EFI and SOT are powerful tools for identifying potentially extreme weather compared to climatology for a given location and time of year. A high EFI value indicates that an extreme event is more likely than usual but the values do not represent probabilities of that event. Users should note:
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 effect).
Windstorms have greater or less impact depending upon the stability of structures or the leaf cover of trees.
Past history is important but is not directly accounted for (e.g. where heavy rain forecast when ground is already saturated).
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 (ENS) information, such as shown by meteograms and plumes, and deterministic information (e.g. from HRES, taking into account the appropriate weighting) in addition to the EFI. Users should note:
Occasionally forecasts or warnings may be based on the likely impact of an event rather than the event itself. Users should note: