Windshear and wake turbulence.

Bottom line

Wake turbulence can impose rolling moments exceeding the roll-control authority of an encountering aircraft, causing possible injury to occupants and damage to the aircraft. The impact of a wake encounter depends on the weight, wingspan, and size of the generating aircraft, the distance from it, and the point of vortex encounter. Avoid the area below and behind the wake-generating aircraft, especially at low altitude where even a momentary wake encounter could be catastrophic.