Stratosphere Temperature Watch 2014/2015

[bluearmy]

Very encouraging ECM op strat charts again and the parallel looks to be offering some support aswell.

Matt - your 7 jan punt might not be far off after all!

Recent strat/trop height coupling looked very close. I wonder if there are any extended ECM ens clusters that follow the op in the strat ? If so, someone will know if these produce a quick trop response or even mimic the upper strat height pattern as we've recently seen.

maybe Chris Fawkes will be due an apology! (Or perhaps he had other data and couldn't reveal that info in his defence).

[BLAST FROM THE PAST]

I have SSW for Jan which I suggested may be the talking point of the month rather than the actual weather.  I have to say that we have seemed t be chasing shadows this winter thus far so still aint holding my breath.  Still the ECM is looking good down the line. is there anything very good in the now time guys?

 

BFTP  

[chionomaniac]

It is great to see the warming forecast - always great to see the split following the displacement. The problem that we have seen so far is that the wave 1 displacement is, in its own right not strong enough to destroy the vortex and just pushes it over to the Atlantic sector. This is when the wave 2 starts forcing itself on the displaced vortex. Because of the wave 1 dynamics, the strongest pinch point on the elongated vortex from the subsequent wave 2 is on the Pacific sector (-EPO) and there is not enough 'pinch' from the Atlantic sector. The danger here, is that is unless we see a full collapse of the vortex that a true SSW will bring, then the vortex will reform in exactly the same elongated position that it is in prior to the split - not favourable at all. What we want to see is that the strongets upper based warming is based on the Canadian daughter vortex - if and when this occurs the -ve NAO follows.

[MPG]

Very encouraging ECM op strat charts again and the parallel looks to be offering some support aswell.

Matt - your 7 jan punt might not be far off after all!

Recent strat/trop height coupling looked very close. I wonder if there are any extended ECM ens clusters that follow the op in the strat ? If so, someone will know if these produce a quick trop response or even mimic the upper strat height pattern as we've recently seen.

maybe Chris Fawkes will be due an apology! (Or perhaps he had other data and couldn't reveal that info in his defence).

This is all way out in FI still, nothing nailed and nothing nailed regarding it causing the UK to go into the freezer. Chris Fawkes is still not right, because it hasn't happened yet.

[bluearmy]

This is all way out in FI still, nothing nailed and nothing nailed regarding it causing the UK to go into the freezer. Chris Fawkes is still not right, because it hasn't happened yet.

No one has said anything is nailed. Everyone's posts are made about what might happen going forward?? I was merely musing about what mr Fawkes my have known courtesy of glosea 5 but not be able to share on twitter.

Ed, the ECM forecasts do predict the stronger warming on the Atlantic side and I wondered if you had noticed (whilst you were looking at the green pastures of the alps last week - what a bummer) the close forecast movement coupling of the upper strat and trop?

To me, any downwelling would seem likely to be quite quick if we do get a reversal.

[feb1991blizzard]

I think we need to hope that the Vortex is still vulnerable by the time any further warming occurs, I really cant see this one having any significant effect on the trop now, the vortex in the mid strat is likely to reform too quickly from what I can see, we surely would be seeing at least a hint of blocking by now in the extended ensembles, especially the ECM ones, I notice Exeter have changed their wording in the 30 dayer regarding a pattern change, they have emphasised a small chance, not sure whether they are suggesting a mid latitude block possible or cautiously wording something more significant.

[Spah1]

I'm still a little confused. Why do 10 day out snow charts get taken with a pinch of salt whilst there seems to be more confidence in strat warming charts 9/10 days away?

Edited December 29, 2014 by Spah1

[feb1991blizzard]

I'm still a little confused. Why do 10 day out snow charts get taken with a pinch of salt whilst there seems to be more confidence in strat warming charts 9/10 days away?

 

Statistically they are a lot more likely to verify.

[BLAST FROM THE PAST]

Statistically they are a lot more likely to verify.

But they don't seem to have thus far?  Until I see them now time they are with pinch of salt for me...strange winter this one thus far

 

BFTP

[chionomaniac]

No one has said anything is nailed. Everyone's posts are made about what might happen going forward?? I was merely musing about what mr Fawkes my have known courtesy of glosea 5 but not be able to share on twitter.

Ed, the ECM forecasts do predict the stronger warming on the Atlantic side and I wondered if you had noticed (whilst you were looking at the green pastures of the alps last week - what a bummer) the close forecast movement coupling of the upper strat and trop?

To me, any downwelling would seem likely to be quite quick if we do get a reversal.

I've been keeping an eye on the output - yes any trop response is initially likely to be quick - still 2-3 weeks away though. Big concern that unless we see total vortex breakup then we won't acheive a strong and prolonged -ve NAO. I kind of expect the Pacific ridge anomaly to pop through to the Atlantic side in lava lamp fashion.

