Changes to the Operational ''Early'' Eta Analysis / Forecast System at the National Centers for Environmental Prediction

This note describes changes that have been made to the National Centers for Environmental Prediction ( NCEP ) operational ‘‘early’’ eta model. The changes are 1 ) an decrease in horizontal grid spacing from 80 to 48 km, 2 ) incorporation of a cloud prediction scheme, 3 ) replacement of the original static analysis system with a 12-h intermittent data assimilation system using the eta model, and 4 ) the use of satellite-sensed total column water data in the eta optimum interpolation analysis. When tested separately, each of the four changes improved model performance. A quantitative and subjective evaluation of the full upgrade package during March and April 1995 indicated that the 48-km eta model was more skillful than the operational 80-km model in predicting the intensity and movement of large-scale weather systems. In addition, the 48-km eta model was more skillful in predicting severe mesoscale precipitation events than either the 80-km eta model, the nested grid model, or the NCEP global spectral model during the March ‐ April 1995 period. The implementation of this new version of the operational early eta system was performed in October 1995.

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