Microbursts
Inside a thunderstorm there are powerful updrafts and, as the storm matures, downdrafts (what goes up must come down). The updrafts can reach many tens of miles per hour. Turns out storm downdrafts can be equally intense. The downdrafts are caused by factors such as the drag heavy masses of rain and hail, and especially the fact that falling precipitation evaporates and cools the air, making it heavier than it's environment. The leading edge of the downdrdaft is called the gustfront. It is sometimes marked by spectacular cloud features called shelf or roll clouds. These downdrafts may be only several hundred yards wide. Recent research has shown that much storm damage once ascribed to tornadoes is actually the result of microbursts. Their winds can equal that of a small tornado. They often have a loud roaring noise, such as a large tornado.
