Being a survivor of the 62-63 winter when the only info readily available was the BBC forecasts and the Met office charts I received daily, what I remember was pre Christmas was a build of pressure over Finland which moved south towards Germany bringing bitterly cold dry air into the British Isles.
Now my point is that at this stage to our North West , mild air was attempting to penetrate from that direction, then the continental high collapsed and wilt high pressure moving north from the Azores the bitter prolonged spell commenced, I wonder in those far off days if we had all todays gizmos we would have had the will it won’t it situation occurring.