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Stratosphere and Polar Vortex Watch


Paul

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
1 minute ago, Glacier Point said:

and a hint on nodal propagation going on there ....

Is that good? Could you explain to us less learned what that means. cheers  

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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.
9 minutes ago, Glacier Point said:

and a hint on nodal propagation going on there ....

Also highlights the lack of immediate trop response following the start of the SSW.

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Posted
  • Location: st albans
  • Location: st albans

Ec op strat looking like it wants to put humpty back together post day 10 whereas gfs keeps a solid split 

berlin charts will be interesting in the morning, especially high up to see if consistency from previous output .....

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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL
6 minutes ago, bluearmy said:

Ec op strat looking like it wants to put humpty back together post day 10 whereas gfs keeps a solid split 

berlin charts will be interesting in the morning, especially high up to see if consistency from previous output .....

Dear me nothing is straightforward is it Blue..

its ironic because thats the 1st reasonable EC det in the trop for a while!

Edited by northwestsnow
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Posted
  • Location: Longden, Shropshire
  • Location: Longden, Shropshire
1 hour ago, northwestsnow said:

Dear me nothing is straightforward is it Blue..

its ironic because thats the 1st reasonable EC det in the trop for a while!

No it has been a nightmare!  At least the EC46 update is decent again tonight.

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Posted
  • Location: st albans
  • Location: st albans
10 hours ago, northwestsnow said:

Dear me nothing is straightforward is it Blue..

its ironic because thats the 1st reasonable EC det in the trop for a while!

Swings back better this morning and the removal of the split at 50hpa is only temporary on this run - also, the Canadian segment is going to become stronger over time .... will it become stronger than the Asian ??? 

8 hours ago, Don said:

No it has been a nightmare!  At least the EC46 update is decent again tonight.

Nightmares like this in dec/jan - happily have more please 

 

that arctic trop ridge at the back end of ec op is around a week behind the upper strat 

Edited by bluearmy
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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Second warming clearly evident currently over Siberia on Berlin/EC and GFS charts, though weaker wave 2 pulse compared to the stronger wave 1 pulse at tail end of December. Any recovery of the PV looking further compromised.

1DCB332F-2417-4EED-9C16-68493DE7EE8B.thumb.gif.bf6c8cb5c2349639f2c3e546f7eff4f3.gifE866D134-C569-4C1F-9518-30F2C5C2B051.thumb.png.6e2ad40710fec92f599c96a8cf402dea.png

FB25023E-3372-4A2C-BDD2-37196224E91B.thumb.gif.a340cd9ed37c777f53201bedc7cae46f.gif

The downward propagation of the easterly winds on yesterday’s EC looked rather underwhelming though, even by day 10, so still improvements in this area and why the operationals for z500 are underwhelming up to day 10 too. Thank goodness the weeklies, for now,  look like they are seeing the strat easterlies eventually coupling with the trop over NAO region to North Pole.

9C2103A5-261C-4EF7-A1DB-63F5AC9A82C4.thumb.gif.3cb3b0a4eb8708cbd41096f4f8459b4c.gif

 

 

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Posted
  • Location: Coniston, Cumbria 90m ASL
  • Weather Preferences: wintry
  • Location: Coniston, Cumbria 90m ASL
5 minutes ago, Nick F said:

Second warming clearly evident currently over Siberia on Berlin/EC and GFS charts, though weaker wave 2 pulse compared to the stronger wave 1 pulse at tail end of December. Any recovery of the PV looking further compromised.

1DCB332F-2417-4EED-9C16-68493DE7EE8B.thumb.gif.bf6c8cb5c2349639f2c3e546f7eff4f3.gifE866D134-C569-4C1F-9518-30F2C5C2B051.thumb.png.6e2ad40710fec92f599c96a8cf402dea.png

FB25023E-3372-4A2C-BDD2-37196224E91B.thumb.gif.a340cd9ed37c777f53201bedc7cae46f.gif

The downward propagation of the easterly winds on yesterday’s EC looked rather underwhelming though, even by day 10, so still improvements in this area and why the operationals for z500 are underwhelming up to day 10 too. Thank goodness the weeklies, for now,  look like they are seeing the strat easterlies eventually coupling with the trop over NAO region to North Pole.

9C2103A5-261C-4EF7-A1DB-63F5AC9A82C4.thumb.gif.3cb3b0a4eb8708cbd41096f4f8459b4c.gif

 

 

Yes Nick, spotted this the other day... https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=15.67,76.44,204/loc=64.206,64.893

Screenshot_20190108-080240.png

Edited by JeffC
Forgot to attach the pic!
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Posted
  • Location: St Albans, 95m asl
  • Location: St Albans, 95m asl
29 minutes ago, bluearmy said:

 - also, the Canadian segment is going to become stronger over time .... will it become stronger than the Asian ??? 

