Page History

...

Generally, whether the ensemble spread is small or large, the EM (or median if applicable) will, beyond the short range, exhibit higher accuracy than the ensemble control (CTRL).  This is particularly true for parameters, such as mean sea level pressure (MSLP) and temperature.  However, with increasing spread amongst ENS members, it becomes more appropriate to couch the forecast information in the form of probabilities rather than as predicted values  - this is particularly true for parameters such as precipitation and cloud amounts.  The EM also displays a higher degree of day-to-day consistency.  Jumpiness in the EM ensemble mean is also markedly less, on average, than seen in CTRLthe ensemble control, particularly when examining forecasts beyond about Day3. 

...