After a reasonably tranquil Sep/Oct, the upper pattern is shifting with more milder influence from west and south as milder, moister air ends the month and looks to stick around through November’s first half looks.

The reason for this shift is the AO/NAO which after being predominantly negative through the summer into early autumn, is, as expected turning positive. This will allow the polar vortex to strengthen, building the winter sea ice pack.

A positive AO in particular will help intensify winter cold at the source region.

Note the strengthening of the vortex at 30 hpa through the next 10 days.

10 days

The positive NAO supports a negative over Greenland and positive over Europe with more westerly influence and continents strongly influence by ocean.

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Yesterday was a rather wet day from Belfast to Bristol while it was dry and quite sunny over western parts of the UK but the same front that hung over Ireland, SW Britain yesterday is now sitting, making for a dreary day from London to Glasgow. Rain is heavy and persistent.

That front will move out later today only to be replaced by another front tomorrow and Friday as well as Saturday. Winds will remain a feature through the next several days and with a squeeze in pressure late week, gales or even severe gales may impact North and West Scotland for a time.

The below GFS surface charts show the setup into the weekend.

Either side of these near stationary frontal boundaries shedding off the big low out over the Atlantic, it’s dry, sunny and mild.

By late weekend on into next week, we catch a bit of a break with ridging building westwards off the continent, pushing back the Atlantic influence certainly through the early part of the week but I think low pressure regains control of at least NW UK air space. This much more fluid, active pattern looks likely to hold rather than fade like we saw during Sep and the first half of Oct.

Despite the return of low pressure towards mid next week, what’s interesting is the GFS ensemble shows a strengthening of the Europe high. Next month could see a really battle between ocean and continent and these types of setups can lead to flood events like we saw in Nov 2009.

With both AO and NAO are firmly positive hence the lack of cold and jet positioned to the NW of the UK, so it appears we remain on the milder south side of the jet probably through mid November.

This may also help expand the Eurasian snowpack westwards, filling in bare western Russia which was snow covered this time last year. Mind that there appears to be linkage between Eurasian snow cover and the winter AO.

Canadian model for November

Apologies for the late post. I’m in Perth and about to head to Oban and laptop did an update which stopped me getting this on earlier in the day.

See video for discussion.

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