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Stratosphere and Polar Vortex Watch


Paul

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Posted
  • Location: Hadleigh, Suffolk
  • Weather Preferences: An Alpine climate - snowy winters and sunny summers
  • Location: Hadleigh, Suffolk
22 hours ago, Interitus said:

It is simplified - the need for westerly winds is for the vertical propagation of planetary waves (and then not too strong which limits propagation also as seen during the middle of the SH winter). The mean easterly wind field at 10 hPa for example doesn't tend to descend en masse through the strat into the troposphere at 60°N. At 150 hPa the mean zonal wind very rarely becomes easterly during winter, and then only marginally -

u15060.thumb.png.78d9b19d2555ba9d386a7c61d502d690.png

In the MERRA data it has done so in the 45 days following SSW on 3 occasions and on one of those it had already been easterly in the days preceding the SSW.

The zonal flow anomalies represent perturbation of mean flow which tends to be regionalised i.e. through the geopotential height field of the waves and associated geostrophic wind, and when the perturbations become well aligned then the zonal wind anomalies can appear to descend, but also ascend of course.

 

 

Thanks for that Interitus. It's interesting that the reversed zonal winds at 60N rarely propagate down below 150hPa. And as you say, to be noted is that any zonal mean wind speed measure is (as the name states) a mean of the winds at that latitude around the globe and there will be regional variances from the mean.

But that wasn't what I had in mind with the musings in my post. I had in mind the downward propagation more generally at higher latitudes, as nicely shown by the ECM ZMZW chart from last February's SSW which shows the reversed winds from the top of the stratosphere to the bottom of the troposphere from 70N to the Pole. A chart of beauty if you want a negative AO and lots of high latitude blocking:

1182369659_ECMZMZW17Feb2018marked.thumb.jpg.3583537bdf9b1eed00860808947b4fdc.jpg

It's good to see that yesterday's (28th Dec) ECM for 7th Jan is a marked improvement in this respect, not quite as good as last Feb's but plenty good enough for high latitude blocking opportunities I would suggest? Here's the charts for 28th Dec and 7th Jan highlighting the progress:

635648207_ECMZMZW28Dec2018.thumb.gif.08bc96ec75950f1efa064b4e39bc63aa.gif52370006_ECMZMZW07Jan2019.thumb.gif.a77e9b28d0d7f318ab593b15c09c7dba.gif

Just a final question please. Is there a better (or alternative) chart available for showing downward propagation of a SSW?

Charts Berlin University. Click on latest date and look for Zonal Wind.

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

 

 

Edited by Blessed Weather
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Posted
  • Location: Slovenia (Maribor)
  • Location: Slovenia (Maribor)
31 minutes ago, Blessed Weather said:

Just a final question please. Is there a better (or alternative) chart available for showing downward propagation of a SSW?

There actually is, the webpage is called weatheriscool. You can find many interesting things there, in terms of stratosfere, troposfere that page is based on GFS weather model.  You can also find some CFS zonal charts there on the graph.

http://weatheriscool.com/index.php/stratosfaren-zonal-mean-u-wind-60n-vcs/

Edited by Redbull165
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Posted
  • Location: Hadleigh, Suffolk
  • Weather Preferences: An Alpine climate - snowy winters and sunny summers
  • Location: Hadleigh, Suffolk

This tweet from yesterday also helpful in explaining the ZMZW charts:

2018887630_ECMcouplingtweet28Dec.thumb.jpg.04d4c27d57fcf9d6c373b6f50a7cf9c0.jpg

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Posted
  • Location: Cwmbran. South East Wales 300ft ASL
  • Location: Cwmbran. South East Wales 300ft ASL
33 minutes ago, Blessed Weather said:

Thanks for that Interitus. It's interesting that the reversed zonal winds at 60N rarely propagate down below 150hPa. And as you say, to be noted is that any zonal mean wind speed measure is (as the name states) a mean of the winds at that latitude around the globe and there will be regional variances from the mean.

