With the IFS cycle 46r1 the Extreme Forecast Index (EFI) and Shift Of Tails (SOT) fields are being extended to include 2-metre weekly mean temperature and weekly precipitation totals in the extended range forecast. The forecasts are provided twice every week - every Monday and Thursday - for the following forecast steps: T+0-168h, T+96-264h, T+168-336h, T+264-432h, T+336-504h, T+432-600h, T+504-672h, T+600-768h, T+672-840h, T+768-936, T+840-1008h and T+936-1104h.
For consistency with other extended-range products (e.g. anomalies, probabilities) these EFI/SOT forecasts share the same Model climate (M-climate) as the one used in the extended-range forecasts. Unlike the medium-range EFI/SOT M-climate, the extended-range M-climate is derived from a set of 3 (rather than 9) re-forecasts centred on the date of the real-time forecast initialisation. The climate sample size comprises of 660 values and therefore it is much smaller than the 1980 values used in the medium range. Information about the M-climate used is coded in the GRIB header via the following GRIB keys:
| GRIB octets | GRIB keys (values shown are as used for extended range EFI/SOT) |
|---|---|
| 57-59 | numberOfReforecastYearsInModelClimate = 20 |
| 60-62 | numberOfDaysInClimateSamplingWindow = 7* |
| 63-65 | sampleSizeOfModelClimate = 660 |
* numberOfDaysInClimateSamplingWindow takes the closest odd number to the length (in days) of the time window in which all the re-forecasts are considered in the preparation of the M-climate, e.g. for the medium-range numberOfDaysInClimateSamplingWindow=31 as a month-long time window is used.
Corresponding Cumulative Distribution Functions (CDFs) of the M-climate and extended-range forecast anomalies complement the EFI/SOT forecasts. This allows for a more comprehensive interpretation of the extended-range forecasts. Each CDF plot displays all extended-range forecasts available for the the requested period together with the M-climate corresponding to the the latest forecast. The time evolution of the extended-range forecast together with the corresponding M-climate can be seen also on the extended-range ensemble meteograms.
