Yes, El Niño ‘favours’ colder weather later in the winter, but that’s only in the sense of increasing the odds from pretty poor to less poor. I think there’s a danger of overestimating the change in probability. The Met Office winter forecast talked, IIRC, of something like a doubling of the chances, from 20% to 40%.
I think, as other have discussed in here, that against the background global warming of 0.1-0.2c per decade, it has to be harder to get very cold air to our shores. We have the triple whammy of the sources of the very cold air shrinking and becoming less cold, the seas becoming warmer, so the lower layers of the air masses are modified more, plus higher CO2 levels mean that more energy is being retained when the sun shines. None of them are significant on their own, but collectively they must play a part, I think.
Originally Posted by: Gandalf The White