Studies of Extreme Gust Storm Events in Bengaluru, India

Many parts of India experience extreme gust and dust storms during the pre-monsoon months of April and May. These events can cause lot of damage to plants and properties. Despite their annual recurrences, their physical nature (e.g. temporal and spatial scales) and mechanism remain unaddressed in the Indian context. Here we present some case studies of pre-monsoon, damage-causing extreme winds reported from Bengaluru, India, in the media, and explore their nature, initiation and propagation using in situ observations, and INSAT-3D and INSAT-3DR infrared channel imageries. These gust events occurred on 24 April 2018, 7 and 26 May as well as 2 June 2019. Among these, the 24 April event was the strongest and the instantaneous wind speed exceeded 75 kmph. It is shown that all these cases share some common features. The first is the arrival of a pool of cold air with its minimum temperature that is at least 10 K less compared to what was prevailing about 15 min earlier. The second is the high rainfall rate; 1 min accumulation-based rainfall rate exceeds 100 mm h^–1. Extreme winds are short-lived and wind speeds exceeding 50 kmph last for less than 5 min. Satellite imageries of the corresponding period show that the associated clouds were organized with a spatial scale of at least several tens of kilometres.