Sudden Stratospheric Warming Event (SH) 2019

[Awhituobs]

Niwa are now saying the next 3 months could see above average temperatures (overall)?

[Richard]

Niwa are now saying the next 3 months could see above average temperatures (overall)?

Fantastic, maybe they believe we are in for a higher chance of blocking highs to the east, better there than to the west.

[Awhituobs]

Yeah,I suspect so.but I have seen other model outputs showing NZ being a bit lower temp than normal for next 3 months ( ecmwf). Will all depend on where the blocking occurs.

[Cyclone Tracy]

Geopotential height anomalies showing the dripping paint effect as the SSW coupled into the troposphere over the last 2 weeks. Currently the SAM (AAO) index still negative 2 and projected to remain negative for the next week. So far it's been all about polar troughs and minimal moisture producing below average temps for the SI in October but it will become interesting with the MJO phase moving into this part of the world around a week from now. Tropical disturbances might start coming into play by sending more moisture into the mid latitudes.

GPH AAO 31102019.jpg

[Awhituobs]

interestingly Antarctic sea ice is decreasing at a fast rate currently, if it keeps the current rate up it will get to a record low for the time of year

[Awhituobs]

ps another Tasman sea (western side) marine heat wave is forming due to the hot air coming off australia and lots of high pressure in that area lately (i.e light winds...but that is about to all change)

[Cyclone Tracy]

Yes, warm anomalies now making it to the surface at over the Antarctic continent has increased the melt rate in the last 2 weeks but when comparing to 1979 and the 30 year averages, all looks fairly normal.

Antarctic sea ice 0111.jpg

[Cyclone Tracy]

The SSW has caused a dramatic change in the stratospheric air chemistry over the Antarctic continent with the Ozone hole no where near size and depth of 12 months ago, displaced and almost non existent. A lot less UV down at the surface. It will be interesting what the longer term tropospheric impacts will be in the over the next 12 months in the southern hemisphere and the globe.

South Pole Ozone 031119.jpg

[Awhituobs]

The north pole gets these events happening every 2 years or so
why do you and Tony T think that a south pole event is going to make different changes that will have any impact on the globe other than what occurs anyway after a northern hemisphere event? (curious to know)

[Cyclone Tracy]

Land at high latitudes in the Northern Hemisphere trigger far more long wave troughs which contributes to the breakdown of the polar vortex. The Southern Hemisphere vortex is far more robust and powerful and breaks down very rarely during the polar night period as modern records show. Global ozone depletion peaks over the Antarctic continent, which is why Mets and Climatologists are watching this very closely, as stratospheric air chemistry changes can vary the globes tropospheric air circulation and temperatures over months to years.

[TonyT]

The north pole gets these events happening every 2 years or so
why do you and Tony T think that a south pole event is going to make different changes that will have any impact on the globe other than what occurs anyway after a northern hemisphere event? (curious to know)

I'm by no means an expert, so take anything I say with a large bag of salt (!) but I would speculate that principal difference lies with the far greater ocean area in the SH. Oceans have a much greater heat capacity than land, so on the one hand that ameliorates the potentially extreme short term effects of a SH SSW event (so we were never going to get the "beast from the east" scenario the Herald told us was likely), but it also means the impacts (although more subtle than in the NH) can last longer and be more widespread. I think the timing of this event occurring with a very weak deep solar minimum (which may or may not be a con-incidence) means that weak and more random jetstream activity provides a mechanism for the downstream effects of the SSW to influence mid latitude weather systems. Its also interesting to note that some NH forecasters are seeing the potential for a NH SSW event this NH winter. SSW's seem to be more common at solar max and solar min.

Edit - there were NH SSWs in the 2018 and 2019 winters, and in the last solar minimum there were SSWs every winter between 2007 and 2010. NH SSWs tend to be more common with a westerly QBO at solar maximums, and an easterly QBO at solar minimums. The current QBO is westerly, but on the changeover to easterly in the next 6 months.

