Stratosphere and Polar Vortex Watch 2020

[sebastiaan1973]

Thanks Snowking.

4th of January is the onset of the SSW.

[Catacol]

Short term upgrades in strat impacts continue. More substantial wave 2 impacts at only 2/3 days’ range 

At 72 hours this is pretty close to splitting. More upgrades to come? Or has wave 2 potential topped out now? Interesting to watch...

[sebastiaan1973]

I see a clear downwelling with at 100 hPa-1000 hPa an increase westerly winds as the easterly winds downwells. At day 10, these westerly winds diminish.

Edited January 2, 2021 by sebastiaan1973

[sebastiaan1973]

Seems to me we see the effect of the SSW: 1030 hPa at the Northpole and cooler than average at large parts of the NH.

[Nick F]

 

27 minutes ago, Catacol said:

Short term upgrades in strat impacts continue. More substantial wave 2 impacts at only 2/3 days’ range 

At 72 hours this is pretty close to splitting. More upgrades to come? Or has wave 2 potential topped out now? Interesting to watch...

Today's 00z EC at 10 hPa similarly squeezes towards a split at t+66 ...

... but never quite does the job before it bounces back at t+120 to one vortex over NE Europe.

By day 10 the displaced vortex still toward NE Europe, on Berlin (yesterday's EC)  the core was more over the Atlantic.

 

Edited January 2, 2021 by Nick F

[ghoneym]

Extreme looking pattern at 3hpa for Monday

Zonal mean temperature for today first then the 11th 

 

[Singularity]

5 hours ago, Nick F said:

By day 10 the displaced vortex still toward NE Europe, on Berlin (yesterday's EC)  the core was more over the Atlantic.

 

...and with renewed pressure from the Atlantic/Europe side. Even if only slight, it's enough that a split becomes possible due to the sheer strength of the anomaly on the other side.

This second split attempt, GFS/GEFS has been toying with for a few days now. Some runs leave the polar vortex not only in pieces but with a serious shortfall of -60*C or colder air to work with.

Interesting to see the rapid downwell of reversal from the first attempted split. Perhaps we don't always need the full partition, if the +GPH anomaly is large enough & hence reversal strong enough at 10 hPa, for a quick tropospheric response to occur?

If that is the case, the forecast models sure will have a hard time resolving such an unusual event.

[Catacol]

We now have 100% ensemble agreement for a 14 day reversal. This will increase.

[chionomaniac]

11 minutes ago, Catacol said:

We now have 100% ensemble agreement for a 14 day reversal. This will increase.

Lol. What? To 200%?  

( I know what you meant - an increase in the longevity, but couldn’t resist!)

[Scott Ingham]

1 hour ago, Catacol said:

We now have 100% ensemble agreement for a 14 day reversal. This will increase.

17 day and counting reversal! 

Jeeeeeeeeez!

[summer blizzard]

It's interesting that it gets deeper around the 15th so it's not even a slow decline back to normality.

[Cheshire Freeze]

Just now, summer blizzard said:

It's interesting that it gets deeper around the 15th so it's not even a slow decline back to normality.

Isn't that the secondary warming the GFS has been hinting at that may split the vortex?

[ICE COLD]

2 hours ago, Catacol said:

We now have 100% ensemble agreement for a 14 day reversal. This will increase.

What’s the lowest negative speed ever recorded ? Just noticed that some of them runs go towards the -40 mark and would that be better the lower we drop ? Thanks  

[chionomaniac]

8 minutes ago, ICE COLD said:

What’s the lowest negative speed ever recorded ? Just noticed that some of them runs go towards the -40 mark and would that be better the lower we drop ? Thanks  

Try looking at Jan 2009. Off the top of my head I think that is a likely candidate for January

[Vikos]

German DWD Stratosphric Synoptic Update from today (translation by google)

[IFS = ECMWF]

The important thing will now be how the SPW (StratoPolarVortex) with the polar vortex in the troposphere (TWP) interacts, because not every weakening from the height can extend into working the troposphere forward. However, the signs are destructive despite tropical background conditions (ongoing La Nina and western "Quasi-Biennial Oscillation (QBO)") is not unfavorable, because the TPW is already quite weak and a constant weakening trend is likely to result in continue the sequence. At least in the GEFS there is a tendency towards coupling indicated (e.g. when comparing the so-called "anomaly of the polar cap temperature", the mean temperature between 60 and 90 degrees north) at the beginning of January initially shows clearly positive anomaly values in the SPW level and in the Follow slowly sink. But whether it is enough remains to be seen. Since the Models at these height levels have significantly fewer model levels for calculations will show changes in the days and weeks to come the question of how good the coupling will be. E.g. IFS is better set up as CFS with around 44 levels above 150 hPa compared to 27 at CFS - and yes, IFS indicates a coupled wind anomaly in the extended Medium term.

