Bengaluru Sees Major Monsoon Deficit, But Not Driest in 20 Years

Bengaluru has recorded a significant shortfall in southwest monsoon rainfall this year, according to data from the India Meteorological Department (IMD). Between June 1 and September 30, the city station recorded 313 mm of rainfall, a departure of -236 mm from the normal. However, this is not the driest southwest monsoon in the last 20 years, as a weather tracking handle on X (formerly Twitter) claimed.

The IMD observatory at Bengaluru recorded 313.3 mm of rainfall against an average of 597.7 mm for the period. A post by @BngWeather on X said this was the driest southwest monsoon in 20 years, but it also noted that the observatory had recorded 298.3 mm in the 2006 season — which is lower than this year's figure. This indicates that while 2023 saw a large deficit, it was not the driest in 20 years. The tweet's claim appears to be inaccurate based on its own data. It is important to rely on official IMD data for accurate information.

Other weather stations in the city also reported deficits. The HAL station received 434 mm of rainfall, with a deficit of -29 mm. The Kempegowda International Airport station recorded 391 mm, though the deficit for this station was not available.

Across Karnataka, the seasonal cumulative rainfall data shows that the state received 564.6 mm against a normal of 831.8 mm, a departure of -32%. This falls under the 'deficient' category according to IMD's classification. Among districts, Bengaluru South (formerly Ramanagara) recorded the highest deficit at -87%, followed by Kalaburagi at -55% and Hassan at -53%. Bengaluru Urban district received 258.7 mm against a normal of 452.4 mm, a deficit of -43%.

Karnataka has three meteorological subdivisions. Coastal Karnataka received 2,228.3 mm against a normal of 3,093.9 mm (-28%). North Interior Karnataka received 329.8 mm against 480.8 mm (-31%). South Interior Karnataka received 433.7 mm against 678.4 mm (-36%).

IMD officials have attributed the rainfall deficit to strong El Nino conditions, which delayed the onset of the southwest monsoon in Karnataka. El Nino is a climate pattern characterised by the warming of ocean waters in the central and eastern Pacific Ocean, often associated with weaker monsoon rains in India. The southwest monsoon, which typically runs from June to September, is crucial for the country's agriculture and water resources. A significant deficit can impact crop yields and reservoir levels. The deficient rainfall could affect kharif crops, which are sown during the monsoon season.

“As forecast, we are witnessing strong El Nino conditions which has severely impacted the southwest monsoon in the State,” said IMD Scientist C.S. Patil.

The IMD's data is based on observations from its network of weather stations across the state. The Bengaluru city station is one of the oldest in the city. The normal rainfall is calculated as the long-period average (LPA) over a 50-year period. A departure of -236 mm means the station received 236 mm less than the LPA.

The southwest monsoon is the primary source of rainfall for Karnataka, accounting for the majority of the annual precipitation. A deficit in the monsoon can lead to water scarcity, affecting drinking water supply, irrigation, and hydroelectric power generation. While the city may have experienced some rainfall in recent days, the overall seasonal picture remains one of a significant shortfall. The IMD continues to monitor the situation and provides regular updates on rainfall patterns.