Stratosphere Temperature Watch

[damianslaw]

Interesting thread tyhis is and whilst I am not professional forecaster it does appear that we about to enter a sustained very cold spell of weather indeed, northern blocking looks like developing in earnest next week setting us up for some very bitter arctic ocntinental air indeed.. this is what those who like sub zero days and bitter cold nights a la below -10 degrees and no thawing of snow need, yes the current situation is great for intense snowfalls but we are not seeing very cold temperatures, it is all rather marginal still. I think the effects of the stratospheric warming will manifest by next weekend - easily could see a much colder version of Feb 2005/March 2005 occur, it is perfect timing for blocking to take hold, mid Feb often sees the atlantic take a break and blocking in favourable spots develop, and with the arctic near its coldest and seas at there coldest, some truely deep cold upper air can easily establish.

[Guest North Sea Snow Convection]

Yes, I think that I may be guilty of misunderstanding the idea of the MMW not being involved in the recent easterly. Apologies if that is the case.

Moving on, the propagation of the MMW is continuing with the zonal anomaly winds now reaching the -10m/s bracket at the tropopause. I wonder if these can propagate any lower as this often seems to be the extent of propagation from this strength of winds in most MMWs.

At the tropopause 100 hPa level the split vortex is being forecast to slowly reform back into 1 main vortex.

Here is todays profile with the two daughter vortices, one situated over Canada the other over Siberia.

Note the area situated over Greenland where pressure is higher. This is translated further below in the troposphere, as slight pressure rises from an elongated mid Atlantic ridge stretching to Greenland, and allows the northerly airflow from a segment of the polar vortex troughing into Scandinavia.

Next T+240

Here the reformation of 1 main vortex is forecast to occur towards the Pacific end of Siberia. This leaves an area towards Scandinavia of higher pressure at this level. I wonder if this is translated lower down then will there be the possibility of future height rises in this area to replace the present Scandinavian trough. As ever how does this fit in with other teleconnections and with GP's thoughts. I await his latest update on the GWO thread as ever with interest.

c

Don't worry - misunderstandings work both ways. I think we are all on a bit of activity overload atm!

Very good assessment - and when I looked at ECM this evening was thinking along the same lines.

I can actually see another easterly happening down the line - this time leading to full height rises across to Greenland with lower heights over mainland europe.

damianslaw - I think you are spot on with your thinking. More sustained arctic/polar continental is the way to go without interruptions. It seems a bit churlish to criticise the easterly incursion we have seen to start this month - it was very potent, produced large amounts of snow, but was too brief. A few days longer and then the low which came up from France would have been surrounded by cold air with no marginality.

I too can see a colder Feb 05 type scenario evolving. We are in a far better position this time around than that winter, although even then there was day after day of convective snow showers and repeated accumulations, albeit they melted rather by day and were topped up/replaced each night.

Edited February 3, 2009 by North Sea Snow Convection

[cheeky_monkey]

With such a warming that we had (are having) in the stratosphere you would probably have to go back to Jan 56, 63 or 47 to see a warming of similar magnitude. I could not see how you would get such sustained northern blocking without it. If this is correct then it would give us a very good idea where the weather will be taking us in the next 4 to 6 weeks.

see the major warming event of nov and dec 1987 that lasted most of those months and see how jan feb 1988 turned out..then maybe rethink where the weather can take us in the next 4-6 weeks...warming dosnt always produce sustained northern blocking in the right areas. So be warned before becoming too complacent!

[AtlanticFlamethrower]

see the major warming event of nov and dec 1987 that lasted most of those months and see how jan feb 1988 turned out..then maybe rethink where the weather can take us in the next 4-6 weeks...warming dosnt always produce sustained northern blocking in the right areas. So be warned before becoming too complacent!

A bit earlier someone said a warming early in the winter is less likely to have an impact than one that happens later in the winter.

Perhaps there's an answer there for you someone could expand on...

[Mikel Nimbus]

The AO ensembles show a slight swing towards +ive for about a week but just about stay -ive. All bar one of the runs are then in good agreement for a a more -ive AO towards the middle of the month. With the jet subdued, this should allow great opportunity for our northern block to build itself.

[JoeShmoe]

No signs of northern blocking in the mid-long range NWP output this morning .. in fact heights are lowering to the North

[Weather-history]

No signs of northern blocking in the mid-long range NWP output this morning .. in fact heights are lowering to the North

The mean ECM and GFS 8 to 10 day charts, its there according to the charts. The interesting thing to note is how meridional its on this side of the hemisphere. Trough, ridge, trough, ridge. No flat zonal pattern evident there.

