IMD's new operational models for long-range forecast of southwest monsoon rainfall over India and their verification for 2003

Abstract

In 2003, India Meteorological Department (IMD) introduced several new models for the long-range fore-cast of the southwest monsoon rainfall. With this, it has become possible to issue the long-range forecasts in two stages. On 16 April, IMD issued the forecast for the 2003 southwest monsoon rainfall for the country as a whole, giving its users an extra lead time of about 40 days. On 9 July, IMD issued a forecast update and additional forecasts for three broad homogeneous regions of India. It also gave a five-category probabilistic forecast. In view of its importance for agriculture, for the first time, IMD also issued a forecast for July rainfall. The development of the new models is discussed in this article. The forecasts issued operationally in 2003 using these new models have proved to be accurate.