Towards predicting high-impact freezing rain events
Forbes, Richard ; Tsonevsky, Ivan ; Hewson, Tim ; Leutbecher, Martin
In the ECMWF Integrated Forecasting System (IFS) cycle 41r1, to be operational in early 2015, there are changes to the cloud and precipitation physics that allow an improved prediction of freezing rain. To this end a new 'precipitation type' diagnostic is added which includes the freezing rain category described here. In addition, there are new diagnostics for convective/stratiform precipitation rates valid at a particular time (rather than averaged or accumulated over a period) which are consistent with the precipitation type diagnostic.
A first evaluation of the freezing rain precipitation type as an experimental product shows promise for providing advance warning of severe freezing rain events. However, more experience needs to be gained over the coming winter and further evaluation of the probability of freezing rain in medium-range ensemble forecasts is required.
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