Weather bureau issues warning, brace for heavy rain in Mumbai today

The city witnessed moderate showers, but negligible rainfall was recorded in the suburbs despite partly cloudy conditions on Tuesday – two days after the onset of

The city witnessed moderate showers, but negligible rainfall was recorded in the suburbs despite partly cloudy conditions on Tuesday – two days after the onset of monsoon in the city was declared.

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The India Meteorological Department (IMD) retained an orange alert for Tuesday in its updated district-wise forecast issued at 1pm. It issued heavy rain warning for Wednesday, but downgraded the forecast to light to moderate showers for Thursday and Friday.

Between Tuesday, 8.30am and 8.30pm, the Colaba weather station recorded – representative of south Mumbai – recorded 13.8mm rainfall, while the Santacruz weather station – representative of the suburbs – recorded 0.8 mm rainfall. However, in 24 hours (between Monday 8.30am and Tuesday 8.30am), south Mumbai recorded 52.6mm rainfall, while the suburbs recorded 37.4mm rainfall, both falling under the ‘rather heavy’ category.

IMD classifies 2.5mm - 7.5 mm as light rain, 7.6 mm - 35.5 mm as moderate rain, 35.6 mm - 64.4 mm as rather heavy rain, and 64.5 - 124.4 mm as heavy rain.

IMD director-general Mrutyunjay Mohapatra explained that associated weather systems, enhancing the monsoon current, had weakened.

“The low pressure area that had developed off Bay of Bengal towards the east coast lost intensity as it moved over the central parts of the country. The orange alert is always issued to ensure the city is prepared in case of heavy rain. We expect monsoon currents to strengthen as another low pressure system is expected to develop over Bay of Bengal by June 19. Meanwhile, the monsoon current is stronger over south Konkan, and may enhance rain activity over north Konkan, including Mumbai on Wednesday,” said Mohapatra.

Private weather forecasters Skymet, which had also predicted heavy to very heavy rainfall for Monday and Tuesday, said the offshore trough (weather system) did not intensify and its impact remained confined to south Konkan and Goa.

“We expect moderate to heavy showers (60-70mm) on Wednesday, with a further reduction in intensity on Thursday of 20-30mm,” said Mahesh Palawat, vice-president (meteorology and climate change), Skymet.

Independent meteorologists said heavy rain alerts for a city like Mumbai must be issued only when there is a high confidence in model predictions.

“Alerts need to specifically mention whether the expected heavy rain is going to be persistent or transient due to thunderstorms. In such a critical scenario, daily heavy rainfall alerts or forecasts can distract the local administration which is dealing with the Covid-19 outbreak,” said Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom.

Deoras added that showers were expected to increase in the Mumbai Metropolitan Region on Wednesday. “Compared to Monday and Tuesday, rain intensity on Wednesday expected to be more persistent due to the proximity of a localised circulation (a weather system). Since monsoon has arrived, the usual intermittent shower pattern will be seen in Mumbai on Thursday and Friday,” he said.