Off target, again

To regain credibility, IMD must refine its monsoon prediction

Proving the India Meteorological Department (IMD) wrong yet again, the monsoon has gone through its four-month term (June to September) with a net rainfall paucity of 9 per cent, bordering the drought threshold of 10 per cent. Its distribution, too, has been erratic. Yet, on the whole, the monsoon has proved benevolent for agriculture and other sectors. This is borne out by the facts that farm production is expected to exceed last year’s peak, the water stock in reservoirs is plentiful, the prospects of hydel power generation are promising, rural demand is looking up, and food inflation is under control and likely to remain so. Barring the deluge in Kerala, the overall incidence of floods has remained low. Some other odd features have also been noticed in this year’s monsoon season. For one, the monthly rainfall has remained below par throughout the season with the deficit mounting progressively from 5 per cent in June to 6 per cent in July, 8 per cent in August and 24 per cent in September. But, the season has ended with the cumulative scarcity of only 9 per cent in the “below normal” category. 

Besides, while the traditionally flood-prone Brahmaputra basin and its adjoining eastern region have got away with relatively few floods, a less vulnerable area like Kerala suffered the history’s worst and the most destructive flooding. Moreover, the maximum rainfall shortage of about 24 per cent has been recorded in the east and northeastern zones, where the paucity of this order is least expected. The other regions have witnessed only marginal shortfalls in rain — just 1 per cent in the northwest and south peninsula and 6 per cent in central India. This explains why kharif sowing has surpassed last year’s record acreage and crop output is projected officially to outstrip last season’s 140.73 million tonnes to an all-time high of over 141 million tonnes. Moreover, the influence of climate change on the monsoon, in evidence in recent years, has been revalidated this year as well. It is most pronounced in the departure of the monsoon, which now starts from around the end of September instead of the beginning of this month. In recent years, its retreat commenced from September 23 in 2014, September 28 in 2015, October 7 in 2016, September 27 in 2017 and September 29 this year.

However, the IMD’s incompetence to accurately foretell the monsoon rainfall stands out this year as well. Its long-term monsoon rainfall prognosis issued in mid-April had put the likely precipitation at 97 per cent of normal. It was kept at the same level even in the updated forecast released on May 30. But the actual rainfall turned out to be way below at 91 per cent. However, it is also worth noting that private weather forecaster Skymet, too, had erroneously claimed the likely seasonal rainfall to be 100 per cent normal in its preliminary forecast in April. But it managed to make amends subsequently by lowering the estimate to 92 per cent, which proved closer to the mark. There is, therefore, considerable scope for the IMD to refine its monsoon prediction skills to enhance its credibility.