[Spah1]

Statistically they are a lot more likely to verify.

Cheers

[feb1991blizzard]

But they don't seem to have thus far?  Until I see them now time they are with pinch of salt for me...strange winter this one thus far

 

BFTP

 

They haven't looked too bad to me at day 10, the really deep FI ones have been poor, the 2013 Jan warming I thought was modelled extremely well even at day 16, with a little exaggeration from the GFS and a little run to run variance of course but the H500 and surface charts have been diabolical the last couple of weeks even as early as day 6, lets hope they are diabolical again and a HLB will appear out of nowhere, I cant see it though.

[bluearmy]

I think we need to hope that the Vortex is still vulnerable by the time any further warming occurs, I really cant see this one having any significant effect on the trop now, the vortex in the mid strat is likely to reform too quickly from what I can see, we surely would be seeing at least a hint of blocking by now in the extended ensembles, especially the ECM ones, I notice Exeter have changed their wording in the 30 dayer regarding a pattern change, they have emphasised a small chance, not sure whether they are suggesting a mid latitude block possible or cautiously wording something more significant.

 

any reversal in upper strat winds as far S as 60N is still more than 10 days away (actually, nearer 12 days +) . how are trop ens going out to day 16 going to show any clsutered response? even a quick response takes a few days to manifest itself with the onset of a quick strong  -AO. if the ecm strat charts remain consistent, then if matt reports no ecm extended clusters responding by mid jan, i would take notice. i see no reason why a reversal would not downwell effectively 

 

incidentally, a reversal is often preceded by the zonal flow being flushed down out of the system but we dont have any real zonal flow in the strat at the moment to speak of above 50N.

Edited December 29, 2014 by bluearmy

[Yarmy]

Not sure if there are verification stats for the top layers, but generally (unless it's a statistical artifact of the real-time measurement) the higher you go, the better the verification:

 

[Spah1]

What's the frequency of ssw events? i.e. How often do they occur? Are they relatively rare or relatively common?

[feb1991blizzard]

any reversal in upper strat winds as far S as 60N is still more than 10 days away (actually, nearer 12 days +) . how are trop ens going out to day 16 going to show any clsutered response? even a quick response takes a few days to manifest itself with the onset of a quick strong  -AO. if the ecm strat charts remain consistent, then if matt reports no ecm extended clusters responding by mid jan, i would take notice. i see no reason why a reversal would not downwell effectively 

 

incidentally, a reversal is often preceded by the zonal flow being flushed down out of the system but we dont have any real zonal flow in the strat at the moment to speak of above 50N.

 

Point taken but the best 30mb chart is already modelled within 144! 

 

The vortex has reformed by 240. all be it weakly.

 

 

 

 

Yes the 1mb chart is very good towards the end on the ECM op as I pointed out yesterday but on the GFS we only have to go a little further and the vortex is starting to reform - consistently showing, if you have access to the the ECM ens and are telling me that that big wedge of heights remains in situ at 1mb right towards the end of the run or at least has a cluster which does then I take back what I say. plus the EP flux chart isn't looking as promising as it did a few days back.

Edited December 29, 2014 by feb1991blizzard

[Captain Shortwave]

I guess the good news is that the GFS and parallel are keen on this Greenland warming as well

The GFS modelling seems to displace a major piece to Siberia before strangely the second warming results in it relocating to Canada which seems a bit odd. Though that might be just me

Edited December 29, 2014 by Captain shortwave

[bluearmy]

Feb1991, the reforming of the vortex was modelled up to 10hpa but now doesn't quite make it that high. At 30 and 50hpa, the 00z ECM is already showing the Atlantic warming effectiing another upcoming split and the new 06gfs run also generates a further split in week 2.

should this Atlantic warming verify and push ne, I think a renewed split is assured. Whether it sustains would be the question.

I think we should wait for the gfs modelling to catch up on this idea before analysing the way it might handle it through week 2.

Edited December 29, 2014 by bluearmy

[feb1991blizzard]

I think we should wait for the gfs modelling to catch up on this idea before analysing the way it might handle it through week 2.

 

Looks like its already started!

 

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2014122906&var=HGT&lev=1mb&hour=300

[ukpaul]

But they don't seem to have thus far?  Until I see them now time they are with pinch of salt for me...strange winter this one thus far

 

BFTP

 

On following the GFS charts from deep FI, in fact they have been likely to have a stronger warming by the time they reach ECM territory. I'm not sure where the idea that they aren't doing so has come from; maybe it's because there has been little trop response, in which case that's a whole different animal.

[Interitus]

Yesterday's charts didn't provide much clarity after all, the GEOS was largely unchanged while the ECM tries to recover the vortex from a difficult position.

