Stratosphere Temperature Watch 2011/2012

[lorenzo]

No real surprise to see the Asian MT event as I had suspected that the strat models were responding to something along the likes.

Agree with GP that this will be the start of weakening of the PV, but that it may need a few swings of the axe before it falls.

That would depend if undercutting were to occur. November shows us what happens with a Scandi High without undercutting!

This is the feared outcome of the 4 or 5 postulated by Phil Warks and Nick Sussex - another limpet high. Please no !

[Bolton67]

No real surprise to see the Asian MT event as I had suspected that the strat models were responding to something along the likes.

Agree with GP that this will be the start of weakening of the PV, but that it may need a few swings of the axe before it falls.

That would depend if undercutting were to occur. November shows us what happens with a Scandi High without undercutting!

Thank you for the reply.. hmm last November, Northampton was in the dry zone ..lol

[damianslaw]

As a cold lover - can't help but wish it was early november rather than mid december - the state of the stratosphere appears to have been a key factor for all the anmoulous warmth this autumn and the rampant PV of the last 2-3 weeks, the suggestions of a more favourable strat for cold in the second half of the winter is encouraging, but if this was early november than going by the timescales we should have been seeing right now a much more favourable strat and not the rampant PV. Alas the strat doesn't do calandars.. and we have been very very fortunate the past two winters with all the early cold. Indeed I think we have done very well so far this month in terms of cold given the state of the strat and the rampant PV - we could be seeing persistant mild southwesterlies and a month like Dec 88, or 94, 97 or 06.. alas we have been spared those 'mild' horror shows (so far..).

[mountain shadow]

Chino,

How do you when a warming is SSW and not just a normal one? Is their a length of time involved or is a SSW in a particular area of the atmosphere?

Thanks in advance.

[chionomaniac]

Chino,

How do you when a warming is SSW and not just a normal one? Is their a length of time involved or is a SSW in a particular area of the atmosphere?

Thanks in advance.

A SSW is defined as an event when mean zonal mean winds reverse at 60ºN and at a level of 10hPa during stratospheric winter (NDJFM).

http://www.columbia.edu/~lmp/paps/charlton+polvani-JCLIM-2007.pdf

[stewfox]

As a cold lover - can't help but wish it was early november rather than mid december - the state of the stratosphere appears to have been a key factor for all the anmoulous warmth this autumn and the rampant PV of the last 2-3 weeks, the suggestions of a more favourable strat for cold in the second half of the winter is encouraging, but if this was early november than going by the timescales we should have been seeing right now a much more favourable strat and not the rampant PV. Alas the strat doesn't do calandars.. and we have been very very fortunate the past two winters with all the early cold. Indeed I think we have done very well so far this month in terms of cold given the state of the strat and the rampant PV - we could be seeing persistant mild southwesterlies and a month like Dec 88, or 94, 97 or 06.. alas we have been spared those 'mild' horror shows (so far..).

Appears to be a key factor, its defacto now, cold strastosphere = No long term emended cold for UK

I dont buy that.

[chionomaniac]

Appears to be a key factor, its defacto now, cold strastosphere = No long term emended cold for UK

I dont buy that.

As has been repeated a number of times this winter already, a cold stratosphere is inhibitive to high latitude blocking. A cold stratosphere in itself is not preventative to cold reaching the UK, but if we want sustained cold through non Scandi blocking then a cold stratosphere is not conducive to this set up. Surely the last month has shown this!

If a block appears to our NW then I am sure there will be some type of tropospheric/ stratospheric interaction, probably through wave breaking, that will lead to this and we will have a heads up through the stratospheric charts first.

And we are already getting signs for January.

Edited December 11, 2011 by chionomaniac

[stewfox]

As has been repeated a number of times this winter already, a cold stratosphere is inhibitive to high latitude blocking. A cold stratosphere in itself is not preventative to cold reaching the UK, but if we want sustained cold through non Scandi blocking then a cold stratosphere is not conducive to this set up. Surely the last month has shown this!

If a block appears to our NW then I am sure there will be some type of tropospheric/ stratospheric interaction, probably through wave breaking, that will lead to this and we will have a heads up through the stratospheric charts first.

And we are already getting signs for January.

i dont buy the fact you can tell me now they won't be any sustained cold for another month and people like JH seem to concur.

As they say one month doesnt make a summer

Last Decembers forecast by the experts were 4/5c too high , I'm happy F1 stays at 168

Edited December 11, 2011 by stewfox

[Rich44]

No one has said that though have they? What has been said is that without a warming event we're unlikely to see high lattitude blocking. I have seen posted many times recently that doesn't mean we cannot get cold but that sustained cold like we have been spoilt with the last 2 years is more unlikely to occur, unlikely NOT impossible

[chionomaniac]

As has been repeated a number of times this winter already, a cold stratosphere is inhibitive to high latitude blocking. A cold stratosphere in itself is not preventative to cold reaching the UK, but if we want sustained cold through non Scandi blocking then a cold stratosphere is not conducive to this set up. Surely the last month has shown this!

