Thunderstorms, lightning and many such events are witnessed during Pre-monsoonal season in India. Explain their formation process and its impact on various regions of India.

Pre-monsoon season is from April to May in India. It is the precursor to the full onset of monsoon. Due to high-pressure over the Indian subcontinent, the moisture bearing winds are not attracted to the mainland.

Process of Pre-monsoon rainfalls:

  • Oppressive heat is common in summer. It leads to warm air rising conventionally.
  • This warm, light air ascends to considerable height in the atmosphere.
  • Moreover the temperature of the air parcel reduces and its humidity capacity also falls.
  • Thus clouds are formed due to condensation of water vapour in the air.
  • The size of clouds increases due to accumulation of water droplets.
  • When clouds become too heavy, torrential rain and lightning occur.
  • Therefore cumulonimbus clouds formed by convectional heating of air, lead to rain.

In some regions, this rainfall has positive impact:

  • Aids coffee cultivation in Kerala and Karnataka (Blossom showers).
  • Helps the mango crop develop in Karnataka (Mango showers).

However, this has an adverse impact elsewhere, in form of natural disasters/discomfort:

  • Kal Baisakh – Rains in West Bengal.
  • Bardoli Chheerha – Heavy rain and rain in Assam.

Therefore the pre-monsoon and thunder storms originate due to unique reasons. They have proven a mixed blessing for India.


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