B’luru records third highest rainfall in Sept in 34 years
IMD director Geeta Agnihotri said even though the department had predicted heavy rainfall, the city witnessed very heavy rainfall on Sunday.
At 131.6mm, Bengaluru has recorded the highest rainfall in September in 34 years from 1998.As per the IMD data analysed by HT, Bengaluru had recorded the first highest rainfall on September 12, 1988, when the city witnessed 177.6 mm of rain. The second highest rainfall was reported on September 26, 2014, at 132.6 mm.
Meanwhile, the India Meteorological Department, Bengaluru, was unable to predict the very heavy rainfall that pounded the state capital on Sunday and Monday, when Bengaluru city recorded 131.6 mm of rain in 24 hours.
IMD director Geeta Agnihotri said even though the department had predicted heavy rainfall, the city witnessed very heavy rainfall on Sunday. “For Monday, the prediction is light to moderate rainfall, but on Tuesday we expect another spell of heavy rainfall in Bengaluru,” she said.
According to Agnihotri, the excess rain was due to a shear zone that had developed nearly 4.5-5.8 kilometres above mean sea level that deposited heavy rains in south interior Karnataka, including Bengaluru City. A shear zone is a monsoon weather feature that is an area filled with opposing winds concentrating heavy rain in that zone. “It’s a normal occurrence during monsoons just as the formation of troughs, circulations, and low-pressure regions that drive monsoonal rains,” she said.
As per the IMD officials, the weather patterns above Bengaluru are likely due to a north-south trough forming over north interior Karnataka to Comorin and across interior Tamil Nadu at nine kilometres above sea level. The monsoonal trough is a low-pressure area, which is a semi-permanent feature of the monsoon circulation. Southward migration of the trough results in an active/vigorous monsoon over major parts of India, said the officials. “A cyclonic circulation also lies over the Comorin area and adjoining the Maldives at lower tropospheric levels,” Agnihotri said.
The India Meteorological Department (IMD) has issued a yellow alert for Bengaluru till September 7.
As per the IMD data for monsoon rains, the two Bengaluru districts — rural and urban — received more than normal rainfall this monsoon and have the fourth and fifth largest rainfall departure among all districts in Karnataka. Mandya has highest departure followed by Tamakuru and Ramanagara.
The Karnataka rain pattern shows huge differences. While Bengaluru on average receives 300 mm of rain during monsoon, districts such as Udupi in coastal Karnataka receives as much as 3,700 mm. However, the IMD data shows that rain in Bengaluru and nearby districts have increased in the past decade, thereby making it more vulnerable to floods.