Numerical simulations of the post-sunrise reorganization of a nocturnal mesoscale convective system during 13 June IHOP_2002

The MCS reorganization consists of a transition from NW-SE oriented convective rainbands near sunrise to a single NE-SW oriented convective rainband with trailing stratiform precipitation later in the morning.

Results indicate the importance of environmental preconditioning on MCS reorganization. In particular, the development of the NE-SW rainband that redefines the MCS organization is facilitated by a similarly oriented zone of antecedent mesoscale upward motion, which increases the depth of large water vapor mixing ratios. This allows convective updrafts to be fed primarily by moist and conditionally unstable air from 1 to 2.5 km AGL in the NE-SW oriented rainband, which lacks a surface cold pool during its incipient post-sunrise stage.