Stratosphere and Polar Vortex Watch

[Catacol]

9 minutes ago, feb1991blizzard said:

Got a feeling going by the models that there will be an SSW but not sure on the type which could be important, i just think the GEFS / GFS may be a bit early with it, i reckon a technical SSW but no earlier than 15th December.

Agree broadly. Wave 2 followed by wave 1 and then a final wave 2 for the knockout blow. Perhaps a little later than Dec 15 - final third for me. First piece in a complex puzzle perhaps....

[feb1991blizzard]

Just now, Catacol said:

Agree broadly. Wave 2 followed by wave 1 and then a final wave 2 for the knockout blow. Perhaps a little later than Dec 15 - final third for me. First piece in a complex puzzle perhaps....

Yes 15th at the very earliest i meant, i would have more confidence in my forecasts though if i could see the old GFS op, anyway would love to see your wave 2 come true - split from Pacific straight through Greenland into the Atlantic with a huge gap and the Canadian chunk pushed right out the way please.

[knocker]

The ecm temp anomaly at 10mb t240

[mountain shadow]

1 hour ago, knocker said:

The ecm temp anomaly at 10mb t240

I'm not exactly sure what a Strat Canadian warming is supposed to be, but I hope it's something like that.

[ArHu3]

2 hours ago, Catacol said:

I’m suspicious of any 2 month average chart in terms of usefulness....but one thing is clear from all those charts - cold air spills into the 2 significant northern hemisphere continents, and this provides a source that can be tapped into. And returning to an earlier point - for the UK we need to stop the Atlantic in order to do this, and this requires a weakening of the westerly momentum at 60-65N (and higher). Cold spells can happen with other major forcings (eg very strong Nina Dec10) but of all potential forcings a SSW offers us the most dramatic chance of an impact on the default circulation. I can understand the frustration at the lack of a clear and obvious correlation, but at some point we have to apply conceptual understanding as much as statistical analysis and an SSW offers opportunity even if it doesn’t offer a guarantee.

True averages don't mean anything because they can average out, that's why I looked at the hellmann number for my region first. Hellmann numbers never average out but are always additive and for de Bilt ssws were very often preceded by cold periods but not followed by marked cold periods. And iirc cold periods here after a ssw always followed a split but not all splits and never displacements 

[feb1991blizzard]

Based previous experience over the last decade, if this were the old GFS, based on the consistency and the temperatures i am seeing, i would certainly be saying that an SSW would be somewhere between highly likely and nailed on.

[Catacol]

27 minutes ago, feb1991blizzard said:

Based previous experience over the last decade, if this were the old GFS, based on the consistency and the temperatures i am seeing, i would certainly be saying that an SSW would be somewhere between highly likely and nailed on.

Hoping so...though Dec SSWs in wQBO phases (we aren't quite in prime eQBO territory yet) are rare in the extreme. I am certainly fully aware that my own forecast is pushing the boundaries of what is likely and that a minor warming followed by a less than gripping reformation of vortex stability is statistically more likely, and likely in turn to lead to a non descript winter.

Good grief - what am I doing?! Enough of the realistic gloom of the standard UK winter. Switching straight back to glass half full, and optimistic thinking. Who needs to live in the real world of statistical logic and probability curves? If I did that I'd never buy a lottery ticket, I'd have to stop supporting Scottish Rugby and my dreams of a 6 foot snowdrift outside my front door would fade into oblivion. Who the hell wants a life like that?

Bring on that imminent SSW...

 

Edited November 19, 2019 by Catacol

[feb1991blizzard]

If anything the signal slightly strengthens on the 18z GEFS compared to the 12.

[Catacol]

2 hours ago, knocker said:

The ecm temp anomaly at 10mb t240

That's a great chart Knocker - shows the wave 2 forcing perfectly. Where can these be found? Not in my bookmarks...

[knocker]

3 hours ago, Catacol said:

That's a great chart Knocker - shows the wave 2 forcing perfectly. Where can these be found? Not in my bookmarks...

Weatherbell

[Recretos]

8 hours ago, feb1991blizzard said:

Meteociel - Cartes Ensemble GFS (ENS/GEFS)

WWW.METEOCIEL.FR

---

meteociel propose des rubriques météo temps réel, forums, modeles...

