The city has logged excess rainfall even as India witnessed the weakest start to the summer monsoon in more than a decade and a half.
Met readings show that from June 1 to the morning of June 28, Calcutta received 336.7mm of rain. The normal quota in this period is 263.3mm. It translates to a surplus of around 28%.
South Bengal as a region has, however, recorded a deficit of 22%, receiving 177.9mm compared to its quota of 227.4mm.
North Bengal and Sikkim, considered a region by the Met office, received 500.1mm of rain, 20% more than the quota of 417.1mm in the same period.
This newspaper reported on Sunday that rainfall across India in June has been 42% below normal, leaving 76% of the country “deficient” or “large deficient” in rainfall.
Forecasters expect July, too, to be drier than usual.
Weather scientists expect the rising sea surface temperatures in the Pacific — a phenomenon called El Nino — to keep the monsoon rainfall below normal through much of July.
The IMD had warned of below-normal rainfall this year for most of India. But east and the Northeast were tipped to receive near-normal rainfall, said Met officials.
“So far, Calcutta has received heavy rain on two days. But both of them were localised thunderstorms. The heavy rain has led to the surplus recorded so far. The intensity and spread of the rain will gradually increase in south Bengal, including Calcutta, over the next few days,” said a Met official in Alipore.
This year, the monsoon reached north Bengal on June 9 and south Bengal on June 11.
However, it was a quiet arrival, with Alipore, the city’s official recordkeeper, getting only 1.5mm of rain.
Till June 18, Calcutta barely received any rain at all. June 18 evening saw a thunderstorm that saw Alipore getting close to 50mm of rain. Another thunderstorm on June 21 afternoon brought 60mm of rain. Two more thunderstorms, on June 23 and 25, brought around 60mm and 85mm of rain.
The absence of any system on the Bay of Bengal has caused a rain deficit in many parts of India.
“The monsoon currents are vigorous when fed by a Bay system. That is missing this year. A Bay system leads to typical monsoon rain, uniform, widespread and persistent. Rain caused by a thunderstorm is often blinding. But thunderstorms are localised events,” said the Met official.
A Met bulletin issued on Sunday said the “seasonal trough at mean sea level from Punjab to Bihar across Haryana and Uttar Pradesh persists”.
“In view of favourable wind pattern and strong moisture incursion from the Bay of Bengal, thunderstorm and associated activities are very likely to continue over some districts of West Bengal. Heavy to very heavy rainfall (7-20cm) accompanied by extremely heavy rainfall (more than 20cm) is very likely to occur over some districts of North Bengal during June 28-29,” it added.