Mean Error (Bias) of Flow Forecasts
Now if we look at the ME for the hydrologic flow forecasts, we see that the high flow events show a very strong negative bias, just like the precipitation input. Although we should expect greater magnitude ME for greater magnitude flows, this is useful information about the behavior of the forecast for important high-flow events. The increase in negative bias is especially noteworthy after the 48-hour lead time when the climatology-based precipitation is used as input.
The strong negative bias in the high flow forecasts is very similar to the negative bias in the precipitation forecasts for the large accumulation amounts. If the bias in the high flow forecast were much different than the precipitation forecasts, then we would have indication that the main error source was something other than the precipitation input.