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Posted
  • Location: Ribble Valley
  • Location: Ribble Valley

This begs the question why there? Why not over Scandinavia? Why not over east Siberian?

I'm wondering whether or not it's a result of the Pacific Ocean, a shot in the dark I know.
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Posted
  • Location: hertfordshire
  • Location: hertfordshire

According to this paper on snow cover in the Autumn and the formation of

the Siberian High warmings can take place later on in the Autumn and through

the winter especially if snow is more abundant promoting a larger and stronger

high pressure cell.

http://www.nws.noaa.gov/ost/climate/STIP/FY11CTBSeminars/jcohen_062211.pdf

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

This begs the question why there? Why not over Scandinavia? Why not over east Siberian?

It's to do with the size of landmass and oceanic feedback. The polar vortex tends to reform in two cores during Autumn over the cooling landmasses of Siberia and North America. Without further research, ( I looked at this in a lot more depth a few years ago and have sadly forgotten the details) the positioning of the warmer areas in some years over the Canadian segment, is due to the larger dominant Siberian vortex segment 'dragging' the weaker Canadian vortex segment into it as it becomes one, creating a weakness in the surf zone in the void. Warming occurs in the 'void'. To a more or less extent this occurs most years but is less significant in some.

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

This will need watching in the coming weeks.

Keep low please.

http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra/u60n_10_2012_merra.pdf

http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra/u60n_30_2012_merra.pdf

The zonal wind mean anomalies are starting below average - it doesn't mean much yet..........

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Posted
  • Location: Isle of Lewis
  • Weather Preferences: Sun in summer, snow in winter, wind in Autumn and rainbows in the spring!
  • Location: Isle of Lewis

See that black line running along the bottomof the second graph, which year does that represent?

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

See that black line running along the bottomof the second graph, which year does that represent?

It,s the mean lots.

Interestingly, if you were to take out SSW's the true mean would be a lot higher - so average winter vortex conditions are a little bit higher than the mean suggests taking this into account.

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Posted
  • Location: @scotlandwx
  • Weather Preferences: Crystal Clear High Pressure & Blue Skies
  • Location: @scotlandwx

Another exciting chart C, it's like a Stratospheric teaser advert for winter..

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

Another exciting chart C, it's like a Stratospheric teaser advert for winter..

Yes, though sadly low mean zonal winds will encourage blocking in the coming weeks - though this could change by winter as last year showed.

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Posted
  • Location: Redhill, Surrey
  • Weather Preferences: Southerly tracking LPs, heavy snow. Also 25c and calm
  • Location: Redhill, Surrey

Yes, though sadly low mean zonal winds will encourage blocking in the coming weeks - though this could change by winter as last year showed.

Indeed as the 11/12 line shows it can rise. Still its a start. Should be a v good year again in this thread and hopefully a stratos that plays ball. BFTP

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Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl

Yes, though sadly low mean zonal winds will encourage blocking in the coming weeks - though this could change by winter as last year showed.

Every now and again I shake my head at my incompetence... but why is this "sadly"? Does blocking at this time of year reduce the chances of SSW later on?

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

Every now and again I shake my head at my incompetence... but why is this "sadly"? Does blocking at this time of year reduce the chances of SSW later on?

No I realise that it is misplaced!

Sad in the fact that it is not later in the season.

Apologies!

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Posted
  • Location: Knowle, Solihull - 400ft (122m) ASL
  • Location: Knowle, Solihull - 400ft (122m) ASL

I just love this thread - I found it absolutely fascinating reading last winter, which was the first time I'd followed it properly. Thank you Chio and all of the other regular contributors for sharing your knowledge with the rest of us.

Bish

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

I just love this thread - I found it absolutely fascinating reading last winter, which was the first time I'd followed it properly. Thank you Chio and all of the other regular contributors for sharing your knowledge with the rest of us.

Bish

Cheers BB. I am tempted to open a new thread this weekend as we are now talking about the forthcoming season.

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Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl

No I realise that it is misplaced!

Sad in the fact that it is not later in the season.

Apologies!

