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May well discard this section.

Using Deterministic and Probabilistic Forecasts

IFS models produce a wide range of output products available online through the website in chart form or or by dissemination or extraction in a GRIB format.  Presentation through ecCharts allows output data to be combined and displayed in a user-friendly way tailored to the needs and requirements of the user.

Relation between deterministic and probabilistic forecasts 

The ECMWF forecast products can be used at different levels of complexity, from categorical, single-valued forecasts to probabilistic, multi-valued forecasts.  They can be used as guidance to forecasters but also to provide direct input to elaborate decision-making systems.  The choice largely depends on user demands but is also influenced by the traditions, and constraints, of the particular meteorological service.  However, the main aims of forecasters in interpretation of available data is to:

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Probabilistic frameworks can and should be adapted whenever specific user requirements have to be taken into account; some examples are given in the appendix.  Any member of the ensemble could be considered deterministic, but in general the skill of a singe member is less than the skill of the ensemble mean and a single member gives no information on the confidence that may be placed on its results.

Differences between short range and medium range operational use of NWP

 There are some fundamental differences between how forecasters work with NWP model output in the short range and in the medium range.

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