The updraft of the thunderstorm is the convectivelly rising moist warm air. It is invisible to the eye below the condensation level and becomes visible as the ‘cauliflower’ cloud above the condensation level.
The updraft varies a lot between different thunderstorms. Its strength, the air velocity within it (i.e. how quickly that air parcel rises), tilt and possibly rotation depends on:
- how buoyant the warm rising air is
- what the CAPE is like: is it short, fat or long, thin
- how wind speed changes with height
- how wind direction changes with height
We will work our way from the bottom up.