What caused thunderstorms during onset of 2024 southwest monsoon in Karnataka? Study reveals

Scientists from the India Meteorological Department (IMD) and Bangalore University in a new study have revealed the reasons which contributed to thunderstorms that accompanied the arrival of the southwest monsoon in 2024.

That year, the monsoon advanced into Karnataka on June 1 and covered the entire State by June 6, and over those six days, thunderstorms occurred across the State, with Bengaluru seeing the most intense activity, recording 111.1 mm of rain on June 3.

In the study, titled ‘Thunderstorms During the Onset of the Southwest Monsoon in Karnataka: A Case Study of Synoptic and Thermodynamic Analysis’, IMD scientists C.S. Patil and Darga Saheb Shaik, along with Kamsali Nagaraja of the Department of Physics, Bangalore University, found that the storms were fuelled by several weather systems acting together.

“Strong southwesterly winds and a strengthening Somali Jet, the cross-equatorial air current that feeds the monsoon, carried a steady stream of moisture from the Arabian Sea towards the Western Ghats and the peninsula,” the scientists said.

They added that the upper-air soundings from Bengaluru showed how unstable the atmosphere had become.

“The Convective Available Potential Energy (CAPE), a measure of the energy available to rising air, reached 2,501 joules per kilogram. The Convective Inhibition, which can suppress storm growth, fell to zero. Other stability measures agreed: a Lifted Index of −3.67 and a K-Index of 42.9 both pointed to a strong likelihood of severe thunderstorms over the Bengaluru region,” they added.

The scientists further said that thunderstorms develop within hours and over small areas, which makes them difficult to forecast. The study shows that combining large-scale wind analysis, satellite cloud-top imagery and stability indices from balloon soundings gives forecasters a clearer and earlier signal of where storms are likely to form.

“Applied routinely, this approach can strengthen early warnings, improve flood management and help protect infrastructure and agriculture across Karnataka each time the monsoon sets in,” they added.