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If the median of a new forecast lies outside the range of the previous forecast then a substantial "ensemble forecast jump" (for a given parameter) has occurred.  This would usually also be shown as a big change in EFI.  Such jumps are very uncommon, although probably they occur slightly more often than they should on purely probabilistic grounds.  They can be very disconcerting for forecasters.  Examples of meteorological scenarios when such behaviour is more likely are organised convective rainfall and extreme cyclonic windstorms.

(FUG Associated associated with Cy50r1)