 

Legacy is the GEFS v10 version. As it says on the site, it is the pre-December (v11) version. That means it is the pre-upgrade version.

It has 42 vertical levels and model top at 2mb. The v11 version (december 2015-present) has 64 vertical levels and model top at 0.2mb.

So the legacy version is underqualfied to be a useful strat forecasting tool. At least in the modern times.

[feb1991blizzard]

3 minutes ago, Recretos said:

Legacy is the GEFS v10 version. As it says on the site, it is the pre-December (v11) version. That means it is the pre-upgrade version.

It has 42 vertical levels and model top at 2mb. The v11 version (december 2015-present) has 64 vertical levels and model top at 0.2mb.

So the legacy version is underqualfied to be a useful strat forecasting tool. At least in the modern times.

What about the op, is the current version or previous version better? are there actually any verification stats for the strat available?

[Mike Poole]

Ooooo!  New strat winds chart on Meteociel!  Looks a bit like a pretzel, GFS T192:

Obviously, some more erudite analysis is appropriate, but not at 5am!

 

Edited November 20, 2019 by Mike Poole

[knocker]

The explanation of this transition is above my pay grade

 

[Recretos]

3 hours ago, feb1991blizzard said:

What about the op, is the current version or previous version better? are there actually any verification stats for the strat available?

There is not much hard data to compare the two as far as I know. There likely is data in existence, that was used during the development, testing and fine tuning phases for the new FV3. But those are probably mostly internal. At least I have not came across any comparison data.

On a general note, I kinda feel an anti-FV3 agenda in this thread. Not sure why, because FV3 is a very capable solver. It is actually appropriate for the strat, as a dynamic core. Has anyone noticed when looking at the strat charts, they look much more realistic? Especially the temperature forecast. You can actually get the feeling of fluidity, even at 1° resolution. You can actually see the eddies in the surf zone, and energy and waves in the forecast. That is not due to resolution, but due to the capability of the FV3. Below is a comparison of GEFS and FV3, both on a 0.5°grid. Now you tell me, where can you see the actual fluid dynamics?   You really get the feeling that you are looking at water motion, when you look at the GFS with the FV3 core. And that is pretty much what this is. It is like motion of water, combined with waves and circulation.

 

This does not automatically mean a better forecast, but as far as I am looking by eye, it is not bad at all! It has the same bias as the old one, trending towards a weaker vortex into FI. But all those biases go out the window and are not important when SSW dynamics start.<-Those are mainly influenced by the trop activity, so any error in the trop forecast will reflect in the strat forecast too. Besides, when a stratospheric warming trend starts in the FI, it can swing the warming air mass 1000-3000km left or right with each run, making big differences from run to run. But the forecast is still a success, because it has seen the developing warming for example, which materializes. 

So to me, the FV3 is quite a capable strat solver. Forget the old GFS, it is gone anyways. So far it seems that FV3 is doing a good job. More time will be needed to make proper actual comparisons.

Edited November 20, 2019 by Recretos

[booferking]

Can anyone tell me please if the EC has started to pick up the warming at 240hrs like the gfs please?

Edited November 20, 2019 by booferking

[knocker]

The ecm at 10mb and 50 (courtesy  Weatherbell)

Edited November 20, 2019 by knocker

[ArHu3]

1 hour ago, booferking said:

Can anyone tell me please if the EC has started to pick up the warming at 240hrs like the gfs please?

Stratosphere diagnostics • Atmospheric Dynamics • Department of Earth Sciences

WWW.GEO.FU-BERLIN.DE

 

[booferking]

8 minutes ago, ArHu3 said:

Stratosphere diagnostics • Atmospheric Dynamics • Department of Earth Sciences

WWW.GEO.FU-BERLIN.DE

 

Thank you very much sir.

[booferking]

54 minutes ago, knocker said:

The ecm at 10mb and 50 (courtesy  Weatherbell)

Are they free are behind paywall @knocker 

[knocker]

14 minutes ago, booferking said:

Are they free are behind paywall @knocker 

Behind paywall

[KyleHenry]

6 hours ago, knocker said:

The explanation of this transition is above my pay grade

 

Charts are showing Canadian warming event. The SPV is being dominated by wave 1 and inside the original Rossby wave process the model believes that it contained a considerable amount of energy. 

During solar minimum the Stratopause is lower in altitude (Electromagnetic compression) and these waves traverse well beyond the 1 hPa level, which allows the SPV to be dominated. 

