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Moisture flow triggers rain forecast for city

Showers that returned to the city on Monday after a 24-hour respite are likely to continue on Tuesday.

“There is a cyclonic circulation spread over Bengal, Jharkhand and Bihar. Because of this intermittent rainfall would continue in Calcutta at least till Tuesday afternoon,” said Gokul Chandra Debnath, director, India Meteorological Department, Calcutta.

There is, however, no forecast for heavy rainfall in the city. The western districts of the state and the Terai and Dooars, however, may receive heavy rainfall on Tuesday.

The cyclonic circulation had formed over the Bay of Bengal on Sunday and moved inland at night. It brought in its wake the monsoon trough to Gangetic Bengal. The cloud cover over Calcutta and the rest of Bengal resulted from these two systems that drew moisture-laden air from the Bay.

The day broke on Monday with grey skies, the rainfall having started in different parts of the city a little before sunrise around 5.20am.

Till 8am, the Met office in Alipore recorded 7mm of rain and in Dum Dum 8mm of rain. As the day wore on, however, it rained more in south Calcutta than in the north.

The day’s maximum rainfall in the city was recorded in Alipore from 8.30am to 11.30am — 32mm of the total 41mm it received till 2.30pm.

Dum Dum, in contrast, received only 9mm.

“The rain gauges in our pumping stations show that north Calcutta got about two-thirds the rain the south received during the day. The north got 20mm on an average against 30mm in the south,” he said.

The rain had a welcome cooling effect, with the maximum temperature climbing four degrees Celsius below normal to 28.1 from Sunday’s 34.5.

“The weather was cool and nice once again on Monday. I hope it stays this way for some more time,” said Antara Banerjee, 32, a resident of Tagore Park off the EM Bypass.

The mercury was, however, expected to rise by two degrees each on the coming two days and reach 32 degrees Celsius on Wednesday.

The cloud cover is expected to thin from Wednesday with the weakening of the cyclonic circulation, resulting in increased solar radiation and a rise in the temperature.

“If there is no fresh formation over the sea in the next couple of days, rain in Calcutta could stop for a while from Wednesday. Over the past couple of years the monsoon had displayed a late surge. We expect a repeat this year, too,” said an official of the India Meteorological Department.

Weather experts think September would receive more than its usual quota of 312.6mm of rain.