Stratosphere and Polar Vortex Watch 2020

[Don]

58 minutes ago, CreweCold said:

A warm, drier than average spring looks likely to me. Perhaps into June.

And a summer similar to 2020 perhaps, preferably without those vile heat spikes that year at the end of July and during August?!

[Cheshire Freeze]

23 minutes ago, Don said:

And a summer similar to 2020 perhaps, preferably without those vile heat spikes that year at the end of July and during August?!

If it brings the storms of August 2020 you won’t hear me complaining. Best electrical storm I’ve ever witnessed.

[MP-R]

44 minutes ago, Don said:

And a summer similar to 2020 perhaps, preferably without those vile heat spikes that year at the end of July and during August?!

The late July to mid August period saved that summer beyond June being a complete dud.

[bluearmy]

Second consecutive date record …and probably a few more to come as the month progresses …

 

Edited February 5, 2022 by bluearmy

[Don]

2 hours ago, bluearmy said:

Second consecutive date record …and probably a few more to come as the month progresses …

 

I just wonder what's caused such a strong PV this year?  Million dollar question I suppose!

[karyo]

5 hours ago, Don said:

I just wonder what's caused such a strong PV this year?  Million dollar question I suppose!

Now the we know that the winter is dead in the water, I hope this super strong pv continues well into spring. It may be proved to be good for the Arctic ice.

[SqueakheartLW]

Wonder if there's a link between vortex strength in late winter and the spring and what we are likely to see weather-wise during the spring and the summer following the winter

I have tended to notice that winters with a weaker stratospheric vortex or a SSW in the second half of the winter, mid Jan to end of Feb tend to be followed by colder springs then better summers overall whereas the years with a strong vortex to end the winter and during the early spring seem to be warmer and drier in the spring before the summer goes downhill.

The most recent notable examples are 2017/18 winter then spring 2018 and summer 2018 as well as 2019/20 winter then spring 2020 and summer 2020.

2017/18

Winter 2017/18 had a relatively late SSW in February and we all know what that caused. I remember the March and April generally been colder than average and at times unsettled as well. No doubt the effects of the SSW continued on for the early to mid part of the spring with northern blocking at times and colder chilly conditions. As would be the case and certainly was during late spring and into summer 2018 the northern blocking went away and we saw a stronger than average tropospheric portion of the polar vortex persisting near Greenland which caused the het stream to stay well to the north of the UK during much of summer 2018 giving us that dry and very warm summer.

2019/20

Winter 2019/20 was the dreaded polar vortex of doom winter which then persisted some way into the spring too. I imagine many of us remember the very dry, sunny and warm spring of 2020, the very conveniently timed lockdown weather. That vortex was going to give us sooner or later and as expected it eventually did. As we got to the summer of 2020 things went downhill, not a washout but on average a mediocre summer with only late July and early August having the most decent spell of weather in what was otherwise a generally below average summer overall.

 

Maybe I should do some research on this one to see if vortex strength at the end of winter and into early spring has any impact on what the spring and summer CET is likely to be

[SqueakheartLW]

That looks so bad for any last gasp hopes of anything cold showing up

Those anomalies at 10hpa coming out at +35m/s above normal is unreal.

As for my random snapshot at the latest zonal wind speeds at 10hpa and how they compare with other years on the record we maintain our position high up on both measures.

Rolling 10hpa Zonal Winds

When looking at overall rolling zonal wind speeds at 10hpa from November 1st through to February 7th we can see how 2022 is still moving up the list as the overall rolling speed has been slowly climbing for a while now. It currently stands at 40.508 m/s which is +9.094 m/s above where the rolling mean should be on 7th February showing we have had an above average vortex strength really throughout the whole season so far.

2016 still stands in top spot but with the SSW's and very early final warming to come then 2016 should soon start dropping away down the list. 2006 is now bottom of the list after the January SSW and reversal has pulled it down to bottom spot although 2019 and 2013 are not far above it after their respective January SSW's as well.

Daily 10hpa Zonal Winds

Looking at my daily snapshot for 7th February sees 2022 well up the list in 5th position with a fairly rapid 47 m/s zonal wind which is a big +23.239 m/s above normal although we set a couple of date records a few days ago and if the forecasts are correct we could soon be setting a few more too.

1988 came out on top on this day at 61.220 m/s whilst 1987 came out bottom at -13.830 m/s with a SSW in progress and a reversal. 2006 and 2009 were also in reversal on this date too but only by small margins.

 

Looks like with the forecast we are still on track to possibly end up with the fastest overall 10hpa 60N zonal wind mean for the November to March period and we only need to overturn a margin to top spot of 6.467 m/s to achieve this and with very strong to record strong zonal winds predicted for the foreseeable then it could very much be possible.

[damianslaw]

39 minutes ago, SqueakheartLW said:

That looks so bad for any last gasp hopes of anything cold showing up

Those anomalies at 10hpa coming out at +35m/s above normal is unreal.