But that wasn't what I had in mind with the musings in my post. I had in mind the downward propagation more generally at higher latitudes, as nicely shown by the ECM ZMZW chart from last February's SSW which shows the reversed winds from the top of the stratosphere to the bottom of the troposphere from 70N to the Pole. A chart of beauty if you want a negative AO and lots of high latitude blocking:

1182369659_ECMZMZW17Feb2018marked.thumb.jpg.3583537bdf9b1eed00860808947b4fdc.jpg

It's good to see that yesterday's (28th Dec) ECM for 7th Jan is a marked improvement in this respect, not quite as good as last Feb's but plenty good enough for high latitude blocking opportunities I would suggest? Here's the charts for 28th Dec and 7th Jan highlighting the progress:

635648207_ECMZMZW28Dec2018.thumb.gif.08bc96ec75950f1efa064b4e39bc63aa.gif52370006_ECMZMZW07Jan2019.thumb.gif.a77e9b28d0d7f318ab593b15c09c7dba.gif

Just a final question please. Is there a better (or alternative) chart available for showing downward propagation of a SSW?

Hi BW

Sorry for a dumb question but where can I view those charts you have posted??

Cheers

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Posted
  • Location: Hadleigh, Suffolk
  • Weather Preferences: An Alpine climate - snowy winters and sunny summers
  • Location: Hadleigh, Suffolk
4 minutes ago, WINTRY WALES said:

Hi BW

Sorry for a dumb question but where can I view those charts you have posted??

Cheers

Apologies. I forgot the links; now added to post above.

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Posted
  • Location: Burton-on-Trent (90m), Larnaka most Augusts
  • Location: Burton-on-Trent (90m), Larnaka most Augusts
13 minutes ago, lorenzo said:

That's a split

ecmwfpv475f192.thumb.gif.96559e73842ce5c468951849d41742cd.gif

Technical SSW for 01 Jan and continues until end of the run where we continue to see warming artefacts in play vs the parent vortex.

ecmwf10f96.thumb.gif.1bdc9b494857c799f0ff215be54e0086.gif

ecmwf10f240.thumb.gif.a38f34b586fc695fa7adaa1f57db50e2.gif

Can't recall seeing a W2 plot like this in terms of its progression to here on this run. Looks odd.

ecmwfzm_ha2_f216.thumb.gif.4f49c8c08a163ee9f06f82e8bf00dc35.gif

Interesting output ahead...especially with MJO about to join in the fun..

That wave-2 graph is really dissapointing compared to yesterday. That is a huge change too, what could have caused that?

 

ecmwfzm_ha2_f240.gif

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Posted
  • Location: Netherlands close to the coast
  • Location: Netherlands close to the coast
14 minutes ago, lorenzo said:

That's a split

ecmwfpv475f192.thumb.gif.96559e73842ce5c468951849d41742cd.gif

Technical SSW for 01 Jan and continues until end of the run where we continue to see warming artefacts in play vs the parent vortex.

ecmwf10f96.thumb.gif.1bdc9b494857c799f0ff215be54e0086.gif

ecmwf10f240.thumb.gif.a38f34b586fc695fa7adaa1f57db50e2.gif

Can't recall seeing a W2 plot like this in terms of its progression to here on this run. Looks odd.

ecmwfzm_ha2_f216.thumb.gif.4f49c8c08a163ee9f06f82e8bf00dc35.gif

Interesting output ahead...especially with MJO about to join in the fun..

EC is taking mjo into the cod though instead of phases 7-1

 

ECMF_phase_51m_full.gif

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Posted
  • Location: Slovenia (Maribor)
  • Location: Slovenia (Maribor)

Is that the first sign of downward propagation that I see on this GFS zonal wind chart. What I mean with downward propagation is when the effect of weaker zonal winds is seen below the 200 hPa area in the troposfere. And some of that might now be seen, starting around the second dekade of january 2019. What do you think, am I missing something here? It might be also the case that its just one run, and the new one will change that, but it doesnt look that bad at all.

Situation now.

01.thumb.png.3f98fbe93a6e804fe07b8a8ee69b6d30.png

And the zonal winds (with EP flux) on 13.1.

30.thumb.png.7cd52da8b3e804a4042d4fa3277aacc3.png

Edited by Redbull165
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Posted
  • Location: st albans
  • Location: st albans
7 minutes ago, Snowy L said:

That wave-2 graph is really dissapointing compared to yesterday. That is a huge change too, what could have caused that?