If a block appears to our NW then I am sure there will be some type of tropospheric/ stratospheric interaction, probably through wave breaking, that will lead to this and we will have a heads up through the stratospheric charts first.

And we are already getting signs for January.

i dont buy the fact you can tell me now they won't be any sustained cold for another month and people like JH seem to concur.

As they say one month doesnt make a summer

Last Decembers forecast by the experts were 4/5c too high , I'm happy F1 stays at 168

Please quote a little more carefully stew.

F1 still has nothing to do with the weather.

[BLAST FROM THE PAST]

Interesting developments and posts. As per posts in past, and pointing to RJS forecast [also watch for SSW event in period 16-22 Dec] and GP mentioning 1984/5 again. Remember if 1984/5 is an analogue, Jan was THE MONTH and colder than Feb. Indications are increasing IMO of Jan being a cold month. Ed / Stew // C / GP.....are you now thinking that cold shot potential is looking earlier than initially looked at? ? ?

BFTP

Edited December 12, 2011 by BLAST FROM THE PAST

[stewfox]

No one has said that though have they? What has been said is that without a warming event we're unlikely to see high lattitude blocking. I have seen posted many times recently that doesn't mean we cannot get cold but that sustained cold like we have been spoilt with the last 2 years is more unlikely to occur, unlikely NOT impossible

I do prefer unlikely yes.

So far this winters model output has been littered with 'zero chance of sustained cold in next month' because of strat too cold , teleconnections etc.'Wait till 15th Jan etc etc.

Interesting developments and posts. As per posts in past, and pointing to RJS forecast [also watch for SSW event in period 16-22 Dec] and GP mentioning 1984/5 again. Remember if 1984/5 is an analogue, Jan was THE MONTH and colder than Feb. Indications are increasing IMO of Jan being a cold month. Ed / Stew.....are you thinking that cold shot potential is looking earlier? ? ?

BFTP

I am as you know not even a amateurs amateur but I was interested in Simon Keelings take although the candian models seem to offer no suport now of the block he suggested in the short term 24 hrs ago but time will tell..

Edited December 12, 2011 by stewfox

[nick sussex]

I do prefer unlikely yes.

So far this winters model output has been littered with 'zero chance of sustained cold in next month' because of strat too cold , teleconnections etc.'Wait till 15th Jan etc etc.

There has been no sustained cold during December, with the cold strat the best we'll do is an easterly but for that to extend into a period of sustained cold we'd need a signal for blocking so that the pattern can retrogress.

I have never seen proper northern blocking occur with a very cold strat. The December so far has been better than might have been expected given the strat profile and you could say the UK has had a some localized wintriness inspite of that profile.

I don't think anyone said cold weather was out of the question but the cold and snow most people in this forum would like to see is very unlikely to occur under the current conditions.

[chiller]

Good morning all - don't often post but always enjoy reading the informed opinions here and of course the banter! Just thought I'd mention that a Houston based forcaster seems to think a SSW may be on the way in Arctic Canada and a pattern change on the way. I'm not sure what the consequences this would have for the UK - would this displace the PV and potentially send cold air our way? Here's the link for those interested: http://www.examiner.com/weather-in-houston/houston-tx-and-vicinity-weather-forecast-monday-october-24-2011-1

Apologies if this has already been picked up.

[Cecil Hogmanay Melchett]

Good morning all - don't often post but always enjoy reading the informed opinions here and of course the banter! Just thought I'd mention that a Houston based forcaster seems to think a SSW may be on the way in Arctic Canada and a pattern change on the way. I'm not sure what the consequences this would have for the UK - would this displace the PV and potentially send cold air our way? Here's the link for those interested: http://www.examiner....tober-24-2011-1

Apologies if this has already been picked up.

I have no idea as to the credibility of this report but i am getting hopeful of some warming of the stratosphere !!

[chionomaniac]

Good morning all - don't often post but always enjoy reading the informed opinions here and of course the banter! Just thought I'd mention that a Houston based forcaster seems to think a SSW may be on the way in Arctic Canada and a pattern change on the way. I'm not sure what the consequences this would have for the UK - would this displace the PV and potentially send cold air our way? Here's the link for those interested: http://www.examiner....tober-24-2011-1

Apologies if this has already been picked up.

Thanks chiller and welcome.

I always wonder in blogs like this Houston forecaster's who he has heard from. I have searched the internet for information as to how predictable and accurate it is to be able to predict an actual date for a SSW but have yet to find to find out. I think it is fair to say that we can give a likelihood that a SSW is about to occur and a timeframe when this is more likely but nothing more than that.

I have always touted for a SSW to occur around mid Jan but this is not set in stone. as things stand we are seeing interesting developments that are reaffirming this thought. The strong stratospheric vortex is being shaken up (forecast) for the first time by tropospheric waves breaking through. Whereas it is not impossible for these to cause a SSW, I very much doubt it will happen this time. However after each event the stratosphere will become more primed for the vortex to being broken.

