Stratosphere and Polar Vortex Watch 2020

[summer blizzard]

6 hours ago, sundog said:

Yes, I think for example in Nov 2018 or 2019 cant remember exactly  which in particular , things looked interesting heading into the winter. But no sooner had we entered the first week of Dec it all turned to S##t.  It was kinda funny in a way,things looking so promising and then suddenly as we entered winter it all feel off the rails rapidly. 

2016 and 2017 were the strongest examples of weak zonal winds early. In 2016 this rebounded significantly, less so in 2017.

[damianslaw]

2 hours ago, summer blizzard said:

2016 and 2017 were the strongest examples of weak zonal winds early. In 2016 this rebounded significantly, less so in 2017.

November 2017 brought some cold weather at times in the second half. Remember a bitter northerly. December started very cold a bit like 2008 then warmed up in the run in to Christmas before turning a bit colder briefly between Christmas and new year. Unusually quite a number of recent Decembers have started off cold.

[SqueakheartLW]

This is the best one of these charts I have seen so far for weaker than average zonal winds

Polar vortex ..... errrmmm .... What polar vortex?

[Don]

5 hours ago, SqueakheartLW said:

This is the best one of these charts I have seen so far for weaker than average zonal winds

Polar vortex ..... errrmmm .... What polar vortex?

Lets hope we can ask the same question mid December!

[Frigid]

I still get flashbacks of the PV resurgence in December 2019. Hopefully it won't happen this time around

[Don]

10 minutes ago, Frigid said:

I still get flashbacks of the PV resurgence in December 2019. Hopefully it won't happen this time around

There were forecasts for a front loaded cold winter 2016/17 due to a weak PV.  However, following a coldish November, the PV ramped up and December was very mild.  Although January 2017 was cold at times, February was very mild overall.  Similar to this year, September 2016 was also very warm at 16C, so I hope we do not get a repeat this coming winter!

Edited September 27, 2021 by Don

[damianslaw]

4 hours ago, Don said:

There were forecasts for a front loaded cold winter 2016/17 due to a weak PV.  However, following a coldish November, the PV ramped up and December was very mild.  Although January 2017 was cold at times, February was very mild overall.  Similar to this year, September 2016 was also very warm at 16C, so I hope we do not get a repeat this coming winter!

The first half of 2016 was quite different to first half of 2021.

[bluearmy]

Latest ec 46 shows a strong positive 10hpa Canadian temp anomoly late October but the zonal winds at 10hpa are not as suppressed as the previous run. Still below average but trending upwards somewhat into November back towards the average. rather than seeing a consistent lessening of forecast zonal flow we are seeing a slight ebb and flow around a weaker than average prediction. 

[jules216]

1 hour ago, bluearmy said:

Latest ec 46 shows a strong positive 10hpa Canadian temp anomoly late October but the zonal winds at 10hpa are not as suppressed as the previous run. Still below average but trending upwards somewhat into November back towards the average. rather than seeing a consistent lessening of forecast zonal flow we are seeing a slight ebb and flow around a weaker than average prediction. 

Courtesy of newly available product 10hPa anomalies the peek of warming event is around 20th October and then slowly returns to just above average in early now, also because atmosphere starts to return to La Nina configuration of Atlantic blocking and Scandi trough which might look cold soon but not conductive to further strat. perturbations.

[bluearmy]

7 hours ago, jules216 said:

Courtesy of newly available product 10hPa anomalies the peek of warming event is around 20th October and then slowly returns to just above average in early now, also because atmosphere starts to return to La Nina configuration of Atlantic blocking and Scandi trough which might look cold soon but not conductive to further strat. perturbations.

We’ve seen scandi troughs modelled in the distance but they’ve been generally transitional ahead of another scrussian block.  Would need to see where ec46 thinks we are going beyond.  Also remember that the ec46 is an ens mean so that high temp anom later in October could turn out to be stronger. However, the zonal winds in early nov don’t see to reflect anything incredible as a consequence of the third week October warning. 
 

certainly worth watching to see how those zonal winds are predicted to respond in nov as the ec46 modelling evolves 

[jules216]

1 hour ago, bluearmy said:

We’ve seen scandi troughs modelled in the distance but they’ve been generally transitional ahead of another scrussian block.  Would need to see where ec46 thinks we are going beyond.  Also remember that the ec46 is an ens mean so that high temp anom later in October could turn out to be stronger. However, the zonal winds in early nov don’t see to reflect anything incredible as a consequence of the third week October warning. 
 

