First downpour: Sobo receives 23% of monthly average rain in 8 hours

MUMBAI: The city on Thursday witnessed its first proper downpour of the ongoing monsoon season with the India Meteorological Department’s (IMD) weather station in Colaba, South Mumbai, receiving 125.6mm of rainfall in the span of eight hours, between 8:30am and 5:30pm.

According to IMD norms, rainfall between 64.5 mm and 115.5 mm in 24 hours is considered ‘heavy’, and between 115.6 and 204.4 is ‘very heavy’.

Thursday’s showers follow a prolonged ‘weak’ monsoon regime over Mumbai, and the surrounding Konkan meteorological sub-division, which has so far, recorded a large monsoon deficit. Officials attributed the downpour to a strengthening of westerly winds, which helped carry rain-bearing clouds over the city’s coastline.

Notably, the IMD’S Colaba weather station received 23% of its normal rainfall for June -542.3mm -- in just a matter of hours, though experts said this is not surprising for an active monsoon day in the city.

“An east-west wind shear zone which had developed over the south Konkan region around June 22 has moved north-westward toward south Gujarat, allowing westerly winds to pick up strength. Also, the offshore trough has strengthened, and there is more moisture available for westerly winds to carry.

This explains the intense showers seen in Mumbai on Thursday. There is a chance of heavy spells in Mumbai on Friday as well, after which the intensity will decrease because there is still no low-pressure zone in the Bay of Bengal which can pull the winds towards the interior. But moderate showers will continue for the next week,” said Mahesh Palawat, vice-president (meteorology and climate change) at Skymet Weather, a private forecaster.

The IMD’S base weather station in Santacruz, meanwhile, received just 52.4mm of rain. In fact, IMD data shows that the interior parts of Mumbai have received significantly less rain than the coastal station of Colaba all through the month. While Santacruz has so far received 344.2mm of rain since June 1 (against the normal of 537mm), Colaba has received 487mm (against the normal 542.3mm).

As of 9:10pm, Colaba had received 164mm of rain while Santacruz received 105mm, since 8:30am Thursday morning.