Stratosphere and Polar Vortex Watch 2020

[Mike Poole]

Quite some differences from run to run on the GFS and parallel.  The 12z parallel has the thing torn in two by T270:

[bluearmy]

2 hours ago, Mike Poole said:

Quite some differences from run to run on the GFS and parallel.  The 12z parallel has the thing torn in two by T270:

I don’t think we can view the parallel strat heights anywhere....

[Mike Poole]

2 minutes ago, bluearmy said:

I don’t think we can view the parallel strat heights anywhere....

No I don’t think so either, but as someone who takes a Bayesian view of the world, it is one more small piece of information to add to our knowledge base...

Edited December 25, 2020 by Mike Poole

[Windysun1]

9 hours ago, Catacol said:

A tough call, but I’d go for a fast downwell this time, so broadly speaking last third of January. Until then ongoing trop forcing is what will direct our weather - and a very disturbed and amplified trop it is. If that amplification sticks around until after mid month and then taps into the downwelling effects of the SSW then, with a lucky dice roll or two, we get the potential for proper intensification of the cold that is already looking to bed in. 

Thanks for reply. Quiet a complex science indeed.

[ALL ABOARD]

GFS and GFSP 

 

Poles apart? 

 

You would think the GFSP would have a better handle being the newer model? 

[Catacol]

1 hour ago, Windysun1 said:

Thanks for reply. Quiet a complex science indeed.

Yes. I have a gut feeling that we will get a split, but gut feelings aren’t what science is made of. However in my line of work interpreting circumstantial evidence goes with the territory and I’m comfortable making that call.

In the end, whether it splits or not, we are too far away from being able to make any judgement vv impacts with anything close to certainty. However I think we can probably rule out the wave 1 displacement over the Atlantic option - one that in the past has not worked well for us, because of the strength of flux energy coming from the Ural High. That flux can be seen very clearly here 

and so whatever is coming down the track with luck is not going to see the intact vortex core dumped 200m off the west coast of Ireland. Pot of gold scenario might be maintenance of the Greenland ridge, linking up to the east to some degree with the Ural ridge, and vortex energy dropping down through Siberia into mid latitudes. If we could get a reversal of more than a week as per 2018 then it would open some very interesting doors.....

 

Edited December 25, 2020 by Catacol

[Catacol]

17 minutes ago, ALL ABOARD said:

GFS and GFSP 

 

Poles apart? 

 

You would think the GFSP would have a better handle being the newer model? 

That GFSP near split, perhaps becoming a split, looks a decent end result for the U.K. - if it happens....

[ALL ABOARD]

25 minutes ago, Catacol said:

That GFSP near split, perhaps becoming a split, looks a decent end result for the U.K. - if it happens....

It splits let me tell you

Just strange to see them so far apart.

Perfect

[bluearmy]

Ec 00z day 10 ..... looks to be splitting although it doesn’t look to be quite the tech reversal we saw on yesterday’s noon run by day 10. 

 

also, the gfs - gefs/ecm/jma stand off continues re temp profile  at 10hpa and now becoming evident in a quite short time period 

can gfs really have this right ??.

[bluearmy]

9 hours ago, ALL ABOARD said:

It splits let me tell you

Just strange to see them so far apart.

Perfect

You would assume that would be a split but we can’t see the heights to be certain where the vortices sit .....

[iceman1991]

So are we going to have sudden strat warming ? 

[SteveB]

4 minutes ago, iceman1991 said:

So are we going to have sudden strat warming ? 

That's a good question,  it can be quite puzzling at times.

It would be nice to know what options are currently on the table,  and the potential ramifications on the ground. 

[bluearmy]

4 minutes ago, iceman1991 said:

So are we going to have sudden strat warming ? 

Yes but will it be a technical ssw ? (Isn’t the be all and end all btw)

will it lead to a displacement or a split of the spv?

Will it be sustained or will the vortex recover and even then, a weakly recovered spv will not interfere with trop patterns which may well maintain a cold outlook 

fwiw, those looking for an ssw to lead to screaming easterlies will probably need to see a fairly substantial reversal and I’m not convinced that’s currently showing up on the models. 

[Catacol]

Using Jan 7 as zero hour for now. Ellipse profile online today much less good for SSW than previous runs. Vortex buckled and skewed....but generally intact. 

[sebastiaan1973]

Plain Language Summary

Predicting climate anomalies more than 2 weeks ahead remains a challenging task. However, there are periods when climate is more predictable. In particular, it is known that in the wintertime Northern Hemisphere midlatitudes, climate may be more predictable during several weeks following sudden stratospheric warmings (SSWs), when a cold stratospheric polar vortex suddenly breaks and the stratosphere warms. In this article we evaluate quality of monthly forecasts by several up‐to‐date forecast systems during a sudden stratospheric warming observed in February 2018 focusing both on predictability of the stratospheric anomalies and on predictability of their surface impacts. We find that models predicted enhanced probability of sudden stratospheric warming at least 11 days before the observed event. Four days before the event it was forecast by all models with a very high certainty. We further show that successful prediction of the SSW required correct forecasting of anticyclonic anomaly over Ural and associated upward propagation of planetary‐scale atmospheric waves. The observed cold anomaly across Eurasia in February 2018 was predicted more than 2 weeks ahead although at this lead time the predictability was more likely associated with persistence of tropospheric anomalies in the forecast, with smaller downward influence of the stratospheric anomalies.

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Perhaps the difference between GFS and EC stratospheric speaking is the positioning of the Ural high.

[snowking]

12z ECM from yesterday still impressive:

 

Reversal at 1mb, Reversal at 30mb, near reversal at 10mb and poleward flux days 9 and 10.