How? Current Scandinavian HP and Aleutian LP at 500 mb level are holding position long enough to allow Rossby wave/s to progress and create this event. 

Personally I believe we will see a reversal at 10 hPa. 

There is no Trop/Strat coupling and the Troposphere PV is actively being disrupted. Southern arm of US jet stream appears that it will push WAA into Greenland region and will continue to do so during December.

As to what happens following SPV disruption I can’t see yet. In short mayhem.

 

Edited November 20, 2019 by KyleHenry

[mushymanrob]

17 hours ago, Mike Poole said:

So to the upcoming SSW, and I'm assuming that this is going to happen now.  This has to be the focus of attention.  The narrative of winter 2019/20 will now be largely determined by what happens after this event, so it is absolutely fascinating, and this thread will busy in the next few weeks.

hi

am i correct in assuming that if we do have a ssw in mid/late december (or even early new year) and it fails to produce a cold spell for us, then its game over for a stratospheric induced cold spell for this year? do we get only 1 shot per season? or is it possible to get another warming event later in the season ?

 

[MattTarrant]

5 hours ago, Recretos said:

There is not much hard data to compare the two as far as I know. There likely is data in existence, that was used during the development, testing and fine tuning phases for the new FV3. But those are probably mostly internal. At least I have not came across any comparison data.

On a general note, I kinda feel an anti-FV3 agenda in this thread. Not sure why, because FV3 is a very capable solver. It is actually appropriate for the strat, as a dynamic core. Has anyone noticed when looking at the strat charts, they look much more realistic? Especially the temperature forecast. You can actually get the feeling of fluidity, even at 1° resolution. You can actually see the eddies in the surf zone, and energy and waves in the forecast. That is not due to resolution, but due to the capability of the FV3. Below is a comparison of GEFS and FV3, both on a 0.5°grid. Now you tell me, where can you see the actual fluid dynamics?   You really get the feeling that you are looking at water motion, when you look at the GFS with the FV3 core. And that is pretty much what this is. It is like motion of water, combined with waves and circulation.

 

This does not automatically mean a better forecast, but as far as I am looking by eye, it is not bad at all! It has the same bias as the old one, trending towards a weaker vortex into FI. But all those biases go out the window and are not important when SSW dynamics start.<-Those are mainly influenced by the trop activity, so any error in the trop forecast will reflect in the strat forecast too. Besides, when a stratospheric warming trend starts in the FI, it can swing the warming air mass 1000-3000km left or right with each run, making big differences from run to run. But the forecast is still a success, because it has seen the developing warming for example, which materializes. 

So to me, the FV3 is quite a capable strat solver. Forget the old GFS, it is gone anyways. So far it seems that FV3 is doing a good job. More time will be needed to make proper actual comparisons.

https://www.emc.ncep.noaa.gov/users/Alicia.Bentley/fv3gfs/updates/EMC_CCB_FV3GFS_9-24-18.pdf

The above is a link a to a presentation (2018) where a few comments are about the stratosphere in the FV3 GFS

These points are found on page 53

FV3GFS Temps are similar to GFS in middle and lower stratosphere

• FV3GFS Temps are warmer in upper stratosphere

• FV3GFS Temp fcsts in winter hem upper strat high lats are colder

• Zonal Winds are slightly worse in FV3GFS at longer fcst times

• Ozone mixing ratio analyses and fcsts are similar

• Total ozone anal are diff at high lats, FV3GFS fcsts are slightly better

• Specific Humidity is much more realistic

• FV3GFS is similar to GFS forecasting the 2018 SSW

[stodge]

Afternoon all :)

I fear I'm a novice at this as well and I don't understand the optimism of some on here.

To me, we are seeing (and still in FI) a strong warming from the Eurasian side - all that will do is displace the PV back to Canada where it will strengthen and re-form in situ and inevitably the trop and strat vortices will connect and the jet will fire up.

We need two or three of these to weaken the PV enough to dislodge it further west and encourage blocking either over Scandinavia or perhaps Greenland.

I accept there may be a lot else going on at different levels and at different ways but I wonder if this is where the UKMET's mild winter forecast originates - a powerful displacement which doesn't split the stratospheric PV but sends it back to Canada where it strengthens and locks us into a zonal Atlantic spell.