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Re: Stratosphere discussion 2020
Posted: Tue 11/08/2020 20:51
by Chris W
The positioning of the warming potentially initially moves the vortex more in our direction, but what that really means is a month or two off. Also, La Niña and a negative Indian Ocean dipole are different to last year. Also, the lower stratosphere doesn’t seem to follow 10hPa as well at this point. So, hmm...
Still, this is cool to see.
0AEDD41B-824A-490E-936A-D02B0EF08C04.png
Re: Stratosphere discussion 2020
Posted: Wed 12/08/2020 08:18
by Cyclone Tracy
Bradley wrote: ↑Tue 11/08/2020 20:26
Cyclone Tracy wrote: ↑Tue 11/08/2020 19:31
2018 (11 Aug image), 2019 & 2020 EC comparison 11th Aug 00Z run for the stratospheric polar vortex temperature @ 10 hPa.
Maybe we will see some extreme events in NZ with this years SSW event, last years event and subsequent flow on effects for NZ was dissapointing to say the least!
Yes, where the jet stream positioned itself certainly had a larger impact on Australia than NZ. Last November was quite remarkable in south eastern Oz.
viewtopic.php?p=186816#p186816
Still early days for this year. Equatorial heat flux seems to be driving the current modelling, whether it can maintain the surge into late August is yet to be seen. The Polar vortex can defeat these surges in late August.
Re: Stratosphere discussion 2020
Posted: Sun 16/08/2020 15:26
by Chris W
10hPa warming starting to downwell through 70hPa and below that level to affect the polar jet:
https://earth.nullschool.net/#current/w ... 41,-56.106
GFS models the warming to hold and strengthen through the next 10 days before dissipating, but it has pushed the dissipation back again and again.
Re: Stratosphere discussion 2020
Posted: Tue 18/08/2020 08:08
by Cyclone Tracy
Lower vortex loosing shape as a propagating Rossby wave launches towards SE Australia this Friday and into the Tasman this weekend.
Re: Stratosphere discussion 2020
Posted: Wed 19/08/2020 20:21
by Cyclone Tracy
Fascinating atmospheric battle is playing out on EC's modelling between the incoming equatorial heat flux and the stratospheric polar vortex on 28th August. The stratospheric polar vortex is the most powerful atmospheric weather system on earth, so it normally just doesn't roll over and give up in late August, which is why the sudden stratospheric warming event last year was a rare event. This EC projection is displacing it well off the south pole.
Re: Stratosphere discussion 2020
Posted: Wed 19/08/2020 22:07
by Chris W
Good ding-dong on the GFS as well, real popcorn time as you say!
Re: Stratosphere discussion 2020
Posted: Fri 21/08/2020 13:27
by Chris W
No time to post details/charts right now, but the GFS operational run is going for another major two-pronged warming at 10mb and a very warped vortex all the way down to the tropopause from about a week out through the end of the month.
Edit - here we go as the 06z (UTC) GFS run ramps it further. The ensembles are beginning the agree quite strongly about this:
98C8A098-1695-4371-A2D4-3C4E419ACEC4.png
87259E8D-7890-4771-995A-963F52F04A7C.png
Re: Stratosphere discussion 2020
Posted: Mon 24/08/2020 19:45
by Cyclone Tracy
Ding Ding - EC is awarding round 1 to the Polar Vortex by 31st Aug.
Round 2 coming up from 3rd Sept with an even stronger heat flux surge on both EC & GFS with some GEFS members going for the first stages of a potential SSW
Re: Stratosphere discussion 2020
Posted: Fri 28/08/2020 23:05
by Chris W
GFS, GEFS and EC are increasingly backing the vortex to fight back strongly early September after the current warming and through the second one early next month. Zonal wind speeds pick sharply back up and overall warming gets delayed. She’s a strong one this year.
Re: Stratosphere discussion 2020
Posted: Sat 29/08/2020 13:00
by Kentish Kiwi
Chris W wrote: ↑Fri 28/08/2020 23:05
GFS, GEFS and EC are increasingly backing the vortex to fight back strongly early September after the current warming and through the second one early next month. Zonal wind speeds pick sharply back up and overall warming gets delayed. She’s a strong one this year.
Hi Chris, have you got any thoughts on what the implications of this are for NZ through early-mid spring? Eg might you expect to see a stronger westerly influence from the vortex fighting against the emerging background of La Niña?
Re: Stratosphere discussion 2020
Posted: Sat 29/08/2020 15:13
by Chris W
I’m very much in the learning camp having only started to ‘study’ the stratosphere in the last year or so, but I guess it depends on where the 10hPa vortex gets steered to by warming areas and how much that downwells to lower levels and the jetstream. Looks like it might be pushed away from us so less westerly from that for a while maybe later in September, then perhaps it comes back in our direction. CT and Tony and maybe others might be able to shed more light on it. I’d guess also that the stronger the vortex stays, the more cold it locks in, so it could reserve a decent cold shot or two once it does start to break down later in spring.
Re: Stratosphere discussion 2020
Posted: Mon 07/09/2020 22:28
by Chris W
Total knockout to the PV, it is rock solid. Zonal winds are through the roof and temperatures remain low, and the compactness of the vortex leads to a positive SAM for a while. That warm area still lingers, it just doesn’t make much headway and really serves to strengthen the vortex by keeping it tight. Not much sign of a breakdown soon.
