So an SSW is all about Zonal wind reversal at 10hpa caused by a warming of the strat. If the warming of the strat does not cause a wind reversal it is merely a warming and not referred to as SSW.

A warming is only called an SSW when it causes the winds to reverse. Right?

So an SSW is all about Zonal wind reversal at 10hpa caused by a warming of the strat. If the warming of the strat does not cause a wind reversal it is merely a warming and not referred to as SSW.

A warming is only called an SSW when it causes the winds to reverse. Right?

At 60N Chris. The latitude is important. The rest of your statement is correct.

Thanks Chion' and nick. I understand the terminology now

http://176.31.229.228/modeles/gfs/run/gfsnh-10-72.png?12

http://176.31.229.228/modeles/gfs/run/gfsnh-10-120.png?12

http://176.31.229.228/modeles/gfs/run/gfsnh-10-144.png?12

Then:

http://176.31.229.228/modeles/gfs/run/gfsnh-10-240.png?12

http://176.31.229.228/modeles/gfs/run/gfsnh-10-300.png?12

http://176.31.229.228/modeles/gfs/run/gfsnh-10-360.png?12

As there seems to be a bit of pessimism regarding cold prospects today I thought i would remind people that two warming events are still on the cards the next one around the 10^th Jan then a much bigger event a week later. Hopefully these could lead to something much colder later in Jan.

Interesting animation.

http://www.cpc.ncep.noaa.gov/products/intraseasonal/temp10anim.gif

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

Thanks Matt.

The PV is facing death by a thousand cuts.

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

Bit more of a warming.

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

Is this the warming that was due to be centred over the Alaskan/Berents area, but has now moderated itself and moved over central Europe?
IMO and no disrespect to the excellent analysis in here but these charts are just as (badly) modelled as surface parameters and therefore I have little confidence. The last warming fell short of expectations and so is the current one.

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng 

The current temperature at 30HPa 90N was (on the model about a week ago) due to be about -40 and we currently have a steady -55. I'm putting more faith in an intervention by aliens than strat temps to shift that damn PV but acknowledge the input in here nethertheless.

Edit: are you sure re. the 30hPa forecast at 90° north? Perhaps the 10hPa value? Incidentally the forthcoming warming (predicted) is being forecast to be much larger than the recent one was modelled to be.

There is now a warming feedback process underway in the stratosphere, with a chain of repeated mountain torgues and wave breaking, that has longer term value in terms of a sustained complete pattern change away from the changeable and strongly cyclonic westerlies of recent months that has lasted to date. We don't yet see a technical SSW, but it is surely only a matter of days before we do.

It won't be like the SSW that occured in late January 2009 amidst an otherwise polar westerly regime. This time round we see the last of the legacy of the autumn westerly QBO downwelling wave which assisted the fast organisation of the polar vortex at the start of the winter now flushing right out of tropospheric influence to be replaced by an increasing easterly phase. Hence ozone has been building slowly and steadily for some time now, albeit from a distincly different base to the start of winter last year, but just as last winter was about to run out of puff, this one is just about to start breathing. The background factors should enable this reversal of pattern with pressure set to start and keep on building over the arctic and a consequent increasingly strengthening period of -AO conditions to be sustained through the rest of the winter and into Spring too. The only question remains is: will the resultant cold air that is expelled from the arctic arrive in this part of the NH or elsewhere? Current early model indications look promising It could be one of those classic end of January, early February scenarios. A bit like 1978 perhaps?

It will be interesting to see if the Met Office pick up on this warming in there 16 to 30 day outlook tomorrow as Friday is the main day it get's updated.

It will be interesting to see if the Met Office pick up on this warming in there 16 to 30 day outlook tomorrow as Friday is the main day it get's updated.

@Neil -

Not sure if you read Darren's post a few days ago but apparently FI strat outlooks are much more reliable than surface parameters.

apparently

It will be interesting to see if the Met Office pick up on this warming in there 16 to 30 day outlook tomorrow as Friday is the main day it get's updated.

I would be extremely doubtful that the author of the MetO update uses strat temp predictions to base his summary on. Much more likely to use current medium and long-range surface charts and signals (which of course are influenced by the above I presume). To say the MetO use a possible SWW in there forecast would be like saying a the police are predicting an increase in gun crime in Brixton because a guy was shot in Carlisle. Now - waiting to be gunned down myself . . . . .

I think that post is telescopically challenged....

I have noticed you seem to have a certain vivid scepticism on this subject....   A better analogy might be that rioting in Brixton might be expected to lead to rioting somewhere else with similar underlying issues (or as we are talking abuot the stratosphere here, overlying issues perhaps)

i'm sure that the meto are well aware of forecast events in the strat. they will not change their 32 day forecasts unless the modelling (which takes account of forecast strat developments) reflects  this change in the trop.  they are currently covering bases for late jan by having a caveat for average - below temps. until the fi modelling strongly points to cold, they will not forecast it.

neil has a point but without analysing closely the fi strat forecasts i wont be able to show how strong it is. anecdotally, i find the upper strat ecm forecasts to be fairly consistent whilst those low down tend to reflect the preceding days 12z 500mb flow. (not surprising really). the past couple of days have seen consistent fi's from ecm 12z so i suspect the overall suite will look consistent. if we got a 12z fi that looks like todays 00z run, the 100hpa chart will be quite different. the upper strat should be better though.

generally very good strat forecasts and by tomorrow, we may have our first forecast of a SSW this winter.  all still into the distance though the initial upper warmings have already fed through to the actual upper strat picture.

