Thanks for posting the link to the MetO original, Retron.
I'm interested in this one, because it's not based on a model output ensemble, which I think is frankly useless three months out, but instead 'based on knowledge of expected global meteorological patterns'. Okay, I suppose that that is just a posh way of saying 'analogues', but I've always felt that probabilities based on analogues is the closest we're ever going to get to a reliable long-range forecast. And you'd hope that the MetO has access to a more comprehensive and appropriate range of analogues than we amateurs do. Or at least that the MetO has a more systematic way of analysing them.
Anyway, being an amateur, I'm still following the TWO Weather Analogue Index page, and I'm interested to see that 2005 has the number 2 spot today, because November 2005 saw one of the all-time great snowstorms for the West Country. And that MetO forecast is for Nov/Dec/Jan, and is noting that the 'global meteorological patterns' they've analysed suggest 'an increased likelihood of higher-than-average pressure to the west of the UK initially'.
So, maybe something is afoot for November!
2 miles west of Taunton, 32 m asl, where "milder air moving in from the west" becomes SNOWMAGEDDON.
Well, two or three times a decade it does, anyway.