Sudden Stratospheric Warming Event (SH) 2019

[Awhituobs]

re summer season:
the SOI is tending towards La Nina
so that could mean more TC's for Queensland ?

[Willoughby]

Marvelous sounding just fully recorded from Amundsen-Scott South Pole!

image.png

Got as high as 1.2C at 8.3 hPa at 30.5 km / 100k feet level. 307 km/h winds up at that level too.

[Cyclone Tracy]

Anyone care to speculate what this could mean for tropical cyclone activity?

The SSW acts to cool the equatorial band upper-troposphere, increasing upwelling along the equator. This favors for strong MJO events which may spark a late season outbreak of hurricanes in the Atlantic and Typhoons in the West Pacific.

IMO, longer term impacts of the SSW on the South Pacific are still unknown at this point but an early season TC would have a higher chance this year.

[Cyclone Tracy]

2 weeks in and just reviewing the observations up to 12 Sept. A historical event observed, especially the air chemistry impact on the ozone hole over the Antarctic continent. Ozone destruction should be peaking but it's volumes are increasing. Start of the SSW collapse looks like occuring around a week from now.

Eddy heat flux anomalies suggest the Polar Jet could start to see an impact within a week. Some GEFS ensemble members have the SAM index plunging at the end of Sept.

Zonal temp 1209.jpg

Zonal GPH 1209.jpg

Ozone hole 11 Sept.jpg

[Andy]

What is the potential outcome for NZ towards then end of Sept?

[snowchaser01]

Model runs are WAAAAYY out today for the system affecting central NZ currently. Do we think they potentially being affected by the SSW... could be completely wrong, just a hunch.?

[Cyclone Tracy]

GFS is starting to become spooked in the medium term, hints of the 'meridonal flow' pattern The 18Z run just launched the 540 thickness line near the Queensland border, large south Atlantic cyclonic gyres, 350 km/h interacting jet streams over the NI and large blocking highs in multiple regions towards the end of September.

[TonyT]

Model runs are WAAAAYY out today for the system affecting central NZ currently. Do we think they potentially being affected by the SSW... could be completely wrong, just a hunch.?

I'm not seeing this, the ECMWF has been pretty consistent for the last couple of days and seems to be verifying.

[snowchaser01]

Model runs are WAAAAYY out today for the system affecting central NZ currently. Do we think they potentially being affected by the SSW... could be completely wrong, just a hunch.?

I'm not seeing this, the ECMWF has been pretty consistent for the last couple of days and seems to be verifying.

Most modelling had more persistent rain this afternoon and drizzle this morning. And 10mm max, already more than that and plenty more to come.
Seems the more persistent rain was this morning. Seems the entire system is about 200km further south than what models were predicting.

[TonyT]

I'm not seeing this, the ECMWF has been pretty consistent for the last couple of days and seems to be verifying.

Most modelling had more persistent rain this afternoon and drizzle this morning. And 10mm max, already more than that and plenty more to come.
Seems the more persistent rain was this morning. Seems the entire system is about 200km further south than what models were predicting.

i must have got lucky then.

[snowchaser01]

Holy Moly! Polar vortex starting to look very odd now, will be interesting to see impacts from this... if it continues to break up of course.

Capture.JPG

[Richard]

Gone from looking more like a Indy car race track to a Roman chariot racing stadium.

[Razor]

I saw Metservice commenting in facebook earlier about SSW. Acknowledging it's happening and it's interesting but basically downplaying any significant risk to our weather as most likely presenting as normal spring stuff, a low chance of as anything outside the norm. Sorry, can't find link.

Certainly the next wee while looks pretty bog standard

[Richard]

A SSW event in the NH sends the weather into a spin following it but a similar event in the south likely to have little effect ? you would think that this current SSW being only the second strong recorded event of it type in the SH would hardly have provided enough historical data thus far to use for predicting any likely outcome.

[Razor]

A SSW event in the NH sends the weather into a spin following it but a similar event in the south likely to have little effect ? you would think that this current SSW being only the second strong recorded event of it type in the SH would hardly have provided enough historical data thus far to use for predicting any likely outcome.

Perhaps more landmass in the NH has an impact?

[Cyclone Tracy]

EC and GFS have the first extreme SSW streamer launching equatorward into the South Atlantic just after the equinox if it verifies. Tropospheric polar vortex pulsing the 516 thickness line to around 43 degrees south, 540 thickness line to around 33 degrees south on both models. Tropopause lowering as the polar jet is cut loose. These streamers can be launched months after the SSW peak.

TP 23 Sept GFS.jpg

GFS EC 24 Sep Sth Atlantic.jpg

[TonyT]

A SSW event in the NH sends the weather into a spin following it but a similar event in the south likely to have little effect ? you would think that this current SSW being only the second strong recorded event of it type in the SH would hardly have provided enough historical data thus far to use for predicting any likely outcome.

Perhaps more landmass in the NH has an impact?

The NH landmass influences the type of surface weather response to the SSW (a type we won't see here for obvious reasons - the long lasting deep cold freeze) but the lack of large land masses poleward of 45deg in the SH doesn't mean there won't be significant effects if the polar vortex gets its knickers in a knot. Its just not clear what those effects will be yet. But CT's latest post above gives an idea.

[Awhituobs]

to be fair South Africa has had severe cold snaps, with snow to low levels, before ..regardless of a SSW event.
i.e polar out breaks and the polar jet stream moving north happens from time to time in the spring anyway
just maybe this faster than normal warming of the stratosphere increases the chances of that occuring this spring..but where..first one looks to be south atlantic

[Cyclone Tracy]

SSW now impacting MJO with the cooling troposphere increasing upwelling along the equator. Many EC ensemble members are swinging wildly outside the circle of calmness in the next 14 days. Northern hemisphere hurricanes are a flow on effect at the end of September into October. The timing for the Pacific regions will be interesting to follow in the weeks ahead.

EC MJO.jpg

[Bradley]

The elongated area of the polar vortex at 70hpa now only has winds of around the 90-100kmh range - things are starting to move quickly now

1112.png

[Chris W]

10hPa vortex now over the Weddell Sea and the 70hPa vortex not far behind.you can see this now downwelling to the troposphere with CT’s projection and the 250hPA jet angling with the tubular stratospheric vortex. I thought it would just become a tiny circular vortex over the West Antarctic Pensinula but as I say it’s looking tube-shaped. It would be really interesting to see the weather in Tierra del Fuego now! I saw the Falklands were under snow the other day.

[Simon Culling]

A fantastic and informative thread. Thanks to all who have contributed.

Looks like the Antarctic temperature has risen above freezing at 8.5km height.

https://twitter.com/rms5539/status/1172878586669404162

[Awhituobs]

thought of the day, at that altitude, the atmosphere is very thin, so does not have the same thermal conductivity
question then is if you were at that altitude, would that mean 0C would feel colder or warmer than 0C at sea level?

[Willoughby]

thought of the day, at that altitude, the atmosphere is very thin, so does not have the same thermal conductivity
question then is if you were at that altitude, would that mean 0C would feel colder or warmer than 0C at sea level?

South Pole sounding from yesterday midday NZT.

image.png

Don't forget the 150 knot winds at that level too, totally negating any 'warmth'.

[Cyclone Tracy]

Latest NASA ozone modelling showing the ozone hole shrinks to half it's size in 120 hours on the equinox (opposite to normal at this time of year). Multiple stratospheric polar vortex streamers launching ozone air parcels into the mid latitudes, can be a precursor to tropospheric change. This chaos is all still occurring above the troposphere.

NASA Ozone map 1609 12Z.jpg