Post monsoon thunderstorm in Nepal: A case study

Abstract:

Thunderstorms are the most common and most extreme hazards that cause many human losses in Nepal, in addition to destroying a lot of crops especially in pre and post monsoon season. This study highlights severe thunderstorm event associated with hailstorm and heavy rain that occurred on 28^th October 2017 in Kathmandu and surroundings where one people was seriously injured and has a major effect on the agriculture with more than five million economic losses.The data sources for this investigation included NOAA and MERRA reanalysis data for geopotential height, OLR, moisture flux and wind analysis. The detail investigations of the event occurred close to 14-15 UTC on that day indicates the storm was initially developed from the Mediterranean Sea and was entered Nepal from Uttarakhanda of India. The synoptic analysis indicates the mid tropospheric deep trough along far west Nepal adjoining Uttarakhanda which is shifted eastward lying at central Nepal at 12 UTC. At the same time marked low pressure area from west Nepal is shifted to be reached at central Nepal. Similarly analysis of 850 hpa level shows west-northwestward movement of wind from Bay of Bengal and the surrounding areas towards the central region. Moisture flux analysis of 850 hpa also supports the wind movement carrying 0.01kgm^-1s^-1 moisture from the Bay of Bengal and the surroundings. High humidity levels at the surface contributed to the potential atmospheric instability with the CAPE value 1735Jkg^-1 in this region producing evening thunderstorm. So the focused study of the event reveals an upper level westerly wind which is supported by lower level moisture from Bay of Bengal along with continental moisture from Bangladesh and Myanmar.