Downbursts, Microbursts, and Macrobursts

When severe thunderstorms impact an area, many times the weather produces damaging winds that down trees and power lines.
Often, the damage is so severe or extensive, it is difficult to fathom that anything other than a tornado produced the damage. Yet, there are straight-line wind features, called downbursts, that can be just as damaging as tornadoes.

A downburst is an area of strong, downward moving air associated with a downdraft from a thunderstorm. As the downdraft impacts the ground, the air is forced outwards in all directions while it also curls backwards. This results in incredible wind damage close to the surface of the ground, as well as horizontal rotation midway up between the ground and the base of the thundercloud.

Often, downbursts can produce straight-line wind damage over an area as small as 1 mile to as large as 250 miles from the center of the downdraft.

In fact, a downburst that spans a distance less than 2.5 miles in diameter is considered a microburst.

http://www.weather.com/storms/severe/news/downbursts-macrobursts-microbursts-tornadoes