Plains Elevated Convection At Night (PECAN) Experiment: Preliminary Analyses of Severe Surface Wind Production in Nocturnal MCSs

The transition from surface-based to elevated convection and the subsequent organization and evolution of MCSs as the nocturnal stable boundary layer (NSBL) develops is not well understood. Importantly, these systems may produce severe surface winds, but the mechanisms through which intense-wind-causing downdrafts reach the surface in the presence of a NSBL remain uncertain, complicating the forecastability of severe wind events. Hydrometeor type, distribution, and evolution within these MCSs, as well as the evolving properties of the NSBL, environmental shear and other factors likely play important roles in the initiation, maintenance and cessation of intense, surface-reaching downdrafts.

The Plains Elevated Convection At Night (PECAN) experiment, (1 June – 15 July 2015) will provide a major opportunity for collecting integrated and targeted observations in severe-wind producing MCSs. PECAN will deploy a diverse array of instrumentation, including mobile and stationary radars, surface weather stations, mobile mesonets, and soundings in and near nocturnal MCSs and convection transitioning from daytime to nocturnal/MCS organization in the presence of a developing NSBL enabling the study of initiation/transition, evolution, internal kinematics and microphysics of severe-surface-wind-producing and potentially severe-surface-wind-producing MCSs.

We will present preliminary analyses of a severe-wind-producing MCS that occurred during PECAN. Dual-Doppler analysis of mobile radar data will be used to quantify the three-dimensional winds through the depth of the MCS. Internal microphysical processes will be inferred from the radar reflectivity and dual-polarization fields and surface disdrometer data. Data from sounding systems and wind profilers will be used to diagnose atmospheric stability, depth of the nocturnal boundary layer, vertical wind structure and the location of the nocturnal low-level jet (LLJ). Mobile mesonet and stationary weather stations will be used to quantify the strength and horizontal span of the surface cold pool, and characterize severe winds at the surface.