I feel a few interesting weeks monitoring coming up.

c

[lorenzo]

Playing through the heights at 30hpa today there is a considerable change in temperature towards the end of the run and what looks like some significant change.

Does this lead to a repositioning of the PV to our NE?

[chionomaniac]

Playing through the heights at 30hpa today there is a considerable change in temperature towards the end of the run and what looks like some significant change.

Does this lead to a repositioning of the PV to our NE?

Yes, at the 30 hPa level, one can see the pressure that this creates on the vortex but the position of this area may change at differing levels due to a spirally effect and potential vorticity spread.

[chiller]

Thanks Chionomaniac for your thoughts regarding my question - very interesting. Fingers crossed for some displacement of that cold air in our direction.

[chionomaniac]

Lots of Discussion over in America on whether we will see a SSW in the next two weeks. I think that Joe B. may have started it going on the 1hPa forecasts.

I don't think that we will see a SSW in the next two weeks - I am pretty certain of that, but what is interesting is the increased wave activity that is continuing to cause warming at the upper levels of the stratosphere. This is propagating down to the 30 hPa level and as one wave finishes it looks likely that there could be another behind.

So far the warming we are seeing is this:

And note that this is already causing distortion of the vortex with the heart displaced over to Siberia.

And ozone levels are increasing all the time.

[kold weather]

I like to view the next 2 weeks as the set-up to any SSW that IMO will get going within the first 10 days of Jan. Hopefully given the forecasts should lead to at least a somewhat less positive AO and weaker PV when any SSW does get going things will already be in place.

[chionomaniac]

I like to view the next 2 weeks as the set-up to any SSW that IMO will get going within the first 10 days of Jan. Hopefully given the forecasts should lead to at least a somewhat less positive AO and weaker PV when any SSW does get going things will already be in place.

If one works out the soonest a SSW would occur then we pretty much rule out most of December now anyway. We are seeing a possible minor warming forecast presently, but that is still to reach its peak over 10 days away.

So normally we will see at 10 days a large disruptive warming affectiing the 1 Hpa level first. This may take five days to filter sufficiently to affect the vortex at the 10 hPa level and probably another 5 days to induce a split or displacement. And then it would need to affect the troposphere.

So we can get a heads up and work out when a SSW would be likely to occur. Even if the first signs of a SSW get picked up on the stratospheric models FI we are still 15-20 days away from it becoming reality.

I have said mid January for a possible SSW and I see no reason to alter that presently.

[Polar Continental]

Tuesday 13th December 2011:

Overnight: Very windy with moderate to heavy showers, maximum wind gust 40mph SSW, turning mild for a short while though. A clearance reached here around 5am. At observation, mostly clear, cool and breezy.

Today's readings for the 24 hrs up to 09:00 GMT:

2 Oktas: Cumulus.

Visibility,5 miles.

Temperature: 3.1°C

Humidity: 84%

Dew point 0.7°C

Wind Direction: Force 5 W

Barometer: 984mb rising.

Maximum temperature to 18:00 GMT yesterday: 7.2°C

Minimum temperature overnight: 2.7°C

24-hour maximum = 9.7°C

24-hour minimum: 2.4°C

Minimum temperature on grass: -0.1°C

Rainfall total: 12.8 mm

Yesterday:

A clearance arrived before midnight and the temperature fell to 1.0c with –2.9c on the grass, so a widespread ground frost. At observation, clear, frost, icy. The morning through to mid afternoon was mainly sunny, high cloud increased along with lower level cloud by the end of the afternoon making for quite a dull end to the day. The evening and night became very windy with light rain.

December: 2011 so far:

Mean temperature: 4.5c (+ 0.2c) of the local average)

Maximum temperature: 12.8 on the 8th.

Minimum temperature: -3.3c on the 10th

Grass Minimum: -5.7c on the 10th

Rainfall = 40.1mm

Wettest 24 hours = 12.3mm on the 12th

Maximum wind gust: 45.6 mph W on the 8th.

2011 so far:

Maximum temperature: 29.1 on the 27th June.

Minimum temperature: -7.0c on the 31st Jan

Grass Minimum: -10.4c on the 31st Jan

Rainfall = 462.3 mm

Wettest 24 hours, 22.5mm on the 24^th Aug

Maximum wind gust: 56.8mph, SSE 7th Feb

[BLAST FROM THE PAST]

And what's the difference on effect Ed? I mentioned that there is a train of thought of a SSW around the 3rd week of Dec and thus could lead to blocking for January. Maybe its SW but leads to same/similar evolution.

BFTP

Is this going to have a bigger effect than anticipated? Siberian HP this Jan?

BFTP

[sebastiaan1973]

In my opinion we don't necesarilly need a SSW for cold weather. Going back to normal temperatures in the stratosphere would increase the chance for some high pressure to develop at a more high latitude.