Long Range Forecast for 2006

South-West Monsoon Season (June-September) Rainfall

India Meteorological Department (IMD) today announced the first stage forecast for 2006 south-west monsoon rainfall over the country as a whole. IMD’s operational Long Range Forecast for the 2006 South-west Monsoon season (June-September) is that the rainfall for the country as a whole is likely to be 93% of the Long Period Average (LPA) with a model error of ±5%.

Estimates also suggest that the probability for the 2006 South-west monsoon season rainfall over the country as a whole to be deficient (below 90% of LPA) is only 22%. Announcing the forecast at a press conference in New Delhi, Shri B. Lal, Director General, Met Department said IMD will issue update for the above forecasts by the first week of July, which will also include forecast for the July rainfall over the country as a whole and seasonal (June-September) rainfall over the four broad homogeneous regions of India.

IMD has also predicted near neutral conditions over the Equatorial Pacific.The weak El Nino conditions that prevailed in 2004 abruptly ended in the first half of 2005. Sea surface temperatures were close to normal over the equatorial Pacific region during the second half of 2005, which became colder during the beginning of 2006. However, during the past two months, equatorial Pacific region has warmed up again to return to near neutral conditions. A majority of the statistical and coupled model forecasts indicate higher probability (around 65%) for near neutral conditions to prevail over the equatorial Pacific during the monsoon season.

IMD has been issuing operational long range forecasts of the south-west monsoon rainfall for a number of years using statistical methods. In 2003, IMD adopted a two stage long range forecast strategy. In the first stage, forecasts for the south-west monsoon season (June-September) rainfall for the country as a whole is issued in April using the 8-Parameter Power regression and Probabilistic models. In the second stage, update forecast for the seasonal rainfall over the country as a whole is issued by the first week of July using the 10-Parameter Power Regression and Probabilistic models. In the second stage, separate forecasts for the July rainfall over the country as a whole and for south-west monsoon seasonal (June-September) rainfall over 4 broad homogeneous regions of India (NW India, NE India, Central India and south Peninsula) are also issued. IMD’s Long range Forecast for the 2005 south-west monsoon season over the country as a whole based on these models was in agreement with the actual value.

In addition, IMD has also taken into account the experimental forecasts prepared by national Institutes like Indian Institute of Tropical Meteorology, Pune, Indian Institute of Science, Bangalore, Space Applications Centre, Ahmedabad and Centre for Mathematical Modelling and Computer Simulation (CMMACS) Bangalore and operational/experimental forecasts prepared by international institutes like National Centers for Environmental Prediction, USA, International Institute for Climate and Society, USA, UK Meteorological Office, European Center for Medium Range Weather Forecasts and Experimental Climate Prediction Center, USA.

As a part of IMD’s consistent efforts to improve the long range forecast capabilities, new statistical models and a dynamical prediction system have been developed and being validated.

Source : Press Information Bureau
Date : April 24, 2006