Stratosphere temperature watch - 2016/17

[chionomaniac]

9 minutes ago, feb1991blizzard said:

Do you think though that the wave showing in the trop could propagate that high and split the vortex so far and wide, the heights don't look that impressive in the trop surely, this split goes nearly to the top of the strat, is this plausible without some help from a top down warming event Ed?  i like to see the oranges on the strop chart at a high latitude, this only has high(ish) heights, not ridiculously high heights. 

Yes, it's happened before 2009/10, 2010/11 ( I think) but the split was Greenland based.

[Nouska]

7 minutes ago, chionomaniac said:

Yes, it's happened before 2009/10, 2010/11 ( I think) but the split was Greenland based.

January 2009 split had heights centred over Greenland.

Compare GFS 06Z forecast split with heights focused on eastern Siberia.

Would the end result not be similar or is there a risk of the two lows rejoining over the Atlantic when the core heights are not in that sector?

[chionomaniac]

6 minutes ago, Nouska said:

January 2009 split had heights centred over Greenland.

Compare GFS 06Z forecast split with heights focused on eastern Siberia.

Would the end result not be similar or is there a risk of the two lows rejoining over the Atlantic when the core heights are not in that sector?

That was the record breaker SSW  - from 'over the top'. The ones I am thinking of occurred late 2009 and 2010 and involved trop induced splitting propagating upwards on a weak vortex before it had a chance to get it's act together.

[Nouska]

5 minutes ago, chionomaniac said:

That was the record breaker SSW  - from 'over the top'. The ones I am thinking of occurred late 2009 and 2010 and involved trop induced splitting propagating upwards on a weak vortex before it had a chance to get it's act together.

OK ... here they are - if same time frames you are thinking of.

Dec 09  Nov 10

 

[chionomaniac]

57 minutes ago, Nouska said:

OK ... here they are - if same time frames you are thinking of.

Dec 09  Nov 10

 

Yes perfect - so they were the trop based splits similar to what is forecast. Critically they were Greenland based rather than Scandi based. That angle of split and the fact the split follows an Atlantic displacement are my only reservations at this point. There is also a big difference between the Jan 09 SSW that you have highlighted. At least we know that because it is trop based that the trop is heavily involved in the split!

Forgot to say thanks @Nouska!

Edited January 30, 2017 by chionomaniac
Manners

[Ruben Amsterdam]

Poof!

[Summer Sun]

 

[bluearmy]

which is what we are expecting anyway

whether it dips slightly below 0 at 10hpa or stays just above really isn't relevant. its what follows which is important. from my perspective i'm hoping that this unsustained reversal will allow a wintry blast for mid feb period and then not scupper a pleasant march/april which is what a big SSW would likely lead to.

 

[iapennell]

12 hours ago, bluearmy said:

What a shame the journalist wasn't able to make a couple of calls to understand that v cold in the strat isn't necessarily v cold low down 

your slightly more intelligent than average John will be v confused if they read that article and try to make sense of it

incidentally , tech SSW somewhere between T66 and T80 on yesterday's ex op

just for ref as makes no difference if it we get reversal at 10hpa/60N or we don't now we know the overall route next 7 days 

@bluearmy Yes, your typical journalists (even those writing for the Daily Telegraph) do not possess much more understanding of the workings of the atmosphere than the general public. However, with reference to the very cold Stratosphere it depends where it is located and where warmer conditions at similar altitudes are located in relation to the pool of very cold Stratospheric conditions. Very cold stratospheric conditions over the entire Arctic with significantly warmer stratospheric conditions (relatively warmer, that is) over mid-latitudes tends to be the worst for cold weather in the UK in the winter months. However, an extremely cold stratosphere over or east of Britain with less cold stratospheric conditions over the Arctic would encourage the jet-stream to move further south over and east of Britain, leading to an increased likelihood of much colder Maritime Arctic outbreaks over the UK. That is not too different to the situation predicted to be played out over coming days vis-à-vis the Stratosphere (though the vortex is to be centred over northern Scandinavia the very cold stratospheric conditions are helping to produce nacreous clouds visible from this country); with the Stratospheric Vortex remaining further north it is questionable how much this will lead to real cold over Britain over coming weeks.

As regards weather-patterns affecting Britain and NW Europe it is the relative temperature-patterns far aloft that matter: If the Stratosphere over the Arctic were very cold but the Stratosphere over most mid-latitude locations were even colder it is not going to promote strong Westerlies on the fringes of the Arctic. It is probable that such a situation would give rise to an expanded Circumpolar Vortex with a strong jet-stream (and deep depressions) in lower latitudes than usual- leading to frequent incursions of bitter cold from the north or east over Britain. Furthermore, if the very strong baroclinic zones normally found at the margins of Arctic sea-ice in the far North Atlantic and Pacific were shifted to (say) 40N consequent upon a colder mid-latitude Stratosphere affecting the circulation below (and extensive snow-cover and cold over Eurasia and North America would help such a scenario to play out) then very strong upper Westerlies will impact the Rockies and central Asian mountains leading to major and sustained losses of Westerly Atmospheric Angular Momentum due to strong mountain torques- leading to weaker Westerlies at the surface in lower mid-latitudes and with easterly winds extending across higher mid-latitude and Arctic locations. This would lead to severe winter weather in Britain with some winter storms moving in over the Med. 

A very cold Stratosphere in mid-latitudes with less cold conditions high over the Arctic (assuming some interaction between the stratosphere and lower layers of the atmosphere which is almost always so in the winter months) can mean very cold conditions over the United Kingdom. It has to be said however, that the journalist was trying to link the very cold stratospheric conditions over Britain and the (consequent) nacreous clouds observed with the very cold and frosty weather that has been recorded in parts of southern England last week. The truth is, the very cold Stratosphere (with even colder conditions over Scandinavia) heralds a shift to more unsettled conditions over coming days, with an end to frosty nights in the South: Said journalist probably does not know that!!       

[Nick F]

Well it looks like the sPV will bounce back towards the pole after day 10 after being displaced over toward Scandinavia this week looking at GFS and EC 10 hPa charts.

Get close to 0 m/s 10 hPa / 60N at T+48 on yesterday's EC on Berlin - but by day 10 its zonal again. So no technical SSW for now

So we'll have to see if trop up wave 2 activity combined with MJO moving into 7/8 around 2nd week of Feb will be enough to retrograde the building block to he east  over Scandi and Norwegian Sea to give us an easterly, certainly looks like the trop PV to our NW will retrograde with time.

Edited January 31, 2017 by Nick F

[Cloud 10]

-0.2 m/s at 60n.

 

[Summer Sun]

 

[Interitus]

5 hours ago, Summer Sun said:

 

Not really different ideas at all, the GFS charts also have the split. The thing is, by and large in the forecast the vortex is (quasi) barotropic again - the vortex is vertical - imagine the vortex at the different pressure levels as a pile of plates or dishes, they are stacked neatly on top of each other, not tottering over. The split is working up from the trop and the only baroclinic warming in the ECM charts is on the edge of the vortex. For the split to be effective there needs to be baroclinic warming in the middle, at the very least some warm advection from lower latitudes. This split appears to be more a hydrostatic adjustment than wave propagation - the geopotential wave 2 height amplitudes at the same time are low (and decline through the run) -

and the wave 2 temperature chart is also unimpressive in the strat, but shows large changes in the troposphere -

The GFS wave 2 tells a similar story, little activity especially higher up where a propagating wave would have a higher amplitude because of lower density air -

The activity also declines later in the run - see http://weatheriscool.com/index.php/stratospheric-forecast-1-wave2-500hpa-gfs/

So while a couple of ensemble members were showing another SSW possibility within the next fortnight, and certainly something to keep an eye on, at the moment it is looking unlikely. The situation is a little similar to the start of the year, though starting with a weaker vortex this time, the trop split looks like maybe it will do something to the strat but probably won't, but it doesn't matter as the trop pattern provides interest enough for most people.

 

 

Edited January 31, 2017 by Interitus

[stodge]

As means of comparison between 2016 and 2017, the 10 HPA for mid Feb 2016 as forecast by the equivalent 06Z OP run this time last year:

Today:

Much smaller and warmer than the equivalent last year.

[bluearmy]

1 hour ago, stodge said:

As means of comparison between 2016 and 2017, the 10 HPA for mid Feb 2016 as forecast by the equivalent 06Z OP run this time last year:

Today:

Much smaller and warmer than the equivalent last year.

