Mumbai: Southwest monsoon onset likely in next 24 hours, two days before due date

“Conditions are favourable for onset of monsoon over the Konkan region, including Mumbai. In the next 24 hours, the onset of monsoon is likely over Mumbai and the rest of the Konkan region,” said Shubhangi Bhute, scientist, IMD Mumbai.

Rains lashed Mumbai and its neighbouring areas on Tuesday morning, bringing respite from the sweltering heat. As per the Regional Meteorological Centre, up to 30 mm rainfall was recorded in areas like Malvani, Borivali & Dahisar till 11 am. (Express photo by Ganesh Shirsekar) pic.twitter.com/ekuyrq7qAk

— The Indian Express (@IndianExpress) June 8, 2021

The normal monsoon onset date for the city is June 11. Last year, the monsoon arrived three days late. In 2019, Mumbai witnessed its most delayed monsoon onset in 45 years — on June 25. In 2018, it was on June 9 and June 12 in 2017.

The NLM, the north-most limit of monsoon up to which it has advanced on any given day, continued to pass through Alibaug and Pune in the state as of Tuesday afternoon.

As per the 48-hour forecast issued by the IMD, Mumbai is likely to see a generally cloudy sky with moderate rain and thundershowers in the city and suburbs. There is also a possibility of heavy to very heavy rain at isolated places in the next 48 hours, starting Tuesday.

“A Low-Pressure Area is likely to form over North Bay of Bengal and neighbourhood around 11th June 2021. Under its influence, fairly widespread to widespread rainfall activity (is expected),” said the IMD.

IMD has issued an orange alert for Mumbai, Palghar, Thane, for Saturday (June 12), indicating heavy to very heavy rain at isolated places, while a yellow alert with a forecast of heavy rain at isolated places has been issued for Thursday and Friday. Extremely heavy rain at isolated places is likely in Raigad, Ratnagiri and Sindhudurg districts on Saturday.

IMD classifies heavy rain between 64.5mm to 124.4mm, while moderate rainfalls in the range of 7.6mm to 35.5mm. Rain above 204.5 mm in 24 hours is classified as extremely heavy.

Meanwhile, pre-monsoon showers were recorded in Mumbai and parts of the Mumbai Metropolitan Region such as Thane, Bhiwandi, Dombivli and Badlapur on Tuesday morning, bringing down the temperature. Some parts of the western suburbs in Mumbai also recorded flooding.

In the 24 hours ending 8:30 am on Tuesday, the Santacruz observatory recorded 20.7 mm rain while the Colaba observatory recorded 21.8 mm rain. A cloudy sky with thundershowers in few areas was also recorded. In nine hours (till 5:30 pm) on Tuesday, 19.6 mm rain was recorded at the Santacruz observatory.

The city saw 27 per cent of the average monthly rain comprising pre-monsoon showers being covered in the first eight days of June. From June 1 to June 8, Mumbai recorded 136 mm rain. The average rainfall for June is 493.1 mm.

Doppler Radar still not functioning

Out of order since May 16, a day before Cyclonic Tauktae brushed past the city, the Met department’s lone Doppler Radar in Mumbai — which surveys weather patterns and forecasts —is still out of commission.

The radar installed in 2010 at the Regional Meteorological Centre in Colaba in South Mumbai can carry out weather surveillance up to 450-500 km radius from its location. Doppler Radar is crucial for gauging the intensity of rainfall and impact area in the city in real-time. It is efficient in tracking clouds that cause thunderstorms. Besides, real-time forecasting helps give out accurate information on areas which may experience heavy rain.

In the absence of a Doppler Radar, satellite pictures and wind profile are used by IMD to issue a forecast.