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Remarks on the Extended Range

Extended Range Structure

The Extended Range (monthly) products cover the period up to Day46.  They are derived from an extension of the normal 15-day ENS twice per week on Mondays and Thursdays.  This is a time scale lying between:

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Re-forecasts provide an Extended Range climate (ER-M-climate) and associated probability distribution functions (pdfs) for several variables.  The latest Extended Range ENS forecasts and the associated probability density functions can be compared with the ER-M-Climate.  If the differences between the two are used as the basis of model products then any model drift is effectively removed. 

Combating Model Drift

Drift of model calculations begins to be significant after 10 days of coupled integrations.  It displays similar patterns to seasonal forecasting after 6 months of integrations, but with less amplitude.

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