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/hgtcomp.html

Edited February 4, 2009 by Mr_Data

[chionomaniac]

The mean zonal winds across the middle stratosphere are again forecast to be easterly for yet another day. FW on the cards perhaps as the return to a westerly vortex is really dragging out.

I make it 23rd Jan until at least 14th Feb if the forecast verifies - that's at least 23 days which is incredible. The longer that these winds stay easterly the longer the chance of cold increases. So just because the models aren't showing synoptics that aren't in line with a severe MMW, the liklihood is that they will at some time during the propagation period. If they is a slight resurgence in the Atlantic this can occur but the general trend will be for blocking.

c

[Guest North Sea Snow Convection]

No signs of northern blocking in the mid-long range NWP output this morning .. in fact heights are lowering to the North

Something has to give - changes will properly show up before long. A west to east atlantic pattern is unsustainable against the background of this propagation and polar easterlies.

[Weather-history]

. A west to east atlantic pattern is unsustainable against the background of this propagation and polar easterlies.

You can see it in that link I posted in a previous post how meridional the Atlantic/Europe pattern is in those two charts.

[Guest North Sea Snow Convection]

You can see it in that link I posted in a previous post how meridional the Atlantic/Europe pattern is in those two charts.

Yes exactly Mr D

No model output is going to be alike with ridges/troughs placement - especially for a small piece of land like the UK.

Edited February 4, 2009 by North Sea Snow Convection

[picog]

If it really is at least 4 weeks from the event initiation through to effects in the weather, then perhaps we should not be looking for anything until around Valentine's day?

[johnholmes]

the major event, assuming it occurs in the UK area, was always going to be from the end of the first week of February, more probably towards the second week.

What many people have had over the past 2-4 days is a bonus.

[chionomaniac]

the major event, assuming it occurs in the UK area, was always going to be from the end of the first week of February, more probably towards the second week.

What many people have had over the past 2-4 days is a bonus.

Welcome back John. I hope you had a great break. I can't believe we have had a record breaking SSW when you had your back turned! A lot of weather to look forward to.

Some pretty amazing classic warm propagation right down to the troposphere on show here.

And the 70 hPa level has joined the fun now

c

[Weather-history]

I notice the 30hpa temperature graph has a forecast rise after a dip

http://strat-www.met.fu-berlin.de/cgi-bin/...mps&alert=1

[Guest North Sea Snow Convection]

I think what John H says underlines what I rather clumsily tried to say yesterday in terms of suggesting the main impact of the MMW was not being directly attributable to the very cold snap of the last few days

The main effects of these are to come. Many of us hope that will involve the UK

Edited February 4, 2009 by North Sea Snow Convection

[johnholmes]

thanks C and T, not quite my back turned as I was able to log on most days, how sad, and check the latest outputs along with the views on here.

As I've just posted in the model thread I am quite convinced something will evolve from the Stratosphere events, and this current spell has little or nowt to do with it.

Its the first time I've returned to a white England (EMA anyway) froma skiing holiday.

Has anyone got any links that might show any similar events in the past?

[Guest North Sea Snow Convection]

A lot of similarity in sequence between how the vortex split at 10hPa in the Jan 85 event and now. The lowest point of negative zonal winds at 10hPa was about -20 m/s during the mid latter half of December. The surface cold spell hit around the first week or so of Jan following a two/three week or so propagation from the central MMW warming date (approx). It led to bitterly cold weather mid month with sub zero temps and heavy snow. Brighton -5C max around 13/14th Jan 85

Another illustration of how the timing of the present MMW in terms of tropospheric propagation looks good. I think the central warming date for this event was around 23 Jan? A look back of the pages will confirm.

The SSW website has an animated geop sequence from which I took this 'still' as an illustration of the almost identical vortex split pattern and sequence to this MMW.

www.appmath.columbia.edu/ssws

Except this is even stronger!

Edited February 4, 2009 by North Sea Snow Convection

[chionomaniac]

A lot of similarity in sequence between how the vortex split at 10hPa in the Jan 85 event and now. The lowest point of negative zonal winds at 10hPa was about -20 m/s during the mid latter half of December. The surface cold spell hit around the first week or so of Jan following a two/three week or so propagation from the central MMW warming date (approx). It led to bitterly cold weather mid month with sub zero temps and heavy snow. Brighton -5C max around 13/14th Jan 85

Another illustration of how the timing of the present MMW in terms of tropospheric propagation looks good. I think the central warming date for this event was around 23 Jan? A look back of the pages will confirm.