certainly worth watching to see how those zonal winds are predicted to respond in nov as the ec46 modelling evolves 

My take on the November progression is connect to expected tropical forcing plus "typical" La Nina pattern more then EC long range forecast, the most useful tool I use are P.Roundys regression maps. The idea behind this is that if new MJO cycle commences in Indian Ocean late Oct/early Nov it teleconnects to pattern faborable to Iceland/Western Europe blocking and Sceru troughing, this was typical and prevelant in lot of La Nina autumns like 2016,2011,2007,1999,1998 etc. Last year was atypical and this year with respect to MJO phasing has different timing,more akin to years I mentioned, what remains a huge question mark is weather we can achieve timing of phases 4 to 7 during November as there is a lot of easteries around Date Line and destructive forcing.

[Griff]

Too soon for me but perhaps a taster... 

[bluearmy]

Back end of the gfs 12z op is picking up the developing high height anomoly over the Canadian side

 

Edited September 30, 2021 by bluearmy

[SqueakheartLW]

I like those negative anomalies on this chart. The biggest so far

The zonal winds weaken throughout the whole depth of the atmosphere from the surface right up to 1hpa. Something weird is definitely going on. Even the jet stream vanishes at the end of the run here too.

[bluearmy]

Latest 46 shows the marked drop off in 10hpa zonal flow mid October and then a recovery to almost average by mid nov 

[Don]

9 minutes ago, bluearmy said:

Latest 46 shows the marked drop off in 10hpa zonal flow mid October and then a recovery to almost average by mid nov 

Not as promising as a week ago then.

[bluearmy]

1 minute ago, Don said:

Not as promising as a week ago then.

As November has progressed on the model the mean has shown a gradual return to the average 

[Don]

21 minutes ago, bluearmy said:

As November has progressed on the model the mean has shown a gradual return to the average 

Well hopefully the zonal flow will remain suppressed enough to deliver a front loaded winter, given a time lag?

[bluearmy]

32 minutes ago, Don said:

Well hopefully the zonal flow will remain suppressed enough to deliver a front loaded winter, given a time lag?

Indeed - over recent winters, the coupling of trop and strat hasn’t been so obvious throughout.  A reasonable zonal flow high up may not be awful for the trop - the spv may well be in a favourable area for nw Europe. I would think that trop patterns will dictate early winter in any case. If the spv isn’t racing away then I doubt it would over ride those patterns. If it really strengthens then I guess it becomes a matter of time but then again, we saw last winter how trop waves can interfere with a strong spv in any case. None of the science is precise …..

[jules216]

9 hours ago, bluearmy said:

Indeed - over recent winters, the coupling of trop and strat hasn’t been so obvious throughout.  A reasonable zonal flow high up may not be awful for the trop - the spv may well be in a favourable area for nw Europe. I would think that trop patterns will dictate early winter in any case. If the spv isn’t racing away then I doubt it would over ride those patterns. If it really strengthens then I guess it becomes a matter of time but then again, we saw last winter how trop waves can interfere with a strong spv in any case. None of the science is precise …..

The observed area of warming in October is one that could favor cold in Europe, the one seen at the end - Siberian warming has in the past favored American cold as far as I have been observing the 10hPa temperatures.

[northwestsnow]

On 24/09/2021 at 14:50, northwestsnow said:

eQBO interference I guess.

Are we going hunting for Scandy highs in November??

 

OK,mid October..

Edited October 1, 2021 by northwestsnow

[Don]

1 hour ago, northwestsnow said:

OK,mid October..

Yeah, Scandy highs mid October when they’re next to useless and then what will we get in December/January?  Billy Bartlett!!

[northwestsnow]

24 minutes ago, Don said:

Yeah, Scandy highs mid October when they’re next to useless and then what will we get in December/January?  Billy Bartlett!!

Why are they next to useless ?

Excellent weather for walkers and outdoor enthusiasts .

[Don]

32 minutes ago, northwestsnow said:

Why are they next to useless ?

Excellent weather for walkers and outdoor enthusiasts .

Sorry, I was referring to them being next to useless delivering cold and snow in October, compared to the winter months.  Otherwise, I quite agree with you!

[bluearmy]

16 hours ago, Don said:

Yeah, Scandy highs mid October when they’re next to useless and then what will we get in December/January?  Billy Bartlett!!

 Not useless at all in October if you’re after trop wave affects on the strat ……

Edited October 2, 2021 by bluearmy