Therein remains my only concern - we have seen on a number of occasions in recent years modelling tendency to remove heights from the Greenland locale too readily

Now in all fairness, both seasonal and now weekly modelling have been fairly consistent in lower heights there until beyond mid Jan, followed by their swift removal, which we have seen happen in a number of the more memorable winter spells...but there’s still just that little voice at the back of my mind (I like to think of it as a miniature @nick sussex) telling me not to buy into it until we’re within at least 7 days.

I was also interested in your views @bluearmy on weeks 5/6 on the weeklies I saw you mention - from the brief glimpse I’ve caught of week 5 and 6 from Twitter, it looked like the risk of an increasingly west based negative NAO as time went on with the core of Greenland H500 heights sucked westwards - but you get to see far more of the suite than me, so hopefully that view is incorrect?

Edited by snowking
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Posted
  • Location: st albans
  • Location: st albans
17 minutes ago, snowking said:

Therein remains my only concern - we have seen on a number of occasions in recent years modelling tendency to remove heights from the Greenland locale too readily

Now in all fairness, both seasonal and now weekly modelling have been fairly consistent in lower heights there until beyond mid Jan, followed by their swift removal, which we have seen happen in a number of the more memorable winter spells...but there’s still just that little voice at the back of my mind (I like to think of it as a miniature @nick sussex) telling me not to buy into it until we’re within at least 7 days.

I was also interested in your views @bluearmy on weeks 5/6 on the weeklies I saw you mention - from the brief glimpse I’ve caught of week 5 and 6 from Twitter, it looked like the risk of an increasingly west based negative NAO as time went on with the core of Greenland H500 heights sucked westwards - but you get to see far more of the suite than me, so hopefully that view is incorrect?

Dw, for the time being, that Canadian lobe should stop a west base nao ... hints of the jet getting back towards the uk days 42/46 ......

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

When studying historical fully-downwelling SSWs, one thing that's clearly apparent is that after it's made it down, the reversed flow persists in the troposphere and lowest levels of the stratosphere for some weeks after the rest of the stratosphere has returned to a mean westerly state. Even if it's a strong one, which this time around it doesn't look to be.

So the stratospheric output above about 100 hPa becomes of little concern once the tropospheric reversal has been achieved. Hopefully we're within a couple of weeks of that point now, and GFS has just dropped the baton a bit out of error rather than spotting anything true.

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Posted
  • Location: Cardiff, Wales
  • Weather Preferences: Snow, Thunder & Lightning, Thundersnow, Storms, Heatwave
  • Location: Cardiff, Wales

You can see from this particular graphic on the MetOffice video that negative zonal winds propagate down to troposphere from I would say 20th or Jan or so gauging from the graph and stay negative for rest of winter even though positive winds return at the top. 

wonder if this is GloSea data?

 

5DDC7F4E-85ED-4892-BB89-52DD7BB2A728.png

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Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL
2 minutes ago, bradythemole said:

You can see from this particular graphic on the MetOffice video that negative zonal winds propagate down to troposphere from I would say 20th or Jan or so gauging from the graph and stay negative for rest of winter even though positive winds return at the top. 

wonder if this is GloSea data?

 

5DDC7F4E-85ED-4892-BB89-52DD7BB2A728.png

As part of my job I receive a farming update for Ireland and their latest weather update for the remainder of Winter and Spring points to below average temperatures across the Island from week three of January right out to the end of May, seems to back up that chart.

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Posted
  • Location: Milltimber, Aberdeen ~ 80m asl
  • Location: Milltimber, Aberdeen ~ 80m asl
7 minutes ago, bradythemole said:

You can see from this particular graphic on the MetOffice video that negative zonal winds propagate down to troposphere from I would say 20th or Jan or so gauging from the graph and stay negative for rest of winter even though positive winds return at the top. 

wonder if this is GloSea data?

 

5DDC7F4E-85ED-4892-BB89-52DD7BB2A728.png

Must be from GloSea as that is the only model that runs that far out. As you say, it is the duration of negativity that is an eye opener. Could be a modelling error but I wonder if previous SSWs had such a lasting impact. Back loaded winter looks odds on based on current data.

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3 hours ago, Singularity said:

When studying historical fully-downwelling SSWs, one thing that's clearly apparent is that after it's made it down, the reversed flow persists in the troposphere and lowest levels of the stratosphere for some weeks after the rest of the stratosphere has returned to a mean westerly state. Even if it's a strong one, which this time around it doesn't look to be.

