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The EFI is a climate-related product which means that it shows how cumulative distribution functions (CDFs) of the ensemble forecast compare with the model climate. Therefore, an anomalous forecast does not necessarily translate into a high-impact one. In case of convection this means that anomalous values of CAPE does not necessarily suggest that convective hazards are likely. For example climatological values of CAPE in winter over the Arctic are so low that severe convection is impossible even if the forecast shows up extreme CAPE. To filter out anomalous but insignificant signals in the EFI, currently CAPE values less than 10 J.kg-1 are set to 0 before computing both model climate and ensemble forecast CDFs. Now with replacing cape with mxcape6 and capes with mxcapes6, CAPE over 10 J.kg-1 will happen more often and therefore this will show up on the EFI (Fig. 3). To correctly interpret the EFI one should always account for the model climate as well.
Fig. 3. The EFI for CAPE and maximum CAPE in the Siberia showing that the latter may show up a bit more often.
Finally, as a result of this change, the model climate also slightly changes globally (Fig. 4a). In the example on Fig. 2b the EFI suggests a bit more extreme CAPE values over NW Spain. The corresponding CDFs show what this signal corresponds to in terms of model climate and ensemble forecast distributions.
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