What is a vertical updraft?
An updraft is a small scale current of rising air, often within a cloud.
Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, and so will rise until it reaches air that is either warmer or less dense than itself. The converse will occur for a mass of cool air and is known as subsidence.
This movement of large volumes of air, especially when regions of hot, wet air rise, can create large clouds, and is the central source of thunderstorms. Drafts can also be conceived by low or high-pressure regions. A low-pressure region will attract air from the surrounding area, which will move towards the center and then rise, creating an updraft. A high-pressure region will attract air from the surrounding area, which will move towards the center and sink, spawning a downdraft.
Updrafts and downdrafts, along with wind shear in general, are major contributors to airplane crashes during takeoff and landing in a thunderstorm. Extreme cases, known as downbursts and microbursts can be deadly and difficult to predict or observe.