CFS daily, ECM and GFS all hinting at change but a significant strat warming is now appearing on GFS, NAVGEM and JMA. On GFS the strat vortex is obliterated out in FI. The strat has been unusually cold over the pole this winter - if this verifies it should shake things up and produce some late Jan/ Feb cold, potentially sustained.

OT, but SSWs are now a common feature of winter. Any ideas on why this is? Ozone is formed by a photochemical reaction, something to do with low solar activity?

OK, now having mentioned strat warming for the 15 millionth time (and noting I'm not the only one commenting on it here) I'm going to duck back behind the parapet and wish you all a HAPPY NEW YEAR!!

Edited

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http://www.wetterzentrale.de/pics/archive/ra/1947/Rrea00119470130.gif

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Slightly off topic, looking at these models, charts and reports.. Are BBC weather forecasts (national) live......? Or pre recorded, so some data used from charts/models are not current (in the now frame) just wondering after todays 1pm weather forecast......?

PS.
Happy new year all..
VSC

looking at the latest models and forecastsa change in the weather is on the way around the 10th onwards . does not look that cold at present but at least it should be drier i thought sudden stratospheric warming was pretty common in the winter, but has to evolve a certain way to give us prolonged cold which at the moment is not forecast.

I believe SSW events occur every other year (on average) in the northern hemisphere winter... So very common, and certainly not the case that each one will put us into an extended deep freeze a la 1963. Interesting only one has ever been recorded in the southern hemisphere for reasons I don't understand.

Andrew

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All speculative at this stage but you can just see the +12C isotherm on the 384h chart! I can't remember seeing anything that high in warmings in the last few winters especially directly over the pole. It is currently about -80C at 10hPa over the pole so that is one hell of a difference.

I imagine the effect of such an extreme warming would be to further disrupt the stratospheric vortex leading to a reversal of zonal winds i.e. a SSW. It could be a dramatically different second half of winter!

It's strange that they are very frequent and almost exclusive to the Northern Hemisphere. It would be interesting to know the cause.

SSWs don't guarantee anything for us weather-wise but the greater the warming/zonal wind reversal the more likely we are to see surface pressure anomalies.

happy new year to all

i would be wary of these strat runs, little on 00z and huge outlier on 06z - see plot from belgian site -

http://weerwoord.be/includes/forum_read.php?id=1930965&tid=1930902 

sorry, no caps shift as right hand in plaster.

I would imagine that such a massive warming would destroy the current intense zonalality and allow very cold arctic air to spill out towards mid latitudes, however, it could as easily head to Greece ad to the uk and we would be left with a mid latitude high.

All speculative if course but such an intense warming especially over the pole will have an dramatic effect of some kind.

Andy

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The wikipedia article on this is quite interesting. It suggests that SSW events in the N hemisphere are caused by a meandering jet that propagates into the stratosphere and causes the winds to slow down there. This in itself is interesting, because strat warming is apparantly caused by stuff going on in the troposphere?! So is the whole thing a positive feedback mechanism? Anyway the implication of all this, is that the southern hemisphere doesnt get SSW events because there are no midlatitude continents bordering oceans (that are perpendicular to the west-east winds - antartica is parallel) so nothing to cause the meandering jet. 

 

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Both , it depends which ones you catch

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But certainly gives us a much greater chance of blocking somewhere around the BI's , as mentioned by J Hammond last year

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