A third of winter gone…

…And not a flake of snow. There’s been lots of talk about how an SSW will eventually usher in a cold January and February but it is by no means guaranteed.

The average maxima for this December will finish 10.2C, precisely the same as December 1985. Other Decembers that finished close to this average maximum are shown below.
As you can see apart from the middle of the month the temperatures are all over the place. And so are the conditions that followed in January and February.

december all.PNG

A closer inspection of every year reveals that just three were very similar to 2018: 1974, 1986 and 1988.

748688.PNG

Again, there’s plenty of spread. The 500mb reanalysis charts below show the situation of the northern hemisphere on December 31st of each year, including this year.

What followed in January 1975, 1987 and 1989?
January 1975 in this area was the warmest on record, back to 1797, while January 1989 was the 12th warmest. Conversely, January 1987 saw one of the coldest spells on record.

Perhaps it is fair to say that there is a 66 per cent chance of a very mild January, though you cannot discount the 34 per chance of another January 1987…

 

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