I’d say of the models I’ve looked at my impression is that the GFS operational run has had the best handle on things; the EC op and GEFS/GFS ensembles have been a bit more carried away with a repeat SSW idea but that has not really eventuated in the end.
Re: Stratosphere discussion 2020
Posted: Sun 20/09/2020 08:34
by Cyclone Tracy
The Polar Vortex wins again in the southern hemisphere, as you would expect. Sudden Stratospheric warming events remain a rare phenomenon with 2 surges of heat flux this year forced out by the vortex. Gradual weakening is now underway as the equinox approaches. This time last year, the ozone hole was under attack but things are back to normal this year.
Re: Stratosphere discussion 2020
Posted: Mon 21/09/2020 08:39
by Awhituobs
I see the sea ice extent is above normal for the time of year, probably related associated circulation wind patterns?
Re: Stratosphere discussion 2020
Posted: Mon 21/09/2020 08:59
by Cyclone Tracy
The southern hemisphere lower troposphere polar region has been mostly below average temperature for the last 5 months.
Re: Stratosphere discussion 2020
Posted: Thu 24/09/2020 20:56
by Chris W
Destabilisation of the lower vortex leading to the severe weather being modelled for this weekend:
B28D7AEF-A9E3-402D-B56C-BD2A7619C19D.jpeg
Re: Stratosphere discussion 2020
Posted: Fri 25/09/2020 16:42
by Chris W
One to watch, but the above 3D vortex chart/GFS op shows a reload for about October 5th-6th that could be just as potent. Vortex potentially getting into distress.
https://stratobserve.com/misc_vort3d
Re: Stratosphere discussion 2020
Posted: Thu 08/10/2020 13:13
by Cyclone Tracy
The Southern hemisphere polar vortex has been recorded by NASA at the 2nd strongest in the satellite era for September. It basically smashed any heat flux that came near it. The last time it was this strong so late in the year was 1993. November 1993 across NZ was the coldest November since 1946. The difference this year is a La Nina event is underway. When the final warming occurs in the next 6 weeks, there is a chance a surge of violent polar streamers emerge equatorward. This is one of the most volatile scenarios the mid latitudes can face in this region, surging polar air and warm moist air. It all seems calm now but this could explode if the ridge weakens through November / December.
Re: Stratosphere discussion 2020
Posted: Thu 08/10/2020 14:04
by Richard
I don't think it's being calm at all lately, the spring NW winds have been terrible this year
Re: Stratosphere discussion 2020
Posted: Thu 08/10/2020 14:37
by Cyclone Tracy
Richard wrote: ↑Thu 08/10/2020 14:04
I don't think it's being calm at all lately, the spring NW winds have been terrible this year
That's why I said calm now.
Re: Stratosphere discussion 2020
Posted: Thu 08/10/2020 14:48
by TonyT
Cyclone Tracy wrote: ↑Thu 08/10/2020 13:13
The Southern hemisphere polar vortex has been recorded by NASA at the 2nd strongest in the satellite era for September. It basically smashed any heat flux that came near it. The last time it was this strong so late in the year was 1993. November 1993 across NZ was the coldest November since 1946. The difference this year is a La Nina event is underway. When the final warming occurs in the next 6 weeks, there is a chance a surge of violent polar streamers emerge equatorward. This is one of the most volatile scenarios the mid latitudes can face in this region, surging polar air and warm moist air. It all seems calm now but this could explode if the ridge weakens through November / December.
Interesting but I'm not buying it. The best analogue to the current pattern is 2010/11 and the October/November was very settled that year with frequent anticyclones and warm temperatures. I'd be going for an absence of southerly quarter airflow over the next 2 months.
Re: Stratosphere discussion 2020
Posted: Thu 08/10/2020 15:33
by Cyclone Tracy
Yes, looking at La Nina in isolation I thought the same. I took a closer look at the Polar Vortex today and looked at the SAM projection over the next 4 weeks. Comparing 1993 to 2010 throws up a different dimension. The 1993 positive SAM outcome is very similar to the latest Access S 4 week outlook, as opposed to the very strong positive SAM of Oct/Nov/Dec 2010. I too think it will be warmer because of La Nina but it could become quite volatile rather than settled.
Re: Stratosphere discussion 2020
Posted: Fri 23/10/2020 10:59
by Chris W
No time for posting charts but the upper vortex is under serious pressure now, -25C air over the continent. Looks to take two major warmings over the current model run so next 10-15 days.
Re: Stratosphere discussion 2020
Posted: Sun 25/10/2020 09:48
by Cyclone Tracy
Shorter term, the polar vortex is about to be the strongest its ever been for the start of November. Remarkably, NASA is forecasting it to strengthen again in the next few days. This time last year the final warming had already occurred. This is going to be a rapid and hostile final warming in November. Fascinating to see what the strongest ever vortex this late does to the weather around NZ leading up to Christmas with a La Nina in the mix. We haven't seen this before in recorded times.
Re: Stratosphere discussion 2020
Posted: Mon 26/10/2020 18:01
by Chris W
Doubling the popcorn order.