Stratosphere Temperature Watch 2014/2015

[lorenzo]

Cohen on board with SSW in latest blog update, preferring the ECM solution, good discussion of thoughts in this thread below and description of the GFS Bias, although does not specify if GFS old or parallel.

 

Fascinating to see ECM continue with strong wave driving beyond the WAFz forecast update in the blog. Go ECM ! Need it to continue and create a pinch point on this seemingly elasticated weeble of a vortex © Ed.

 

Extract

 

The models do disagree on the strength of the polar vortex weakening.  The GFS predicts a relatively quick polar vortex recovery and is predicting that the polar vortex will return to normal and even slightly above normal strength by the end of the period (Figure 2).  The quick recovery in the polar vortex is directly attributable to the large deficits in the WAFz predicted by the GFS this period (Figure 3).  The ECMWF in contrast shows continued wave driving after January 5 that continues to perturb and weaken the polar vortex even beyond January 5.  Based on the ECMWF forecast, the SSW will get close to a major SSW (defined as a zonal mean easterly wind at 10 hPa and 60°N) and would likely achieve major SSW strength with further wave driving.  The GFS has displayed a bias all winter of under-predicting the vertical WAFz and over-predicting polar vortex strength.  Therefore we favor the ECMWF forecast of a more perturbed and longer duration polar vortex weakening.

 

Re: classification the semantics just now are of interest, it seems in other areas the activity we are seeing with the wave 2 action and temp increases are being referred to as SSW, whereas this is not precisely the technical definition. Some clarity below where Cohen mentions an SSW and also a major SSW ( i.e one which meets the WMO definition). So we have 2 different uses of the term SSW it would seem.

 

Healthy caveats continue regarding the destructive interference of the position of the vortex with the SSW fallout and route to cold not an easy road. Nice to see the Berlin charts on the blog too.

 

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

 

 

[bluearmy]

The 12z parallel does look similar to the ECM 00z run at 30hpa.

At 10hpa, the parallel does split the vortex on a temperature basis by T300 though can't see the heights. Just waiting for 30hpa to load on NW but looks similar but later. Gfsp passing the lower temps from the Russian to Canadian side so that the second split occurs svaalbard rather than Greenland as per ECM.

Will be interesting to see the ECM 12z run to see if the 00z run is a trend to relax the warming a tad or if it swings back again.

What we do have is a gfs op run is now a run that splits the upper vortex again as recently, all gfs output hasn't showed this after it recovered the split around T200.

Are we seeing the output beginning to come together on a second split (ECM too progressive and gfs not progressive enough over recent output) or are we seeing gfs slowly coming around to the ECM script? (Though after the 00z run, not quite sure what that is re first split surviving or needing a second hit of wave 2)

[Weather-history]

Cohen on board with SSW in latest blog update, preferring the ECM solution, good discussion of thoughts in this thread below and description of the GFS Bias, although does not specify if GFS old or parallel.

 

Fascinating to see ECM continue with strong wave driving beyond the WAFz forecast update in the blog. Go ECM ! Need it to continue and create a pinch point on this seemingly elasticated weeble of a vortex © Ed.

 

Extract

 

The models do disagree on the strength of the polar vortex weakening.  The GFS predicts a relatively quick polar vortex recovery and is predicting that the polar vortex will return to normal and even slightly above normal strength by the end of the period (Figure 2).  The quick recovery in the polar vortex is directly attributable to the large deficits in the WAFz predicted by the GFS this period (Figure 3).  The ECMWF in contrast shows continued wave driving after January 5 that continues to perturb and weaken the polar vortex even beyond January 5.  Based on the ECMWF forecast, the SSW will get close to a major SSW (defined as a zonal mean easterly wind at 10 hPa and 60°N) and would likely achieve major SSW strength with further wave driving.  The GFS has displayed a bias all winter of under-predicting the vertical WAFz and over-predicting polar vortex strength.  Therefore we favor the ECMWF forecast of a more perturbed and longer duration polar vortex weakening.

 

Re: classification the semantics just now are of interest, it seems in other areas the activity we are seeing with the wave 2 action and temp increases are being referred to as SSW, whereas this is not precisely the technical definition. Some clarity below where Cohen mentions an SSW and also a major SSW ( i.e one which meets the WMO definition). So we have 2 different uses of the term SSW it would seem.

