO developing, it will probably be more of a 'front-end' cold.

GP this must be one of the earliest long range winter forcasts I think I have ever seen.

Detail is a little vague though. lol.

[DAVID SNOW]

What is 'front end cold' please Stuart?

Cold in the early part of winter rather than later perhaps

[kold weather]

not complicated i dont think - first part=front end ???

Yeah thats what I would read into it as well, front loaded winters tend to be like 96-97 or the most extreme version I suppose being 81-82.

I just wonder, why has the tropical stratosphere been so cold in the last 12 months?

[johnholmes]

Thanks for putting an old man straight folks.

But why not in English?

The first part of winter?

[Mark Bayley]

not complicated i dont think - first part=front end ???

I did think that but wasn't completely sure

[chionomaniac]

Latest ECM stratosphere charts suggest no overall change in the present direction.

We have seen a MMW which has produced negative mean zonal winds throughout all levels of the stratosphere which have also propagated into the troposphere. This has led to Northern blocking and a - AO which has assisted in the current cool pattern that we are seeing. However striking cold has failed to materialise. One of the reasons for this is that the blocking has been centred directly over the North Pole and has not shifted southwards in any direction. I believe that is why the current pattern is stagnant and that any deep cold has been relying on this pressure system shifting away perhaps towards us. The NP ridge is clearly seen on the tropospheric NH ECM output:

The current stratospheric 100 hPa forecast for 6 days gives no overall change in signal:

One of things that is suggested on the stratospheric forecasts is that the period of negative mean zonal winds may be coming to an end and will be replaced with the reformation of the polar vortex. One can see here the rapid forecasted changeover:

T+6 Days

T+8 days

This to my eye seems too quick an evolution from negative to positive, however if this does occur then it will result in the change of pattern that the current lack of positive stratospheric signal has helped create. The question that I ask is where will the tropospheric NP ridge be deflected too or will it dissipate without trace. Presently the favoured area for displacement is NW Siberia to Scandinavia. Again more candy just out of reach.

c

[chionomaniac]

I would say that there is still no major stratospheric long range signal (around 10 days) for any definitive northern blocking to occur. There is also no change in the signal for the current pattern of weak troughing extending out into the Atlantic towards Madeira so perhaps no change in the current pattern for a little while still.

The theme of the reduction of the stratospheric negative zonal wind anomalies by positive ones remains but it is less drastic than forecast a couple of days ago and I would say that there is uncertainty of how these may effect the troposphere. The northern blocking seen as a result of the MMW has remained firmly on the north pole surrounded by an area of troughing. It is this that has lead to the distinct cooler gradient from south to north rather than severely displaced cold in a meridional pattern. This NH GFS chart shows this up well at T+96.

My thoughts are that this Arctic ridge will slowly in time fade

[Rollo]

Thanks for the update Chio,a question I would like to ask regarding warmings is what effect would one have during the summer months.

[chionomaniac]

Thanks for the update Chio,a question I would like to ask regarding warmings is what effect would one have during the summer months.

Rollo, we have a stratospheric warming every summer. The polar night jet deep cooling and subsequent stratospheric cooling is consequential to the lack of sunlight seen over polar regions over winter. Once the days lengthen and the sunlight returns the stratosphere warms and the polar vortex dies out and westerly winds are replaced with easterly winds. Here are the mean temperature and zonal wind charts for last year to illustrate that point.

Edited February 24, 2010 by chionomaniac

[Don]

My thoughts are that this Arctic ridge will slowly in time fade

Thanks for the update C. Sounds like at the moment you feel that Winter will gradually fade into Spring rather than go out with a bang?

[chionomaniac]

Thanks for the update C. Sounds like at the moment you feel that Winter will gradually fade into Spring rather than go out with a bang?

I think that very much depends upon what pattern takes hold after this occurs and where any ridging subsequently occurs.

[cooling climate]

I just posted this in the model thread and thought it would fit in here as well.

Posted Today, 12:01

Looking at these stratospheric charts it looks like I was wrong calling for this blocking

and potent cold spell some two weeks back.

The stratospheric charts below show that the warming in November did not really impact

upon us until some 6 weeks later and although we have felt the influence of high latitude

blocking during February the MMW over Svalbard and Scandinavia has not shown up (blocking)

in the models until now. Again this looks to be roughly six weeks since the warming

commenced that the blocking in the areas mentioned are now showing up in the models.

http://strat-www.met...t=temps&alert=1

http://strat-www.met...ot=town&alert=1

http://ds.data.jma.g...e/pole30_n.html

Due to the warming further norht than where the models show the block to form I would not be

surprised to see the block further north on future runs.

Edited February 25, 2010 by cooling climate

[chionomaniac]

Quick update from me today.

The signals from both the GFS and ECM support the idea of a mid latitude block forming, with potential for it to be far enough north to draw in cooler continental air. The polar vortex, at the base of the stratosphere, looks to be reforming and gaining strength over the coming days with a change from negative mean zonal winds to positive mean zonal winds being propagated down to the troposphere from the stratosphere. Luckily, the core of the reforming PV is centered in the Pacific region which opens the door for Atlantic ridging to occur. Presently it still looks that this will not extend north enough to create a true high latitude block say over Greenland because of the PV positioning not allowing this. I would suggest that the block will initially extend no further than 65-70ºN and more west than east of the UK. I feel therefore that there is a high likelihood of the colder air reaching us to give a cold start to March with good snow potential. The following charts suggest where the block is most likely to form.

One would need to keep an eye on the positioning of the centre of the polar vortex here; if it shifts more towards us then the high could sink very quickly.

c