Delay in the onset of la Nina has cast a cloud of uncertainty over monsoon predictions of weather experts. The gap in deficit has gone up to five per cent, and sources in the IMD fear that rainfall in September could be up to 15 per cent less than average.
Rains are said to be over for Peninsular India and North, but a cyclonic circulation near the North Arabian Sea is causing fairly heavy showers in parts of Gujarat, Maharashtra, and Madhya Pradesh, besides heavy to very heavy rains in North Coastal Maharashtra particularly Mumbai.
To add to it, a fresh cyclonic circulation has developed in west-central Bay of Bengal that will bring scattered light to moderate rain and thundershowers over parts of Northeast India and foothills of Bihar and East Uttar Pradesh.
However, there has been a decrease in rainfall over northwest and adjoining central India, indicating that the south west monsoon is withdrawing. Monthly rainfall in the country has so far been mixed, with a deficit of 11 per cent in June followed by a 7 per cent excess in July and a 9 per cent shortfall in August.
The country will require good rains in September to close the deficit, said weather experts from IMD. However, the current deficit this week ending stood at 29 per cent, as per IMD data. The season's total rainfall since June 1 was 5 per cent below average at 766.1 mm as against the average of 808.1 mm.
The India Meteorological Department (IMD) had forecast surplus rains in August and September, largely because of the la Nina. It is a weather phenomenon that cools the waters of the Pacific Ocean off the coast of South America, resulting in stronger monsoons across Asia. There was at least a 75 per cent chance of the development of la Nina in June this year, but chances of its occurrence is now dim, say the weather scientists.
According to Skymet, country's private forecaster, the monsoon is likely to conclude with about 95 per cent of average rainfall. Depending on the final surge of rains, at best it can go up to 97-98 per cent. Monsoon is said to be below normal if it is 95 per cent of long Period Average (lPA). It is normal if the lPA is between 96 per cent — 104 per cent.