Microbursts - powerful downdrafts generally associated with thunderstorms that occur in hot, humid weather - have caused a number of aircraft crashes. To prevent future accidents, air traffic controllers must be able to detect, and predict, microburst events. All microbursts are not alike, however; several distinct weather patterns can produce microbursts. Thus a categorization of the different types of microbursts is an essential part of understanding these hazardous phenomena Using this categorization, the relative hazard to aviation of the various types of microbursts can be assessed.