Stratosphere and Polar Vortex Watch 2020

[Catacol]

It has been interesting to see ECM strat disruption undermodelled this season so far. The wave 1 warming we have been going through was upgraded at short range, and again we have an upgrade in wave 2 forcing at only 4 days out. Roughly speaking this forecast has increased in magnitude by between 25 and 30% since it was picked up at 240h range.

This is, of course, linked to sustained wave breaks and a blocking pattern around the hemisphere which has confounded long term forecasting. Instead of downgrades we appear to be locked into successive upgrades as a result, the latest glosea SSW forecast being another case in point, and this forecast being another.

 

This ensemble forecast has also upgraded over time, and with only a couple of ensemble members calling for anything less than 12 days of reversal it is a staggering picture.

 

Wading through the model thread just now left me shaking my head in disbelief at the inability of some to appreciate the whole context of the current cold spell that looks set to endure for at least 2 more weeks and quite possibly a good bit beyond that too. When there isn’t a foot of snow in the back garden we seem to have members unable to grasp the vagaries of NWP output, the fact that January only begins tomorrow and perhaps are too young or unable to remember the usual U.K. winter context since the end of the mid 1990s. The strat forecast is an extreme one, we have anything but a westerly pattern and we have plenty to look forward to.

[Lloyd1]

40 minutes ago, Catacol said:

It has been interesting to see ECM strat disruption undermodelled this season so far. The wave 1 warming we have been going through was upgraded at short range, and again we have an upgrade in wave 2 forcing at only 4 days out. Roughly speaking this forecast has increased in magnitude by between 25 and 30% since it was picked up at 240h range.

This is, of course, linked to sustained wave breaks and a blocking pattern around the hemisphere which has confounded long term forecasting. Instead of downgrades we appear to be locked into successive upgrades as a result, the latest glosea SSW forecast being another case in point, and this forecast being another.

 

This ensemble forecast has also upgraded over time, and with only a couple of ensemble members calling for anything less than 12 days of reversal it is a staggering picture.

 

Wading through the model thread just now left me shaking my head in disbelief at the inability of some to appreciate the whole context of the current cold spell that looks set to endure for at least 2 more weeks and quite possibly a good bit beyond that too. When there isn’t a foot of snow in the back garden we seem to have members unable to grasp the vagaries of NWP output, the fact that January only begins tomorrow and perhaps are too young or unable to remember the usual U.K. winter context since the end of the mid 1990s. The strat forecast is an extreme one, we have anything but a westerly pattern and we have plenty to look forward to.

Apologies Sir, I’m new to this thread and SSW Events for that matter, 

The current cold spell you are referring to ‘lasting 2 more weeks’, is this due to the effects of the first wave or are you taking into account Wave 2 within the 2 week effect? Should this Wave 2 Split event occur within the next 4 days when will we likely see the effect of this on our troposphere (should it effect it)? Do you see it creating colder conditions than the current weather or is this too hard to predict at this current moment in time?

A lot of charts flying about on this thread that are very dissimilar in there approach and I’m just trying to get some understanding to all this and your message seemed the most self explanatory on this matter. 

I usually follow the 2 week weather predictions from Standard Weather forecasts. However, they’re predicting it going back to A Westerly Pattern middle of January but I’m not sure if this truly reflects what’s going on in this thread on current predictions. 

Also, That Zonal Wind Graph you have exemplified showing a depreciated effect in January. What does this effect refer to where it’s dipping to -20 in Jan? Also, what effect would this have on our UK Weather? (Like I say I’m new to this so don’t go in on me haha).

I would greatly appreciate it if you could get back to me regarding this matter,

 

Thanks, 

Lloyd.
 

 

Edited December 31, 2020 by Lloyd1

[bluearmy]

2 hours ago, Catacol said:

It has been interesting to see ECM strat disruption undermodelled this season so far. The wave 1 warming we have been going through was upgraded at short range, and again we have an upgrade in wave 2 forcing at only 4 days out. Roughly speaking this forecast has increased in magnitude by between 25 and 30% since it was picked up at 240h range.

This is, of course, linked to sustained wave breaks and a blocking pattern around the hemisphere which has confounded long term forecasting. Instead of downgrades we appear to be locked into successive upgrades as a result, the latest glosea SSW forecast being another case in point, and this forecast being another.

 

This ensemble forecast has also upgraded over time, and with only a couple of ensemble members calling for anything less than 12 days of reversal it is a staggering picture.