[Singularity]

37 minutes ago, Catacol said:

Using Jan 7 as zero hour for now. Ellipse profile online today much less good for SSW than previous runs. Vortex buckled and skewed....but generally intact. 

Yeah - we really don’t want GFS to beat all of the other models on this one!

Main uncertainty now is how much wave-2 makes it to 10 hPa and whether that will be enough to widely split the polar vortex and facilitate a sufficiently strong reversal for a quick troposphere response, which tends to be within a week or so.

Otherwise, it appears flux will continue to periodically spike upward enough to maintain pressure on the polar vortex and perhaps produce a more lagged response of some kind, even if no technical SSW occurs. Probably a more displacement-style response if we go down that route.

[SqueakheartLW]

My daily update on ECM zonal wind speeds at different levels of the Stratosphere

As with the previous 2 updates we see a general decrease in zonal wind speeds as we progress from the latest figures out to day 10. By day 10 the ECM appears to have backed off the idea of zonal winds dropping right down at lower levels but is still going for the reversal higher up. We get a reversal right down to 10hpa on ECM today so a technical SSW then. At 1hpa we go to a very low -23m/s

It appears ECM is still on for a split of the vortex too with this 10 day chart at 10hpa

Another warming is appearing on the Atlantic side at the perfect moment here when the vortex is already stretched out by the first warming. This should be only headed one way from here, a split vortex.

GFS on the other hand appears to be sticking with more of a displaced vortex idea and most options are pushing it into a bad area for cold fans in the UK. Most of them are pushing it above the Atlantic, Greenland or east USA and that will only lead to one thing, a firing up of the Atlantic jet and the return of zonality to our part of the world whilst USA and Siberia get all of the cold and Europe heads into the winter furnace yet again.

However the good news from GFS is that in their extended range they are playing with the idea of another warming around the 10th or 11th of January. Below are the full selection of GFS 00z Op, Control and Ensembles that show this new warming

GFS 00z Operational Run                     GFS 00z Control Run                              GFS 00z Member 1

GFS 00z Member 2                                 GFS 00z Member 3                                GFS 00z Member 5

GFS 00z Member 6                                 GFS 00z Member 7                                GFS 00z Member 8

GFS 00z Member 10                              GFS 00z Member 12                               GFS 00z Member 13

GFS 00z Member 14                              GFS 00z Member 16                              GFS 00z Member 17

GFS 00z Member 18                              GFS 00z Member 19                              GFS 00z Member 21

GFS 00z Member 22                              GFS 00z Member 23                              GFS 00z Member 27

GFS 00z Member 28                              GFS 00z Member 29                              GFS 00z Member 30

As you can see, 24 or the 32 runs going for another warming so even if the displacement looks bad this other warming if it comes off could split or even finish off the weakened vortex.

A 75% chance of another warming event around the 10th or 11th of January if GFS has it right and if ECM has it right then a reversal and much more effective disruption or even destruction of the vortex around the 5th or 6th of January

The ECM is the quick route to the SSW and reversal whilst the GFS takes a bit longer to maybe get to the same outcome in the end

[bluearmy]

56 minutes ago, Catacol said:

Using Jan 7 as zero hour for now. Ellipse profile online today much less good for SSW than previous runs. Vortex buckled and skewed....but generally intact. 

Given gfs is so different to the other models, how reliable is its forecast data full stop ??.

[Duane S.]

20 minutes ago, snowking said:

12z ECM from yesterday still impressive:

 

Reversal at 1mb, Reversal at 30mb, near reversal at 10mb and poleward flux days 9 and 10.

I think you have the 10mb and 30mb forecasts mixed? I make it a technical SSW.  It does look that way at first glance on the chart you posted though!

Edited December 26, 2020 by s4lancia

[bluearmy]

8 minutes ago, s4lancia said:

I think you have the 10mb and 30mb forecasts mixed? I make it a technical SSW.  It does look that way at first glance on the chart you posted though!

Yes, too much Sherry for kris yesterday .......

[Bricriu]

20 hours ago, bluearmy said:

I’m not an expert but I am confident that none of the experts can answer either of your questions yet .....

I disagree about that. You post in this thread a lot and other posters often look to you for information on this subject. So there is no need for the false modesty.

I take your point that no one can say for certain what is going to happen at that stage.

[booferking]

Para looks decent split by day 10 like Ec.

Edited December 26, 2020 by booferking

[SqueakheartLW]

GFS 06z continues the theme of a displaced vortex around the 5th/6th January and also continues its idea of another warming taking place around the 10th/11th January. Here is the latest selection of new warming options from the 06z runs

06z GFS Operational Run                      06z GFS Control Run                             06z GFS Member 1

06z GFS Member 3                                 06z GFS Member 5                                06z GFS Member 7

06z GFS Member 8                                06z GFS Member 10                              06z GFS Member 11

06z GFS Member 12                               06z GFS Member 13                              06z GFS Member 14

06z GFS Member 15                              06z GFS Member 16                               06z GFS Member 18

06z GFS Member 19                              06z GFS Member 20                              06z GFS Member 22

06z GFS Member 23                              06z GFS Member 24                                06z GFS Member 25

06z GFS Member 26                               06z GFS Member 27                              06z GFS Member 30

Yet again just like with the 00z there are 24 out of 32 runs going for this new warming event. What is even better is that both of the higher resolution Operational and Control runs feature it too

Still maintaining this 75% chance of another warming around the 10th or 11th January. Lets see if this starts to come closer than the 350+ hours timeframe

[Allseasons-Si]