At the beginning of December the opening par for my forecast for winter read:
The mean temperature for winter 2017/18 is looking average overall with average precipitation. While that doesn’t sound exciting for anyone looking for colder weather and snow I think the figures mask frequent 3 or 4 day-long cold snaps from the Arctic interspersed with milder interludes from Atlantic incursions; typical characteristics of a pattern driven by the troposphere. For anything longer term we have to hope for a warming of the stratosphere, a sudden stratospheric warming over the Arctic, that downwells into the troposphere, reversing the general westerly circulation. We are overdue an ‘SSW’ event but, even if one were to happen, its effects wouldn’t be felt until much later in the winter.
Figures generated using QBO statistics in the run up to December were identical to the outcome of 5C. It is figures generated using ENSO statistics, however, that produced the best results considering December, January and February alone.
It would seem that the winter was most influenced by the ENSO variable up until February when the effects of the SSW were enough to overcome it?