 

Wading through the model thread just now left me shaking my head in disbelief at the inability of some to appreciate the whole context of the current cold spell that looks set to endure for at least 2 more weeks and quite possibly a good bit beyond that too. When there isn’t a foot of snow in the back garden we seem to have members unable to grasp the vagaries of NWP output, the fact that January only begins tomorrow and perhaps are too young or unable to remember the usual U.K. winter context since the end of the mid 1990s. The strat forecast is an extreme one, we have anything but a westerly pattern and we have plenty to look forward to.

The 12z gfs op has a pretty short reversal but ends up with a nice profile 

gfs and ecm at day 10 are on the same page. Maybe we’re close enough to the onset of the warming for the strat to be well modelled now ???

[bluearmy]

       

newest first 

Edited December 31, 2020 by bluearmy

[ALL ABOARD]

3 minutes ago, bluearmy said:

       

newest first 

A mean reversal of almost 14 days? 

[bluearmy]

23 minutes ago, ALL ABOARD said:

A mean reversal of almost 14 days? 

That’s been the average we’ve seen and also ties in with glosea 

I'm more intrigued by the number of runs that maintain a neg flow and even if we discount these runs, the number that get the flow back to an average speed by mid feb is less than half ......

Edited December 31, 2020 by bluearmy

[phil nw.]

We are certainly seeing a remarkable period of wave attacks on the spv which iirc has been ongoing since November.

Viewing the latest outputs surely another wave 2 attack after the displacement would finally split the vortex quite soon after.

 

[bluearmy]

Gsf and gefs strat were on the same page right out to day 16 earlier 

the 18z op repeats the pattern with split late on through Greenland 

[Snowman.]

2 hours ago, bluearmy said:

Gsf and gefs strat were on the same page right out to day 16 earlier 

the 18z op repeats the pattern with split late on through Greenland 

Prolonged strat attacks? Trop is in charge and is not allowing the strat to have any upper hand.

[Duane S.]

This is quite a 48 hour transformation at the top of the srat

My only slight concern is are we seeing a propensity of increasing westerly winds in the troposphere seeping in, in response? 

I get a feeling that we may have to endure a bit of a relaxation of cold conditions in about 12 days time or so. That’s not a moan. Firstly that would be after a very long, by UK standards, continuous cold spell. Secondly, just out of range, I suspect there are some frigid charts waiting to make an appearance on the scene.

[sebastiaan1973]

Seems to me 75N-90N

8 minutes ago, s4lancia said:

 

 

My only slight concern is are we seeing a propensity of increasing westerly winds in the troposphere seeping in, in response? 
 

 

That's 75N-90N, 75N lies in the middle of Greenland

[bluearmy]

29 minutes ago, sebastiaan1973 said:

Seems to me 75N-90N

That's 75N-90N, 75N lies in the middle of Greenland

And other areas of the globe ! 

[bluearmy]

Gefs day 16 and gefs 10hpa day 16 ......strat - trop disconnect ?????  Not in gefs world 

 

    

 

 

[Doctor96]

Lloyd1 I too am new to this area but highly interested , if anyone can answer your questions I would appreciate it . I too am unclear if we are seeing a further wave two attack and SSW of some sort why I’d Gfs and others going for zonal winds in the time period of 10 days , or is gfs not picking up the likely SSW . Or is it still marginal for a SSW which may or may not influence the Atlantic .

thanks in advance 

[bluearmy]

Looking at the gefs and Ec46 zonal flow, it looks like a double dip which may be indicative of a secondary drop in zonal flow from a split which follows the displacement a few days later 

[SqueakheartLW]

My Daily Stratospheric update

GFS 00z

I will begin like always with the 00z GFS and its ensembles. GFS is sticking to its displaced vortex outcome from the current warming event but still has strong hints of another warming in the middle of the month. 276 hours away appears to be the favoured time for the peak of this second warming but there are some members going for it at a different time but all 32 are going for another warming.

Here are the warmest options from the 00z today for the second warming

What is even better about the 00z was how many of the members ended their runs with a split vortex. There were so many that I split them up into stronger splits and weaker ones and there were a lot of weaker split options in there. Almost half of the runs ended with barely any vortex left at all. 24 of 32 ended with a split and 14 of those were weak or very weak vortex options. Of the 8 displacements, half of those were weak ones too.