On further consideration of the initial split effecting from lower levels upwards in response to the troposphere, how much does the current ongoing wavebreaking increasing geopotential height anomalies in the upper strat influence the trop to help cause a split?

The anomalies can be seen working their way down at the moment - http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_HGT_ANOM_OND_NH_2014.gif

 

Anyway just for curiosity value, the CFS is claimed to have similar stratosphere forecasting capabilities as the GFS with warmings supposedly forecast within the 12-14 day region. The CFS does churn out some outrageous charts at times, but interestingly the 18Z run from yesterday shows the kind of SSW response in the right kind of time frame of the last week of January / first week February with the kind of charts which would send these forums into meltdown.

On meteociel - http://www.meteociel.fr/modeles/cfse_cartes.php?ech=534&code=0&carte=1&mode=0&run=14

Needless to say it vanished on the next run!

[bluearmy]

The very end of the gfs op and control are not uninteresting hemispherically. Could just be coincidence - the gfs didn't split the upper strat until late in its run, despite the warmth breaking through earlier.

Andrew should gave left us the keys to his array of strat model links!

Edited December 29, 2014 by bluearmy

[Weather-history]

This from knocker

"I freely admit that the intricacies of the Strat are above my pay grade and i leave to the experts on here but a simple question. If the vortex in ten days time is over Greenland at the 100mb level why should we expect in any change in the tropospheric heights in that area any time soon.?"

https://forum.netweather.tv/topic/81281-model-banter-moans-and-ramps-autumnwinter-2014/?p=3102005

What are the more knowledgeable thoughts on this subject on the above question?

Edited December 29, 2014 by Weather-history

[bluearmy]

This from knocker

"I freely admit that the intricacies of the Strat are above my pay grade and i leave to the experts on here but a simple question. If the vortex in ten days time is over Greenland at the 100mb level why should we expect in any change in the tropospheric heights in that area any time soon.?"

https://forum.netweather.tv/topic/81281-model-banter-moans-and-ramps-autumnwinter-2014/?p=3102005

What are the more knowledgeable thoughts on this subject on the above question?

 

has anyone said that we will see a greeny block within a fortnight ??

 

the atmosphere is fluid and we have seen many occasions in the past where heights have risen quickly in that part of the NH. expecting the upper strat and upper trop to be mirror images of each other at the same time is not to understand what is going on. at the moment, we have a change in strat modelling post day 8/9 so i would be cautious about any latter week 2 modelling, be it trop or strat.

[lorenzo]

Found this paper which specifically examines splits and displacements in some detail and a nice evolution described of a split vortex and what to expect re: daughter vortices shaping and re-shaping. It gets hardcore technical later on and will need a couple of re-reads to digest in full.

 

http://discovery.ucl.ac.uk/18711/1/18711.pdf

 

Relevant to the modelling now this part - 

 

• Each type of SSW exhibits a distinct life cycle, in the sense that the centroid position, orientation and elongation of the Arctic polar vortex evolves in a similar fashion during the onset and occurrence of individual splitting events, with a separate behaviour during displacement events. 

 

Splitting events are characterized by a rapid increase of the aspect ratio of the vortex a few days prior to the SSW (Ï„ = −4 to −2 days), followed by the roll-up of the elongated vortex into two distinct ‘daughter’ vortices (Ï„ = −2 to 0 days). The daughter vortices propagate rapidly apart to a distance of up to 5000 km by Ï„ = 1 day, after which they experience a retrograde rotation around their common centroid, usually leading to the destruction of the weaker Canadian vortex and reformation of  the main vortex around the stronger Siberian vortex. 

 

 

Re: trop response, Andrew showed a recent vid of the W2 SSW creating a troposhpheric bounce, the warming cascading down through the strat, then achieving a mirrored response with a troposheric block shooting up from the Atlantic, just prior to the full SSW event, so we can look for an instantaneous shift in trop. modelling and also a lagged shift as the vortex breakdown completes and the centroids move. RE: downwelling - this from Charlton-Perez paper describes the impact of a split rather than a displacement warming wrt. AO conditions.

 

The midstratospheric NAM signal following splitting events is weaker than that which follows displacements events, but importantly anomalies can descend from the mid stratosphere to the surface, unlike displacement events. The evolution of the anomalies are also far more barotropic than during displacement events. ( Barotropic - independent of height of vortex vs. Baroclinic - height dependent e.g tilted westwards in regards to displacements).

 

d For 60 days following a splitting event a coherent  negative AO anomaly is observed. Consistent with this, high-latitude blocking in both the Atlantic and Pacific basins increases while blocking in the mid-Atlantic, Europe, and western Eurasia decreases. Ultimately

the largest effect from these events is observed over northern Eurasia with low temperature anomalies of up to 23 K.