In two days of heavy downpour, Kolkata received 282 per cent more rainfall than the normal in a week. The amount of rainfall received in excess by the city from 1-8 May was the highest among various districts of the state.

According to the data available with the Regional Meteorological Centre, six districts, including Kolkata, Howrah, South 24-Parganas, North 24-Parganas, Bankura and Murshidabad received a rainfall of more than 100 per cent than normal during the period. After Kolkata, the departure in North 24-Parganas was 239 per cent followed by Howrah that recorded 186 per cent in one week. South 24-Parganas, Bankura and Murshidabad are said to have received 134, 131 and 152 per cent deviation from the normal respectively during the period.

According to the local weather office data, even in terms of seasonal rain, the city has received 38 per cent more rainfall than the normal between 1-10 March. As per the information available, a departure up to +19 or -19 per cent is considered normal while that above 20 per cent and below 59 per cent is termed as ‘excess.’ The seasonal rainfall data revealed that the districts of south Bengal namely Kolkata, North 24-Parganas, East Midnapore and Hooghly had higher rainfall than the normal. On the contrary, districts of north Bengal including Cooch Behar, Jalpaiguri, North Dinajpur, South Dinajpur along with western fringes like Purulia registered deficit rains during the period.

For Kolkata, a deviation of 38 per cent for the season, as informed by the weather scientists, is a good amount of rain. The weather officials are attributing the increased rainfall to the mesh of trough lines and ‘weather systems’ around South Bengal. As per the information available the mesh of the trough lines continued even today. While an east-west trough ran from a cyclonic circulation over northwest Rajasthan to south Assam across Madhya Pradesh, Jharkhand and Gangetic West Bengal another crossed from above cyclonic circulation over north Bihar to north Odisha across Jharkhand and Gangetic West Bengal. The two lines coupled with a cyclonic circulation over north Bihar and neighbourhood are tipped to bring rainfall and thunderstorms in Kolkata and adjoining districts.

The weather office has tipped the formation of a weather system in the Andaman Sea during 17-22 May. The exact location, intensity and impact of the system is yet to be known as the ‘lead time is more than 10 days, according to the weather scientists. For now, Kolkata along with other districts of south Bengal are tipped to get continuous rainfall till 17 may.