On 10/01/2019 19:46, John Hall wrote:
In message ,
Graham Easterling writes
Being a bit cynical, I cant' help noticing that every cold spell we
get seems to be down to SSW. If it occurs at the same time or just
after, then it's the cause. If it occurs 3 weeks after, it's still the
cause due to the reason you describe.

There's a useful list of Major SSWs in this article (not quite up to date):

https://www.earth-syst-sci-data.net/...-9-63-2017.pdf

See Table 2 on page 66. From that it's evident that many weren't
followed by notable cold spells in the UK and, conversely, that many
notable UK cold spells weren't preceded by a SSW.

Some more recent NH approx SSW central dates, that may or may not fit
their definition.
04 Mar 2016
31 oct 2016
16 Feb 2018
12 Dec 2018
06 Jan 2019

My pc would throw in the towel confronted by a 300GB file.