 

Healthy caveats continue regarding the destructive interference of the position of the vortex with the SSW fallout and route to cold not an easy road. Nice to see the Berlin charts on the blog too.

 

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

That area of low pressure over the Barents Kara sea region is causing real headaches.

"However longer-term prospects for the AO continue to hinge on the anomalous polar low in the Barents Kara-seas region that has temporarily weakened. It is predicted to strengthen again across the north slope of Siberia and eventually move back over the Barents Kara seas region. Perhaps the current temporary relaxation is a foreshadowing of a longer term weakening trend but for as long as the Barents-Kara seas low persists, it destructively interferes with an externally forced negative AO (from the SSW). The biggest impact would to inhibit the flow of Siberian air into Europe. It’s impact would be less on North American temperatures where in the near term, ridging across western North America and a polar low in eastern Canada will direct arctic air into the lower 48."

"However this winter there has been an additional level of uncertainty due to anomalous area of low pressure in the Barents–Kara seas region, which has destructively interfered with the negative AO forced/associated with high Eurasian snow cover. The models last week were predicting that low pressure to split into two with each piece being absorbed into the climatologically favored polar lows in East Siberia and Hudson Bay. Though this has happened, allowing for increased wave driving and wintery weather across Europe, the models now forecast for the low pressure to reform, though based on the vortex split likely on the inland side of the Eurasian north slope.

It is hard to predict how long this area of low pressure will persist, which is likely to be at least somewhat supported by the relatively extensive North Atlantic sea ice extent compared to recent years and to the North Pacific side of the Arctic. As long as low pressure remains near the Barents-Kara seas any tropospheric influences from the stratosphere this time period will be favored across North America relative to Europe. However if a piece of the polar can move over Europe then this could help force much colder weather into Europe."

[Mark Bayley]

The strongest warming yet on the NAVGEM, although not sure on its accuracy (old NOGAPS model?). A contrast to the GFS 12z. Interesting update from Cohen lending more support to the ECM. Unfortunately i've been busy this winter so mainly followed the posts as opposed to the data however it looks as though its about to get interesting!

 

@WS: Yeah, it seems sea ice conditions in this region may have acted to counter the SAI feedback. There's a few recent papers suggesting that positive sea ice anomalies in this region correlates with a stronger PV. 

Edited December 30, 2014 by Mark Bayley

[Interitus]

 

Re: classification the semantics just now are of interest, it seems in other areas the activity we are seeing with the wave 2 action and temp increases are being referred to as SSW, whereas this is not precisely the technical definition. Some clarity below where Cohen mentions an SSW and also a major SSW ( i.e one which meets the WMO definition). So we have 2 different uses of the term SSW it would seem.

 

 

Minor SSW of course are normally defined as positive poleward temperature gradient i.e. pole warmer than 60°N but without zonal wind reversal.

[ITSY]

 

Big Warming again on JMA

 

Annoyingly I don't have much time and don't have access to the ECMWF strat info, but might be worth looking at that following the 12Z and following the slight progression towards this solution from the GFS. NAVGEM is widely at freezing for the strat above Greenland too, so the ECM might hold interesting clues this evening...

[bluearmy]

The updated ECM strat from the 12z run sees the gfs and ECM slowly approaching a common solution. At 30hpa, ECM and gfsp look pretty well together. At 10hpa, ECM has higher polar temps and squeezes the Canadian extension out completely such that it isn't really a split but a displacement on the Siberian side of the pole with a trough extension towards Canada. to my untrained eye, it seems that we will need that second input of wave 2 and the extended gfsp could well be in the right ballpark. Anyone know where the 10hpa heights can be found for the gfsp?

In case Berlin fails to update again in the morning, here are the 12z day 10 charts for 50/30/10 hpa

. .

Shouldn't be any issue placing these here as the noon issue are freely available via the Berlin site.

Edited December 30, 2014 by bluearmy

[phil nw.]

The updated ECM strat from the 12z run sees the gfs and ECM slowly approaching a common solution. At 30hpa, ECM and gfsp look pretty well together. At 10hpa, ECM has higher polar temps and squeezes the Canadian extension out completely such that it isn't really a split but a displacement on the Siberian side of the pole with a trough extension towards Canada. to my untrained eye, it seems that we will need that second input of wave 2 and the extended gfsp could well be in the right ballpark. Anyone know where the 10hpa heights can be found for the gfsp?

