A microburst is a violent, localised column of sinking air under a cumulonimbus. When it reaches the ground it fans out in all directions, like a jet of water hitting the floor, producing sudden severe winds across a wide circle around the impact point.
For a small drone it is one of the most dangerous weather phenomena: the airflow can pin it down or slam it into the ground within seconds. And it arrives with little warning — even several kilometres away from the storm core itself.