Here are the 4 weak displacements first

Finally here are the 14 weak split options

All I can say from this general output is that with 18 of 32 going for weak or very weak vortex by the end of the run and 24 of 32 with splits then it is looking at this stage like the polar vortex is toast by the middle of the month

GEFS Legacy

GEFS Legacy is following GFS with a displacement followed by another warming event but with the legacy run this warming is on average a few days later than the GFS version but some very big warmings are showing up in the legacy model. The top 3 are below

As always the legacy model is throwing in another +12 warming like it has done since I started looking at this model

GFS Parallel

GFS Parallel is following the path of the GFS now and is going for an initial attempt at a split before it ends up a displaced vortex. The parallel is also showing signs of the second warming too

As with GFS the parallel is ending the run with a vortex badly beaten up

JMA

JMA is still attempting a split

This turns into a displacement but then the vortex itself just seems to evaporate away after that and at the end of the JMA run this is all that's left of it

GEM

GEM now following a similar path to GFS. Still can't believe GFS has the displacement nailed on from so far back compared with the other models

However GEM ends with a weaker displaced vortex

ECM

ECM also going for displacement with the current warming. Still no real sign of the second warming showing up at 10hpa either

Here is the daily zonal wind data and forecast from ECM

Even though the reversal looks certain now it appears that high up it is very short lived as at 1 and 2 hpa we see a rapid recovery of the vortex but when looking at 1 hpa it seems there is a hint by day 10 of another possible slow down of the zonal winds again. Also around 70 hpa we seem to be seeing a battle between the lower stratosphere and the higher levels as the reversal doesn't get any lower. Perhaps we may see another 2019 where the warming has little or no effect on the troposphere again

[bluearmy]

The gfs 06z op strat charts at the top are the same evolution as yesterday’s 12z op 

I wait to see the back end of the ec op runs to check that they continue to follow what is becoming a fairly consistent gfs extended pattern 

[summer blizzard]

Can anybody tell me what the dates were for the Jan 09, 13 and almost SSW of Jan 12 were.

[ALL ABOARD]

5 minutes ago, bluearmy said:

The gfs 06z op strat charts at the top are the same evolution as yesterday’s 12z op 

I wait to see the back end of the ec op runs to check that they continue to follow what is becoming a fairly consistent gfs extended pattern 

Split? 

[bluearmy]

1 minute ago, ALL ABOARD said:

Split? 

Not quite - see the gefs day 16 above.

the strat gfs data is also freely available on weather is cool and instantweathermaps 

[feb1991blizzard]

32 minutes ago, summer blizzard said:

Can anybody tell me what the dates were for the Jan 09, 13 and almost SSW of Jan 12 were.

24th Jan 09, 7th Jan 2013.

[feb1991blizzard]

Been looking for the 2012 Jan but as it wasn't a technical reversal, hard to find, can't find minimum zonal winds 60N 10hpa but it was late Jan i am sure it was.

Edited January 1, 2021 by feb1991blizzard

[summer blizzard]

52 minutes ago, feb1991blizzard said:

Been looking for the 2012 Jan but as it wasn't a technical reversal, hard to find, can't find minimum zonal winds 60N 10hpa but it was late Jan i am sure it was.

I think it was stupidly close like 1.x something at 60N. 

The reason I was looking though Is because all three produced a fairly severe spell around 10 days afterwards lasting close to two weeks (the timing fits for 2012 even if not that snowy) and then about a month of UK high type weather before they diverge.

[sebastiaan1973]

The analogue of february 2010 seems to me the best we have. We had in 2010 a split SSW, a quick deceleration, weak vortex at 100 hPa and Greenland blocking at the day of onset (theory Domeisen et al).

Just like 2010 we first had a period of GL blocking, followed by high pressure Northpole, Greenland but no high pressure in Scandinavia, just like 11-15 days ahead EC shows. The following step is a westerly negative NAO in which the danger exists of mild air pusht into Europe. It's a development we saw in 2010.

 

Edited January 1, 2021 by sebastiaan1973

[snowking]

@sebastiaan1973 synoptically it might not be too far away from our expected set up on Jan 6th at a very broad brush scale (Siberian high, Aleutian low and heights in the vicinity of the N Atlantic)

 

However I think Feb 2010 was a straight split SSW, where as what we have coming up is a displacement followed, hopefully, by a split. My expectation would therefore be that we would see entirely different dynamics to this warming vs the Feb 2010 warming. Not to mention that with this one taking place over a month earlier, there’s less risk of any consequences of the SSW being prone to seasonal wavelength changes.

Thats all just theoretical from me though, and I guess we will just have to wait and see what happens through the second half of Jan. It’s a fascinating watch regardless of how it unfolds