When using recreated forecasts, the percentiles are based on the unadjusted forecasts made from a number of 168 hours long forecasts with chunk length 168 hours. The frequency of these forecasts are set in the extracted period length control seen below. In the example below, a forecast is made which starts every 6 hours, each of these having a time stamp, two hours after the forecast starts. This means that the prediction horizon for the forecasts starts at -2 hours or equivalently -120 minutes.
Since we are estimating the uncertainty depending on the prediction horizon, it is important to restrict the availability of weather observations, which is done in the extract settings. In addition, there must be a sufficiently amount of weather forecasts as well during the period estimated. Check that the “trim fc-file”-settings is either unchecked or that the period for which the fc-files are saved is long enough.
