The updraft is the engine of every convective cloud. Typical speeds range from 1–5 m/s in cumulus humilis to over 50 m/s in supercells. The updraft strength determines the maximum hail size it can support.
Severity indicator
An updraft exceeding 25 m/s indicates high potential for severe storms, large hail, and possible tornadoes. The CAPE parameter measures the energy available for these updrafts.