Drought ravages India

India is facing one of its worst droughts in over six decades. Reservoirs across the country are running out of water, 14 of India's 29 states have already declared a drought and some 330 million people are suffering as a result. The torrid summer has only made matters worse.

In the midst of all this, India's leading weather forecasters can't agree on when exactly the monsoon rains will arrive.

Last week, India's public forecaster, the India Meteorological Department (IMD)said that the monsoons—that account for 70% of India's total rains—was delayed and is likely to arrive only by June 7.

But on May 17, the country's biggest private forecaster, Skymet, said that that the monsoon is likely to arrive by May 28.

While the IMD hasn't given any specific reason for the delay in the arrival, except that its "statistical model" suggested so, Skymet said that its "available data" suggest that the monsoon will hit the southern Indian state of Kerala between May 26 and 28.

"Conditions are favourable for monsoon to arrive between May 26 and 28," GP Sharma, a vice president at Skymet said. "There is very little difference between pre-monsoon showers and the actual monsoons. 

According to the IMD, there are few parameters through which we assess the onset of monsoons, and we believe all of them show the onset of monsoon, much earlier than the normal."

According to the IMD guidelines (pdf), the arrival of monsoon is announced when the rainfall at eight of the 14 monitoring stations record 2.5 millimetre for two consecutive days. The guidelines also suggest that the outgoing longwave radiation—a phenomenon where the earth sends out electromagnetic waves—is less than 200 units and the wind speed is in the range of 25 knots at a certain latitude and longitude.

"We have received more data over the past few weeks and according to that, we believe that the rains will arrive earlier," added Sharma. "We also believe that the rainfall will be at 109% of the long period average (LPA). The El Nino is close to zero now." Last year, the El Nino—a condition that warms the sea surface in the Pacific Ocean leading to lower rainfall in parts of Asia—wrecked havoc with India's monsoons.

This year, the IMD has predicted thatthe rainfall during the four-month period between June and September is likely to be at 106%. India's LPA is around 89 centimetres currently.

Lately, Skymet and IMD have been engaged in a battle to accurately predict the monsoons.

Last year, the IMD surprised many by forecasting that the country’s annual rainfall would be 12% lower than theaverage. But Skymet, with a network of 2,500 weather stations and a team of 10 climatologists and meteorologists, had predicted that the country would see a year of normal rainfall.

Skymet had argued that it was unlikely that India was going to have consecutive years of below normal rains and that the Indian Ocean Dipole (IOD), also known as the Indian Nino—caused by the differencein sea surface temperature between parts of the western and eastern Indian Ocean—was expected to remain positive, bringing more rains.

Eventually, the IMD's prediction came trueas India's annual rainfall was 14% short of the annual benchmark.

This time, it'll only be a matter of days before a clear winner emerges.