Kolkata: Riding a low-pressure system, the south-west monsoon entered the city on Tuesday morning when most Kolkatans were asleep. The wait for monsoon ended with the city recording a decent rainfall of 23.1 mm on the first day.

The Met office expects more intense showers between Wednesday and Thursday in the city as well as in other Bengal districts.Monsoon onset in Kolkata also comes 24 days after its arrival in Kerala and 19 days after it hit north Bengal. Despite the early arrival in Kerala and N Bengal, the monsoon current entered a sluggish phase, delaying its entry to Kolkata and the rest of south Bengal. The normal date for monsoon arrival in Kolkata is June 10.

Last year, it entered Kolkata on June 21."South-west monsoon has advanced and covered the entire south Bengal on June 17, and it advanced further to the remaining parts of north Bengal," said a special bulletin from IMD.In the past decade, the earliest monsoon arrival date in Kolkata was June 11, 2021, and the longest wait for it in south Bengal was June 22, 2018.According to Met office, under the influence of an upper air cyclonic circulation over north-west Bay of Bengal and neighbourhood, a low-pressure area formed over south-west Bangladesh and adjoining Gangetic West Bengal on Tuesday morning.

The associated upper air cyclonic circulation extends up to 7.6 km above mean sea level, tilting southwards with height. It is likely to move slowly west and north-westwards and become more marked over Gangetic West Bengal and its neighbourhood during the next 24 hours."This low-pressure area will gradually move over to the land area and pass over many parts of south Bengal by Tuesday. As a result, we can expect more intensified rain between Wednesday and Thursday," said meteorologist H R Biswas, head of the weather forecast section at RMC Kolkata.While low-pressure systems generally intensify into depressions over the sea, Met officials said this system can transform into a depression over the land during monsoon. RMC Kolkata is tracking the system closely so that any signs of it turning into a depression are detected on time, as this will have impact on the intensity of rain.A cloud-covered sky with spells of rain pushed the maximum temperature down to 28.4 degrees Celsius, which was 5.4 notches below the normal mark.

Even minimum temperature at 26.6°C was slightly below the normal mark. The mercury will remain below the normal mark for now."Since the flow is in an active phase now, even if the rain intensity decreases by Friday, we can expect a few spells daily for now. Due to the wet spell, the mercury will not shoot up," said Biswas.Monsoon arrival dates2024 | June 212023 | June 192022 | June 182021 | June 112020 | June 122019 | June 202018 | June 222017 | June 152016 | June 162015 | June 13KKKA low-pressure area over Bangladesh and neighbouring Gangetic BengalThis system is expected to become well-marked by WednesdayIt will inch towards land and pass over S Bengal A heavy rain alert has been issued for many parts of S Bengal