Extreme Forecast Index (EFI) Precipitation (based on GEFS)

The Extreme Forecast Index (EFI) quantifies the difference between the ensemble forecast distribution and the model climate distribution. Developed at ECMWF (Dutra et al. 2013; Lalaurette 2003; Zsoter 2006), it enables the detection of extreme weather events without defining a threshold in either space or time. Thus it can be applied to even observation sparse regions. The EFI ranges from -1 to +1 with magnitudes between 0.5-0.8 indicating the likelihood of unusual weather and magnitudes greater than 0.8 indicating the likelihood of very unusual weather.

References:
1) Dutra, E., M. Diamantakis, I. Tsonevsky, E. Zsoter, F. Wetterhall, T. Stockdale, D. Richardson, and F.Pappenberger, 2013: The extreme forecast index at the seasonal scale. Atmos. Sci. Lett., 14, 256–262, doi:10.1002/asl2.448
2) Lalaurette, F., 2003: Early detection of abnormal weather conditions using a probabilistic extreme forecast index. Quart. J. Roy. Meteor. Soc., 129, 3037–3057, doi:10.1256/qj.02.152
3) Zsoter, E., 2006: Recent developments in extreme weather forecasting. ECMWF Newsletter, No. 107, ECMWF, Reading, United Kingdom, 8–17