Given that NH SSWs are much more common than SH ones, I think that alone makes the SH one worth watching closely, so we can see how it is different.

[Awhituobs]

antarctic sea ice is heading for a record low for the time of year now I see, as its melting fast
and the tasman sea is warming up quickly currently too with the current weather pattern
so for NZ we could end up having a warmer than normal summer (which is what Niwa are now hinting at)

[Awhituobs]

November globally currently has the largest above normal temperature I have seen
http://models.weatherbell.com/climate/n ... m_anom.png
(due to antarctica being mainly above average temperature)
ps solar minimum is only 0.1% less solar output

[TonyT]

antarctic sea ice is heading for a record low for the time of year now I see, as its melting fast
and the tasman sea is warming up quickly currently too with the current weather pattern
so for NZ we could end up having a warmer than normal summer (which is what Niwa are now hinting at)

November globally currently has the largest above normal temperature I have seen
http://models.weatherbell.com/climate/n ... m_anom.png
(due to antarctica being mainly above average temperature)
ps solar minimum is only 0.1% less solar output

You have given some examples but I'm not sure what your point is. You seem to want to counter every point other people make, but don't make any points of your own. If your point is that it appears to be getting warmer and that this is contrary to what you expected from this SSW event then I would remind you that with a SH SSW this early in the season and of this magnitude then nobody knew what the outcomes would be, and if you look far enough back in this thread you will find posts from me suggesting that anomalous warmth is as possible as anomalous cold. By way of counter, I would remind you that the last two months have had below normal temperatures for NZ, the first time in a couple of years that has happened. SSW or coincidence? It could be either.

As you point out Antartica is now warmer than the long term normal, but you can clearly see why - the time/height cross sections clearly show the SSW propagating down towards the surface, as expected. So the SSW is certainly having an impact on the Antarctic atmosphere. It remains to be seen what the downstream impacts of this will be on the rest of the SH and globe. It may well be not much at all, but how often does the atmosphere confound us with unexpected impacts from seemingly innocuous happenings - so keeping eyes and minds open is a sensible approach. One of the most valuable pieces of advice I ever got was from a very eminent meteorologist who told us to "be attune to weak signals".

Finally, as I am sure you are no doubt aware from the extensive reading you must do on the subject, the 0.1% change in TSI is not the most consequential outcome of solar cycle min and max changes. No doubt 0.1% of TSI does have some impacts (in the same way that 0.04% of C02 has some impacts) but the driving mechanism for most of the well researched, documented, and scientifically accepted atmospheric changes which correlate with the solar cycle is geomagnetic in origin, operating via a poorly (but increasingly ) understood mechanism of magnetic and energy flux changes in the upper atmosphere. It can be hard to appreciate, but the sun modulates energy fields over and around the earth in many more ways than just TSI. Just because we cant see them, doesn't mean we cant see the impacts of them. Thats why solar is one of the biggest and most exciting research areas in climatology at the moment.

[Awhituobs]

I would remind you that the last two months have had below normal temperatures for NZ,

the NZ average temperature has not actually been at the point to be below average though (i.e has not reached the 0.5c threshold) for either Oct or Nov
anyway, I can see I have hit a nerve so I will not comment anymore on this thread as you are being rather condescending

[Bradley]

I would remind you that the last two months have had below normal temperatures for NZ,

the NZ average temperature has not actually been at the point to be below average though (i.e has not reached the 0.5c threshold) for either Oct or Nov
anyway, I can see I have hit a nerve so I will not comment anymore on this thread as you are being rather condescending

If you use NIWA's definition of below average where even -0.4C isn't considered "below average" then it's hard to point out obvious facts to you, I see Tony's efforts were in vain...

[RWood]

October 7SS value was 0.3C below the 1981-2010 average, so 2 months in a row below the mean, for the first time since Jan-Feb 2017.

