Stratosphere temperature watch - 2016/17

[lorenzo]

Jason Furtado is certainly not a troll - well respected Professor of Meteorology. The Aleutian low is a starter pistol for wave driving into the stratosphere hence the discussion around losing that to an Aleutian High and different impacts. The Wave Activity Flux plot is not dissimilar from the one you will see posted from time to time by Judan Cohen.  

A few seasons back we had a Kamchatka ridge - the K ridge that dictated the NH set up - the Aleutian ridge is cranking in with serious MB potential and has the potential to do the same. Will be of interest to see how it plays out given the already bashed up vortex.

[Yarmy]

1 hour ago, Singularity said:

That heat flux chart contrasts greatly with what Lorenzo posted earlier, and indeed what's generally expected by pros as a result of the poleward ridge.

That he uses 40-80 instead of 30-80 might have something to do with it? Also the lack of mention of the poleward ridge and likely disruptive effect on the tropospheric vortex makes me suspect he's either poorly informed or carrying out a bit of trolling activity. Then again I don't know who he is so I might be insulting an expert in the field for all I know  (in which case I apologize... IF my other points are also wrong ).

He's a co-author on a few Cohen papers, e.g. 

http://www.nature.com/ngeo/journal/v7/n9/abs/ngeo2234.html

But I've seen them engage on twitter a couple of times, and it appears they are no longer entirely simpatico.

[Singularity]

12 minutes ago, lorenzo said:

Jason Furtado is certainly not a troll - well respected Professor of Meteorology. The Aleutian low is a starter pistol for wave driving into the stratosphere hence the discussion around losing that to an Aleutian High and different impacts. The Wave Activity Flux plot is not dissimilar from the one you will see posted from time to time by Judan Cohen.  

A few seasons back we had a Kamchatka ridge - the K ridge that dictated the NH set up - the Aleutian ridge is cranking in with serious MB potential and has the potential to do the same. Will be of interest to see how it plays out given the already bashed up vortex.

Thanks for clearing that up Lorenzo, my apologies to Furtado if by any chance he comes across this discussion.

Still a bit puzzled by the WAFz plots looking so different to one another though?

[ArHu3]

29 minutes ago, lorenzo said:

Jason Furtado is certainly not a troll - well respected Professor of Meteorology. The Aleutian low is a starter pistol for wave driving into the stratosphere hence the discussion around losing that to an Aleutian High and different impacts. The Wave Activity Flux plot is not dissimilar from the one you will see posted from time to time by Judan Cohen.  

A few seasons back we had a Kamchatka ridge - the K ridge that dictated the NH set up - the Aleutian ridge is cranking in with serious MB potential and has the potential to do the same. Will be of interest to see how it plays out given the already bashed up vortex.

Not exactly the same but not to dissimilar either:

 

[bluearmy]

Looking at the recent height charts for the upper strat, it seems that the idea the vortex will begin to twist further anti-clockwise and drift towards Alaska is gaining some traction - in conjunction with the high Canadian anomoly heading east into the Atlantic as a consequence 

the upcoming set up of elongated trough parallel to the meridian followed by blocking over Greenland/e Canada/ Svalbard to follow is a strat imprint that we would do well to see heading down to the trop! 

[bluearmy]

Some marked changes late on in yesterday's 12z ECM op, now the berlin data is through. as it's late on, we'll leave it until tomorrow to see if it repeats. 

[mountain shadow]

22 minutes ago, bluearmy said:

Some marked changes late on in yesterday's 12z ECM op, now the berlin data is through. as it's late on, we'll leave it until tomorrow to see if it repeats. 

Is the marked change good or bad? Is it showing a strengthening PV?

[MattH]

This would be interesting...

...Certainly one to keep an eye on, but the GFS is keen to almost split the vortex, but then re-develop the main vortex over Canada towards the middle of December. With one small vortex over N Russia and, again, the main vortex over N Canada this does seem to promote more in the way of 'ridged conditions' across Greenland and up into the polar region between the two features. Must admit though my confidence over any GFS data longer term is now low, as it has shown once again already this season using the GFS, even the GEFS at any longer time frames is a risky thing to do.

Within the shorter term it does look as though there will be a strengthening of the vortex and it is also trying to return to a more polar position, but never quite makes it really. Certainly nothing to 'worry about', but as Tony mentioned the other day in his excellence post after such a disruptive autumn season for the vortex it really needs to remain 'under the thumb' as best as possible as we are still in that period of the year when 'rapid intensification' can occur. Any short term SSW is most certainly unlikely now, so at the earliest I would suggest mid to late December for one, if everything comes together mind.

An unusual season indeed...

Matt.

[Singularity]

Just look at that ridge on the Pacific side near/across the Aleutians... it's stronger than in previous runs and ties in with the increased wave activity and progress toward a split vortex at least at the lower levels and perhaps mid-levels too.

Often these Arctic highs are brought on a bit too quickly as a response to changes in tropical forcing, but on the other hand they are sometimes overlooked and/or under-cooked until quite short range. So it's difficult to second-guess the models on this. ECM fancies a strong high more toward Alaska but with similar impacts down the line (if perhaps a little slower).

