Moderate showers on Tuesday with intense isolated spells

Contrary to the weather bureau’s forecast of reduced intensity of rain on Tuesday, the city saw moderate to heavy showers while a few spells of intense showers were

Contrary to the weather bureau’s forecast of reduced intensity of rain on Tuesday, the city saw moderate to heavy showers while a few spells of intense showers were witnessed in the suburbs.

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The India Meteorological Department (IMD) updated its original forecast from ‘light to moderate rain’ to a yellow alert (heavy rain across isolated areas) on Tuesday afternoon. While no alert has been issued for Wednesday, IMD issued a yellow alert and predicted the possibility of heavy rain from Thursday to Saturday.

On Tuesday, a Nowcast warning for intense rain spells for Mumbai, Thane, and Satara districts was issued at 2 pm. The suburbs recorded an intense rain spell of 30mm between 11.30 pm and 2.30 pm.

Between 8.30 am and 5.30 pm Tuesday, the Santacruz weather station, representative of the suburbs and Mumbai, recorded 45.2 mm rain while Colaba, representative of south Mumbai, recorded 49.4 mm. IMD classifies 15.6-64.4 mm as moderate rain while 64.5-115.5 mm rain as heavy.

For the season so far, Mumbai suburbs have received 972 mm rain from June 1 to July 7 at 5.30pm and is just 28 mm short of the 1,000 mm mark while south Mumbai has received 991mm rain during the same time. While Mumbai has already received 69% of its July average rain, 42% of the seasonal average rainfall has been received over five weeks.

“Monsoon conditions are active along the west coast. Under the influence of a well-marked low-pressure area near the Saurashtra-Kutch region, rain intensity over north Konkan including the Mumbai region increased on Tuesday. The weather system is influencing strong westerly winds, which is pulling a lot of moisture from the Arabian Sea and strengthening the offshore trough extending from Gujarat to north Kerala coast,” said KS Hosalikar, deputy director-general, western region, IMD.

Location-wise rain in the suburbs showed 87mm rain in Mulund, 84 mm in Borivali, 80mm in Kandivali, 75mm in Thane 59mm in Malad, Vikhroli 52mm between 8.30 am and 5.30pm. During the same time, central Mumbai received 35-40 mm rain while the southern tip of the island city recorded 45-50 mm.

Independent meteorologists said Tuesday’s intense downpour was unexpected. “This was due to the offshore trough. The trough itself has a periodic north and south oscillation, and on Tuesday, it was active near Ratnagiri since morning but later shifted up towards Raigad. The southwesterly winds further pushed cloud bands towards Mumbai,” said professor Sridhar Balasubramanian, department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology-Bombay, adding that until the Arabian Sea weather system remains active, such sudden changes could be expected. “Until July 9, we could expect such rainfall episodes in Mumbai.”

Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom said, “More moisture availability increased rain activity on Tuesday. But that low-pressure system is likely to lose intensity from Wednesday due to which moisture will reduce leading to momentary weakening of the offshore trough. This will lead to light intermittent showers at least until July 12. Rain intensity is expected to increase again next week.”

Almost a month after the onset of monsoon, the water stock in city’s seven lakes finally saw a significant increase of 3%in the past two days. The rise in the lake levels was witnessed after heavy downpour in the catchment areas between July 5 and 6. The total water quantum in the seven lakes has gone up to 1.60 lakh million litre which is 11.10% of the required water stock from 1.15 lakh million litre (7.98%) of water stock two days ago. The total storage capacity of these lakes is 14.47 lakh million litre.