During which stage of a thunderstorm does the growth rate of the cloud exceed 3000 fpm?

The stage during which the growth rate of the cloud exceeds 3000 feet per minute is the cumulus stage. This is the initial stage of a thunderstorm where strong updrafts begin to form and the cloud rapidly develops in height and volume due to the intense convection taking place.

During the cumulus stage, warm, moist air rises and cools as it ascends, leading to the formation of cumulus clouds. As the moisture condenses, latent heat is released which further fuels the updraft, resulting in a significant rate of cloud growth. It is in this stage where the upward vertical motion can surpass 3000 feet per minute, setting the stage for the next phases of the storm.

In contrast, other stages of a thunderstorm, such as the development stage, mature stage, and dissipating stage, serve different purposes within the lifecycle of the storm, with varying characteristics of cloud growth and dynamics, but the cumulus stage is notably marked by the rapid ascent of air and cloud formation.