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng  The current temperature at 30HPa 90N was (on the model about a week ago) due to be about -40 and we currently have a steady -55. I'm putting more faith in an intervention by aliens than strat temps to shift that damn PV but acknowledge the input in here nethertheless.

 

I am unsure where your scepticism lies. Is it regarding stratospheric forecasts or the role of the stratosphere in influencing the troposphere itself?

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng  The current temperature at 30HPa 90N was (on the model about a week ago) due to be about -40 and we currently have a steady -55. I'm putting more faith in an intervention by aliens than strat temps to shift that damn PV but acknowledge the input in here nethertheless.

 

I am unsure where your scepticism lies. Is it regarding stratospheric forecasts or the role of the stratosphere in influencing the troposphere itself?

Both!
I see my role as a 'moderator of hopes' that many here have in the relationship between forecast or realised strataspheric temp profiles and the likelihood of surface blocking and the influence of polar wind vectors.
I truely believe the relationship - on surface blocking at least - is not scientifically sound but as with any science I am more than happy to listen to and get involved in discussion on the subject and I'll be even happier to be proved wrong if and when the time comes.
Please don't get the impression I am trolling this thread - meerely presenting an alternative view.

---

Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng  The current temperature at 30HPa 90N was (on the model about a week ago) due to be about -40 and we currently have a steady -55. I'm putting more faith in an intervention by aliens than strat temps to shift that damn PV but acknowledge the input in here nethertheless.

 

I am unsure where your scepticism lies. Is it regarding stratospheric forecasts or the role of the stratosphere in influencing the troposphere itself?

Both!
I see my role as a 'moderator of hopes' that many here have in the relationship between forecast or realised strataspheric temp profiles and the likelihood of surface blocking and the influence of polar wind vectors.
I truely believe the relationship - on surface blocking at least - is not scientifically sound but as with any science I am more than happy to listen to and get involved in discussion on the subject and I'll be even happier to be proved wrong if and when the time comes.
Please don't get the impression I am trolling this thread - meerely presenting an alternative view.

Not sure that you aren't rather skewing things in a particular direction by doing so. The chart you picked for 08 January was a 384 chart. So unlikely to be spot on. And the chart you've put it beside would indicate it doesn't turn out like that. But if you roll forward a little bit you get similar warming in a similar location to the 384 chart lasting a couple of days. The way you present it completely neglects to mention that. A chart at that range is always going to be a bit out, but it doesn't seem to be unreasonably so?

http://176.31.229.228/modeles/gfs/run/gfsnh-10-288.png?0

Bit of a warming

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng  The current temperature at 30HPa 90N was (on the model about a week ago) due to be about -40 and we currently have a steady -55. I'm putting more faith in an intervention by aliens than strat temps to shift that damn PV but acknowledge the input in here nethertheless.

 

I am unsure where your scepticism lies. Is it regarding stratospheric forecasts or the role of the stratosphere in influencing the troposphere itself?

Both! I see my role as a 'moderator of hopes' that many here have in the relationship between forecast or realised strataspheric temp profiles and the likelihood of surface blocking and the influence of polar wind vectors. I truely believe the relationship - on surface blocking at least - is not scientifically sound but as with any science I am more than happy to listen to and get involved in discussion on the subject and I'll be even happier to be proved wrong if and when the time comes. Please don't get the impression I am trolling this thread - meerely presenting an alternative view.

I think that to have scepticism over the FI forecasts whether they be in the stratosphere or the troposphere is very wise indeed. The stratosphere is far more stable than the troposphere and so longer range forecasts are more reliable especially in the mid stratosphere. However, that reliability goes out of the window when an 'event' occurs. When we see a wave breaking event following a strong mountain torque event then any reliability drops - but one shouldn't dismiss out of hand that there won't be a significant event.

This winter monitoring the stratsophere has been illuminating. We have started out with a period of vortex intensification which has been caused by very cold November temperatures due to a lack of ozone. Rest assured that it is no coincidence that a very zonal pattern and positive AO has followed. If ever one wanted to see how inhibitive a strong stratospheric vortex is to promoting HLB's then the evidence is there for all to see. But the reverse is also true! I have previously linked a number of papers showing evidence of how stratospheric warming events can alter the cause of events in the troposphere. I do hope that you have read or at least glanced through them.

 

I have always maintained that it is very difficult to achieve HLB's with a strong stratospheric vortex and I hoped to be proved wrong this winter. But, alas, that is not going to be the case. A weaker stratospheric does not necessarily mean blocking is going to occur, but will significantly increase the likelihood. We could be left with a situation where weaker westerlies prevail around the northern hemisphere rather than blocking patterns, but that tends to be very unlikely across the whole hemisphere.

We currently have an upper stratosphere that has already been warmed by a number of waves and is weakening as each one hits. We know that there has been a strong Asian mountain torque event over the last few days and that this will have repercussions with wave breaking into the stratosphere. How this is exactly modeled we do not know, however, it is safe to say that an already weakened stratosphere wil be weakened further and that it is looking more likely with every hit that a SSW is possible.

 

So that leaves us to the current picture presently. The mean zonal winds in the troposphere and lower stratosphere have not subsided yet from the earlier strong vortex conditions so it is no surprise that the tropospheric models do not pick any stratospheric changes up in the higher resolution parts of their run. But as soon as the zonal mean winds and/or displacement of the polar vortex comes into higher resolution territory then I am sure we will see changes.

I expect to see NH HLB's by the end of this month and into Feb. There is a strong case for an Aleution and Atlantic based block currently for the last third of the month.

c

Edited by user  05 January 2012 14:49:24  | Reason: Not specified