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• most commonly as absolute values:  
  • instantaneous values,
  • averages over a period,
  • totals over a period,  
  • maxima or minima over a period.
• sometimes as:
  • anomalies relative to re-forecast data
  • an assessment of how extreme the anomalies might be (Extreme Forecast Index and Shift of Tails).

Medium range forecasts

The "high resolution" model (HRES):

• • is run four times daily:
    • base times 00 UTC and 12 UTC, producing a 10 day forecast (T+0 to T+240).
      • Dissemination schedule - Atmospheric model ensemble 10-day forecast (HRES) and model analysis and forecast output parameters (Set I-i, I-ii, I-iii as shown for 00UTC and 12UTC base times).
      • Dissemination schedule - Ocean wave model ensemble 10-day forecast (HRES-WAM)  and model analysis and forecast output parameters (Set II as shown for 00UTC and 12UTC base times).
    • base times 06UTC and 18UTC, producing a 6 day forecast (T+0 to T+144). Results from these runs are:
      • Dissemination schedule - Atmospheric model 90 hour forecast (HRES) and model analysis and forecast output parameters(Set I-i as shown for 06UTC and 18UTC base times).
      • Dissemination schedule - Ocean wave model ensemble 90 hour forecast (HRES-WAM) and model analysis and forecast output parameters (Set II as shown for 06UTC and 18UTC base times).
  • has horizontal resolution of 9 Km and vertical resolution of 137 model levels.  These values are the same as those of the medium range ensemble.
  • has land-atmosphere and ocean-atmosphere coupling.

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).
      • Dissemination schedule - Atmospheric model ensemble 10-day forecast (HRES and CTRL) and model analysis and forecast output parameters (Set I-i, I-ii, I-iii as shown for 00UTC and 12UTC base times).
      • Dissemination schedule - Atmospheric model ensemble 15-day forecast (ENS) and model analysis and forecast output parameters (Set III as shown for 00UTC and 12UTC base times).
      • Dissemination schedule - Ocean wave model ensemble 10-day forecast (HRES-WAM)  and model analysis and forecast output parameters (Set II as shown for 00UTC and 12UTC base times).
      • Dissemination schedule - Ocean wave model ensemble 15-day forecast (ENS-WAM)  and model analysis and forecast output parameters (Set IV-i, IV-ii, IV-iii as shown for 00UTC and 12UTC base times).
    • 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.
      • Dissemination schedule - Atmospheric model 90 hour forecast (HRES) and model analysis and forecast output parameters(Set I-i as shown for 06UTC and 18UTC base times).
      • Dissemination schedule - Atmospheric model 3 day ensemble forecast (ENS) and model analysis and forecast output parameters (Set III as shown for 06UTC and 18UTC base times.  Tropical Cyclone Tracks are also available for 06UTC and 18UTC base times).
      • Dissemination schedule - Ocean wave model ensemble 90 hour forecast (HRES-WAM) and model analysis and forecast output parameters (Set II as shown for 06UTC and 18UTC base times).
  • 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 .

The horizontal and vertical resolutions of the medium range ensemble (ENS) became the same as for the HRES after the upgrade to IFS (Cy48r1) introduced in June 2023.  The HRES forecast and the unperturbed ENS control forecast are meteorologically equivalent and equally skilful on average.  They have the same physical and dynamical representation of the atmosphere and use the same parameterisation of sub-gridscale effects.  However, they can diverge on a day-to-day basis due to small technical differences and the chaotic nature of the atmosphere.  The HRES will continue for the time being for ease of use by customers and users.

Extended Range forecasts

The extended range ensemble:

• • is run once daily:
    • base time 00UTC, producing a 46 day forecast (T+0 to T+960/1104).
      • Dissemination schedule - Atmospheric model ensemble extended forecast (ENS extended). See also model analysis and forecast output parameter means and anomalies (Set VI).
      • Dissemination schedule - Ocean wave model ensemble extended forecast (ENS-WAM extended). See also model analysis and forecast wave parameters and means (set VI-v-c)

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Precipitation forecasts are provided as values accumulated from the start of the forecast integration.  The range of the daily variation of the forecast 2m temperature and wind gust is best estimated by retrieving the forecast maximum and minimum values.  The combination of accumulated and instantaneous forecast information can occasionally lead to inconsistencies as in both cases the valid time is defined as the time at the end of the period (e.g. during the passage of a cold front when significant precipitation amounts might be accumulated by the IFS models over the whole time interval though instantaneous cloud-free conditions will be shown at the end of the interval).

Seasonal forecasts

The seasonal range ensemble:

• • is run once monthly:
    • base time 00UTC on 1st of each month and run on the 5th of each month producing a 7 month forecast (13 months every quarter).
      
      • Dissemination schedule - Seasonal forecast (SEAS).  See also model forecast seasonal output parameter means and anomalies (set V)
      • Dissemination schedule - Seasonal forecast (SEAS).  See also model forecast seasonal output wave monthly means (set V-iii-c) and (set V-v-e))
  • has horizontal resolution of 36 Km and vertical resolution of 91 model levels.
  • has land-atmosphere and ocean-atmosphere coupling.
  • has 50 ensemble members plus an unperturbed control member.

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