Lightning strikes when the thunder clouds are hanging around in any area. Super cells of thunderstorms carry threat of severe lightning strikes with fatal consequences. These cells are mostly a result of convergence of two airmasses with opposite characteristics or on account of large instability prevailing in the atmosphere over certain areas. ‘Dry Line’ are the triggers for severe activity. These lines are narrow and nearly vertical transition zone with a sharp moisture gradient and separates the moist air and dry air with nearly same dry bulb temperature. Dry line is favourable for regeneration of thunderstorms also over a particular area.
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The thunder clouds have millions of volts of electrical charge and different polarity with in the cloud itself. Though the mechanism of lightning generation with in a thunderstorm is not fully known but a broad understanding has been arrived at the logical process. The electrification of the storm cell is on account of the condensation of water vapors in to droplets and also freezing of water droplets in to ice particles with the help of very strong updrafts with in the cloud cluster.
Usually the positive charge is in the upper portion and negative charge on the lower part of the cell. This negative charge at the bottom induces a positive charge close to the earth which otherwise is negatively charged. The charge inside the cloud keeps building as the convective activity increases. The storm at some stage becomes super charged with electrical energy.
This results in large amount of potential difference. Air as such is not a good conductor of electricity but this huge potential difference causes electrical break down of air which can now conduct electricity easily. This ‘break down’ of air is a very narrow path through which an intense amount of electricity flows.
Enormous amount of heat is generated which causes explosive expansion of the air. In this process, electrical discharge of millions of volts is seen as lightning strike and expansion of air sends shock waves to be heard as thunder.
The atmospheric conditions are quite conducive for formation of severe thunderstorms in the pre - monsoon season. There are sensitive weather pockets which enhance the ferocity of these storm. Eastern parts comprising of Bihar, Jharkhand and Odisha and plains of north India including Rajasthan and Uttar Pradesh are vulnerable to fatal lightning strikes.
Hilly areas both in the north and northeast are prone to this calamity. Lightning along with high velocity winds and heavy downpour form a deadly combination to reckon with. Sufficient precautions are the only safeguard to minimize damage.
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