Prior to IFS cycle 47r1, the EFI (and SOT) for both CAPE and CAPE-shear were based on instantaneous CAPE (ShortName=cape; parameter ID=59) and CAPE-shear (ShortName=capes; parameter ID=228044) fields, in 6-hour steps, from which 24-hour maximum values were computed (more details can be found in ECMWF Newsletter 144). For example for the nominal T+24-48h EFI forecast, four CAPE values, at T+30h, T+36h, T+42h and T+48h, were used to compute the maximum for this forecast period. In IFS cycle 45r1 two new model output parameters, maximum CAPE in the last 6 hours (ShortName=mxcape6; parameter ID=228035) and maximum CAPE-shear in the last 6 hours (ShortName=mxcapes6; parameter ID=228036), were are introduced (see details here). In IFS cycle 47r1, for the respective EFI and SOT computations, mxcape6 and mxcapes6 will be used instead of cape and capes respectively. This change is aiming for a better sampling in the computation of the 24-hour maxima needed for the EFI. In effect with the change we extract the maximum within 24 hourly values, instead of using 4 6-hourly values. The impacts of this change are described in detail below.
Firstly this changes has a neutral impact in terms of the EFI skill, as measured by the area under the Relative Operating Characteristic (ROC) curve.
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