Abstract/Summary

A natural disaster in the form of severe flash floods due to extreme precipitation occurred at Kedarnath (Uttarakhand), India, on 16–17 June 2013 and is being considered as one of the worst disasters in India (Das in J Geol Soc India 82:201, 2013). The catastrophe in the form of flash flood and associated debris flow caused major devastation leading to a high death toll of locals and visiting pilgrims. The very early migration of monsoon trough (MT) towards northern India and its interaction with an incoming western disturbance (WD) formed a transient cloud system that led to extreme precipitation. Using WRF model with triple-nested domain for simulation at finer resolutions, this high-intensity precipitating event is analysed. Interaction of the MT with WD over the foothills of the Himalayas usually causes a break period in the Indian monsoon, but the interaction of MT and WD during this storm event showed different characteristics. Such an association of WD with the MT has been termed as pulsatory extension of the monsoon (PEM) towards Himalayas (Pisharoty and Desai in Indian J Meteorol Geophys 7:333–338, 1956; Mooley in Indian J Meteorol Hydrol Geophys 8:253–260, 1957). The interaction of the WD with the MT exactly over the Uttarakhand region forms an occluded discontinuity between the mid to upper-tropospheric WD frontal system (colder) and the lower-troposphere MT (warm and humid). The precursor of this front caused formation of steep temperature gradient over the Indian region that led to the early advance of MT towards Himalayas. Formation of this strong front develops augmented convective instability, which is further enhanced by orographic lifting, leading to the configuration of this large organized storm causing extreme precipitation over a large spatial region.