In the recent contingency planners forecast from the Met Office for this Winter, I commented that it would be difficult for a cold or very cold December to be followed by a very mild January and February, as they were suggesting could possibly happen this Winter. I couldn’t back that up with any statistics, so I decided to add another viewer to my monthly CET application and investigate just how many cold Decembers, had indeed been followed by a very mild January and February. The best way to approach this I thought was through the use of quintiles of monthly mean CET. What I needed to do was sort all Winters since 1659 on their closest match of their individual months December, January and February to quintiles 1-5-5, and here are my results (fig 1).
As you can see there have only been two occurrences of a 1-5-5 Winter in the last 358 years. One of them was the Winter of 1772-33 and the other that of 1927-28 (fig 2). December 1927 was infamous for the Christmas blizzard across the south. On Monday 26th December 1927, Biggin Hill awoke to 17 foot snow drifts, and this website has an interesting collection of photographs of the event. The MWR headlines for the three months of that meteorological Winter read:
- December 1927 – Cold and dull; unusual prevalence of easterly winds; severe snowstorm 24th-27th; abnormally dry in Scotland.
- January 1928 – Mild, stormy and extremely wet
- February 1928 – First-half wet and unsettled with severe gales 10th-11th; then mainly sunny and relatively dry
There were other cold-mild-mild winters of course, but none as marked as those two. As you can see from the table (fig 1) there was a 2-5-5 Winter that occurred as recently as 2001-02, so what the Met Office are proposing will happen in their contingency forecast is perfectly possible, but which I still think is highly unlikely.