Features of the Indian summer monsoon 2004 - Observed and model forecasts

The observed and the model forecast rainfall and other atmospheric fields are compared To determine the skill of the National Centre for Medium Range Weather Forecasting (NCMRWF) model in forecasting precipitation and circulation features over India, we compared observed and forecast rainfall and other atmospheric fields for the boreal summer monsoon season of 2004. This season was an important period within the period 4 of the Coordinated Enhanced Observing Period (CEOP). For comparison of observed rainfall with predicted values, station values are averaged over the area represented by each grid point of the model. For other fields, comparisons were made between the analysis and forecast values at the same horizontal resolution. The model showed considerable skill in predicting the daily and seasonal accumulated rainfall amounts when averaged over the whole of India. The predicted all-India average precipitation tends to increase in magnitude with increasing forecast period. The model forecasts that were undertaken especially for the CEOP project reproduced the important features of the summer monsoon over India. The onset of monsoon is captured in terms of both the convective precipitation and diabatic heating fields forecast by the model. Variations in monsoon activity between July and August are also well simulated in the monthly averaged forecast fields for these two months.