The sky started clearing in Calcutta from Monday afternoon, after a rainy start to the day.

The deep depression that triggered formidable rain in Calcutta and the rest of south Bengal for the past few days was near the Bengal-Jharkhand border on Monday afternoon, said a Met official.

The weather in Calcutta is set to improve further from Tuesday, said the Met
official.

The Met office had earlier predicted that the deep depression would lose steam and turn into a depression by the end of Sunday. But that did not happen. The system sustained its intensity and remained a deep depression longer than expected.

“It moved at a slower speed than expected and stayed over Gangetic Bengal for a longer duration than expected. Gangetic Bengal provided enough moisture to the system and it remained a deep depression,” said H.R. Biswas, head of the weather section at the Regional Meteorological Centre, Calcutta.

“The conditions in the upper atmosphere were not conducive for normal movement of the system. A westerly trough slowed the system,” he said.

A Met bulletin on Monday afternoon said: “The deep depression over Gangetic West Bengal and adjoining Jharkhand moved west-northwestwards with a speed of 12kmph during past six hours and lay centered at 11.30am over the same region, about 10km south of Purulia, 70km west-southwest of Bankura, 50km north-northeast of Jamshedpur (Jharkhand) and 110km east of Ranchi (Jharkhand).

“It is likely to continue to move west-northwestwards across Gangetic West Bengal and Jharkhand and weaken into a depression during the next 12 hours. Thereafter, it will continue to move west-northwestward across Jharkhand and North Chhattisgarh during subsequent 24 hours.”

Exactly 24 hours ago, the deep depression was “moving west-northwestward with a speed of 8kmph” and was 90km south-southeast of Bankura.

Around Sunday midnight, the speed had dropped to 3kmph, said a Met official.