How does a thundercloud form, and how does it differ from an ordinary cumuliform cloud? The first possible answers based on serious physical considerations were put forward between 1946 and 1948 as a result of the Thunderstorm Project. This was one of the first large-scale modern experiments to understand the structure of these clouds. Among its participants, Horace R. Byers and Roscoe R.
Braham Jr described the physical mechanisms involved in a single storm cloud, referring to it as a ‘cell’ due to its overall appearance. The genesis, evolution, and dissipation of a single-cell or air-mass thunderstorm can be viewed as taking place in three successive stages: the cumulus stage, the mature stage, and the dissipation stage.
In the initial stage, it is no different from an absolutely normal cumulus except that there is more energy involved and the cloud develops upwards under the effects of strong updraughts. These allow the production of large amounts of liquid and solid hydrometeors (water droplets and ice crystals), including graupels and hailstones which characterise the mature stage. At this point, downdraughts of cold...
