The India Meteorological Department (IMD) on Friday predicted the southwest monsoon could advance into some parts of south Arabian Sea, cover the Maldives-Comorin area and expected to hit Kerala on May 29, three days ahead of its normal onset date. The normal date for monsoon’s onset over the Indian mainland, usually the Kerala coast, is June 1.
The Met Department said conditions were favourable for the onset of monsoon over the Andaman Sea normally around May 20 and southeast Bay of Bengal from May 23. “The southwest monsoon is expected to set over Kerala on May 29 with a modelled error of plus or minus four days,” the IMD said.
According to the prediction, monsoon’s advancement over Kerala seemed imminent with the strengthening of westerlies and northward shift of shear zone - typical of monsoon onset. Similar favourable conditions also prevail in Northeast India, and could cover Nagaland, Manipur, Mizoram and Tripura.
IMD official said one of the criteria to declare the monsoon onset over Kerala is based on the data from 14 weather stations — Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Alappuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore. If these weather stations report rainfall of 2.5mm or more for two continuous days from May 10 onwards and if other criteria are also met, then the monsoon onset is declared. The other criteria include specific features in the wind pattern and Outgoing longwave Radiation to indicate favourable condition for the arrival of monsoon.
The Met Department has predicted ‘normal’ monsoon this year. IMD’s prediction stands at a moderate error estimated of plus-minus 5 per cent of the long Period Average (lPA). A figure between 96 to 104 per cent is considered normal monsoon. Earlier, on April 4, private weather forecasting agency Skymet also predicted normal monsoon keeping it at 100 per cent, with an error estimate of plus-minus 5 per cent. This will come as a welcome relief, even as the Modi Government looks to achieve an 8 per cent GDP growth in 2019 as its policies and plan depend on the good monsoon.
The Southwest monsoon is critical not only for agriculture growth as less than half of the cultivable land is under irrigation, but also boosts the general economy. “A good monsoon not only helps in boosting the chances of bumper kharif harvest but also helps in rejuvenating reservoirs and groundwater sources, which are critical for rabi crops. Almost 70 per cent of India’s annual precipitation comes in the months of June to September,” said officials of Agriculture Ministry.
IMD’s operational forecasts of the date of monsoon onset during the past 13 years (2005-2017) were proved to be correct except in 2015.
“Past data suggest that there is no association of the date of monsoon advance over the Andaman Sea either with the date of monsoon onset over Kerala or with the seasonal monsoon rainfall over the country,” it said.