The weathermen got their forecasts wrong more often than not this monsoon. But, according to them, it was mostly a cunning plan to help citizens prepare better for graver eventualities.
The Indian Meteorological Department accurately forecast rainfall in June and July only 40 per cent of the time, but officials claim it is standard practice to over-predict.
“Our accuracy rate could have easily been 90 per cent, but we purposely issue false alarms so that people are not caught unprepared,” said A B Majumdar, who, as deputy director-general of meteorology (weather forecasting) at the Met’s Pune office, collates national data and analyses its accuracy.
To predict rainfall, climate scientists monitor parameters such as atmospheric pressure, cloud formation, sea level rise, wind speed and direction of movement. And sometimes a level of caution they deem needed.
For instance, on July 15, it rained 240 mm in Mumbai, a ‘very heavy downpour’. The same evening, when the weathermen looked up the charts to predict the next day’s skies, the parameters did not indicate it would continue raining heavily.
But they still put out alerts of ‘heavy rainfall’ (120 mm) and ‘very heavy rainfall’ (200 mm). In the end, it rained only mildly on July 16. “But it made people careful,” claimed Majumdar.
The Met is planning a pilot project in Mumbai aimed at knowing “what people expect from us”, said Majumdar.