Extreme Forecast Index

The Extreme Forecast Index (EFI) ranks the departures between the Ensemble Prediction System forecasts and the model climate to identify unusual meteorological situations (e.g. related to temperature, wind, storms rainfall or snow).

Description & Technical Information

Description

The Extreme Forecast Index (EFI) ranks the departures between the Ensemble Prediction System forecasts and the model climate to identify unusual meteorological situations. EFI is applied on a daily basis to the following variables: temperature, wind speed, wind gust, Convective Available Potential Energy (CAPE), snowfall and total precipitation.
Experience suggests that EFI values of 0.5 – 0.8 (irrespective of sign) can be generally regarded as signifying that “unusual” weather is likely and values above 0.8 as usually signifying that “very unusual” or extreme weather is likely.

Technical information

Hazard
References Lalaurette F. 2003. Early detection of abnormal weather using a probabilistic Extreme Forecast Index. Q. J. R. Meteorol. Soc. 129: 3037–3057.
Developer ECMWF

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