The SSW website has an animated geop sequence from which I took this 'still' as an illustration of the almost identical vortex split pattern and sequence to this MMW.

www.appmath.columbia.edu/ssws

Except this is even stronger!

You have beaten me to this!!!

I have looked back at every vortex split SSW in the records and this (1985) is the only one that comes close. However large differences still remain and the main conclusion I can draw is that no SSW is the same.

The main difference, besides the overwhelming strength and duration, that I have found is critically at the 100 hPa level. The pattern of split, strength of respective daughter vortices and pattern of reformation have important differences. In 1985 the main split was centered over the Pacific end leaving rejoining of the vortex over Greenland. The present one is almost a mirror image of that. Now I reckon that this has favourable sequelae keeping the main vortex as far away as possible, hopefully ultimately encouraging height rises at our end rather than the Pacific end.

Also worth noting that I would rather have a vortex split MMW than a vortex displacement MMW as the split will act in our favour (as it already probably has). Also no other SSW has come close in terms of easterly wind duration especially for January so we really are in uncharted waters here!

c

Edited February 4, 2009 by chionomaniac

[Guest North Sea Snow Convection]

You have beaten me to this!!!

I have looked back at every vortex split SSW in the records and this (1985) is the only one that comes close. However large differences still remain and the main conclusion I can draw is that no SSW is the same.

The main difference, besides the overwhelming strength and duration, that I have found is critically at the 100 hPa level. The pattern of split, strength of respective daughter vortices and pattern of reformation have important differences. In 1985 the main split was centered over the Pacific end leaving rejoining of the vortex over Greenland. The present one is almost a mirror image of that. Now I reckon that this has favourable sequelae keeping the main vortex as far away as possible, hopefully ultimately encouraging height rises at our end rather than the Pacific end.

Also worth noting that I would rather have a vortex split MMW than a vortex displacement MMW as the split will act in our favour (as it already probably has). Also no other SSW has come close in terms of easterly wind duration especially for January so we really are in uncharted waters here!

c

Very nice post

No SSW is going to be exactly the same as you say, but the placement of vortex split gives good cause for optimism. There was talk in the model thread this morning of a question mark wrt to height rises over Greenland.

It could be that in the upcoming modelling days 9/10 ish we see a mid latitude high with WAA to the west of it towards Greenland. This could be the trigger that produces initially a mid latitude high which transfers initially to Scandinavia/Iceland which then in turn retrogresses to Greenland as heights push out of the arctic in conjunction with the main thrust of the MMW arriving and the AO going strongly negative mid month. The placement of the vortex split should IMO mean that the latter height rises over Greenland should be achievable - in turn sustaining an initial cold shot from the NE.

Interesting to see if that is how the modelling works out up to mid month.

Edited February 4, 2009 by North Sea Snow Convection

[bluearmy]

Very nice post

No SSW is going to be exactly the same as you say, but the placement of vortex split gives good cause for optimism. There was talk in the model thread this morning of a question mark wrt to height rises over Greenland.

It could be that in the upcoming modelling days 9/10 ish we see a mid latitude high with WAA to the west of it towards Greenland. This could be the trigger that produces initially a mid latitude high which transfers initially to Scandinavia/Iceland which then in turn retrogresses to Greenland as heights push out of the arctic in conjunction with the main thrust of the MMW arriving and the AO going strongly negative mid month. The placement of the vortex split should IMO mean that the latter height rises over Greenland should be achievable - in turn sustaining an initial cold shot from the NE.

Interesting to see if that is how the modelling works out up to mid month.

that evolution has been a repeating trend in the ensembles, though not the majority view. i know steve isnt keen on a greeny height rise but i think we will end up there - lets hope its sooner rather than later.

[chionomaniac]

Still a negative forecast with easterly winds persisting.

Slight changes also in the 100 hPa forecasts which I will try and go through some time later.

c

[Gray-Wolf]

http://www.cpc.ncep.noaa.gov/products/intr...emp10anim.shtml

nice animation showing how dramatic the warming was at the 10hpa level.

Edited February 5, 2009 by Gray-Wolf

[Jack Wales]

nice animation showing how dramatic the warming was at the 10hpa level.

Yes indeed, also the warming event looks to continue for the forseeable future at mid and lower levels. This should serve to continue the meridonal flow of the jet stream

[chionomaniac]

http://www.cpc.ncep.noaa.gov/products/intr...emp10anim.shtml

nice animation showing how dramatic the warming was at the 10hpa level.

Yes, thanks for that GW. Pretty spectacular heh?