The southwest monsoon will hit the Kerala coast on May 29 said the Indian Meteorological Department. The prediction model has an error margin of four days, which means that, in effect, the monsoon could arrive anytime between May 24 and June 1.
Usually, the southwest monsoon sets in over Kerala on June 1, with a standard deviation of seven days. This year, then, our godsend of rain relief could come in early.
IMD, in the last 13 years, was successful in predicting the arrival date of the monsoon accurately except on one occasion. In 2015, it said the rains would arrive on May 30 but it arrived only on June 5.
The southwest monsoon advances over the Andaman Sea around May 20, with a standard deviation of a week. IMD says conditions are favourable for the advance of southwest monsoon into parts of the Andaman Sea and Bay of Bengal by May 23.
"Past data suggests that there is no association of the date of monsoon over the Andaman Sea either with the date of monsoon onset over Kerala or with the seasonal monsoon rainfall over the country," said the IMD.
The IMD model for forecasting the onset date uses predictors such as minimum temperatures over northwest India, pre-monsoon rainfall peak over the peninsula, outgoing long-wave radiation over South China Sea, lower tropospheric zonal wind over the east equatorial Indian Ocean and outgoing long-wave radiation over southwest Pacific region.