[David]

the NZ average temperature has not actually been at the point to be below average though (i.e has not reached the 0.5c threshold) for either Oct or Nov
anyway, I can see I have hit a nerve so I will not comment anymore on this thread as you are being rather condescending

If you use NIWA's definition of below average where even -0.4C isn't considered "below average" then it's hard to point out obvious facts to you, I see Tony's efforts were in vain...

I'm a little confused, what you just said and what Awhituobs post said is the same thing, that the threshold for below average hasn't been reached?

[Chris W]

There appears to have been a slight splitting of the stratospheric vortex with a weak lobe southeast of Australia, as CT mentioned weeks ago. This seems to be organising the powerful jet interaction to the west of NZ and maybe some kind of sustained upper trough activity for a little while?

[Cyclone Tracy]

Water vapour 1pm 0811 NZT.jpg

Yes, an aggressive upper trough now launching into SE OZ from over the Antarctic shelf with multiple associated cold pools. Snow is projected to fall to around 600 to 700m ASL 50km from Melbourne's city centre tonight, only 3 weeks from summer. This is rare to this level beyond September on the mainland. The upper trough will head into the Tasman tomorrow. As mentioned in the Australian weather thread, the other side of the coin is heat and bush fires to the north.

[Cyclone Tracy]

OZ 09112019.jpg

A picture tells a thousand words. Significant jet stream surge equatorward impacting southern and eastern Australia in the last 24 hours.

[Chris W]

That’s the end of the 10hPa vortex as an anticyclone has fully taken over. 70hPa bent well out of shape over towards Africa and South America, and throwing out some weak lobes over the Antarctic continent.

[Avalanche]

Question: The Polar Vortex has completely fallen apart in Antarctica to the point where its unrecognisable to the round shape it used to be. Does it transfer itself to the Arctic Circle instead? As ive noticed alot more wind activity starting to develop at 70hPa. Does the Polar Vortex change to the Southern and Northern Hemispheres every Summer and Winter season? Thanks appreciate the answer. On another note, ive not really noticed major changes to the weather in our neck of the woods. Other than a increase in high pressure over Australia and warmer temps for them.

[Cyclone Tracy]

Question: The Polar Vortex has completely fallen apart in Antarctica to the point where its unrecognisable to the round shape it used to be. Does it transfer itself to the Arctic Circle instead? As ive noticed alot more wind activity starting to develop at 70hPa. Does the Polar Vortex change to the Southern and Northern Hemispheres every Summer and Winter season? Thanks appreciate the answer. On another note, ive not really noticed major changes to the weather in our neck of the woods. Other than a increase in high pressure over Australia and warmer temps for them.

My 2 cents worth. The 2 hemispheric polar vortex's are separate systems. Their seasonal life cycle is dependent on the temperature difference between the equator and the poles. The southern stratospheric polar vortex generally warms and disburses in late November to early December , with this year being earlier due to the SSW. Early warmings like this years change weather patterns like we have seen in September and October with cooler than average months for NZ as a whole. Even though the stratospheric polar vortex leaves, tropospheric disturbances can linger for months if it warms early. Australia has seen this first hand in the last 2 weeks with extremes on either side of the jet stream. Currently the SAM (AAO) index is showing this behaviour with it now being negative for an extended period which has involved an abnormal warming the Antarctic surface.

SSW 12 Nov.jpg

[Chris W]

Bang on CT, the two polar vortices are not directly connected. My own two cents is that the rapidly shortening hours of sunlight over either polar region after the respective autumn equinox cools the atmosphere there rapidly resulting in the contrast in temperature with the tropics that CT has explained. Then in spring the sun returns and warms the pole, meaning that the vortex disintegrates.

It looks like there'll be a lot of ongoing disturbance to the jetstreams in our hemisphere through the summer. That's just a guess but I don't see how there won't with such a major disturbance in the stratosphere.

By the way CT that graphic sums the whole warming up superbly. It shows that downwelling and coupling did happen but just took its time.