‘Need faster weather updates’, says IMD chief
The India Meteorological Department’s (IMD) ‘red alert’ warning with a forecast of extremely heavy rain for Mumbai on Sunday was amiss as light showers were recorded through the day. The IMD chief said the frequency of changing weather updates needed to be improved.
Though IMD got its forecast for intense rain between Friday and Saturday correct by issuing an ‘orange alert’ with 219.2mm (extremely heavy) rain over 24 hours, incorrect forecasts for ‘extremely heavy rain’ were issued twice this month.
Dr KJ Ramesh, director general, IMD, said, “There is a need to issue advisories and forecast updates to citizens much faster than the current information dispatch pattern. This will ensure the public is aware of any changes in weather conditions.We will be directing our team to look into this and enhance the current framework”
The district rainfall forecast on IMD’s website was revised at 1pm on Sunday to ‘heavy to very heavy rain at few places’ for Sunday and Monday, and ‘heavy rain at isolated places’ for Tuesday.
On July 8, IMD had predicted over 200mm rain for 24 hours (from July 9 to 10) when its Doppler weather radar was not functioning. On July 10, the city recorded 7mm over 24 hours. A similar incident occurred on Sunday when 0.5mm rain was recorded between 8.30am and 8.30pm in the suburbs and 4.8mm rain in south Mumbai, against an ‘extremely heavy’ rain warning.
As per the IMD standard operating procedure, the local forecast for Mumbai is updated four times a day and considering the rapid intensification of a weather event, Nowcast warnings are issued four hours in advance and updated every six hours.
“Weather models over the last two days had indicated a surge in rainfall activity over the north Konkan, including Mumbai, with extremely heavy rain expected. While predictions for Friday and Saturday were accurate, the intensity of rain shifted to the east of Mumbai, with increased showers towards interior areas on Sunday,” said Dr Ramesh.
A closer look at forecasts for significant or special weather events over the past two years shows that IMD issued 28.3% incorrect 24-hour forecasts for an average of four months (June to September) in 2018, while 31.8% incorrect forecasts were issued for 48 hours during the same period. The data was acquired through an RTI query filed by activist Chetan Kothari. In 2017, IMD’s response to a separate RTI filed by Kothari showed that of 32 rainfall warnings during monsoon, 14 were incorrect, accounting for a 44% error rate. (see box).
Dr Ramesh said that the addition of a network of 160 rain gauges and four small X-band Doppler radars next year will improve forecasting drastically.