In case Berlin fails to update again in the morning, here are the 12z day 10 charts for 50/30/10 hpa

image.jpg. image.jpg. image.jpg

Shouldn't be any issue placing these here as the noon issue are freely available via the Berlin site.

 

Here you are Nick-courtesy of NWxtra- temps and pressures.

 

Day 10 and 15

 

stretched but not yet split.

Edited December 30, 2014 by phil nw.

[bluearmy]

thanks phil. expected to see it split by T384 but good to see confirmation. unusual to have such uncertainty in what is usually a fairly reliable timeframe for the upper strat. (ie T180/T240) although the output is coming closer together now as both models edge towards the middle ground of each others solutions.

[phil nw.]

thanks phil. expected to see it split by T384 but good to see confirmation. unusual to have such uncertainty in what is usually a fairly reliable timeframe for the upper strat. (ie T180/T240) although the output is coming closer together now as both models edge towards the middle ground of each others solutions.

Looking at all the levels over recent runs it looks to me we could see 2 main centres Canada/Siberia as time goes on Nick.

Possibilities of some temporary Atlantic ridging if we get enough weakness in the lower heights between but at the moment to my untrained eyes no strong signal for a complete split out to day 15.

Edited December 30, 2014 by phil nw.

[feb1991blizzard]

The vortex is totally destroyed at 1mb most the way through the second half of the 18z but its even struggling to propagate down to 3mb (for any longjevity before it reforms anyway) let alone the mid strat, its clear now that the split in the reliable timeframe isn't alone going to affect the troposphere significantly enough to cause HLB to develop else we would be seeing evidence in the output by now so no question that further reinforcements are required, whether from below or above or both.

Edited December 31, 2014 by feb1991blizzard

[Trom]

Makes me think the signal is MJO related. 

 

 

I'm all ready struggling with how the strat affects the troposphere in terms of predictability.  Can you explain how the MJO has this effect on the strat and it's follow on potential repercussions at a lower level?  I'm just trying to get a handle on this.  

[Skin]

I'm all ready struggling with how the strat affects the troposphere in terms of predictability.  Can you explain how the MJO has this effect on the strat and it's follow on potential repercussions at a lower level?  I'm just trying to get a handle on this.  

The MJO effects the planetary waves, which can propagate poleward, depending on the phase, the waves form and the potential heat is there waiting to effect the strat level. That is how I perceive it to work. anybody can interject, please do. this is my 3rd year following so I am not the expert on this still. 

[bluearmy]

Berlin not updating again today

really would like to see those wave charts

The z00z ECM start output drifts ever closer to general diluted gfs with no renewed split evident and the vortex drifting over to Greenland (now in line with all extended ens trop guidance as to where it always wanted to be) . The strongest warming over the Atlantic sector. We are under the east of the Atlantic block whilst the vortex hangs a trough over west Russia and into se Europe and a less marked one into north east n America .

How that translates into the trop is sort of borne out by the op ECM long wave pattern at day 10 but I doubt it will play out like that.

What has gone missing over the past few days with the ECM strat output is the n pacific/Alaska ridge which has gone AWOL. No longer pushing into the vortex and squeezing it apart after day 7.

[BLAST FROM THE PAST]

Problem is that there is a fair lag time for the effect with an SSW and to my calculations that's a bit of a wait yet [end of Jan maybe early Feb?] as we haven't had one yet and is still not within 10 day timeframe .  Early bets are that those that went for average to mild January are in a better position than those that went for cold. 

What has kept that omnipresent HP to our SW in place....that has been and is going to be for some while yet a serious thorn in the side

 

BFTP

[bluearmy]

Problem is that there is a fair lag time for the effect with an SSW and to my calculations that's a bit of a wait yet [end of Jan maybe early Feb?] as we haven't had one yet and is still not within 10 day timeframe .  Early bets are that those that went for average to mild January are in a better position than those that went for cold. 

