Stratosphere Temperature Watch 2012/2013

[sebastiaan1973]

But will it stay cold in the coming weeks? That's the question.

[bluearmy]

ecm 12z 14 day ens output has no appetite for mild temps in london. whilst i have to agree with ed re the upper/lowerstrat, something seems a bit different this year. no doubt we'll know more afterwards (as always)

[chionomaniac]

Hi Chiono, do you think it less likely that a Canafian warming will happen now?

Not at all. That forecast still holds.

The question remains how long can the disturbed trop vortex continue whilst the strat vortex increases in strength. And I don't know the answer to that!

[phil nw.]

It will be interesting to watch developments Ed.

We have still got Zonal wind reversals forecasted over the pole at the lowest levels out to T240 on the ECM.

At the same time the gradual increase in the westerlies trying to filter further down to mid-levels-increases now forecasted down to 30hPa.

The above from yesterdays 12z ECM- but looks like the switch in the overnight modelling at 500hPa starting to reflect things above.

Have to agree unless we get some effective wavebreaking then a more zonal outlook across the Atlantic seems to be beckoning-if this trend continues.

[Catacol]

Ha - we have a 3 way split emerging here, more exciting than watching the vortex itself broken to pieces, or following the build up to the Hatton comeback!

GP (sig cold event late November on the back of building heights over Greenie and Iceland with low pressure over Europe) vs Blast (block too far west and very mild courtesy of trough to the west and pressure building over central Europe) vs Chio (oh no my head is telling me that the vortex is going to fire up and ruin everything...)

Love it. Presumably if the Canadian Warming actually happens then it will be all bets off and back to square one?

:-)

Edited November 3, 2012 by Catacol_Highlander

[Gavin Hannah]

I'm in GP's corner, only out of preferential outcome of course.

Out of curiosity, does the fact that the sun is nigh on asleep have any influence on the upper atmosphere temp profile?

Edited November 3, 2012 by IBringTheHammer

[Relativistic]

I'm in GP's corner, only out of preferential outcome of course.

Out of curiosity, does the fact that the sun is nigh on asleep have any influence on the upper atmosphere temp profile?

There is less solar irradiance relative to normal, but it's a tiny amount and will have an unmeasurable effect. Other than that I don't know if it has any known effects.

[damianslaw]

Always a good read this thread. Correct me if I'm wrong, but historically don't we normally experience SSW's event in late January and they often occur after a time lag of 6 weeks? - the signals start to appear in mid december.

The stratosphere does look to be cooling somewhat, I suspect it was only a matter of time..

The next couple of weeks willbe very interesting, will we see the PV ramp into gear aided by the cooling, and more importantly will it set up shop to our NW.. if it doesn't and continues to remain in a weak disruptive state against a cooling strat background... then it will suggest other forces are having a much greater influence over the strat.

[Glacier Point]

Might be worth keeping on Wave 2 forecasts in about 10 days time.

Longer range modelling is keen to split the developing high pressure cell over Siberia and develop a strong ridge over western Russia and eastern Europe. That's in the 'sweet spot' for wave 2 direction poleward. Current modelling has this development around 11th November. Add 20 days for stratospheric impact, and that gives us a date of around 1st December for earliest sign of vortex split.

[sebastiaan1973]

Stewarts story reminds me of: http://web.mit.edu/jlcohen/www/papers/CohenandJones_JC12.pdf

Many tropospheric Arctic Oscillation (AO) events are preceded by stratospheric AO events and even earlier in time by anomalous upward energy flux associated with Rossby waves in the troposphere. This study identifies lower-tropospheric circulation anomalies that precede largeAOevents in both the troposphere and stratosphere and the anomalous upward energy flux. Compositing analysis of stratospheric warming events identifies regional tropospheric precursors, which precede stratospheric warmings. The tropospheric precursor is found to vary when compositing over polar vortex displacements and splits separately. Prior to vortex displacements the main anomaly sea level pressure center of the tropospheric precursor is located across northwest Eurasia and is associated with the Siberian high. Prior to vortex splits a similar anomaly center is identified in the tropospheric precursor but is weaker and appears to be more strongly related to a shift in the storm tracks. Differences in the sea level pressure anomalies in the North Atlantic and the North

Pacific are also observed when comparing the precursors prior to vortex displacements and splits. Identification of a unique tropospheric precursor to stratospheric warming and subsequent tropospheric AO events can help to improve understanding troposphere–stratosphere coupling. Furthermore, the observational evidence presented here can be compared with model simulations of winter climate variability and lead to potential model improvements.

[chionomaniac]

First FI signs of a distressed vortex?

[Glacier Point]

Following on from earlier posting...

This is GFS end of run, so pinch of salt and other caveats etc. although cited because the timing might represent a rapid atmospheric response to wave 2 activity.

Lower stratosphere appearing to be undergoing split or attempts at it with Pacific and Eurasian Ridge pushing poleward:

this is traceable all the way up to 30 hPa.

Edited November 4, 2012 by Glacier Point

[chionomaniac]

Following on from earlier posting...

This is GFS end of run, so pinch of salt and other caveats etc. although cited because the timing might represent a rapid atmospheric response to wave 2 activity.

