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Occasions when there is a clear divergence between the latest and previous developments in the ensemble or ensemble mean occur increasingly rarely -  but if it does the forecasters is in a difficult position.  Nevertheless, there can be some agreement between the spread and jumpiness.

Combining and comparing results from different model runs can be achieved by:  

• Grand ensembles:  An ensemble of model runs using different models but starting from the same data times.
• Lagged ensembles:  An ensemble of recent past and latest model runs merged into a grand ensemble.  Lagged ensembles can include results from past ENS runs and/or from different models or both.  (See Fig6.3.5). 

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