Mumbai’s only Doppler radar is defunct again

The city’s only Doppler weather radar (DWR), operated by the India Meteorological Department (IMD), remained defunct on Wednesday when the southwest monsoon made an early entry into Mumbai

The city’s only Doppler weather radar (DWR), operated by the India Meteorological Department (IMD), remained defunct on Wednesday when the southwest monsoon made an early entry into Mumbai.

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DWR at Navy Nagar in Colaba is the only radar in the city but has been out of commission since May 16, a day before Cyclone Tauktae hit.

Mrutyunjay Mohapatra, director general of meteorology at IMD said DWR was defunct owing to technical glitches. “We are working on it and the radar is likely to be operational within a week or two,” said Mohapatra.

This is not the first time that the instrument, used for tracking clouds and forecasting weather patterns, has been inoperable at a crucial moment. On December 4, 2017, when Cyclone Ockhi brushed past the Mumbai coast, the radar was not functional. The radar was also not functional on multiple days during extreme rainfall events in June and July 2019, and also on June 1, 2020, about 48 hours before Cyclone Nisarga made landfall in Maharashtra.

KS Hosalikar, head, surface instrument division, Climate Research & Services, IMD, directed queries to Jayanta Sarkar, director, IMD, Mumbai. However, despite repeated attempts, Sarkar did not respond to calls or messages.

“Wednesday’s event is a perfect example of why we need a radar. From satellite pictures, we could see clouds forming near Mumbai. In the absence of a Doppler radar, it becomes difficult for forecasters to track clouds, the direction in which they are moving and the estimated rainfall over different areas,” said Akshay Deoras, an independent meteorologist and PhD student at the University of Reading, England.

Not having a functional DWR can be dangerous in terms of disseminating correct information to the public and civic officials for preparing for any disaster-like event or flooding, said Deoras, who maintained that Wednesday’s heavy rainfall was the last of the pre-monsoon activity.

DWR was installed in the city in 2010 for weather surveillance up to 400kms from the coastline and was first recommended soon after the floods of July 26, 2005. While satellite pictures can be used in lieu of radar images, experts said, the latter is limited in value. “If an x-ray is a satellite image, then a doppler radar is a CT scan. The quality and range of data it gives are simply much better, allowing us to make better predictions about where the cyclone’s spiral banks will be located, where they will bring more rain,” said Deoras.

MS Reddy, former vice-chairperson of the National Disaster Management Authority (NDMA), said there was a pressing need for setting up at least two more DWRs. “Mumbai as a city is becoming increasingly prone to urban flooding, especially because of recurring high-intensity short-duration rainfall events. DWRs give us a lead time of three to six hours and tell us the temporal and spatial variation of rainfall for different areas. This means we can know where exactly it is going to rain and how intense the rain will be. These are crucial details, especially for warning commuters or moving people from low-lying areas,” said Reddy.

Reddy said with recurring low-pressure and cyclones in the Arabian Sea, Mumbai is now vulnerable to floods even before the onset of the monsoon season.

“Maharashtra has to be prepared for such events. The disaster management plan is not updated enough, not enough mock drills are conducted and not having a DWR is going to be detrimental in managing a disaster,” Reddy said.