What has kept that omnipresent HP to our SW in place....that has been and is going to be for some while yet a serious thorn in the side

 

BFTP

Fred- that's true if the vortex is in a standard type arrangement where the upper strat reverses but the middle strat has a decent zonal flow and the reversal has to downwell below 10hpa, forcing the zonal flow below to reverse. (Takes time). The current strat profile top to bottom at 50/70N is benign and any reversal will downwell quickly. (Mind you, haven't seen a zonal wind forecast chart for two days!)

[ITSY]

FYI the navgem has warming of +8c over Greenland overnight, with even the gfs op reaching -8c. Still awaiting jma + ecm.

[BLAST FROM THE PAST]

Fred- that's true if the vortex is in a standard type arrangement where the upper strat reverses but the middle strat has a decent zonal flow and the reversal has to downwell below 10hpa, forcing the zonal flow below to reverse. (Takes time). The current strat profile top to bottom at 50/70N is benign and any reversal will downwell quickly. (Mind you, haven't seen a zonal wind forecast chart for two days!)

Let's hope for a reversal soon then......I think the odds are very good for one to come....sooner is better though.  My guestimate is 14-20 Jan for SSW 

 

BFTP

Edited December 31, 2014 by BLAST FROM THE PAST

[bluearmy]

FYI the navgem has warming of +8c over Greenland overnight, with even the gfs op reaching -8c. Still awaiting jma + ecm.

problem is ITSY, the recent ECM trend to force those higher temps over the pole and split the upper vortex assunder has backed off. at the mid levels, the polar temps stay on the low side whilst warmings are strongest around Greenland/n Atlantic.

we saw the Berlin zonal wind forecasts were predicting the flow to become very relaxed throughout the strat at higher lats. That presumably remains the situation though I suspect the reformation of the vortex around Greenland will increase the zonal flow somewhat. I just think the strat is not the current driver of the whole dynamic. it's not preventing anything happening in the trop (eg. a strong zonal cold strat would prevent HLB in the trop) but it certainly doesn't seem to be influencing a relaxed flow in the trop!

Note that the gfs deep fi shows an upper warming wave right at the top from n America into the pole which is the opposite of what we saw before where it came from Europe and drove into the pole from Asia.

[aginob]

Hi to all

Hello bluearmy

can you Please post the original Link ( Source ) of this Models ?

Thanks !

https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/page-51#entry3103208

i not can find via Berlin site ... Sorry !

Off Topic

[feb1991blizzard]

Hi to all

Hello bluearmy

can you Please post the original Link ( Source ) of this Models ?

Thanks !

https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/page-51#entry3103208

i not can find via Berlin site ... Sorry !

Off Topic

 

I think those charts are only available on the ECMWF website for subscribers to the ECMWF dataset.

[bluearmy]

I think those charts are only available on the ECMWF website for subscribers to the ECMWF dataset.

Those charts are from weatherbell

Given that they are usually free via Berlin - I can post the noon charts (as I did yesterday). Will do so again later if new year festivities allow.

The 00z charts are another step towards the broad gfs output.

[karyo]

Despite the recent warmings, the stratospheric temperatures at the 50hpa level are around average. http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra/t90n_50_2014_merra.pdf

 

It will be interesting to see whether the next warming can edge those temperatures up a bit.

 

The 6z GFS P enhances the warming which edges even more towards parts of Greenland. 

[Paul_1978]

Bluearmy - hope you don't mind me pasting your post in from the MOD thread?

"There is no longer a SSW predicted. ECM has backed off. Gfs hasn't forecast one. Given the current state of the strat, I think any strong reversal high up will show quite quickly on the trop modelling. Seems the ECM op strat modelling can be as over amped as the trop! "

[bluearmy]

Bluearmy - hope you don't mind me pasting your post in from the MOD thread?

"There is no longer a SSW predicted. ECM has backed off. Gfs hasn't forecast one. Given the current state of the strat, I think any strong reversal high up will show quite quickly on the trop modelling. Seems the ECM op strat modelling can be as over amped as the trop! "

I think most over here appreciate this Paul. I posted it on the MOD thread because I saw too many refs this morning which seemed to still be hanging on a SSW delivering a cold scenario. Really missing thie Berlin wave charts and to make matters worse, Andrej is making lovey dovey when he has more important things to be doing ! Edited December 31, 2014 by bluearmy