Monsoon bounty: On IMD's weather forecasts

The monsoon has finally set in over Kerala in keeping with the textbook date of June 1. In May, the IMD had forecast a four-day delay in the onset over Kerala. This was premised on a relatively mild summer, in early May, in north India and several spells of Western Disturbances, which are rains from the Mediterranean, as well as the impact of super cyclone Amphan in the Bay of Bengal. A private meteorological company had, however, forecast an early monsoon arrival — on May 28 — because its models seem to suggest diminished impact of Amphan. But last week, the IMD updated its onset forecast to say that ‘favourable conditions’ for the monsoon onset were likely on June 1. The IMD has clearly defined criteria for declaring the onset: eight of 14 designated meteorological stations in Kerala and Karnataka must register 2.5mm rain for two consecutive days, there must be 30-40 kmph westerlies (winds from the equator reaching India) at a certain height and a certain value of radiation. Heavy rains over Kerala alone do not determine onset, the IMD has been at pains to emphasise. However, it is also true that usually it was the only agency with the equipment to measure windspeeds and radiation at higher elevations, along with multiple weather stations. It therefore has a monopoly of declaring onset.

While the IMD is a primarily scientific organisation, it faces competition from domestic and international companies in providing weather-related services. In crop insurance, power distribution and short-range forecasts, the IMD no longer has a monopoly on providing weather information. The latter has consequences for the IMD’s other major role — to give its outlook on how the monsoon might pan out over India and how much rain is likely in July and August, the key months for the summer crop. This year, save for India’s northeast, the IMD has forecast above normal rains in other areas, especially the northwest, the central parts and the southern peninsula. Though reassuring, it is worth remembering that just last year the IMD failed to communicate that 2019 would turn out to be the wettest in two decades. However, every year of normal monsoon has brought with it both torrential floods and long dry spells. The complexity of climate change is now such that excess rains in a year seem to have long-ranging impact with reports of a second consecutive year of a locust plague in India on the horizon which can affect the kharif crop. It is therefore time that along with improved science and forecasting, the IMD works on disseminating more precise localised weather forecasts. While its public interface and technology adoption is improving, particularly in cyclone forecasts, the organisation has a long way to go in communicating these improvements to a wider population.

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Printable version | Nov 30, 2021 4:15:47 AM | https://www.thehindu.com/opinion/editorial/monsoon-bounty-on-imds-weather-forecasts/article31734047.ece

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