Ah - thank you. :-) I feel happier now - good not to be a total amateur. I guess you are right though - would be asking a lot to have blocking in place solidly from October to March, so would rather see October more zonal, with blocking then creeping onto the radar by late November onwards.

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Posted
  • Location: Longden, Shropshire
  • Location: Longden, Shropshire

Cheers BB. I am tempted to open a new thread this weekend as we are now talking about the forthcoming season.

And why not? Seeing as the Winter 2012/13 thread is already so active!

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Posted
  • Location: Barnoldswick, Lancs, 500ft
  • Location: Barnoldswick, Lancs, 500ft

I'll creep back out of the summer woodwork to reiterate the usefulness of this kind of discussion and the information presented within it. I look forward to the early discussions in the new thread and as is often the case, here's hoping the polar vortex/zonal winds et al are all playing ball early on in the season, as otherwise as we found out last year, the rest of this year could be particularly infuriating...

In summary from what i've looked at of late on my blog, the early signs are all half decent towards a more blocked winter, but clearly that doesn't mean another 09/10 winter is on the cards and the importance of the strat conditions will no doubt be a front-runner as to how we end 2012 and start yet another winter season. Also in my opinion, getting the right synoptics earlier on in the winter season are better than late on. Clearly 09/10 was a prime, stunning example of that scenario. Whilst late winter can often deliver some interesting wintry weather, again, in my opinion, the best time for it is from late November until the end of January at the latest.

Cheers, Matt.

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Posted
  • Location: Longden, Shropshire
  • Location: Longden, Shropshire

In summary from what i've looked at of late on my blog, the early signs are all half decent towards a more blocked winter, but clearly that doesn't mean another 09/10 winter is on the cards and the importance of the strat conditions will no doubt be a front-runner as to how we end 2012 and start yet another winter season. Also in my opinion, getting the right synoptics earlier on in the winter season are better than late on. Clearly 09/10 was a prime, stunning example of that scenario. Whilst late winter can often deliver some interesting wintry weather, again, in my opinion, the best time for it is from late November until the end of January at the latest.

Cheers, Matt.

I think that an 09/10 type winter would perhaps be asking a bit much this year as that was unusual. However, I feel we could be in with a fair chance of having a winter similar to that of 1990/91 or 1995/96? Cold, but not exceptionally so.

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Posted
  • Location: hertfordshire
  • Location: hertfordshire

I think that an 09/10 type winter would perhaps be asking a bit much this year as that was unusual. However, I feel we could be in with a fair chance of having a winter similar to that of 1990/91 or 1995/96? Cold, but not exceptionally so.

There was nothing exceptional about the winter of 2009/10 really except the negativity of the AO.

The winter overall could only be classed as cold. If it had been severe or worse (thinking of 79 or

colder) then it could of been classed exceptional perhaps. The thing about the winter of 2009/10

is that we were on the cusb of seeing a exceptionally cold winter with all the norherly blocking that

took place and in the end I think the UK got off quite lightly, although Scotland saw some prolonged

severe weather in December.

It would be lovely to see that sort of blocking again this winter although you do not need blocking

that extreme to see a similar cold or colder winter than 09/10.

February can certainly delivery the goods. In past winters you could see some of the coldest,

wintriest weather during the month with prolonged freezes (1947anyone) although we have not seen

a very cold February for a long time and upper air temps have to be that bit colder than in December

or January.

As far as the stratosphere and vortex are concerned I often wonder what is better a strong vortex that

is ideally placed for northern blocking to have maximum effect on the UK and Europe(ie somewhere like

Hudson Bay or slightly further south. But then you run the risk of the vortex becoming overpowering and

a westerly zonal +AO results. The other option being for a much weaker vortex that is continually being

pulled apart but then although you may have plenty of northern blocking the broken off segments of

vortex act as spoilers stopping a proper classical cold spell (freeze) from developing.

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Posted
  • Location: Ribble Valley
  • Location: Ribble Valley

There was nothing exceptional about the winter of 2009/10 really except the negativity of the AO.

The winter overall could only be classed as cold. If it had been severe or worse (thinking of 79 or

colder) then it could of been classed exceptional perhaps. The thing about the winter of 2009/10

is that we were on the cusb of seeing a exceptionally cold winter with all the norherly blocking that

took place and in the end I think the UK got off quite lightly, although Scotland saw some prolonged

severe weather in December.

