Kinematics and Thermodynamics of the Severe 5-6 July 2015 South Dakota MCS during PECAN

This study documents the evolution of deep moist convection and the mesoscale cold pool of the severe 5-6 July 2015 South Dakota nocturnal mesoscale convective system (MCS) using observations from the Plains Elevated Convection At Night (PECAN) project and a diabatic Lagrangian analysis (DLA) of thermal and hydrometeor fields.  PECAN observed the later stages of the merger of an externally-driven (Type 1) quasi-linear MCS and an internally-driven (Type 2) bowing MCS that produced several severe wind reports, at least one low-level mesocyclone, and a weak tornado in the left bookend-vortex location of the bowing segment of the 5-6 July MCS.  A series of wind syntheses incorporate observations from a unique pre-deployed array of 7 mobile Doppler radars, while in situ and MCS-environmental observations of thermal variables and airflow from mobile mesonets, pre-deployed lidars and AERI profilers, mobile and pre-deployed soundings, and research aircraft augment the DLA retrievals.

We will focus on the maintenance and evolution of the merged MCS's mesoscale 3-D airflow and cold pool structure in relation to its stable nocturnal boundary layer (NBL) inflow environment in the 04-06 UTC time period on 6 July.  A PECAN hypothesis asserts that severe surface winds may be achievable given favorable environmental convective available potential energy and bulk shear ingredients (which were present in the 5-6 July case), provided that the mesoscale nocturnal cold pool is surface-based and contains a strong thermal solenoid via precipitation-forced diabatic cooling to assist the descending rear-to-front (RTF) flow (e.g., see attached radar analysis image).  The Lagrangian air trajectories will help indicate whether the nocturnal convective and mesoscale updrafts and downdrafts and the mesoscale cold pool are surface-based or elevated, while also helping to define the thermodynamic evolution along trajectories that feed the deep convection, the cold pool, and the trailing stratiform region.