So the stratospheric output above about 100 hPa becomes of little concern once the tropospheric reversal has been achieved. Hopefully we're within a couple of weeks of that point now, and GFS has just dropped the baton a bit out of error rather than spotting anything true.

How and where are you measuring this reversed tropospheric flow? It may be locally reversed associated with increased meridionality and quasi-stationary blocks but at 60°N for example, the longest continuous reversed mean 500mb zonal flow (1979-2014) in winter was 7 days up to 25/12/00, at 850mb 16 days up to 31/12/00 - there was no technical SSW at that time (close - u1060 down to ~2.8 m/s on 25/12/00).

Looking at 30-day mean zonal flow at 850mb, for January it has been negative in 2010, 2001, 1985, 2011 and 2013 - only 1985 followed an SSW (2013 was preceding).

In February negative 30-day mean in 1985, 2010, 1980, 1986, 2007, 1994, 1979. Of these 1985 and 2010 followed full SSW, though of course 2010 was already low as shown above.

Flow anomalies may be significant, but there isn't wholesale tropospheric reversal at 60°N as seen at 10mb. The predisposition and variability of the troposphere would appear to be more important.

Edited by Interitus
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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)
1 hour ago, Interitus said:

How and where are you measuring this reversed tropospheric flow? It may be locally reversed associated with increased meridionality and quasi-stationary blocks but at 60°N for example, the longest continuous reversed mean 500mb zonal flow (1979-2014) in winter was 7 days up to 25/12/00, at 850mb 16 days up to 31/12/00 - there was no technical SSW at that time (close - u1060 down to ~2.8 m/s on 25/12/00).

Looking at 30-day mean zonal flow at 850mb, for January it has been negative in 2010, 2001, 1985, 2011 and 2013 - only 1985 followed an SSW (2013 was preceding).

In February negative 30-day mean in 1985, 2010, 1980, 1986, 2007, 1994, 1979. Of these 1985 and 2010 followed full SSW, though of course 2010 was already low as shown above.

Flow anomalies may be significant, but there isn't wholesale tropospheric reversal at 60°N as seen at 10mb. The predisposition and variability of the troposphere would appear to be more important.

Ah right - it must have been zonal anomalies I was looking at then. I can't check for sure due to the partial shutdown of the U.S. Gov't but given what you say, I can't explain it otherwise!

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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.

Having enquired about the stall in propagation on Twitter ( see my feed) a couple of reasons were given by Ant Masiello.

One was the complex systems of vortices in the lower to mid strat preventing a clear downwell. The other was the primed state of the atmosphere derived from the tropics acting as an inhibitor to further downwell. With these removed then we have a clearer path.  And I also like to see a push from the upper strat in the form of recovery of u winds from the top..

see the 1hPa profile forecast. All good

AA7674CD-1F4E-429E-823A-A75801CD6D73.thumb.png.0c3d13d0b97ab161da75364b4cd9575d.png

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Posted
  • Location: Worcestershire
  • Weather Preferences: Forecaster Centaurea Weather
  • Location: Worcestershire
On 09/01/2018 at 16:56, chionomaniac said:

NH_TMP_10mb_384.thumb.gif.a52d17f53675e06f18b6a5c7e13ca738.gif

Absolutely want to see the upper strat u wind resume westerly to aid in flushing through the -u wind signal

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

It's funny how intuitive it all seems once you've found the answers to questions like that.

The reversal is achieved in the upper stratosphere. It can't realistically exist throughout the entire depth of the stratosphere at once, so a sign of downward propagation is a recovery of the zonal winds in the uppermost layers. Complications in the flow, horizontally and/or vertically, may then stall the propagation for a time, but in the meantime can further add to the positive GPH anomalies and - regionally - negative zonal wind anomalies, increasing the potential duration of the polar vortex disruption and zones of positively anomalous stratosphere-troposphere heights.

It strikes me as being the way to construct the most difficult to attain driver for one of the very longest periods of unusually cold, snowy conditions affecting wide swathes of the mid-latitudes. The other is of course co-operative tropical cycling... and today's model trends on that have been very positive .

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The GFS parallel has attracted some attention in recent runs with increased meridionality towards the end which can be seen with reversed tropospheric zonal flow at 60°N. However the interesting thing is that this is led from the troposphere to the strat as can be seen in this plot of zonal wind at various pressure levels -

894670882_zonalwindseriesfv319011000.thumb.png.8e8b621770ceb2149a74ccbb7c371496.png

There is a marked dip around Jan 22nd which propagates from the lower trop with a minimum at 30mb 51 hours later. This is not to say that the SSW hasn't potentially caused this in the first place, but concluding that these events are the result of SSW is fraught with uncertainty.

Edited by Interitus
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