Mumbai: The overnight downpour in the first 24 hours of the much-delayed monsoon onset pushed the city’s rain gauges into triple digits, with several pockets crossing 300mm, even as the IMD Colaba observatory recorded its heaviest 24-hour June rainfall in over a decade.According to India Meteorological Department (IMD) data, the 24-hour period ending Wednesday 8.30am, the Colaba observatory received 247.8mm of rain, breaching its 24-hour June rainfall record of 208.8mm in 2015, and the Santacruz observatory logged 224.8mm surpassing its 2019’s record of 234.8mm. These figures also indicated that Colaba received nearly 46% of its average June rainfall quota of 542.3mm and Santacruz 42% of its average June rainfall quota of 537.1mm in just one night.The intensity, however, was far more severe in isolated pockets. Automatic Weather Stations (AWS) recorded that areas such as Parel, Powai and Malwani in Malad received over 300mm of rain highlighting the highly localised and intense nature of the downpour. Many areas also recorded over 200mm of rainfall.For Thursday, IMD has issued a ‘yellow’ alert indicating heavy rainfall for Mumbai, Thane, and Raigad, indicating thunderstorms accompanied with lightning, light to moderate rainfall, and gusty winds at isolated places. .The rain, officials said, built up rapidly through the night rather than falling uniformly over 24 hours. At Santacruz, rainfall rose from 57.8mm by Tuesday 11.30pm to 164.2mm by Wednesday 2.30am, crossed 210.6mm by 5.30am and reached 224.8mm by 8.30am. Nearly 106mm of the rain fell within a three-hour window between 11.30pm and 2.30am, leading to the IMD to issue a nowcast red alert that remained in place till 7am.The heavy rain led to waterlogging in several low-lying parts of the city during the early morning hours. Civic officials reported water accumulation at key locations including Hindmata, Andheri Subway, Malad Subway and parts of Sion, though drainage operations were quickly deployed and traffic movement was largely restored.Navi Mumbai received an average of 126mm rainfall during the same period. Belapur recorded the highest rainfall of 140mm. Thane recorded barely 3mm rainfall in four hours, but witnessed nine tree collapses at different places.The Morbe dam catchment area on the outskirts of Panvel, which is the key source of drinking water for Navi Mumbai and Panvel, registered 81mm rainfall in a 24-hour period, taking the total rainfall to 105.4mm in the season. The dam level revived to 69.5m with 26.3% storage in the reservoir.Explaining the sudden surge, weather expert Athreya Shetty said multiple monsoon systems worked together to intensify the rainfall. “A cyclonic circulation over Mumbai, a mid-level trough extending from Vidarbha to Mumbai, and a strong offshore trough from Palghar to north Raigad combined to create highly favourable conditions for deep moisture-laden monsoon flow. This led to strong wind convergence and the development of towering cumulonimbus clouds reaching nearly 9km in height. Once formed, the system became self-sustaining, resulting in intense downpours between 11pm and 3am,” Shetty said.Another weather expert, Akshay Sunil of WeatherEx @ Experiqs Pvt Ltd, said the spell was driven by an active monsoon surge and organised convective cloud bands moving in from the Arabian Sea. He added that rainfall may ease slightly, with a relatively quieter phase expected around June 27, before another spell of moderate to heavy showers around June 28–29.(Inputs by B B Nayak & Manoj Badgeri)