But why is that of interest? The reason is that such events (coupled) being able to ensure harsh winter weather regionally. Statistically a negative NAO is likely for such a development Answer, i.e. a positive geopotential anomaly in the Iceland / Greenland area instead of the usual Iceland low. And the NAO is already in the negative Area and remains so according to the probability density function distribution in the IFS-EPS, which maximizes well into January in the "NAO negative" sector can be found. The AO / NAM is also in the deeply negative area. In summary, it means that for the time being there is no "low pressure highway" from the Atlantic. is to be expected, but that a strongly meridional deflected Flow configurations with a strong wedge (Northeast Atlantic / Greenland) and Long wave trough (West Central Europe) established. In addition, the low pressure areas on the southern flank of the blockage to the east (frequent merging of Polar front and subtropical jets), so that North Africa in particular gets lush wet. These low pressure areas then move north-east depending on the position of the trough Central / Eastern Europe further. Statistically, such a striking SSW event would have been particularly important for Northern Europe Clearly too cold temperature deviations result. The forecast is currently increasing in the "extended range" of the IFS-EPS especially the Ural region and large areas Siberia. The 1% percentile sometimes reaches negative record values within the weekly averaged 2m temperature anomaly forecast. Also Scandinavia is cooling down significantly. Thus the chances increase that the low pressure areas moving in from the southwest increasingly on the the cold air that forms (snowfall) or strong on the back Can bring outbreaks of cold air.

Central and Western Europe consistently remain under one aging and quasi-stationary Rossby wave, which is also facing the v-wind distribution (level of the tropopause) between 30 and 60 degrees north in the Hovmöller diagram only marginal zonal for regeneration / incoming waves Has displacements. Thanks to the negative NAO including abnormally high geopotential in Greenland and Scandinavia the trough is only made up of small-scale Troughs / low pressure areas renewed, the north-east Atlantic on a southern orbit cross. Hence the constant tendency towards a positive axis inclination with a lot of warmth for the eastern Mediterranean. The In the medium term over repeated bridging between high air pressure south from Greenland and Scandinavia, which suppresses the effective KLA from the north, but the cold of the brand "in-house production" is gradually sending southwards. Across Europe, the focus remains on the brisk rotogravure printing activity in the southern and southern regions Eastern flank of the Rossby wave and the question arises how this vortex is connected interact with the colder air mass over Central Europe. In this IFS run we seem to be lying between the chairs, so a very quiet one Medium term segment can be expected.

However, be careful, as the numerics have problems with the strongly meandering Flow configuration and the difficult-to-measure in-house production (in addition to weak advection) of cold air as well as cyclogenesis processes in rather unusual Regions (e.g. off Morocco under a strongly abnormally powerful jet with +3 to +4 sigma). In any case, it remains an exciting development (from synoptic Visibility) and it could increase in tension as a result.

[Duane S.]

3 hours ago, ICE COLD said:

What’s the lowest negative speed ever recorded ? Just noticed that some of them runs go towards the -40 mark and would that be better the lower we drop ? Thanks  

-40 would smash the biggest reversal recorded.

 

Clearly this would be very much an outside bet currently but it’s still amazing to see it’s not just one rogue run, there are 4 going for it! 

[Interitus]

8 hours ago, Catacol said:

We now have 100% ensemble agreement for a 14 day reversal. This will increase.

 

2 hours ago, s4lancia said:

-40 would smash the biggest reversal recorded.

 

Clearly this would be very much an outside bet currently but it’s still amazing to see it’s not just one rogue run, there are 4 going for it! 

This is at 65°N, here is a rough and ready plot at 60°N

[chionomaniac]

4 minutes ago, Interitus said:

 

This is at 65°N, here is a rough and ready plot at 60°N

Hi interitus. What are the x and y on that chart. Otherwise it means nothing to me? Thanks

[Interitus]

14 minutes ago, chionomaniac said:

Hi interitus. What are the x and y on that chart. Otherwise it means nothing to me? Thanks

Y is u m/s, X is time steps of run, pretty obvious really,

[sebastiaan1973]

Excellent EC12h run of yesterday. Please notice the 'blue area' stretching all the way from 1 hPa to 1000 hPa from 65N till 90N.

[JeffC]

Pictorial view of what's going on at 10 hPa

 

 

[Duane S.]

Best ECM run yet for reversal down into the trop, with -70 m/s showing at the top now . What a lovely graphic at D10, full connection, top to bottom. Also, a continuation of the under estimation of the wave 2 intensity. 

 

 

[sebastiaan1973]

We see a displacement of the vortex situated in the Atlantic Ocean. In GFS -which is quite similiair to this point- it ends in a split. We have to wait and see.

[ArHu3]

keep track of this guys twitter, he's been posting quite a bit of EPS of the vortex recently 

 

https://twitter.com/TradeWpower

 

@sebastiaan1973

 

Edited January 3, 2021 by ArHu3

[Battleground Snow]

Would this support the GFS with its continuation of more northern blocking and a less flat profile?