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The ENS runs are extended on Mondays and Thursdays from Day15 to Day46 based on 00UTC data time.

The Extended Range extended range (monthly) forecasts provide a range of possible future weather states in the extended range and bridge the gap between medium-range and seasonal forecasting. 

The extended range forecast suite  It is not an extension of the medium-range forecasts but is a completely separate system.  It runs daily from base time times 00 UTC out to day 46 with 100 members.  It has horizontal resolution of 36 km, 137 model levels in the vertical and has andland-atmosphere and ocean-atmosphere coupling.  The ensemble consists of 100 perturbed members with their initial states and model physics 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 ER-M-Climate.   The extended range forecast suite is not an extension of the medium-range forecasts but is a completely separate system.  

Twice each week, on Mondays and Thursdays, Every day the ENS is extended to run to 46 days ahead at a reduced resolution (currently 36km) but still with land-atmosphere and ocean-atmosphere coupling.  The extended-range forecast provides an overview of the atmospheric evolution for the 32-day period (Day15 to Day46).  The standard ECMWF 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.

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