IMD's Weather Forecasting Set-up

Weather forecasting is a very important activity of IMD and it caters to a wide spectrum of user requirements ranging from agriculture to aviation. Short range forecasting involves prediction of weather conditions at any given place two days in advance, whereas in long range forecasting, rainfall for the country as a whole is predicted before the commencement of  the monsoon season.

IMD provides very comprehensive forecasting services for aviation, shipping, fisheries, agriculture, flood forecasting, cyclone warning and many other special users besides forecasts for the general public. For this purpose, IMD has forecasting offices at its 6 Regional Meteorological Centres and Meteorological Centres at the State capitals. In addition it has two major forecasting centres at New Delhi and Pune. The Northern Hemispheric Analysis Centre at New Delhi serves as a high-level interface between IMD and the various government agencies and it provides inputs to the electronic and print media. It also functions as a Regional Specialised Meteorological Centre under the WMO system and executes much wider responsibilities towards other neighbouring countries. The Indian Ocean and Southern Hemispheric Analysis Centre is located a Pune. The Office of the Deputy Director General of Meteorology (Weather Forecasting) and the "Weather Central" at Pune coordinate the weather forecasting activities of IMD, particularly in times of events like tropical cyclones.

Cyclone warnings, bulletins for fishermen and bulletins for ships in the seas, are issued by IMD's Area Cyclone Warning Centres at Chennai, Calcutta and Mumbai and Cyclone Warning Centres at Ahmedabad, Bhubaneshwar and Visakhapatnam.

Agrometeorological Advisory Bulletins for farmers are issued by 17 IMD Centres in various states. They also issue Farmers Weather Bulletins.

IMD provides specific forecasts for mountaineering expeditions, national events, sports events, yatras, elections and such other special purposes.

Numerical Weather Prediction (NWP) is the methodology to predict the future state of the atmospheric circulation and weather from a knowledge of its present (initial) state, using known physical and hydrodynamical laws of atmospheric motions. NWP was initiated in IMD as early as in 1973 with a simple model on an IBM 360/44 computer. A new computer, Cyber 2000U, supported by many peripheral equipments, was installed and commissioned at IMD in New Delhi in 1995. The New Delhi centre functions as a Regional Specialised Meteorological Centre (RSMC) under the WMO system for World Weather Watch. Most of the RSMC activities such as plotting of data on weather charts for synoptic analysis and production of prognostic charts, have been automated on the Cyber system with its comprehensive applications and graphics software package.

A Limited Area Analysis and Forecast System (LAFS) which comprises an advanced NWP model, has been implemented for short range forecasting. The analyses and prognostic charts produced by LAFS are disseminated to centres in other countries as a part of RSMC's responsibilities. The forecast model is also used for generating tropical cyclone track predictions. The Cyber system also processes grid point data received from World Area Forecast Centres at Washington and Bracknell for production of documentation charts for aviation purposes.

IMD issues every year the Long Range Forecast for the southwest monsoon rainfall. The scientific basis for long range forecasting is that there are several signals prior to the monsoon which are indicative of its likely performance. The parameters having a bearing with the monsoon rainfall should not only be statistically well-correlated but also be physically relevant. Developing better techniques and improving the accuracy of the long range forecasts are two continuous research activities of IMD.