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The ensemble consists of one unperturbed control member (the control) and 100 perturbed members. These are similar to the control member but differ only that initial states and model physics have been perturbed. This allows exploration of the currently understood range of uncertainty in the observations and the model. A set of sub-seasonal range re-forecasts provide a basis for the sub-seasonal range model climate (ER-M-climate). The sub-seasonal range forecast suite is not an extension of the medium-range forecasts but is a completely separate system.
The sub-seasonal-range forecast provides an overview of the atmospheric evolution for the 32-day period (Day15 to Day46). Standard output products focus mainly on the week-to-week changes in the weather. The chart products generally are presented in terms of anomalies relative to the sub-seasonal range model climate (ER-M-climate). The anomalies are mainly shown as 7-day means for calendar weeks Monday to Sunday. From these one can infer whether conditions (e.g. temperature, rainfall, etc) are likely to deviate from the average for a location and time of year, and whether such an anomaly could be extreme.
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The sub-seasonal range output is available on the ECMWF web charts and ecCharts. Guidance Guidance on the the Interpretation of the sub-seasonal range products is discussed elsewhere in the guide.
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(Note: In older material there may be references to issues that have subsequently been addressed)
- Read more on the justification for extended range forecasting, on the structure of the extended range ensemble, the extended range output. Note from Cy49r1 the extended range is renamed the sub-seasonal range.
- Read about the simulation of the Madden-Julian oscillation and its impact over Europe.
- Some information on the principle of ECMWF Variable Resolution Ensemble Prediction System (VAREPS) may be found at:
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