Stratosphere and Polar Vortex Watch

[bluearmy]

I guess this isn’t the time to post that the latest ec strat isn’t as good as the earlier run .....slight changes but changes nevertheless ........ Atlantic a little more marked later on .....no need for any panic yet .....

[Bristawl Si]

4 minutes ago, bluearmy said:

I guess this isn’t the time to post that the latest ec strat isn’t as good as the earlier run .....slight changes but changes nevertheless ........ Atlantic a little more marked later on .....no need for any panic yet .....

Ties in with Meto latest, though. 

[Catacol]

Just spent some time playing with comparisons. The current warming is much more marked than the last one that successfully downwelled in 2013. The shape of things is also very different to what happened in Feb/March. Each warming unique.

However after scanning all angles the current prognosis looks pretty good. There is a strong suggestion of an arctic high that will cut through multiple layers, and with the bulk of the vortex displaced over Asia I see no thing other than favourable conditions for northern blocking to become established soon. We will need to see whether any vortex energy backs west to give a strong continental flow and precipitation. 

Tropical signal, despite ongoing uncertainty on the MJO, also good.

To be honest - all good.

[Don]

14 minutes ago, bluearmy said:

I guess this isn’t the time to post that the latest ec strat isn’t as good as the earlier run .....slight changes but changes nevertheless ........ Atlantic a little more marked later on .....no need for any panic yet .....

Feet kept firmly on the ground.......

[Catacol]

11 minutes ago, bluearmy said:

I guess this isn’t the time to post that the latest ec strat isn’t as good as the earlier run .....slight changes but changes nevertheless ........ Atlantic a little more marked later on .....no need for any panic yet .....

ECM for 11th Jan. Lower strat at 150hpa from today

Same layer from yesterday

Today's is better. Ridging stronger, average wind speeds lower. Today has a day's less signal degradation to deal with of course - but no downgrade at this 150hpa level.

Higher up at 30hpa today for 11th Jan

Yesterday it was

Very little difference. Vortex to me shunted a bit further off its axis and held back further east which is good, but average winds a touch higher.

Nothing concerning, and if anything I see it as an upgrade for disruption.

Obviously just a single snapshot which is of limited value I accept.

 

[bluearmy]

1 minute ago, Don said:

Feet kept firmly on the ground.......

Don’t forget that most of the good LR predictions had an active Atlantic jet piling into Iberia/France ..... wouldn’t expect to see nothing to our west 

[bluearmy]

Just now, Catacol said:

ECM for 11th Jan. Lower strat at 150hpa from today

Same layer from yesterday

Today's is better. Ridging stronger, average wind speeds lower. Today has a day's less signal degradation to deal with of course - but no downgrade at this 150hpa level.

Higher up at 30hpa today for 11th Jan

Yesterday it was

Very little difference. Vortex to me shunted a bit further off its axis and held back further east which is good, but average winds a touch higher.

Nothing concerning, and if anything I see it as an upgrade for disruption.

Obviously just a single snapshot which is of limited value I accept.

 

You’re looking at yesterday’s ec op 12z ..... look at Berlin in the morning to see what I’m referring to ..... not a huge difference but it’s a difference 

  

[Catacol]

2 minutes ago, bluearmy said:

You’re looking at yesterday’s ec op 12z ..... look at Berlin in the morning to see what I’m referring to ..... not a huge difference but it’s a difference 

  

Ah - you're a day ahead. OK - I'll check in the morning...though those 30 and 50 hpa charts look pretty damned good to me. Flow to the south is required.

[bluearmy]

Btw, I’m not a fan of days 8/10 and beyond operational strat charts below 30 hpa. I’ll just about take 50hpa. those below are good for seeing what pattern is influencing the trop but I don’t believe they are stable enough, run to run the further down in the strat you go. Just as you wouldn’t take 500 hpa ops beyond days 7/8 too literally. Are there any verification stats 100hpa and above ??

[bluearmy]

Just now, Catacol said:

Ah - you're a day ahead. OK - I'll check in the morning...though those 30 and 50 hpa charts look pretty damned good to me. Flow to the south is required.

Yes, they’re not bad at all .... just a small change from previous guidance ..... we are going to see a change in direction at some point and as I said earlier, some activity from our west is required to bring moisture if we get the n Atlantic blocking 

[MR EXTREMES]

14 hours ago, Catacol said:

And here's a better GFS 10hpa representation perhaps of that stormy undercut scenario that GFS is painting

That's a pretty good image if you ask me....provided you aren't after warm south westerlies that is.

no you are extremely right i see this chart yesterday and today i tend to agree in fact all your posts are very note worthy many thanks. 

[Blessed Weather]

9 hours ago, bluearmy said:

SNIPPED

Are there any verification stats 100hpa and above ??

The only info I could find was from a 2016 ECMWF newsletter that included a section on 'stratospheric forecast verification'. It appears to be the results of an exercise comparing one version of ECM against an updated version. The chart suggests that even by day 3 the model's verification has fallen away significantly at 10hPa:   

Link to newsletter: https://www.ecmwf.int/en/newsletter/149/meteorology/use-forecast-departures-verification-against-observations

[Interitus]

32 minutes ago, Blessed Weather said:

The only info I could find was from a 2016 ECMWF newsletter that included a section on 'stratospheric forecast verification'. It appears to be the results of an exercise comparing one version of ECM against an updated version. The chart suggests that even by day 3 the model's verification has fallen away significantly at 10hPa:   

Link to newsletter: https://www.ecmwf.int/en/newsletter/149/meteorology/use-forecast-departures-verification-against-observations

Here is their latest technical memorandum from October 2018 - "Evaluation of ECMWF forecasts, including the 2018 upgrade"

https://www.ecmwf.int/sites/default/files/elibrary/2018/18746-evaluation-ecmwf-forecasts-including-2018-upgrade.pdf

50 hPa verification to day 5 only.

Edited January 4, 2019 by Interitus

[Interitus]

Further to the above the ECMWF have created a "stratosphere task force" to improve forecasts - they have an in depth (very!) report from June 2018 with download link here -

https://www.ecmwf.int/en/elibrary/18259-report-stratosphere-task-force

An obvious challenge to start with is that verification is against observations which may have significant errors.

Less obvious is that increasing horizontal resolution degraded some performance -

Quote

Conclusions: The global-mean cold bias in the lower stratosphere (between 100 hPa and 50 hPa) was found to get worse as horizontal resolution increases. Such a sensitivity is surprising, but can be understood if the energy deposition from upward-propagating gravity waves is a significant contributor to the thermodynamic budget at these altitudes. Preliminary results suggest this is indeed the case, at least for the IFS. The problem does get better as vertical resolution increases, and 200 m vertical resolution in this region (via L198) seems to be enough to eliminate the difference in bias between TCo199 and TCo1279. Already 250 m (via L162) considerably improves the problem, and would avoid having to retune the physics in the troposphere. Further investigation of this issue is warranted. More generally, it would be timely to revisit the classic study of Lindzen and Fox-Rabinovitz (1989) concerning vertical resolution requirements, in view of the latest horizontal resolutions affordable with the IFS.

 

[lorenzo]

3 hours ago, Interitus said:

Further to the above the ECMWF have created a "stratosphere task force" to improve forecasts - they have an in depth (very!) report from June 2018 with download link here -

https://www.ecmwf.int/en/elibrary/18259-report-stratosphere-task-force

An obvious challenge to start with is that verification is against observations which may have significant errors.

Less obvious is that increasing horizontal resolution degraded some performance -

 

Thank you for the bedtime reading @Interitus 

What's your take statistically on duration of the reversal and how it compares to other split events.. GEFS hints at continuation to circa 20th, whereas heading back to mean westerly u earlier in Berlin this morning. How does this event stack up vs. the others? Any cool graphs to hand?

