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 Center s 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 o f the original static analysis system with a 12-h intermittent data as similation system using the eta model, and 4) the use of satellite-sen sed total column water data in the eta optimum interpolation analysis. When tested separately, each of the four changes improved model perfo rmance. A quantitative and subjective evaluation of the full upgrade p ackage during March and April 1995 indicated that the 48-km eta model was more skillful than the operational 80-km model in predicting the i ntensity and movement of large-scale weather systems. In addition, the 48-km era model was more skillful in predicting severe mesoscale prec ipitation events than either the 80-km eta model, the nested grid mode l, or the NCEP global spectral model during the March-April 1995 perio d. The implementation of this new version of the operational early era system was performed in October 1995.