We have a shift in the pattern now taking place with the return of milder westerlies and active Atlantic pattern just in time for New Year. This is removing the first proper ‘cold spell’ of winter and really of 2014 but without a -NAO this happens more often than not (short lived cold spells). The reason for this is simple, the strong MJO signal is in phases 4 and 5 which support mild and unsettled with a +NAO.

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The reason for that +NAO is this. A strong stratospheric cold pool of vortex between Greenland and Scandinavia.

That vortex has reorganised in the last 2 weeks.

However, look at the split which occurs in 10 days from now.

ECMWF 10mb temps at 180 hrs

Note WHERE the model sees the warm pool developing, right where we want to see a blocking high and by warming the stratosphere in this area, this supports the building of high pressure underneath. Where’s it’s cold, you usually get lower pressure underneath. Also note where the vortex goes, into Siberia/Eurasia. IF we see this and I am becoming increasingly confident we’re heading for this towards mid-January, we should see a -NAO and Greenland block develop with the displacement of the coldest air being pushed south out of the Arctic into mid-latitude Eurasia. Have that blocking high west and north of the UK and you draw this Siberian cold westward towards the UK.

There’s a good chance that the MJO will push through the warm phase 4, 5, and 6 into colder phases 7 and 8 over the next 2 weeks.

The ENSO is also becoming more favourable for this solution as the strip of cold water over the N Atlantic is now reaching the UK while the El Nino and it’s warmest waters are now transferring towards the central Pacific with cooling off and against the SA coast. Weak, central Pacific based Ninos tends to be a cold signal mid and late winter for the UK and Western Europe.

This idea remains uncertain for the simple fact we’re still talking at least 15-20 days away and models have a strong tendency to flop around and change. The reason I’m more confident in this solution for colder times say from the 18th of Jan on is that this fits my overall thinking. Interesting times ahead. Keep checking back.

See video for the discussion.

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Tags: arctic oscillation, negative nao, polar stratosphere, sudden stratospheric warming event, uk cold, UK Snow