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Model Configurations

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* and ENS control for detail in the forecast during the first 10 days, Ensemble (ENS) to investigate uncertainty in the forecast during the first 15days, and extended ENS and Seasonal runs to give probability of general conditions at longer ranges).   There are some slight differences, but generally the same model structure is used in each of the different model configurations.  The relative skill of the models and their strengths have been investigated.

Some major changes were made to the IFS with the introduction of the Cy48r1 in Spring 2023.  These are:

  • the resolution of the medium range ensemble forecast system (ENS) was increased to 9 Km, the vertical resolution remained at 137 model levels.  These values are identical to that of the High Resolution (HRES**) in earlier versions of IFS.
  • the number of members in the medium range ensemble forecast system remained at 50 members plus a control member.    
  • the vertical resolution of the extended range ensemble was increased to 137 levels.  This is the same as High Resolution (HRES*) and the medium range ensemble.  The horizontal resolution remains unchanged at 36 km.
  • the number of members in the extended range ensemble forecast system was increased to 100 members plus a control member.
  • the extended range ensemble is run daily from Day0-Day46.
  • HRES** was retained for the time being to maintain continuity of output for users and to enable the products of HRES* and the unperturbed medium range ENS control member to be compared.  
  • 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.  Two sets of re-forecasts, one for the medium range and one for the extended range. 




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