Which process releases the energy that eventually produces lightning in a thunderstorm

Water condenses to form clouds.

When the mist compresses, this occurs in the liberation of energy. The energy prompts the atmosphere to be heated and effects in the increase of air in the uppermost environment. This method issues in the variability in the environment and cumulonimbus vapors are produced. These vapors subsidize lightening at the time of thunderstorm.

The process that releases energy which causes lightning is known as Glaciation.