In IFS cycle 46r1 the Extreme Forecast Index (EFI) and Shift Of Tails (SOT) fields will be available for Water Vapour Flux. This parameter is the magnitude of the combined vertical integrals of the eastward and northward water vapour flux components. The average value of each component over a specified forecast period (e.g. 24 hours) is computed using the instantaneous values from each output forecast step; these are then combined to make the total wvf, which is then used to compute the model climate and the Extreme Forecast Index (EFI) for Water Vapour Flux (wvfi)