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Friday, Dec 13, 2019

IMD errs again: Light showers give respite to city

Overnight showers, between 11.30 pm on Wednesday and 8.30am on Thursday, were negligible, with 0.4mm in the suburbs and 2.4mm in south Mumbai.

mumbai Updated: Sep 05, 2019 23:27 IST
Mumbai, India - Aug. 6, 2019:People deal with rain at Bandra in Mumbai, India, on Tuesday, August 6, 2019. (Photo by Ragul Krishnan/ HT PHOTO)
Mumbai, India - Aug. 6, 2019:People deal with rain at Bandra in Mumbai, India, on Tuesday, August 6, 2019. (Photo by Ragul Krishnan/ HT PHOTO)(HT PHOTO)

A day after Mumbai recorded its second highest 24-hour September rainfall in 10 years that left the city in a mess, the city on Thursday saw sunny conditions followed by light showers, contrary to the weather department’s forecast.

Overnight showers, between 11.30pm on Wednesday and 8.30am on Thursday, were negligible, with 0.4mm in the suburbs and 2.4mm in south Mumbai. Between 8.30am and 5.30pm, brief isolated showers led to 8.9mm rain in the suburbs and 8mm in south Mumbai. The city recorded 242.2mm rain (extremely heavy) between 8.30am on Wednesday and 8.30am on Thursday, surpassing its September average rainfall and 3,000-mm mark for the season. Mumbai received over 533.2mm in the past 72 hours, against 327mm, the month’s average.

The India Meteorological Department (IMD) had issued an ‘orange alert’ (directing authorities to be prepared) for Thursday with forecast for ‘heavy to very heavy rain at a few places’. At 1pm, IMD downgraded its warning to a ‘yellow’ alert (directing citizens and authorities to be updated).

“Rain intensity reduced over Mumbai as the cloud mass moved westwards with heavy showers over the Arabian Sea and weather systems helped increase rainfall north of the city, towards Gujarat,” said Mrutyunjay Mohapatra, director general, IMD. “However, rainfall warnings were still in place as moderate to heavy showers was not ruled out.”

Independent weather experts said false weather alarms had been high this season. “Thousands stranded in the Mumbai Metropolitan Region (MMR) during these heavy rainfall events this season is an indication that official weather forecasts aren’t making the required impact,” said Akshay Deoras, independent meteorologist and PhD researcher, University of Reading, UK.

However, in the latest event, IMD correctly predicted (as early as August 30) that the city would receive heavy rain from September 3 onwards; forecasts closer to the date were inconsistent with what actually happened. “This entire rain spell was well predicted with forecasts issued over a week ago,” said Mohapatra. “It is correct that on the day of extreme heavy rain, we changed the warning to red. Accordingly, discussions with all stakeholders (state bodies) were done to ensure the situation was addressed. On Wednesday the forecast was downgraded to ‘orange’, which can have varying rainfall probability. Thereafter, forecasts were changed on Thursday depending on weather synoptic factors. Our forecasts are checked, revised and communicated to all state bodies every few hours. By next monsoon this process will be enhanced further.”

Weather forecasts abroad like the UK are seamless, enough to keep people off the road during extreme weather events, said Deoras. There was a cyclonic circulation north of Mumbai, which led to Wednesday’s heavy rain. Whatever was built of the weather system got destroyed on Wednesday itself allowing a sharp drop in rain activity on Thursday, he said.

Citizens and former government officials were miffed with IMD. “I spent four hours in a traffic jam on Western Express Highway on Wednesday only to reach my office in knee-deep water. If an extreme rain forecast was issued on Tuesday, I would have stayed home,” said Suresh Mankar, Mahim resident who works at Borivli.

Urban planners said IMD forecasts were now comical. “There is no excuse for getting these forecasts wrong. Using supercomputers to interpret algorithms, mathematical calculations, and using data collated over decades to issue predictions is not an unachievable task. We need to introspect deeper into the problem,” said Pankaj Joshi, director, Urban Design Research Institute.

Former BMC municipal commissioner Karun Srivastava said, “IMD forecasts are leaving all state agencies, including BMC, flummoxed. Accurate forecast could have helped rehabilitate 1,700 people along Mithi much earlier.”

According to the IMD standard operating procedure, local forecasts for Mumbai are updated four times a day and considering the rapid intensification of a weather event, Nowcast warnings are issued four hours in advance and updates are issued every six hours. “Predicting dynamic rainfall changes is becoming more difficult under current climate change abnormalities. However, timely warnings and continuous updates are reaching state authorities on time. The entire process is much more robust with swift information transmission to railways, municipal authorities, and all other state bodies in a real-time manner,” said Dr KJ Ramesh, former director general, IMD.