Mumbai to get hyperlocal forecasts from IMD soon

Known to experience heavy rainfall, Mumbai has, in recent years, witnessed brief but intense spells of rainfall with a slowly rising number of “extreme rainfall” days and, consequently, episodes of waterlogging and suspension of transport services.

The India Meteorological Department (IMD) will soon make locality-specific weather forecasts for big cities. For Mumbai, this would mean a highly localised forecast for an area, like Malad, Chembur or Bandra. “This is the need of the hour as people want to know predictions for their area. Big cities need a different approach,” KS Hosalikar, deputy director-general (western region), IMD, told The Indian Express.

Also, in a bid to reach out to people more effectively, the IMD is in the process of releasing a mobile application. “Our Delhi team is looking into it and we should have an app soon. Through this, people do not have to believe a third party and can check the weather themselves,” said Hosalikar.

This initiative comes close on the heels of the IMD facing a major challenge from an unlikely quarter — social media. Every time Mumbai receives heavy rainfall, messages begin circulating on WhatsApp, often with inaccurate predictions or reminding people of the July 2005 deluge. “We thought the IMD is the only authority on weather but now there are many others. These are not genuine and often do more harm than good not only for the society but also for the disaster management teams. This misuse of technology costs us valuable time, money and resources,” said Hosalikar.

Known to experience heavy rainfall, Mumbai has, in recent years, witnessed brief but intense spells of rainfall with a slowly rising number of “extreme rainfall” days and, consequently, episodes of waterlogging and suspension of transport services. “We are observing that there are more days of extreme rainfall and fewer days of moderate or light rainfall. This has created a situation in which the soil does not get enough time to recharge and most of the water flows into the sea. We have seen this pattern developing in recent years,” said Subimal Ghosh, a professor at IIT Bombay.

In this year’s monsoon, Mumbai received extremely heavy rainfall on August 29 with 315 mm recorded in 24 hours and on September 19 with 304 mm rainfall in the same duration. The rain brought Mumbai to a halt with many parts of the city being waterlogged. Simultaneously, building structures in Mumbai have been a factor contributing to heavy rainfall concentrated in a locality. “We observe that there is no uniform intensification of rainfall in the city. While some pockets get heavy rainfall, others do not. This shows that buildings and roads are factors making the atmosphere unstable,” said Ghosh.

The city also experienced several thundershowers at night this season. On some days, like September 13, the intense thunders even woke people from their sleep. “These are not normal for Mumbai and it is a sign that the cloud properties are changing,” he added. However, IMD officials feel there is no cause for worry as thunders are a regular feature in September and October.

“It is normal to receive thundershowers after evening in these months as it rains on alternate days, causing ground heating and moisture. The convection causes huge thunder clouds at a height of 12-16 km,” said Hosalikar. In any eventuality, an increase in rainfall intensity on some days could mean more flooding incidents in coming years. While the Brihanmumbai Municipal Corporation has blamed the IMD for poor rainfall predictions for August 29, Ghosh believes they have done a commendable job.

“IMD has been doing a very good in predicting extreme rainfall and it is doing better than the international models. It is wrong of government agencies to criticise IMD. These agencies do not have the expertise to analyse the forecast. The forecast issued by IMD will be successful only if they hire the expertise to interpret it right,” Ghosh said.