Given the signs we have for low pressure to focus in the western N. Atlantic during the run-up to the proposed vortex split, with cold air across the NE of N. America, if we can see the troposphere follow the lower stratosphere, some deeply cold air can transfer to N. Eurasia with the weaker daughter vortex to 'load the cannon' ready for HLB centred N/NW of the UK to fire it west. 

It can do that, but will it? If only we could be sure!

[Glacier Point]

On 14/11/2016 at 11:42, Glacier Point said:

GFS op and EPS / GEFS means beginning to offer a little more evidence to a substantive stratospheric disturbance as we start the winter.

Keep in mind that the pattern from around 19th Nov for a period of several days builds a strong mid tropospheric ridge over East Europe / Western Russia.

That is perfect for upward wave 2 deflection into the stratosphere. The vortex is already very weak and it won't take much to break it down, wave 2 probably timed for late Nov into early December. My early season analogues hinting at a new vortex forming over the Canadian sector, well displaced from the Pole.

This would be my punt for early December as to how the pieces of the jigsaw will be arranged in the stratosphere...

Door wide open for Arctic ridge and deeply negative AO.

So GFS comes up with a split..

Timing is towards the end of the envelope, but still within the traceable period for tropospheric ridging in mid to late November.

Could well be worth keeping a eye on this as we have model agreement on the North Atlantic stratospheric ridge. Any Wave 1 activity on the Pacific side will squeeze and pinch the vortex. In the next two to three days we get a deep upper low passing through the Aleutians (probably the last for some time).... 

Note also the plot annotated above. That's primarily based on Indo-Pacific tropical forcing, which looks increasingly likely over the coming weeks.

Edited November 28, 2016 by Glacier Point

[Singularity]

Great update, thanks GP 

Regarding the Indo-Pacific forcing...

 

Is that a CC Kelvin Wave crossing the Pacific at the moment? Linked perhaps to the models showing the La Nina easing off. Could that also be distorting the Hendon-Wheeler MJO plots in a way that reduces the amplitude shown relative to 4/5/6?

Cheers 

[Glacier Point]

Some low level westerlies pushing through the West Indian Ocean, but upper level easterlies still dominant, so no coherent wave signature just yet but forecasts depict some eastward propagation and wouldn't be surprised to see convective anomalies begin to strengthen over Indonesia.

Convective anomalies further east are Kelvin wave related, with main MJO component centred over East Indian Ocean.

GFS forecast for eastward propagation, and takes us to a similar point to mid September. Prospects for a sustained high angular momentum phase looming.

Edited November 28, 2016 by Glacier Point

[Interitus]

The suggested split vortex in long range is an imprint of the tropospheric pattern upon the stratosphere vortex which shows little distortion with height hence little warming. Intensification is the default because of cooling during the polar night in the absence of sufficient disturbance. Forecast MERRA 10mb 60-90°N temperatures for 6/12/16 would suggest a statistical chance of a classic SSW of no more than ~25% within 21 days, indeed it is the average temp 59 days prior to SSW.

edit: and with latest GFS, long range troposphere geopotential height pattern changes so split vanishes *poof*

Edited November 28, 2016 by Interitus

[Singularity]

The GFS 12z is a bit of an oddball with the placement of the strong ridge on the Pacific side, out of step with recent trends and GEFS.

So I view it with great suspicion!

[snowbunting]

Bingo from our pub run on the GFS, though not sure if it is in the right spot!

[bluearmy]

Berlin charts picking up the inevitable uptick in wave 2 (courtesy of the ridging both sides of the NH) 

note that the zonal flow high up is pushed further north into higher  latitudes  for the second day running.  It doesn't seem to be intensifying though as wave activity continues to disrupt. point being that you should expect to see zonal flow at 60N looking less healthy from a weak strat perspective.  At This juncture, with the wave activity continuing, it might be a good thing to see that prior to any split occurring if the wave two persists. 

[Glacier Point]

This from Cohen's latest blog which I would agree with in respect of how the stratosphere - troposphere will interplay during the coming few weeks..

"If the WAFz does remain relatively quiet I believe that for the first time in a while the troposphere can settle into a more stable large-scale pattern, consistent with the PV disruption, for an extended period lasting several weeks.  Key gross features include northerly flow out of the Arctic directed at Northern Europe, troughing over Siberia, ridging in the eastern North Pacific with downstream troughing over North America.   It is harder to anticipate the details that will be important in determining the sensible weather in Western and Central Europe and the Eastern US.   However, if the pattern is progressive (moving to the east) this will likely favor colder temperatures in the Eastern US relative to Europe while a retrograding (moving to the west) pattern will favor colder temperatures in Europe relative to the Eastern US.  Also if the long-wave pattern starts to rotate then the WAFz could become more active and potentially lead to a significant rearranging of the large-scale wave pattern across the NH."

https://www.aer.com/science-research/climate-weather/arctic-oscillation 

Beyond the culmination of the autumn blocking phase (should mature in the mid stratosphere during mid / early December), I suspect we will see a cooling in the upper and mid stratospheric layers as we loose favourable WAFz patterns. Zonal winds should increase at these levels.

