Question

What is cloud burst and why does it occur?

Answer 1

It is actually a sudden aggressive rainfall falling for a short period of time over a small geographical area.

Basically , it happens when the inter-molecular forces between the H2O molecules get very high due to the rapid decrease in the temperature or excess of electrostatic induction in the clouds causing the lighting to remain inside the cloud only, which causes hyperactive energy inside the cloud.
The water molecules get denser and denser and get condensed but do not leave the cloud due to excess of electroforces.

As the water concentration get higher and higher and so the weigh gets heavier the water no longer is able to maintain force with the clouds and so they fall and it precipitates.