 

ecmwfzm_ha2_f240.gif

Less interesting at the top - certainly and the new 00z run is similar with the split higher up not as large as that fri 00z run 

the better activity lower down is the other side of that coin and as the trop delivers our actual weather, I’m ok with it ! 

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

Regarding the much less impressive upper-level wave-2 days 9-10, could it be that when downwelling occurs, the patterns associated with the wave-2 are mostly wiped out by the processes involved in the downward propagation? 

As far as I understand it, a normal feature of downward-propagating SSWs is a recovery of the polar vortex at the highest levels of the stratosphere immediately afterward. It then comes down to the blocking response patterns as to how long the lower stratosphere can sustain negative zonal wind anomalies via trop-strat interactions sustaining a disconnect between the upper and lower stratosphere. While we were seeing those major impacts late Feb this year, I remember noticing that the vortex at 1 hPa was quite organised and intense. Not that my memory is faultless, mind...!

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Posted
  • Location: st albans
  • Location: st albans
1 hour ago, sebastiaan1973 said:

Why aint Fawkes discuss the downwelling from EC of last night? Cherry picking. 

Maybe the eps agree with gefs ? 

12z gefs look to be allowing downwelling above 70N/75N 

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Posted
  • Location: Cwmbran. South East Wales 300ft ASL
  • Location: Cwmbran. South East Wales 300ft ASL

I think Chris Fawkes is about as welcolm in his thinking as his brother guy is in the Houses of Parliament 

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

The NAM in the lower levels is a lot less positive than it was as of 12z GFS yesterday. Doesn't look like it's going to take much more adjustment in the negative (zonal wind) direction.

As for Chris Fawkes, well I hate to agenda-assign but honestly, having kept an eye on his tweets for a number of years now, he does seem to favour whatever model output suggests milder rather than colder outcomes up to the point that they cease to exist... but hey, maybe it's just extreme caution... who can say for sure?

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Posted
  • Location: Netherlands close to the coast
  • Location: Netherlands close to the coast
10 hours ago, Singularity said:

The NAM in the lower levels is a lot less positive than it was as of 12z GFS yesterday. Doesn't look like it's going to take much more adjustment in the negative (zonal wind) direction.

As for Chris Fawkes, well I hate to agenda-assign but honestly, having kept an eye on his tweets for a number of years now, he does seem to favour whatever model output suggests milder rather than colder outcomes up to the point that they cease to exist... but hey, maybe it's just extreme caution... who can say for sure?

Today's Berlin's charts from ec looks a bit worse though

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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL
7 minutes ago, ArHu3 said:

Today's Berlin's charts from ec looks a bit worse though

They look better in the trop though

Edited by northwestsnow
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Posted
  • Location: st albans
  • Location: st albans

I don’t spend a lot of time looking at the Berlin data at 1hpa except in times like this ...... not sure I ever recall that level looking as unstable/inconsistent as it has been the past few days ......... it’s usually the one place where things move at an expected fairly sedate pace, day by day. 

as others have noted, the downwelling on yesterday’s op doesn’t get down to the trop by day 10. Similar look to the gfs 00z run. 

decent split maintained on the updated ec op strat data, especially further down, whilst we retain the 3 vortex centres at 10hpa as per yesterday’s run, with the Canadian daughter more defined than the previous run in this regard. 

A3BBC580-E29B-4E6D-8D9E-3085FAD1BEC8.thumb.jpeg.75ae01b96eef22c3a8c3238c14322461.jpeg

Edited by bluearmy
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Posted
  • Location: Cambridge, UK
  • Weather Preferences: Summer > Spring > Winter > Autumn :-)
  • Location: Cambridge, UK
14 hours ago, sebastiaan1973 said:

Why aint Fawkes discuss the downwelling from EC of last night? Cherry picking. 

He’s hoping this ssw fails so he can say I told you so about his prediction of a mild and wet January. If people like dr ventrice and strat experts like dr Amy butler still don’t know what’s happening, I wouldn’t be too worried. Looks ok to me.

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Posted
  • Location: Poole, BH14
  • Location: Poole, BH14

The temperature at 10hPa over the North pole seems a bit higher than expected, closing in to -10C whereas models only expected the peak temps in the North Pole to be around -20C. I take it this is good news? 

FB_IMG_1546164403030.jpg

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