As per tweet - not sure what the vortex has to be smiling about right now!

Edited January 4, 2019 by lorenzo

[Catacol]

14 hours ago, bluearmy said:

You’re looking at yesterday’s ec op 12z ..... look at Berlin in the morning to see what I’m referring to ..... not a huge difference but it’s a difference 

  

Berlin chart always makes more sense to me - can see the greater westerly impact at 150hpa today. GFS extended at 30hpa still sees an arctic high extend down to Iceland before retreating slightly and letting the US and Asian vortex remnants regather - but it is a pretty weak regathering and HP stays over the pole. Direction of travel still good, but I'd not want to see this chart get any more westerly tomorrow!

[bluearmy]

@Catacol 00z ec op broadly similar at 30/50 hpa - could be argued a little better if anything 

certainly 10hpa is better with the three vortex split as previous guidance 

[mountain shadow]

25 minutes ago, Catacol said:

Berlin chart always makes more sense to me - can see the greater westerly impact at 150hpa today. GFS extended at 30hpa still sees an arctic high extend down to Iceland before retreating slightly and letting the US and Asian vortex remnants regather - but it is a pretty weak regathering and HP stays over the pole. Direction of travel still good, but I'd not want to see this chart get any more westerly tomorrow!

Catacol, if this was mirrored at the surface would it not indicate a fairly potent North to North Westerly airstream? Sure, not great for widespread snow in the South but decent for more North and North Westerly areas?

[Skyraker]

26 minutes ago, mountain shadow said:

Catacol, if this was mirrored at the surface would it not indicate a fairly potent North to North Westerly airstream? Sure, not great for widespread snow in the South but decent for more North and North Westerly areas?

I don't think it quite works like that.

You can't just colour in the troposphere the same as the strat.

This thread ain't painting by numbers, so I should heed my own advice and let those that know continue to post in here.

[mountain shadow]

29 minutes ago, Skyraker said:

I don't think it quite works like that.

You can't just colour in the troposphere the same as the strat.

This thread ain't painting by numbers, so I should heed my own advice and let those that know continue to post in here.

I'll post whenever and where ever I like thanks very much.

I know perfectly well that you cannot always match the strat to the trop but that chart is 150hpa so much nearer the trop than 10hpa for example and therefore more likely to imprint itself on the trop.

[lorenzo]

Some charts from GEOS for the point in question, although caveats being 10 days out for 100hPa and given state of events unfolding and discussions around verification - subject to change.

FWIW - perhaps not has potent as Berlin would suggest and looks quite 'slidey'.

[Catacol]

1 hour ago, mountain shadow said:

Catacol, if this was mirrored at the surface would it not indicate a fairly potent North to North Westerly airstream? Sure, not great for widespread snow in the South but decent for more North and North Westerly areas?

In a word - yes. But exactly mirrored is unlikely. It provides guidance only at 500 and 850hpa, and the trend is for heights to the NW and not a trough. A signal maybe for transient NW support, but I'd emphasise transient. And previous runs had less of a westerly component. Tropospheric forcing is also pushing heights.

[Interitus]

6 hours ago, lorenzo said:

What's your take statistically on duration of the reversal and how it compares to other split events.. GEFS hints at continuation to circa 20th, whereas heading back to mean westerly u earlier in Berlin this morning. How does this event stack up vs. the others?

A few from MERRA (1) data -

18/01/03 1 day

09/02/10 3 days

24/03/10 3 days

01/01/85 5 days

22/02/79 8 days

08/12/87 9 days

21/02/89 9 days (initially - after 5 day break another 15 days)

11/02/01 14 days

12/02/18 17 days

26/02/99 21 days

06/01/13 22 days

24/01/09 29 days

 

Edit: as mentioned previously and as tweeted below, this is not a typical split though, it is a displacement / wave 1 event.

Edited January 4, 2019 by Interitus

[Summer Sun]

 

[WINTRY WALES]

I take it these 2 don’t see this SSW being favourable for us if it’s cold you are after?