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The ensemble forecast suite (ENS) provides a range of possible future weather states in the medium range.  This allows investigation of the detail and uncertainty in the forecast during the first 10 days or 15 days.

The medium range ensemble (ENS):

• • is run four times daily:
    • base times 00 UTC and 12 UTC, producing a 10 day forecast (T+0 to T+240) and also a 15 day forecast (T+0 to T+360).
    • base times 06UTC and 18UTC, producing a 6 day forecast (T+0 to T+144). Results from these runs are:
      • used in Early cut off analysis (SCDA) and Long window data analysis (LWDA).
      • disseminated T+0 to T+72.
  • has horizontal resolution of 9 Km and vertical resolution of 137 model levels.  These values are the same as those of the High Resolution (HRES) in earlier IFS versions.
  • has land-atmosphere and ocean-atmosphere coupling.
  • has 50 ensemble members plus an unperturbed control member (CTRL).
  • the unperturbed control member (CTRL) corresponds to the High Resolution (HRES) in earlier IFS versions.  CTRL forecasts maintain continuity of output for users.
  • documentation gives details of medium range products and dissemination schedules

The ensemble consists of one unperturbed control member (CTRL) and 50 perturbed members that are similar to the control member but their initial states and model physics have been perturbed to explore the currently understood range of uncertainty in the observations and the model.  A set of medium range re-forecasts provide a basis for the medium range model climate medium range model climate (M-Climate).

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