Form of Output
ECMWF provides data from several different IFS models, each available according to when the IFS models are run, and each with different temporal resolutions in the output data.
Output data is in the form:
- most commonly as absolute values:
- instantaneous values,
- averages over a period,
- totals over a period,
- maxima or minima over a period.
- sometimes as:
Medium range forecasts
The "high resolution" model (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 6 day forecast (T+0 to T+144). Results from these runs are:
- has horizontal resolution of 9 Km and vertical resolution of 137 model levels. These values are the same as those of the medium range ensemble.
- has land-atmosphere and ocean-atmosphere coupling.
The 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:
- 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).
- has land-atmosphere and ocean-atmosphere coupling.
- has 50 ensemble members plus an unperturbed control member (CTRL).
- the unperturbed control member (CTRL) corresponds to the High Resolution (HRES).
The horizontal and vertical resolutions of the medium range ensemble (ENS) became the same as for the HRES after the upgrade to IFS (Cy48r1) introduced in June 2023. The HRES forecast and the unperturbed ENS control forecast are meteorologically equivalent and equally skilful on average. They have the same physical and dynamical representation of the atmosphere and use the same parameterisation of sub-gridscale effects. However, they can diverge on a day-to-day basis due to small technical differences and the chaotic nature of the atmosphere. The HRES will continue for the time being for ease of use by customers and users.
Extended Range forecasts
The extended range ensemble:
- is run once daily:
- base time 00UTC, producing a 46 day forecast (T+0 to T+960/1104).
- has horizontal resolution of 36 Km and vertical resolution of 137 model levels.
- has land-atmosphere and ocean-atmosphere coupling.
- has 100 ensemble members plus an unperturbed control member (CONTROL).
Note:
Extended range products cover the period beyond the medium range forecasts (i.e. from day 15 to day 46).
Precipitation forecasts are provided as values accumulated from the start of the forecast integration. The range of the daily variation of the forecast 2m temperature and wind gust is best estimated by retrieving the forecast maximum and minimum values. The combination of accumulated and instantaneous forecast information can occasionally lead to inconsistencies as in both cases the valid time is defined as the time at the end of the period (e.g. during the passage of a cold front when significant precipitation amounts might be accumulated by the IFS models over the whole time interval though instantaneous cloud-free conditions will be shown at the end of the interval).
Seasonal forecasts
The seasonal range ensemble:
- is run once monthly:
- base time 00UTC on 1st of each month and run on the 5th of each month producing a 7 month forecast (13 months every quarter).
- has horizontal resolution of 36 Km and vertical resolution of 91 model levels.
- has land-atmosphere and ocean-atmosphere coupling.
- has 50 ensemble members plus an unperturbed control member.
Further information: