Sudden Stratospheric Warming Event (SH) 2019

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Chris W
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Chris W »

Coriolis wouldn't have as much of an influence at 250hPa however, I would think, compared to ground level. So I'm not surprised that the two hemispheres' winds could link up, albeit rarely and due only to a significant disturbance. Just a guess, I have never studied the upper atmosphere before except first year geography at university looking at the basics of meteorology and atmospheric circulation.
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Cyclone Tracy »

Yes, needs a closer look. It happens every so often, so certainly not unprecedented. I found this one interesting as it is currently flowing from both hemispheres as 2 seperate weather events.
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Chris W »

As I just mentioned in the October thread, now that the stratospheric vortex bounced back towards the Weddell Sea we are in line for more southerly impacts again. Any time I look at the vortex movements at 10/70hPa I see pretty clear responses in the tropospheric wind fields at 250hPa and 500hPa and of course then down to lower levels. To my untrained eye that is coupling.

Have a look at the Metcheck Antarctic charts through the end of the month, the vortex gets severely weakened and shunted right out and almost into the Atlantic! The end is nigh. I have no link to these guys, but to me these charts have been nailing the vortex behaviour since day 1:
https://www.metcheck.com/SEASONAL/strat ... ecasts.asp#
Chris W
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Chris W »

Cyclone Tracy wrote: Sat 12/10/2019 12:34 EC 12Z today splits the lower stratospheric polar vortex into 2 vortices on 22nd October. The new vortex launching equatorward to the SW of Australia and couples with the troposphere. Quite an aggressive development if it verifies.

EC 100 hPa 22 Oct.jpg

Take a look at the 250hPa vortex as modelled today, there is a sizeable u-turn going on SW of Australia and a weak cross-Antarctic wind linking to it.
CEA8BA18-E733-4AA0-B87E-5367656714C6.png
Meanwhile the 70hPa vortex is now extending to Cape Town.
https://earth.nullschool.net/
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Chris W
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Chris W »

Signs building of a vortex split as CT foretold, both at 70 and 250hPa. Raging SW jet heading our way linking with a mini jet crossing the ice leading to this week’s weather.

Popcorn time for me.
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Rogue »

I've run out of popcorn to be honest!
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Chris W »

Split potential seems to have waned as the u-turn is gone, but there are still odd things going on. Metcheck takes the stratospheric vortex centre to the Drake passage and then looks to end it about the second week of November.
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Cyclone Tracy »

2 cents worth.

No need for anymore popcorn. Coupling is happening between the stratopshere and troposphere. 2 minor breaches in early September and October and now the main course is arriving at 700 hPa. 150 hPa now breaking daily mean wind zonal records over polar region. It took 32 days for the disturbance to arrive from the peak on 16 September. How long the negative SAM (AAO) continues for is still is unknown, GPH image is the latest up until 20 October but the forecast shows a prolonged negative phase.

2002 coupled much faster into the troposphere with 18 days from peak warming to peak negative SAM (AAO) at the surface and continued negative for around 2 months having a secondary surge 35 days after the initial 26 September warming. Initial comparisons of 2019 to 2002 certainly shows different behaviour and timings, especially the split vortex in 2002 and the displaced vortex in 2019.

For comparison , Northern hemisphere events average from 10 to 40 days when coupling occurs after the peak of the SSW. Sometimes coupling does not occur.
GPH height 20 Oct.jpg
Zonal wind Polar region 22 Oct Nasa 150 hPa.jpg
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Awhituobs »

I cant see anything too out of the ordinary in the model runs for the rest of the month though
Oct should end up maybe slightly below aeverage temperature for NZ as a whole , but within the 0.5c range from normal, so probably will be classified as normal
October has been windy with a lot of SW winds, but that is tradional anyway (being a windy month, but there has been less rain bearing NW winds, due to the Indean Ocean di pole)
so what is November going to bring?..more of the same topy turvey spring weather?
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Cyclone Tracy »

Nice article and hot off the press. The BoM jumping onboard the SSW / Negative SAM train now :smile:
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Cyclone Tracy »

SAM (AAO) index has now dropped to -3.

NASA and most North American ensembles showing 10 hPa winds turning easterly on Friday. The stratospheric polar vortex is unlikely to recover which would mean it’s the final warming. This would be the 2nd earliest ‘final warming’ of the SPV since records began in 1979. 1988 was 27th October, 2002 was 1st November. As well as the current spring impacts, this seems likely to go into summer. NIWA, MS and BoM's monthly outlooks coming up will be interesting.

Experimental modelling by stratospheric experts are linking the positive IOD to the delaying of the SSW downward propagation. The positive IOD is also being linked to the record extended Indian monsoon. Signals of major air circulation changes are flashing in multiple locations across hemispheres. There will be multiple papers written in the coming years on this event and the related triggers no doubt.
NASA 10 hPa 25102019.jpg
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Awhituobs »

models are hinting at nice weather for a change for NZ for the start of November, i,e a big pattern change
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Willoughby »

Very warm week globally coming up, both Antarctic and Arctic in both a very positive anomaly territory:
image.png
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by spwill »

Looking like we will have a warmer than average start to November here in NZ.
The SAM is looking very negative in the two week outlook however the current GFS has the westerlies and highs further south to start November compared with what we have seen in October
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Awhituobs »

so it must be someone else's turn in the southern hemisphere to cope the negative SAM lol
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Storm Struck »

Something thats been on my mind :-k , would the SSW because the temperatures are increased high up affect the ground surface temperatures?.
Would normally warm upper air that comes across from QLD with temperatures in the mid 30,s like this week, bring simular temperatures here as a result? And therefore continue into summer bringing very hot surface temperatures..
I know you guys were saying that SSW can affect all facits of the weather, from increased severe weather to improved high pressures.
Canterbury, home of good rugby and severe storms
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Awhituobs »

There was a claim on this thread of colder than normal for coming months and whole globe cool down even
Due to the escaping polar air due to weaker polar vortex
That has happened a couple of times but has been short lived
NZ might have an early start to summer instead ( but then somewhere else the opposite)
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Cyclone Tracy »

2 cents worth. The pattern is changing, so surface temperatures will depend on the position of the southern hemisphere omega blocks. Multiple blocking highs are now appearing on most models around the southern hemisphere within the next 7 days, one in the Tasman next weekend. The warmth from OZ will arrive with this high. It's going to be about abnormally warm and then anomaly cold spells in November, depending on where the upper lows are positioned with the meridional flowing jet.

SAM now below negative 3 :smile:
EC for 3 Nov.jpg
AAO 25 Oct.jpg
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by treetopkk »

With Tasman sea temps of 14-18 deg there will be a lot of heat loss for air crossing over unless there are 3 0r 4 days of continuous NW winds without SW changes, which is not happening at the moment .
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Awhituobs »

depending on where the upper lows are positioned with the meridional flowing jet.
yes, that is the million dollar Q
it might mean we have a blocking high(s) over NZ for November
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by TonyT »

Storm Struck wrote: Sat 26/10/2019 11:20 Something thats been on my mind :-k , would the SSW because the temperatures are increased high up affect the ground surface temperatures?.
Would normally warm upper air that comes across from QLD with temperatures in the mid 30,s like this week, bring simular temperatures here as a result? And therefore continue into summer bringing very hot surface temperatures..
I know you guys were saying that SSW can affect all facits of the weather, from increased severe weather to improved high pressures.
The answer to your question is no, not via a direct advection of warmer than normal air from the stratosphere into the troposphere and then to the surface. But via a mechanism of changing the wind and pressure patterns allowing more periods of warm air transport from the Australian interior then yes, that is possible. Strong day to day and week to week temperature variations are most likely when the jetstreams break down and a weakened polar jet starts flirt with a weakened sub-tropical jet. And that is more likely to happen this summer than most.
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Chris W »

The stratospheric vortex is mostly now centred over Drake Passage and weak on its Antarctic continental side. Metcheck continues to get its modelling nailed on and forecasts the disintegration of the vortex by mid-month.
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Cyclone Tracy »

Stratospheric vortex winds at 10 hPa have turned easterly in the last 24 hours. 2nd earliest 'final warming' recorded since records began in 1979. Large blocking highs and a meridional flowing jet are now coming into place. NZ getting served a southern hemispheric omega block for the start of November. West side has a large upper trough into southern and eastern Australia the other side has the 540 thickness line hitting 29 degrees south below the Cook Island on Sunday. SAM (AAO) index continues significantly negative and trending that way for the next week.
SSW 3010.jpg
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Re: Sudden Stratospheric Warming Event (SH) 2019

Unread post by Awhituobs »

Am looking forward to a easing of the cold salt laden SW winds here :)
My poor manuka plants I planted are badly salt burnt now after 2 months of SW winds here!
(I do now blame down stream effects of the SSW surely LOL )
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