London winter forecast 2019/20

For this year’s winter forecast, because of time constraints, I am sticking purely to what the local analogues reveal.

Meteorological autumn was the wettest for 18 years and the coolest for 6 years, revealing some interesting similarities with past climate. Considering data back to 1797 I was able to make the following suggestions on how the next 90 days may unfold.

December is most likely to be on the cold side with rainfall slightly below average.

January is most likely to finish average temperature-wise and wetter than December.

London’s February extremes temperature also look average overall and the precipitation signal also creeps up in comparison to the first two winter months.

Best chance for snow? Impossible to pin down but the coldest weather is likely to be at the beginning of February, the third week of January and just after Christmas.

The warmest period looks to be around January 10th while there’s also a signal for that often phenomena of milder temperatures just before Christmas day.

Most of the probabilities in the above statements are relatively low and are explained in the table below.

Mean temperature 2019/20

December January February
1981-2010 average 5.6 1981-2010 average 5.3 1981-2010 average 5.3
Forecast median 4.4 Forecast median 4.7 Forecast median 5
Rather cold 40% Normal 40% Normal 44%
Normal 28% Rather cold 32% Rather cold 32%
Mild 20% Very cold 12% Mild 16%
Cold 4% Mild 12% Cold 4%
Very cold 8% Cold 4% Very cold 4%

 

Rainfall 2019/20

December January February
1981-2010 average 53.2mm 1981-2010 average 55mm 1981-2010 average 40.1mm
Forecast median 48.3mm Forecast median 55mm Forecast median 40mm
Wet 32% Wet 32% Wet 36%
Normal 20% Normal 28% Normal 36%
Dry 48% Dry 36% Dry 28%

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