Met forecasts 'near-normal' monsoon

18 April 2009

The Indian Meteorological Department said on Friday that rainfall during this year's southwest monsoon season (June to September) would be 'near normal' for the country as a whole. Quantitatively, the seasonal rainfall is likely to be 96 per cent of the long period average (LPA), with a model error of plus/minus 5 per cent, the IMD said in its much awaited long-term forecast issued in New Delhi. 

IMD will update the forecast in June as a part of the second stage forecasts. Separate forecasts for the monthly (July and August) rainfall over the country as a whole and seasonal (June-September) rainfall over the four geographical regions of India will also be issued.

The IMD said in its forecast statement that following the 2007/08 La Nina event (considered a good monsoon augury), near-neutral conditions prevailed in the tropical Pacific from early June to November 2008. It said La Nina conditions returned in early December 2008. From early March, 2009 contributing sea-surface temperatures (SSTs) over central and eastern Pacific have weakened and as of now, only weak La Nina conditions prevail, it said. 

For preparing the first stage forecast for the 2009 South-west monsoon rainfall for the country as a whole, the same 5-parameter statistical ensemble forecasting system employed for generating the 2008 forecasts has been used.

The operational forecast for the 2008 seasonal rainfall was accurate as the first and second stage forecasts were 99 per cent and 100 per cent of the LPA respectively and the actual rainfall 98 per cent, it said. 

The IMD's predictive skills have often been questioned, as its forecasts tend to vary substantially from the actual June-September monsoon rains, vital for key crops such as sugarcane and rice and overall rural activity. Last year's forecast was only off by 1 per cent, but in 2002, rains were far short of the forecast, leading to the country's worst drought in 15 years.