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In summary, in extreme situations during the transition seasons, cold EFIs in particular will typically be damped to be of smaller magnitude than they should be.  This is because the M-Climate range is artificially extended in those seasons.  Users should expect equivalent adverse impacts on the SOT also, which by definition focuses on the distribution tails where the issue lies.

Fig8195.AFig8.1.9.5-1: EFI forecast for 2m minimum temperature T+24 VT 14 May 2020, DT 00Z 14 May 2020.  Minimum temperatures over SE England between 0°C and -2°C observed widely.

Fig8195.BFig8.1.9.5-2: Central England Minimum temperatures (source Met Office) highlighting the changes in minimum temperatures through the year.  The black bars show the four-week period used to compute M-Climate minimum temperatures for the central point of the bar.  In practice re-forecasts, which will also show the seasonal variations in temperatures, are used to define the M-climate.  

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