What defines a microburst?

A microburst is defined specifically as a severe downdraft associated with thunderstorms. This phenomenon occurs when a pocket of cold air rapidly descends from a storm cloud and then spreads out horizontally when it reaches the ground. The downdraft can be extremely strong, often exceeding 100 miles per hour, and can result in hazardous conditions for aircraft, particularly during takeoff and landing.

Understanding microbursts is crucial for pilots and meteorologists because they can lead to sudden changes in wind speed and direction, which can be perilously challenging for aircraft control. Unlike other weather phenomena, a microburst is short-lived, typically lasting less than 15 minutes, but its impact can be significant, especially in the vicinity of airports.

The other options provided do not capture the essence of a microburst. For instance, an increase in altitude with no downdraft does not align with its definition, nor does a gentle shift in wind direction or a type of cloud formation accurately convey the rapid descent of air that characterizes a microburst.