Convection » Microbursts: Wet vs. Dry Introduction

Microbursts are defined as severe downdrafts that do not exceed 4 km in horizontal extent. Aircraft that encounter a microburst may suddenly lose airspeed and experience an associated loss of lift, with potentially catastrophic results. Forecasters need to recognize some of the common sounding characteristics associated with microbursts, so that aviation interests can be alerted when their potential exists.
The downdrafts associated with microbursts are driven by negative buoyancy due to evaporative cooling. Once these strong downdrafts reach the surface, they spread horizontally, producing hazardous wind shear. Microbursts fall into two basic categories: those associated with precipitating thunderstorms, known as wet microbursts, and those observed in thunderstorms with little or no precipitation, known as dry microbursts.