Page History

...

The IFS models the dynamics of the atmosphere and the physical processes that occur, and also other processes that influence the weather e.g. atmospheric composition, surface energy fluxes, the marine environment and processes at the atmosphere/surface interface (then scroll down to soil/surface section).  Several configurations of the atmospheric model are used, each tailored towards a specific aim:

• HRES to investigate detail in the forecast during the first 10 days.
• Ensemble ENS to investigate detail and uncertainty in the forecast during the first 10days or 15days.
• Extended ENS and Seasonal runs to give probability of general conditions at longer ranges.

...

After the introduction of  Cy48r1 in Spring 2023 the:

• High Resolution (HRES):
  •  is run four times daily:
    • base times 00 UTC and 12 UTC, producing a 10 day forecast (T+0 to T+240).
    • base times 06UTC and 18UTC, producing a 3.75 day forecast (T+0 to T+90).
  • has horizontal resolution of 9 Km and vertical resolution of 137 model levels.
  • documentation gives details of HRES products and dissemination schedules.
• 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 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.
• extended range ensemble:
  • is run once daily, base time 00 UTC, producing a 46 day forecast (Day0 to Day46).
  • has horizontal resolution of 36 Km and vertical resolution of 137 model levels.  
  • has 100 members plus an unperturbed control member.
  • documentation gives details of extended range products and dissemination schedules.
• a multi-layer snow scheme was introduced.

The extended range forecasts are not just an extension of the medium-range forecasts but are completely separate systems both starting from their own analyses.  There are two sets of re-forecasts, one for the medium range and one for the extended range.

...