It would be lovely to see that sort of blocking again this winter although you do not need blocking

that extreme to see a similar cold or colder winter than 09/10.

February can certainly delivery the goods. In past winters you could see some of the coldest,

wintriest weather during the month with prolonged freezes (1947anyone) although we have not seen

a very cold February for a long time and upper air temps have to be that bit colder than in December

or January.

As far as the stratosphere and vortex are concerned I often wonder what is better a strong vortex that

is ideally placed for northern blocking to have maximum effect on the UK and Europe(ie somewhere like

Hudson Bay or slightly further south. But then you run the risk of the vortex becoming overpowering and

a westerly zonal +AO results. The other option being for a much weaker vortex that is continually being

pulled apart but then although you may have plenty of northern blocking the broken off segments of

vortex act as spoilers stopping a proper classical cold spell (freeze) from developing.

IMBY 2009/10 was the better of the last 3 winters and after 63 and 79 one of the best. Both December and January brought sustained cold and lying snow, and even in February we had 3 worthy snow events.
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Posted
  • Location: Worcestershire
  • Weather Preferences: Forecaster Centaurea Weather
  • Location: Worcestershire

If I could throw this one into the mix..

Over the last two seasons I've started to look at stratospheric profile going into a winter / summer on the basis that stratospheric variables are less complicated than tropospheric ones, and, are reasonably predicatable given assumptions made about the QBO / solar modulation - but are likely to represent a significant influence on phasing of the AO.

So looking at this, we have an east QBO at approaching solar maxima. This is not a 'regular' solar maxima though, with persistent low levels of planetary p index and much lower flux at the relative point of the cycle. Last winter behaved just like an east QBO and solar maxima should do though, with a well defined cold vortex event although the La Nina over the previous 24 months may have also contributed to this. Interestingly, the southern hemisphere has endured a very similar QBO / stratospheric scenario to the previous boreal winter with a solidly positive AAO.

But, how do east QBOs interact with the solar signal when the east phase extends over two winters as this one will likely do ?

Looking at the current profile of zonal winds at 30 hPa, I could only find one similar match over the last 6 months.

The previous 6 months..

post-2478-0-73937700-1348951814_thumb.jp

Analogue year is 1968.

post-2478-0-14347100-1348951778_thumb.jp

1968 is interesting, as it almost perfectly matches the autumn start to the east QBO phase, strengthening into the winter and summer, weakening into the second winter.

During 1968, the upper level zonal winds reversed at 40N from east to west around the 13th September. During 2012, around the 20th September. The relative solar flux and position within the cycle will be similar to that this year, so a useful predictor perhaps ?

Looking at what might lie ahead, zonal winds at 30 hPa using 1968 suggest a generally weak westerly flow with several bouts of reversals potentially indicative of blocking.

post-2478-0-59548500-1348951794_thumb.jp

As an anomaly, we see just how weak the stratospheric vortex was during 1968/9. Note the persistent winter -ve zonal wind anomaly there.

post-2478-0-16480600-1348951831_thumb.jp

Edited by Glacier Point
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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

Stu IF this winter, as you seem to be inferring is similar let alone identical to 1968/9 it does not prove anything if we look at things scientifically would you not agree?

How many factors that are present now were present at the same time in 1968?

Equally how many factors were not present in 1968 that are present now?

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Posted
  • Location: Ireland, probably South Tipperary
  • Weather Preferences: Cold, Snow, Windstorms and Thunderstorms
  • Location: Ireland, probably South Tipperary

If I could throw this one into the mix..

Very interesting GP.

1968 was the solar cycle after the strongest on record that peaked in '59, with the solar minimum in the few years before 68 being much higher than this time round. How do you think that may change things this year?

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Posted
  • Location: Headington,Oxfordshire
  • Weather Preferences: Snow
  • Location: Headington,Oxfordshire

Just had a read through some of the last few pages and am finding this thread very interesting, will be close watching over the coming week's. Keep up the good work guys! good.gif

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