If you are wondering about the origins of Monday night’s thundershowers (after all the southwest monsoon officially beat a retreat September-end), the weatherman will tell you that they owe it to new weather systems, which are poised to make this week a rainy one for Bangalore, Chickballapur and Kolar.

Very early on Tuesday morning, a “local weather trough” over south Karnataka unleashed thunderclaps, lightning and heavy showers. Chickballapur, the worst impacted, recorded a huge 120 mm rainfall that left more than 250 homes flooded, especially in Nakkalakunte.

The Junior Women’s College was flooded and classes suspended even as staff and students spent the day bailing out water.

Sources said that the flooding has brought to the fore indiscriminate encroachment of lake beds, raja kaluves and drains. The district administration will pay the households Rs. 2,000 each as immediate relief and one week’s free rations, according to officials.

In a freak incident, in Bhagat Singh Nagar, a group of six monkeys died when they were struck by lightning. Kolar recorded 80 mm, Bangalore Rural 90 mm and parts of the city 64 mm. While this trough is likely to blow over in a couple of days, a cyclonic storm will take its place, according to B. Puttanna, director of the met centre here. “We have observed a deep depression in Bay of Bengal which is likely to intensify into a cyclone as it moves towards northwest.” The cyclonic system, which is still over 1,000 km away from the eastern coast, could hit the coast of Andhra Pradesh or Odisha in three days, according to a bulletin by the India Meteorological Department (IMD).

The cyclone could bring in the northeast monsoon earlier than schedule, he added. “The normal onset date of the northeast monsoon is October 20, but the cyclone system could accelerate the onset.” The northeast monsoon, which accounts for 30 per cent of annual rainfall in Karnataka, is felt significantly only in south Karnataka, said Mr. Puttanna. The IMD has forecast “normal” northern monsoon this year

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