Page History

...

Strictly, for different lead times (i.e. for the different coloured curves) the M-climate will vary a little bit (due to model drift and under-sampling) but also more particularly in spring and autumn when day-to-day climatic changes are at their greatest (see Limitations of twice weekly updates to the M-CimateClimate).   In spite of such variations it is still reasonable, helpful and recommended to inter-compare the M-climate curve (black) with all the coloured curves (even if this is only strictly valid for the same lead time that it represents - i.e. the red curve).  Note, incidentally, that the M-climate, as used here and on meteograms, is now based on re-forecasts initialised from ERA5 data; this is higher quality output, and has greater compatibility with actual forecasts, than was the case previously when the re-forecasts were initialised from ERA-Interim data (i.e. before model cycle 46r1 was introduced in June 2019).

...

The median and any other percentile is given by reading the point on the x-axis where a horizontal probability line intersects the curve.  The most likely values are associated with those where the CDF is steepest.  Similarly, the PDF shows peaks in the curve at the highest probability intervals.  The EFI can be understood and interpreted with both the CDF and PDF in mind; the former relates to the EFI value, the latter clarifies the connection to probabilities.  A steep slope of the CDF, or equivantly equivalently a narrow peak of the PDF, implies a high confidence in the forecast.

...