Report on the severe Thunderstorm activity that took place over Delhi on 30 May, 2014

Thunderstorm development is a rapid process occurring within a short period of a few hours. Prior to this development, there is a continuous and gradual change in the atmospheric conditions and the conditions just before the time of occurrence of the thunderstorm may be different from the conditions earlier at the time of routine RS/RW ascent at 0000 UTC.A severe thunderstorm affected Delhi and adjoining region between 1630 Hrs IST and 1730 hrs IST of 30 May. As per the GFS wind analysis at 0000 UTC of 30 May for 925 hPa and 850 hPa levels , a circulation lay over west Uttar Pradesh (east of Delhi) with a strong horizontal wind shear supporting lower level convergence (Fig.5a &b). The 200 hPa wind analysis indicated the core jet stream passing over Delhi region (Fig.5c). A jet at 200 hPa is generally associated with more number of occasions of thunderstorms than a westerly trough at 500 hPa level.

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