But we didn't have a technical SSW 3 feb last year stodge ??

as I have said - I don't want a big SSW mid Feb as all it will do is ruin the spring (chances of any quick trop response are unclear)

the current warming will help deliver an opportunity for the trop to generate a pattern conducive to bring deep cold into europe during feb 

whether that reaches here , who knows 

[stodge]

1 hour ago, bluearmy said:

But we didn't have a technical SSW 3 feb last year stodge ??

as I have said - I don't want a big SSW mid Feb as all it will do is ruin the spring (chances of any quick trop response are unclear)

the current warming will help deliver an opportunity for the trop to generate a pattern conducive to bring deep cold into europe during feb 

whether that reaches here , who knows 

Indeed and last year's event wasn't an SSW but an early and very dramatic Final Warming into March.

Signs the PV will recover slightly from the near SSW going into mid month and I'm interested to hear your view on that being a potential positive for UK cold. I'd always surmised a weakened PV would be vulnerable to further displacement (to Canada) which would aid the tropospheric response in the form of a westward-moving Eurasian HP but it seemed counter-intuitive to the argument a split PV would be helpful. I suppose the possibility with a split PV is one bit stays over Greenland with the other lobe over Siberia. 

 

[Interitus]

17 hours ago, iapennell said:

Very cold stratospheric conditions over the entire Arctic with significantly warmer stratospheric conditions (relatively warmer, that is) over mid-latitudes tends to be the worst for cold weather in the UK in the winter months.

If the Stratosphere over the Arctic were very cold but the Stratosphere over most mid-latitude locations were even colder it is not going to promote strong Westerlies on the fringes of the Arctic. It is probable that such a situation would give rise to an expanded Circumpolar Vortex with a strong jet-stream (and deep depressions) in lower latitudes than usual- leading to frequent incursions of bitter cold from the north or east over Britain.

Well the first situation is the normal state with a strong stratosphere vortex, and the second is basically the situation with a stratospheric warming and a weak or non-existent vortex. It's either been described inadvertently or in a very roundabout way!

With an average 60-90°N temperature greater than that at 50°N throughout the atmosphere from 150 to 10mb, the maximum 60°N 10mb zonal wind speed in the MERRA data is only 9.65 m/s.

Here is the relationship between 60°N 10mb wind speed and the difference in 50°N and 60/90°N temperature at 30mb (T50 - T6090), the correlation is 0.979 - temperature is critical -

 

Edited January 31, 2017 by Interitus

[Summer Sun]

 

[stodge]

It was surely unrealistic to expect the near SSW to "finish off" the vortex - it's only early February.

Some recovery was inevitable but the PV will be weakened and the zonal winds much slower - we've had winds running at 80-90 m/s. We may get a short period of reversal before a recover yo what 20-30 m/s at best.

More evidence of a weakened PV liable to further displacement. 

 

[Catacol]

Fairly swift recovery forecast... and we had a similarly swift vortex recovery in December. For the start grogs out there - is this the strong wQBO at work or is it some other factor? I don't recall seeing such swift vortex recovery from stressed states in the past but maybe my memory is playing tricks on me.

[Nouska]

On 07/12/2016 at 17:10, Nouska said:

The one long range model I have been impressed by - NCAR CESM - had been consistently showing a very cool picture for February - blinked last month - now back again . I know it is ice anomaly coupled but no idea as to whether it has stratosphere forecasting abilities. This sees the October/November pattern re-establishing with the cold managing to penetrate as far as the UK.

This is the model that Dr Ventrice has been singing the praises of, from a USA point of view. A rare success in model terms for October too, Eurasia wise.

http://www.cesm.ucar.edu/about/

 

In view of current modelling, thought I would repost this again.

Will this be another success for the NCAR CESM and will the cold get as far as it forecasts it to - I have more confidence this time - in both the model and what it shows.

[feb1991blizzard]

Ive got a feeling within the next 2 days, we will start to see another top down warming coming into the far reaches of the GFS, does anyone else agree?, got a feeling the 6z tomorrow will set the ball rolling.

[bluearmy]

Ironic that on the day we are possibly seeing a technical SSW occur, this thread is so quiet !

[chionomaniac]

By a hair's breadth lol

[Interitus]

4 hours ago, bluearmy said:

Ironic that on the day we are possibly seeing a technical SSW occur, this thread is so quiet !

Except with the Berlin ECM it was on the analysis chart, so it was yesterday!