Lower stratosphere appearing to be undergoing split or attempts at it with Pacific and Eurasian Ridge pushing poleward:

this is traceable all the way up to 30 hPa.

I much prefer this type of wave break as a way of getting cold to these shores rather than an over the top SSW. Especially as it has a habit of recurring. And yes usual caveats.

[phil nw.]

Looking again at those 100hPa forecasts.I assume that this being the lowest level and just above the trophosphere the pattern forecasted is going to be close to the 500hPa pattern.If so we can see that first attempt by the Scandi.high is pushed east at T168-but later on-this at T300 indicates a proper block developing.

so a second bite around mid-month could be flipping point to the pattern change.

This would tie in with GFS ens mean hts from the 12z for 384hrs showing height anomols. well developed.

As Stewart said pinch of salt but interesting to see how all these long range tools start to link together.

Edited November 4, 2012 by phil n.warks.

[lorenzo]

Following on from earlier posting...

This is GFS end of run, so pinch of salt and other caveats etc. although cited because the timing might represent a rapid atmospheric response to wave 2 activity. Lower stratosphere appearing to be undergoing split or attempts at it with Pacific and Eurasian Ridge pushing poleward:

this is traceable all the way up to 30 hPa.

From Jan 2009 wave 2 is interesting in respect of this paper and 3 key conclusions..

The lower res Ensembles at the end of the GFS runs are complete carnage just now, so many solutions on the go.

C, are there any definitive pre-cursors for CWs? Not sure with what I have read if this has been identified specifically.

This pattern seemed unusual and was thinking just maybe, the add on top BDC and Ozone coming online with EP Flux simultaneously>?

[chionomaniac]

From Jan 2009 wave 2 is interesting in respect of this paper and 3 key conclusions..

The lower res Ensembles at the end of the GFS runs are complete carnage just now, so many solutions on the go.

C, are there any definitive pre-cursors for CWs? Not sure with what I have read if this has been identified specifically.

This pattern seemed unusual and was thinking just maybe, the add on top BDC and Ozone coming online with EP Flux simultaneously>?

Great post with link, L.

I have never come across a paper suggesting tropospheric precursors to a CW, though I am sure that the large Eurasian ridge is the perfect start point.

[chionomaniac]

I think we are seeing one of the most complex situations since I started monitoring the strat.

We have a cooling of the upper strat continued in the forecasts upto T+240

with a corresponding warming forecast in the lower strat up to the same period.

So we have the upper stratospheric polar vortex increasing in strength whilst the lower stratospheric polar vortex will battling against this strengthening.

If the lower strat wave action is strong enough then it should hold at bay the upper strat forcing.

But will it be strong enough?

Edit ; FI evidence again of the stressed/ spliting lower vortex up to the 30 hPa level on the latest GFS 6Z run.

Edited November 5, 2012 by chionomaniac

[Glacier Point]

... and what happens down the line Ed when the NH wavelengths begin to generate Wave 1 and 2 activity if and when we get the lower stratospheric split at the end of the month, particulary in mind of the favourable lower stratospheric profile ? Hot knife and warm butter spring to mind.

[bluearmy]

I think we are seeing one of the most complex situations since I started monitoring the strat.

I think that says it all ed. i've thought for a while that nothing i've seen looking through this thread for the past few winters or the berlin/ncep forecasts is currently making much sense. are we in new territory ? without any confidence as to the effect the upper strat will have on the trop do we just ignore it when thinking about events a month hence ?? to factor it in as currently anomolously cold wouldnt necessarily be the right call, given what we are seeing.

[geoffw]

hot knife and warm butter relating to the strat means?

[johnholmes]

chio and ba

yes to my less than experienced eye I do not recall anything similar to what we are seeing this autumn re the Stratosphere. Whatever happens it should be another learning curve to note for future years.

[jonboy]

hot knife and warm butter relating to the strat means?

I think it means its a signifgant step towards the holy grail!!!

[chionomaniac]

I would agree with Nick and John. Normally I can give a good guide at this point as to where the start of December will be heading. But not this year.

Today,it would be something along the lines of becoming increasingly zonal with +ve AO if the zonal mean positive anomalies propagate towards the troposphere or we could see lower stratosphere wave breaking from the troposphere leading to a split vortex and -ve AO and holding the positive mean anomalies in the upper strat.

Take your pick!

[Fozfoster]

I would agree with Nick and John. Normally I can give a good guide at this point as to where the start of December will be heading. But not this year.

Today,it would be something along the lines of becoming increasingly zonal with +ve AO if the zonal mean positive anomalies propagate towards the troposphere or we could see lower stratosphere wave breaking from the troposphere leading to a split vortex and -ve AO and holding the positive mean anomalies in the upper strat.

Take your pick!

Hi C,

so that could mean .

(a) increasingly zonal with +ve AO = mild December

(http://forum.nwstatic.co.uk//public/style_emoticons/<#EMO_DIR#>/cool.png split vortex and -ve AO = cool/cold December ??

Edited November 5, 2012 by Fozfoster

[Mark Bayley]

Hi C,

so that could mean .

(a) increasingly zonal with +ve AO = mild December

( split vortex and -ve AO = cool/cold December ??

A split vortex and -AO would increase our chances of a cool/cold December, however it all depends on where blocking that forms, is located

Edited November 5, 2012 by Mark Bayley