The effect of Cyclone Asani is expected to lead to an early onset of monsoon over the Andaman islands and Kerala, said a Met official.
But it was too early to say if Calcutta, too, would have an early date with the monsoon, said the official.
The usual date of the onset of monsoon in north Bengal is June 5. For south Bengal, the date is June 8. There is an error margin of four to five days with the dates, said a Met official.
Riding the cyclone, the monsoon is expected to set foot in the Andaman and Nicobar islands on May 15, five days before the usual date, said the Met official. In Kerala, the usual onset date is June 1. But this year, it is expected to reach by May 27.
“But it is still too early to predict the date of the onset of monsoon in south Bengal. In the past, there have been years when the monsoon came to Kerala before time but was late in south Bengal and vice versa,” said G K Das, director, IMD, Calcutta.
Apart from widespread rain, the monsoon is marked by wind blowing from the southwest, the direction of the Bay of Bengal, instead of blowing from north India. The change is already taking place over the Bay of Bengal, said a Met official in Calcutta.
The minimum relative humidity, a measure of moisture in the air in the daytime, has also been on the higher side.
A weather system like a cyclonic circulation or a low-pressure area can propel the monsoon into Calcutta, said a Met official.
On Friday night, the city received a sharp spell of thunderstorm. Barrackpore and Dum Dum received close to 50mm of rain. The clouds that triggered the storm came from Jharkhand. But it was not a typical Nor’wester that strikes the city in the afternoon or evening.
Saturday was hot. The maximum temperature was around 34 degrees Celsius. But it felt hotter because the sunlight was more piercing than usual, said Das.
“The rain last night had washed the pollutants in the atmosphere. That is why the sun seemed to shine more brightly than usual,” he said. The city is tipped to get another spell of thunderstorm over the next two days, according to the Met forecast.
The maximum temperature is likely to be around 34-35 degrees Celsius.