Sudden Stratospheric Warming Event (SH) 2019

[Bradley]

If anything the heat anamoly at 10hpa is forecast not only to continue until at least the 16/09 but to substantially increase in area over Antarctica as well. You can see in the map below the area of -30C or above is basically the entire size of Antarctica, at present it would be lucky to be half the size so this event is a long way from finishing, we could be looking at seeing the effects of this on New Zealand continuing well into November at this rate...

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[Razor]

Whatever this does the foreseeable future (week or 2) looks mostly settled and uneventful for Canterbury, good news for feeding and growing.

[Chris W]

Looks at present like we may see a return towards the end of next week of northwesterlies rather than anything from a southerly direction. It doesn’t look to be dominated by high pressure. Could be quite windy.

[Willoughby]

If the GFS is anything to go by, the southern continent could go under significant cooling the next week, especially in the east. I wonder though how much of the cold-bias problem has been fixed for the new GFS.

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Has a big effect on southern hemisphere temperatures which could also bring the globe to a more 'normal' temperature for a change.

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GFS V ECMWF (12Z runs) comparison:

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Meanwhile, the BoM ACCESS-G model increases it's severity of the SSW with 10mb temps to a massive 31C on the 11th. ECMWF a lot more conservative showing 10mb temps to 14C on about the 11th.

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[wembley]

Hard to tell what summer will be like after this...

[TonyT]

Hard to tell what summer will be like after this...

Cool.

[Bradley]

Quiet hard to believe that it is warmer 30km above the South Pole at the moment then it was here in Christchurch this morning!

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[stepr]

From a UK perspective this is quite interesting, as we get SSW events more frequently, and we know exactly what their effects are likely to be somewhere.

I do wonder what influence the sea will have on the SSW event there because in the northern hemisphere there's a lot of land mass around in the mid latitudes, so when surface cold incursions occur they can be very cold, locally. However in NZ's case, I wonder if the relative lack of landmass at the mid latitudes will mean any effects would be more subdued than they would be in the northern hemisphere (ie not quite as cold, comparatively). But then again, the source (Antarctica) is colder than the Arctic generally.

I also wonder how this will effect feedback cycles around the globe. Though knowing what I do about Arctic SSW events, any influence on the northern hemisphere will be minimal.

[Bradley]

From a UK perspective this is quite interesting, as we get SSW events more frequently, and we know exactly what their effects are likely to be somewhere.

I do wonder what influence the sea will have on the SSW event there because in the northern hemisphere there's a lot of land mass around in the mid latitudes, so when surface cold incursions occur they can be very cold, locally. However in NZ's case, I wonder if the relative lack of landmass at the mid latitudes will mean any effects would be more subdued than they would be in the northern hemisphere (ie not quite as cold, comparatively). But then again, the source (Antarctica) is colder than the Arctic generally.

I also wonder how this will effect feedback cycles around the globe. Though knowing what I do about Arctic SSW events, any influence on the northern hemisphere will be minimal.

Another point which you may not be factoring in is that this event happening above Antarctica is 3-4 times stronger then the SSW that happened in 2018 in the northern hemisphere. Your event was approx a 25C anomaly at 10hpa (as per graph below) whereas this event is already 75C above the long term mean and is forecast to go above 100C in around 5 days time. As to what the effects of this will be, only time will tell!

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[talbotmj15]

The Vortex has clearly begun to break apart. Can the gurus pass any more guidance and speculate on any potential possibilities yet. I see next weekend is looking quite warm? Shouldnt we be starting to see effects in the troposphere and it upsetting the weather by now?

Also what happens when the vortex breaks up?

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[RWood]

I have a distinct memory of talks about vortex disruption in/around February 2004, but presumably there was no SSW event then. That month was of course cool, wet, windy and cyclonic - the wettest on record for about 30 locations.

[Ash]

According to Niwa Feb 2004 was a historic month, massive flooding and historic wind events as well as cooler than average temps.

[TonyT]

The Vortex has clearly begun to break apart. Can the gurus pass any more guidance and speculate on any potential possibilities yet.

I wrote a list further up this thread.

I see next weekend is looking quite warm? Shouldnt we be starting to see effects in the troposphere and it upsetting the weather by now?

No.

Also what happens when the vortex breaks up? received_907383229646143.png

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[Chris Raine]

Oh well. We will see what happens in due course. Currently it is cold in Southland .I have an air temp currently of -1.8C and still dropping .One of the coldest nights of the year

[Bradley]

Latest GFS output has the SSW event basically taking over the continent of Antarctica in 10 days time - we already have drastically higher then normal 10hpa temps of -30C or above over half of Antarctica but this extends to 90% of Antarctica on the 18/9 - this event still has a long way to go before it's over and you can't help but think October is going to be an extremely active month for New Zealand

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[snowchaser01]

Safe to say the Polar Vortex is under extreme duress currently. God knows what implications this will have down here in the coming weeks and months, but it seems to be breaking up extremely quickly currently.
Not that I know much about this sort of thing, but it seems it has split out over South America. The "loose red patches" to about southern Bolivia or northern Argentina are also showing in surface observations.... at the very least it is interesting and something to watch.

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[treetopkk]

anyone know what conditions are currently occurring at the bottom of S America compared to the norm ? They are a lot closer to the action now . A taste of what we might expect perhaps ?

[Cyclone Tracy]

I've just had a quick look at surface temps and Antarctic sea ice extent since the stratosphere warming commenced.

Southern hemisphere and the Antarctic surface temps have dropped significantly, which has readjusted the global temperature downward by 0.3c to now only 0.1c above the 1979-2000 ave. The Antarctic sea ice extent has grown by half a million square km's in same period and is virtually at the 1980-2010 median.

Looking forward to having a close look at NASA's latest stratospheric data tomorrow morning (NZT)

[snowchaser01]

I've just had a quick look at surface temps and Antarctic sea ice extent since the stratosphere warming commenced.

Southern hemisphere and the Antarctic surface temps have dropped significantly, which has readjusted the global temperature downward by 0.3c to now only 0.1c above the 1979-2000 ave. The Antarctic sea ice extent has grown by half a million square km's in same period and is virtually at the 1980-2010 median.

Looking forward to having a close look at NASA's latest stratospheric data tomorrow morning (NZT)

This is quite shocking!

[Willoughby]

Nice to see a balloon ascent from Amundsen-Scott Station (South Pole) not burst at about 150 hPa which it seems to do often, enabling a full sample of the troposphere, and part of the stratosphere.

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-7.7C to 8 hPa above 10mb beyond that graph.

[Awhituobs]

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Antartic sea ice extent is very variable at the best of times
its below normal by a lot in some places
but then above in others
there does seem to be a split in the temperatures across the southern hemisphere, south america is much colder than normal currently

[Cyclone Tracy]

Incredible air chemistry observations coming in from NASA associated with ozone levels sharply increasing over the Antarctic continent. The ozone hole is being pushed towards Sth America and off the polar continent. EC is projecting it to virtually close off as the SSW peaks tomorrow. Normally, ozone should be degrading at this time of year (Aug-Oct) over the pole, as the sun takes over from the polar night. IMO this will have an impact global air circulation.

On temperatures and circulation, U.S Hurricane met's are also picking up on this and the impact its about to have on MJO. The SSW acts to cool the equatorial band upper-troposphere, increasing upwelling along the equator. This favors for strong MJO events which may spark late season hurricanes in the Atlantic.

Here is last year's comparison to now for the ozone hole as of 7 Sept along with EC's forecast.

[Bradley]

Signs this morning the polar vortex at 70hpa repairing itself with the large area of winds around the 100kmh mark now up to 140kmh and the diamond shape now more of a traditional circle - all this is going directly against the notion that the vortex is losing shape and/or breaking up all together, very strange...

[snowchaser01]

Signs this morning the polar vortex at 70hpa repairing itself with the large area of winds around the 100kmh mark now up to 140kmh and the diamond shape now more of a traditional circle - all this is going directly against the notion that the vortex is losing shape and/or breaking up all together, very strange...

I noticed it did the same thing last week... maybe it goes through cycles when it breaks up? I'm not reading too much into it currently.

[Cyclone Tracy]

My 2 cents worth on the stratospheric polar vortex subject. The event so far has been driven by a wave 1 pattern which is in line with a displaced vortex, rather than a split (both are drastic). As the earlier timing of the SSW event for the southern hemisphere is unprecedented in recorded history, I think even the models are having a stab in the dark on the end result. The vortex behaviour at 100 hPa and 150 hPa will determine the impact on the Jetstream and ultimately NZ's weather.

More popcorn please