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• Extreme weather indicated by EFI and SOT:
  • has been assessed against IFS model climatology as derived for M-climate, ER-M-climate or S-M-climate and these can differ from observed climatology.

  • does not necessarily indicate high impact as:

    • Rainfall has varying significance according to location (e.g. 2mm rainfall in the desert might be very unusual but have little physical impact).

    • Windstorm impact can depend on whether trees are in leaf, whether ground is saturated, stability of buildings, etc.

    • Past history is important but is not directly accounted for (e.g. the impact of a heavy rain event on saturated ground is greater than if the ground can absorb the water).

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Although a high EFI value indicates that an extreme event is more likely than usual, the values do not represent probabilities.  Any forecasts or warnings must be based on a careful study of probabilistic information derived from ensemble forecasts.  Examples are meteograms and plumes in addition to the EFI.   Users should note:

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