Versions Compared

Old Version 55

changes.mady.by.user Bob Owens

Saved on

compared with

New Version 56

changes.mady.by.user Bob Owens

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

This edition of the Forecaster User Guide applies to the ECMWF Integrated Forecast System (IFS) and meteorological products after June 2023 using IFS Cycles 48r1 and later.

Aim of the Forecaster User Guide

The aim of this User Guide is to help meteorologists make the best use of the forecast products from ECMWF - to increase understanding of the ensemble forecast process, to develop new products, to reach new sectors of society, to satisfy new demands.  The User Guide presents the Integrated Forecasting System (IFS) and advises on how best to use the output, not least on how to build up trust in the forecast information.  A good forecast that is not trusted is a worthless forecast.  The emphasis is on the medium-range forecast products, as this is ECMWF’s primary goal, and because medium-range NWP output generally differs significantly from that dealing with short-range or seasonal NWP.   Extended range forecast (days 16 to 42) output concentrates on the probabilities of anomalies from the norm during a 5-7day forecast period at a given location for any time of year.  Seasonal forecasts give an indication of likely conditions beyond six weeks ahead.  These are run monthly giving forecasts to 7 months ahead, and run quarterly with forecasts extended to 12 months ahead.  Output concentrates on the anomalies relative to the seasonal climate.  

The ECMWF IFS is upgraded at roughly half yearly intervals to incorporate better representation of physical processes and/or higher vertical or horizontal resolution.   New products increasingly aid early warning of severe or hazardous weather.  Information on the latest upgrade is given below.

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

The IFS models are:

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:

...

  • the horizontal resolution is increased to 9 Km
  • the vertical resolution remains unchanged at 137 model levels. 
  • the number of ensemble members remains unchanged at 50 members plus a control member.
  • the horizontal and vertical resolutions are identical to those of the High Resolution (HRES) in earlier versions of IFS.
  • the medium range ensembles are run twice daily from Day0-Day10 and slightly later from Day-0 to Day15.  

...

)

...

)

...

.Note:

The extended range forecasts are not just an extension of the medium-range forecasts but are completely separate forecast systems.  However, both start from very similar analyses.  There are two sets of re-forecasts, one for the medium range and one for the extended range. 

The HRES and medium range control member of the medium range ensemble (CTRL) have the same horizontal and vertical resolution and are virtually identical.   Nevertheless the HRES will continue for the time being for ease of use by customers and users.

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.

...


Latest cycle of Integrated Forecast System (IFS) model upgrades. 

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

  • For the medium range ensemble forecast system:
    • the horizontal resolution is increased to 9 Km
    • the vertical resolution remains unchanged at 137 model levels. 
    • the number of ensemble members remains unchanged at 50 members plus a control member.
    • the horizontal and vertical resolutions are identical to those of the High Resolution (HRES) in earlier versions of IFS.
    • the medium range ensembles are run twice daily from Day0-Day10 and slightly later from Day-0 to Day15.  
  • For the extended range ensemble forecast system:
    • the horizontal resolution remains unchanged at 36 km.
    • the vertical resolution is increased to 137 model levels.  This is the same as the medium range ensemble (and the High Resolution (HRES) in earlier versions of IFS).
    • the number of ensemble members is 100 members plus a control member.
    • the extended range ensemble is run daily from Day0-Day46.
  • A multi-layer snow scheme was introduced.

Note: The extended range forecasts are not just an extension of the medium-range forecasts but are completely separate forecast systems.  However, both start from very similar analyses.  There are two sets of re-forecasts, one for the medium range and one for the extended range. 

The HRES and medium range control member of the medium range ensemble (CTRL) have the same horizontal and vertical resolution and are virtually identical.   Nevertheless the HRES will continue for the time being for ease of use by customers and users.

Full details of the current Integrated Forecast System (IFS) is given in the official ECMWF IFS documentation of CY48r1.


Users are advised to keep themselves updated about changes and improvements to products and model processes through the ECMWF Newsletter and web site (e.g. via the Forecast User portal)

...