Heavy rain, accompanied by incessant bolts of lightning, lashed Calcutta between Saturday night and the early hours of Sunday.
The streaks, one after another, jolted many Calcuttans out of bed. Almost every bolt seemed to strike at a touching distance. The bright flashes, which seemed to light up the vicinity, were followed by rumblings of thunder.
The police reported that there were no casualties in Calcutta. “It was fortunate that the lightning occurred during the early hours, when most people were indoors,” stated a meteorological official.
The Met office attributed Sunday’s showers to tall cumulonimbus clouds. “It was a local thunderstorm. The powerful thunderclouds were 15km tall. Alipore and neighbouring areas were the most affected,” said H.R. Biswas, head of the weather section at the Regional Meteorological Centre in Alipore.
The showers in Calcutta abated from Sunday morning, but the sky remained cloudy for the rest of the day. The overcast conditions dragged the temperature down. The maximum temperature was 29.4 degrees, around four notches below normal.
In Calcutta, the sky is set to be clearer than it was on Sunday. Rain, however, is not ruled out. “A combination of heat and humidity can cause local thunderstorms,” said the Met official.
The Met office recorded 70mm of rain in Alipore between Saturday morning and Sunday morning, most of it during the night. In Met parlance, 60mm or more in 24 hours qualifies as heavy. Alipore is the official recordkeeper for Calcutta.
The timing of the showers instilled in many, who were awake, the fears of a rerun of the September 23 deluge. The city was battered by torrential rain in the early hours of September 23. Garia got over 300mm of rain in a few hours. Ballygunge and Jodhpur Park got over 250mm. The downpour turned roads into rivers and flooded classrooms and hospital wings and disrupted the power supply. Swathes of Calcutta descended into darkness. At least nine people were electrocuted.
Eventually, the latest round was nothing like the calamitous rain on September 23, which was caused by a moving system on the Bay of Bengal.
Readings at the pumping stations of the KMC showed that Maniktala got 53mm of rain from midnight to 4am on Sunday; Mominpore got 46mm and Kalighat got 38mm. Most other parts of the city got less.
“The low-pressure area over north Bihar and the neighbourhood had become less marked. However, the associated cyclonic circulation was over northeast Bihar and neighbourhood and extended up to 4.5km above mean sea level,” said a Met bulletin on Sunday.
It is the same system that intensified into a deep depression in the Bay of Bengal. It entered land near the sea resort of Gopalpur in Odisha around 5pm on Thursday, unleashing strong winds that clocked up to 75kmph.
After landfall, the system moved across Odisha. The system kept losing steam as it moved on land. It then went through Jharkhand before reaching Bihar.
“Initially, the system moved in a north-northwest direction. Then, it first moved north and eventually in a northeast direction. This was because of the anticyclonic wind pattern in the upper atmosphere. This usually happens when the southwest monsoon is in retreats. Had it been a month ago, the system would have kept moving west,” said a Met official.
Bihar’s proximity to north Bengal meant the intensity of the rain was much higher in the hills than in south Bengal. The downpour triggered multiple landslides and cut off key roads connecting the hills with the rest of Bengal. At least 18 people have died. Many tourists are trapped, according to reports.
A previous Bay system, which also hit land in Odisha, stuck to its northwestern path and ended up reaching the Arabian Sea. The system received nourishment from the sea and intensified into Cyclone Shakti. The storm will weaken while still at sea, according to the Met forecast. But it is expected to trigger heavy rain along the western coast of India.
The latest low-pressure system will weaken further, and the intensity of the showers will dip, both in the north and south of Bengal, from Monday. There is a heavy rain alert for only Alipurduar on Monday. For the rest of the state, light to moderate rain is in store, according to the forecast.