The India Meteorological Department (IMD) has erred on its forecast for monsoon rain in August. In June, it said that India would get more rain than it usually did but as of August 31, the country got significantly less — or 8.5 % less rain — than what’s normal for the month, according to the IMD website.
While this wouldn’t affect water availability for agriculture and the storage in reservoirs, it suggests that the agency’s weather models are still not robust enough to capture changes in global climate that could affect the Indian monsoon.
As The Hindu reported in July, the IMD is planning to shift next year to a forecast system that relies on a supercomputer-led dynamical weather-modelling. Moreover, unless September gets 150% more rain than normal, it is unlikely that India will meet its forecast target of 6% surplus rains for the monsoon season. So far the all-India monsoon deficit as of August 31 is 3%.
In June, the agency’s updated forecast said the country would receive 6% more than the 89 cm it normally gets between June and September and that August rains would be 4% more than the 26 cm that the country usually gets. An error margin of 9% is built into the IMD’s forecasts of monthly rainfall but even so, an 8% deficit lies well outside the margin of error. IMD officials said they weren’t perturbed by the August deficit, because India, on the whole, had received well distributed rains, and this had led to improved sowing.
Also, all forecast models — even global ones — expected a “stronger” La Nina, the converse of an El Nino and usually associated with good rains over India, to set in around August. So far La Nina has been extremely weak.
“The big deficiency we couldn’t anticipate was the reduced rains in the South,” said D.S. Pai, Chief Forecaster, IMD Pune. “There were other factors such as a negative Indian Ocean Dipole and an unfavourable Madden Julian Oscillation (MJO) that obstructed La Nina.”
Both of these refer to phenomena in the seas surrounding India and global atmospheric disturbances known to affect the monsoon during July and August. Mr. Pai and B.P. Yadav, spokesperson, IMD said the agency was unlikely to revise its numbers for the season, but Mr. Pai said India could “still end up with above normal rains” at the end of the season.
Monsoon break
Typically the monsoon tends to take a “break” in July or August and this year the break began around mid-August. As IMD’s weather chart shows, India didn’t meet its weather quota even for a single day between August 12 and Aug 30. Private forecaster Skymet has already revised its forecast for the monsoon downwards mid-August, and said India wouldn’t register surplus rains. “We don’t expect much change in weather conditions for the rest of the month,” said Jatin Singh, CEO, Skymet, “However September is going to be better.”
On the back of successive droughts in 2014 and 2015 — because of one of the strongest El Ninos on record — weather agencies had said 2016 would be a good year because El Nino had receded and was likely to give way to La Nina.
