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The medium range 10 day ensemble consists of 50 members and the unperturbed control member (CONTROL-10CTRL).

The medium range 15 day ensemble consists of 50 members and the unperturbed control member (CONTROL-15CTRL).

• The control member Analysis = the Analysis without any perturbations added.  
• The 50 sets of EDA perturbations and 50 sets of SVs are combined together to give 50 sets of global perturbations for model initialisation:
  • ENS member 1 Analysis = Analysis + (EDA member 1 - EDA mean) + SV Perturbation 1
    
  • ENS member 2 Analysis = Analysis - (EDA member 2 - EDA mean) + SV Perturbation 2
  •         and so on until 
  • ENS member 49 Analysis = Analysis + (EDA member 49 - EDA mean) + SV Perturbation 49
  • ENS member 50 Analysis = Analysis - (EDA member 50 - EDA mean) + SV Perturbation 50

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The extended range ensemble consists of 100 perturbed members and one unperturbed member (the extended range control member, CONTROL).

• The control member Analysis = the Analysis without any perturbations added.  
• The 50 sets of EDA perturbations and 100 sets of SVs are combined together to give 100 sets of global perturbations for model initialisation:
  • ENS member 1 Analysis = Analysis + (EDA member 1 - EDA mean) + SV Perturbation 1
    
  • ENS member 2 Analysis = Analysis + (EDA member 2 - EDA mean) + SV Perturbation 2
  •         and so on until
  • ENS member 49 Analysis = Analysis + (EDA member 49 - EDA mean) + SV Perturbation 49
  • ENS member 50 Analysis = Analysis + (EDA member 50 - EDA mean) + SV Perturbation 50
  • ENS member 51 Analysis = Analysis + (EDA member 1 - EDA mean) + SV Perturbation 51
  • ENS member 52 Analysis = Analysis + (EDA member 2 - EDA mean) + SV Perturbation 52
  •         and so on until
  • ENS member 99 Analysis = Analysis + (EDA member 49 - EDA mean) + SV Perturbation 99
  • ENS member 100 Analysis = Analysis + (EDA member 50 - EDA mean) + SV Perturbation 100

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Consequently, the proportion of the perturbed analyses that are better than the control (i.e. unperturbed ) analysis (control) for a specific location and for a specific parameter (e.g. 2m temperature or MSLP at Paris) is only 35% (see Fig5.1.4).  Considering more than one grid point lowers the proportion even further.

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• better than the predictive skill of the Control control; with this gap widening for longer forecast leads

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