However, as I Cohen notes, that should pave the way for the downwelling of negative zonal winds currently in the mid and lower stratospheric layers. There is therefore likely to be disconnect between the lower stratosphere and mid and upper layers. Some very good examples of this..

There is a almost a tangible tightening of the troposheric blocking signal as the stratospheric blocking signal matures and fades. So analysis of stratospheric temperatures and zonal winds may not be wholly useful in the coming weeks - it's more about what the troposphere does in response to downwelling and other drivers.

[SteveB]

Hi GP,

I assume this a good thing, and re-enforces the likelihood of Northern blocking in our neck of the woods? 

[MattH]

1 hour ago, Glacier Point said:

This from Cohen's latest blog which I would agree with in respect of how the stratosphere - troposphere will interplay during the coming few weeks..

"If the WAFz does remain relatively quiet I believe that for the first time in a while the troposphere can settle into a more stable large-scale pattern, consistent with the PV disruption, for an extended period lasting several weeks.  Key gross features include northerly flow out of the Arctic directed at Northern Europe, troughing over Siberia, ridging in the eastern North Pacific with downstream troughing over North America.   It is harder to anticipate the details that will be important in determining the sensible weather in Western and Central Europe and the Eastern US.   However, if the pattern is progressive (moving to the east) this will likely favor colder temperatures in the Eastern US relative to Europe while a retrograding (moving to the west) pattern will favor colder temperatures in Europe relative to the Eastern US.  Also if the long-wave pattern starts to rotate then the WAFz could become more active and potentially lead to a significant rearranging of the large-scale wave pattern across the NH."

https://www.aer.com/science-research/climate-weather/arctic-oscillation 

Beyond the culmination of the autumn blocking phase (should mature in the mid stratosphere during mid / early December), I suspect we will see a cooling in the upper and mid stratospheric layers as we loose favourable WAFz patterns. Zonal winds should increase at these levels.

However, as I Cohen notes, that should pave the way for the downwelling of negative zonal winds currently in the mid and lower stratospheric layers. There is therefore likely to be disconnect between the lower stratosphere and mid and upper layers. Some very good examples of this..

There is a almost a tangible tightening of the troposheric blocking signal as the stratospheric blocking signal matures and fades. So analysis of stratospheric temperatures and zonal winds may not be wholly useful in the coming weeks - it's more about what the troposphere does in response to downwelling and other drivers.

I think one of the problem's this year is that the overal scenario is 'up in the air', crudely put and no pun intended, that an array of different comments and forecasts continue to crop up. That is one of the difficulties myself and Tony had when looking at the strat and how it may well play out. A few weeks back, when it really was 'under attack' we thought that the coming weeks may well signal an SSW, but clearly that isn't to be the case, with the GEFS from Hanna Attards site, for example, doing a complete turn around. Depending on who you ask you seem to get a different answer as to how the SPV will influence the coming weeks. As you rightly say, once the downwelling begins then it may well aid in northern blocking, but IMO it seems a fine line to walk to be looking at a vortex that may return to its normal position and then potentially strengthen.

Whilst some background signals are clearly unlikely to change I have a feeling the SPV will be a particular unknown in the coming weeks in terms of how it will behave and how it may or many not influence things within the troposphere.

Matt.

[Catacol]

1 hour ago, Glacier Point said:

 So analysis of stratospheric temperatures and zonal winds may not be wholly useful in the coming weeks - it's more about what the troposphere does in response to downwelling and other drivers.

Well - there's an encouraging post if ever I read one. Cleverly done Stewart.

Standard impact in time scales would appear to stretch from 1 - 2 months looking at the examples you have provided. Given that the vortex is already so heavily impacted will the lag time be longer or shorter than usual before downwelling impacts? And do you think the impacts will be longer lived as 2009 or shorter as per 1995? I'm at the limit of my understanding in trying to project potential timescales.

Also - if it isn't barred by your contract - do you see a retrograde or a progressive signal in the long wave pattern? Again I'm at the limit of my knowledge and unsure what seasonal wavelengths in December might do under the current setup.... but am I right in supposing that a spike in AAM would encourage retrograde movement?

Sometimes I wish I was a scientist or geographer rather than a historian.......

[knocker]

 

[Singularity]

So - by late Dec we could find ourselves with an upper stratospheric vortex furiously spinning away but for some 1-2 months unable to propagate down and take apart a disrupted vortex and blocking regime in the mid-lower levels and troposphere?

I like the sound of that, particularly if the longer persistence is achieved and we save a warm-up until the sun is gaining appreciable strength again anyway.

Funnily enough, when I was thinking about the QBO last month, I wondered if the easterly lowest levels set against westerly upper levels might promote such a disconnect with abundant zonality high up in the atmosphere but a marked deficit lower down. Interesting times.

[Catacol]

Can someone explain Ventrices tweet to me? How does a decline in the Siberian high allow perking up of tropical convection (never heard that said before...) 

Edited November 29, 2016 by Catacol

[Dennis]

wow thats impressive

[sea swim]

1 hour ago, Dennis said:

wow thats impressive