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Rare: Sudden Stratospheric Warming in the Southern Hemisphere — cold weather coming?

Posted By Jo Nova On August 30, 2019 @ 2:44 am In Global Warming,Meteorology | Comments Disabled

Right now a very rare southern SSW (Sudden Stratospheric Warming) is taking place, possibly peaking today or this weekend over Antarctica. In the Northern Hemisphere SSW’s happen more often and in the month afterwards, wild polar blasts like the “Beast from the East” can peel off. So somewhere way up at 10hPa or 30 – 50 km, there is an area that’s warmed from -60C  to close to zero. The warming up high throws a spanner in the normal jet streams and weeks later, down at the surface, blobs of  cold air from the poles may end up wandering far from “home”.

We (as in Africa, Australia, Argentina, or New Zealand) may get bumper snow and severe frosts, or we may not. Some researchers are getting excited and are using the word “historic”.

SSW, Southern HEmisphere, Antarctica, NIWA, graph.

These are rare over the Southern Hemisphere — due to Antarctica being shaped like a circular cheesecake right over the pole and surrounded by water. The geography is cleaner and simpler than at the north pole, and that generates a strong circumpolar jetstream.  The strong pattern normally stops these sudden warmings up high which occur with wandering jetstreams.

In the Southern Hemisphere there have only been two officially recorded SSW’s in the last 50 years, one in 2002 and a more minor one in 2010. Though I’d venture to guess that we haven’t got much data on temperatures 30km above Antarctica in 1922 (or whenever). In the northern Hemisphere, some are already discussing the odds of another one for this winter, #PolarVortex.

Dr Amy Butler at CIRES/NOAA ESRL is excited.

“… this plot gives a sense of how large planetary-scale atmospheric wave propagation is in the mid-stratosphere (in the SH, the biggest values are more negative). These waves can break (think waves breaking on a beach) and rapidly slow the normal circulation there.”

While those with crystal balls and CMIP5 models may blame any freak weather on CO2, none of the models can predict this. Indeed, the modelers are still trying to define SSW’s Is it a wind reversal, or a temperature gradient change? (Junsu Kim 2017).  The best meteorologists can only predict a Sudden Stratospheric Warming a whole week in advance.

Time to arm up on ways to explain to the superstitious that any cold snaps that may come are not another spooky sign of A CO2 Effect.


The Stratobserve site is good for data geeks — set up by a PhD student. Nice!

See the NIWA report of cold weather that might be headed for New Zealand. @niwaweather

News.com: Rare Antarctic phenomenon could plunge Australian temperatures to midwinter lows

h/t Greg in NZ,  Andrew V.


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