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This guide is intended to give an outline of structure and use of the ECMWF IFS.  It also aims to show how the IFS models inter-depend and interact.  The IFS models are:

• the 10-day ensemble forecast (ENS).
• the 15-day ensemble forecast (ENS).
• the 46-day extended range forecast including the extended range control member.
• the 7 or 13 month seasonal forecast.

Links to more detailed descriptions of processes are given, mainly at the end of each section, whilst separate online ECMWF training resources are also available to explain aspects of the ECMWF IFS more visually.  Education is a key component of the work at ECMWF and further educational material is available through the web site (e.g. Webinars (recordings), Slidecasts (slides and audio recordings), Tutorials, Training lectures (presentations in PDF)).

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

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The User Guide is broadly divided into two parts.  Sections 2 to 5 describe the structure of the ECMWF Integrated Forecasting System, while Sections 6 to 11 describe how the IFS may be used to best advantage by forecasters.

A glossary is included in an Appendix.

• Section2: The ECMWF Integrated Forecasting System (IFS)
• Section3: Availability and interpolation of NWP output
• Section4: NWP evolution versus reality
• Section5: Forecast ensemble (ENS) - rationale and construction
• Section6: Using ENS forecasts
• Section7: Dealing with uncertainty
• Section8: ENS products - what they are and how to use them
• Section9: Physical considerations when interpreting model output
• Section10: Interfaces for displaying model output
• Section11: Conclusion
• Section12: Appendices

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