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which is the accuracy of climatological weather information used as forecasts.  Climatological averages can be found in tourist brochures. To add value, any deterministic medium-range forecast to an end-user must be more accurate than the published climatological averages.  Comparison of manual- and computer-generated deterministic forecasts shows, with a good NWP model at some forecast range, the differences between forecast values and observed values must exceed differences between climatological values and observed values.  However, errors in a user-orientated forecast produced by a forecaster using model forecast data should not exceed differences between climatological values and observed values.

i.e. At some forecast range:

E_{NWP forecast}  >  E_climate      but     E_human  ≤  E_climate

where ENWP forecast = (f_NWP - a) = Error of forecast based on NWP,    E_human = (f_human - a) = Error of forecast based on human forecaster and NWP,    E_climate = (c - a) = Error of forecast based on climatology,    a = observed value,  c- climatological value.

Error Saturation Level (ESL)

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