Conceptual Models of Precipitation Systems

Abstract

Imagery from radars and satellites is one of the main ingredients of nowcasting. When used to provide very detailed forecasts of precipitation for a few hours ahead, the imagery needs to be interpreted carefully in terms of synoptic and mesoscale phenomena and their mechanisms. This paper gives an overview of some conceptual models that are useful for this purpose. The models represent a variety of systems associated with midlatitude cyclones and also mesoscale convective systems in the tropics and midlatitudes. Specific phenomena discussed are warm conveyor belts, including those with rearward- and forward-sloping ascent in ana and kata cold frontal situations, respectively; cold conveyor belts ahead of warm fronts; narrow rainbands associated with line convection at the boundary of a pre-cold-frontal low-level jet; wide mesoscale rainbands associated with midtropospheric convection; squall lines in the tropics and midlatitudes; nonsquall mesoscale convective systems in the tropics and midlatitudes; subsynoptic-scale comma clouds associated with cold-air vortices; polar-trough conveyor belts and instant occlusions.