As for my random snapshot at the latest zonal wind speeds at 10hpa and how they compare with other years on the record we maintain our position high up on both measures.

Rolling 10hpa Zonal Winds

When looking at overall rolling zonal wind speeds at 10hpa from November 1st through to February 7th we can see how 2022 is still moving up the list as the overall rolling speed has been slowly climbing for a while now. It currently stands at 40.508 m/s which is +9.094 m/s above where the rolling mean should be on 7th February showing we have had an above average vortex strength really throughout the whole season so far.

2016 still stands in top spot but with the SSW's and very early final warming to come then 2016 should soon start dropping away down the list. 2006 is now bottom of the list after the January SSW and reversal has pulled it down to bottom spot although 2019 and 2013 are not far above it after their respective January SSW's as well.

Daily 10hpa Zonal Winds

Looking at my daily snapshot for 7th February sees 2022 well up the list in 5th position with a fairly rapid 47 m/s zonal wind which is a big +23.239 m/s above normal although we set a couple of date records a few days ago and if the forecasts are correct we could soon be setting a few more too.

1988 came out on top on this day at 61.220 m/s whilst 1987 came out bottom at -13.830 m/s with a SSW in progress and a reversal. 2006 and 2009 were also in reversal on this date too but only by small margins.

 

Looks like with the forecast we are still on track to possibly end up with the fastest overall 10hpa 60N zonal wind mean for the November to March period and we only need to overturn a margin to top spot of 6.467 m/s to achieve this and with very strong to record strong zonal winds predicted for the foreseeable then it could very much be possible.

Which other years saw similar high values Feb into March. Might it be a dramatic implode at some point? Will be alot of very cold arctic air bottled up and ready to drain into mid latitudes this Spring.

[Mike Poole]

13 minutes ago, damianslaw said:

Which other years saw similar high values Feb into March. Might it be a dramatic implode at some point? Will be alot of very cold arctic air bottled up and ready to drain into mid latitudes this Spring.

I can’t see a dramatic implode without a SSW and there just doesn’t seem to be that kind of pressure on the strat vortex to cause one even now. It is funny, we were very keen on the apparent disconnect between the strat and the trop in December, but unfortunately I think this cuts both ways, the precursors to a SSW are trop patterns too, and they have never got a foothold on the strat vortex all winter.  And won’t now either, in my view.  

My prediction, is that a warm spring with ridging from the Azores will have taken hold for our locale long before the strat vortex just peters out in the final warming above, and winter will be gone without ever happening this year.  

[damianslaw]

16 minutes ago, Mike Poole said:

I can’t see a dramatic implode without a SSW and there just doesn’t seem to be that kind of pressure on the strat vortex to cause one even now. It is funny, we were very keen on the apparent disconnect between the strat and the trop in December, but unfortunately I think this cuts both ways, the precursors to a SSW are trop patterns too, and they have never got a foothold on the strat vortex all winter.  And won’t now either, in my view.  

My prediction, is that a warm spring with ridging from the Azores will have taken hold for our locale long before the strat vortex just peters out in the final warming above, and winter will be gone without ever happening this year.  

Same as 2020 then?

[Mike Poole]

3 minutes ago, damianslaw said:

Same as 2020 then?

I wouldn’t bet against it would you?

[damianslaw]

14 minutes ago, Mike Poole said:

I wouldn’t bet against it would you?

Well I wouldn't complain if we see a Spring akin to 2020, the summer though wasnt up to much.. always get itchy feet when we have early summer warmth in April.. 87, 97, 11, 18 spring to mind.. very poor second halves to summer at least here..  we have a 9 month wet season mid June to mid March and a 3 month less wet season mid March to mid June!

Edited February 8, 2022 by damianslaw

[BruenSryan]

17 hours ago, damianslaw said:

Which other years saw similar high values Feb into March. Might it be a dramatic implode at some point? Will be alot of very cold arctic air bottled up and ready to drain into mid latitudes this Spring.

1990, 1997 and 2020, as Simon mentions in his tweet. Sure you know what each of those springs were like but 1990 very warm with a marked north/south contrast in rainfall (particularly in March). 1997 dry and warm March/April with a very changeable and showery May. 2020 exceptionally sunny and predominantly dry after first half of March.

 

[Weather-history]

17 minutes ago, BruenSryan said:

1990, 1997 and 2020, as Simon mentions in his tweet. Sure you know what each of those springs were like but 1990 very warm with a marked north/south contrast in rainfall (particularly in March). 1997 dry and warm March/April with a very changeable and showery May. 2020 exceptionally sunny and predominantly dry after first half of March.

 

All three of those had a particularly poor spell during the summer months (June 1990, second half of June 1997, July 2020 and warm Augusts.) 

