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The ensemble consists of one unperturbed member (the control) and 100 perturbed members that are similar to the control but their initial states and model physics have been perturbed to explore the currently understood range of uncertainty in the observations and the model.  A set of extended range re-forecasts provide a basis for the extended-range model climate (ER-M-climate).  The extended range forecast suite is not an extension of the medium-range forecasts but is a completely separate system.  

The extended-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 extended-range model climate (ER-M-climate) and 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.

Extended Range forecasts are coupled to the Wave model (ECWAM) and the Dynamic Ocean model (NEMO) run with resolution of ~28km.

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The extended range output is available on the ECMWF web charts and ecCharts. Guidance on the  Interpretation of the extended range products is discussed elsewhere in the guide.

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Specialised products for the Extended Range include information on potential tropical cyclone activity and evolution of the Madden-Julian Oscillation (MJO).   The MJO is characterized by an eastward propagation of an area of more organised convection in the tropics, typically initiated over the Indian Ocean and is important as it can influence developments elsewhere on the globe:

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