[SqueakheartLW]

4 hours ago, Weather-history said:

All three of those had a particularly poor spell during the summer months (June 1990, second half of June 1997, July 2020 and warm Augusts.) 

Maybe we can finally end the trend of poor Augusts then at last

[damianslaw]

1997 produced a short potent arctic blast in early May, gave a cover of snow here. 

[North-Easterly Blast]

August 2020 was actually a pretty wet month as well as being warm overall, a bit like August 2004, so not all warm summer months are dry as these two examples show.

[North-Easterly Blast]

I am not sure when all SSWs have taken place in the past, but I know that they can lead to notably cold outbreaks in the UK as the examples from Jan 2013 and Feb 2018 show, but I am not sure that a SSW guarantees a significant cold spell for the UK, as the dice has to still land as to if the blocking sets up favourably to get the UK cold.  I am also of the opinion and I question if a SSW can bump the UK out of a cold spell, as I believe there was some stratospheric warming prior to the cold spell in February 2021 but after a week it disappeared abruptly and the UK went very mild.  I also think that there was an SSW prior to the cold spell in Feb 2009, but that disappeared abruptly in mid-month and the UK again went very mild.

[mushymanrob]

18 hours ago, Weather-history said:

All three of those had a particularly poor spell during the summer months (June 1990, second half of June 1997, July 2020 and warm Augusts.) 

.................. but were those cold spells anything exceptional or just normal cold spells other years have produced?

 

[Weather-history]

1 minute ago, mushymanrob said:

.................. but were those cold spells anything exceptional or just normal cold spells other years have produced?

 

Poor does not necessarily equate to "cold/cool" 

June 1990 and July 2020 were cloudfests, June 1997 is the wettest June of the 20th century for the EWP.

 

[mushymanrob]

3 hours ago, Weather-history said:

Poor does not necessarily equate to "cold/cool" 

June 1990 and July 2020 were cloudfests, June 1997 is the wettest June of the 20th century for the EWP.

 

fair comment (poor/cool).. but are these events not normal in many others summers anyway so cant be attributed to how the strat behaved months earlier?

 

[BruenSryan]

17 hours ago, North-Easterly Blast said:

I am not sure when all SSWs have taken place in the past, but I know that they can lead to notably cold outbreaks in the UK as the examples from Jan 2013 and Feb 2018 show, but I am not sure that a SSW guarantees a significant cold spell for the UK, as the dice has to still land as to if the blocking sets up favourably to get the UK cold.  I am also of the opinion and I question if a SSW can bump the UK out of a cold spell, as I believe there was some stratospheric warming prior to the cold spell in February 2021 but after a week it disappeared abruptly and the UK went very mild.  I also think that there was an SSW prior to the cold spell in Feb 2009, but that disappeared abruptly in mid-month and the UK again went very mild.

The 2021 major SSW occurred in early January with a central date (the day reversal at 60N 10hPa occurred) of 5th January. There was a sudden stratospheric cooling meanwhile through the second week of February when the easterly was going on and it is perfectly normal for this to happen as SPV disruptions cut off wave activity reaching the mid to upper layers of the stratosphere. Depending on when the SSW occurs, radiative cooling due to the time of year (combined with the aforementioned wave activity) also leads to a strong SPV. This is why early SSWE are not necessarily great. 

If you want to look at previous major SSW events, there's a compendium here. There's also an archive of 60-90N height anomalies here for winters since 1979.

It's not only a case of getting the blocking position correct, it's also a case of whether the warming will propagate back downward to impact the troposphere. Karpechko et al (2017) found that 43% of major SSW events are nSSW (non-downward propagating) which is not far from half of the events. Whether a SSW is nSSW or dSSW (downward propagating) is defined by the 1000hPa NAM index. 

[BruenSryan]

4 minutes ago, mushymanrob said:

fair comment (poor/cool).. but are these events not normal in many others summers anyway so cant be attributed to how the strat behaved months earlier?

 

Think he mentioned it as a quirk rather than being a culmination of what happened in the stratosphere. The only time I've heard the stratosphere possibly impacting the summer is that of 2019 when we got a very dynamic final warming in late April 2019 that was followed by the most negative May NAO index in the record and the summer of 2019, despite being pretty warm and occasionally extremely hot, also featured a notably negative NAO index for all months as well as the longest run of -NAO days for any season. 

I think there's a good argument to be made there that the dynamic final warming led to the very blocked May and perhaps first half of June 2019 too but after that not so sure due to the non-existence of the SPV at that time of year of course. 

 

[Don]

On 08/02/2022 at 21:27, Mike Poole said:

I wouldn’t bet against it would you?

That would suit me fine, providing we don't have those crazy heat spikes late July and during the first half of August.  The cooler second half of August 2020 was a welcome relief for me, even though it was wet! 

Maybe we can then have a similar winter to 2020/21, nothing special in the scheme of things but epic compared to the pathetic excuse we have right now!