Rachel L. Miller1,2,3, Conrad L. Ziegler1, Michael I. Biggerstaff3, and A. Addison Alford3
1NOAA/OAR/National Severe Storms Laboratory (NSSL), Norman, OK
2Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma (OU) and National Oceanic and Atmospheric Administration (NOAA), Norman, OK
3School of Meteorology, University of Oklahoma, Norman, OK
This study analyzes a nocturnal mesoscale convective system (MCS) that was observed in northeast Kansas by the Plains Elevated Convection At Night (PECAN) field project on 25-26 June 2015. Over the course of the observational period, a broken line of nocturnal convective cells initiated beginning around 0230 UTC (all times are Universal) on the cool side of a surface cold front and subsequently merged into a quasi-linear MCS that later matured and developed strong outflow and a trailing stratiform region. The present study combines 3-D wind syntheses of observations from 4 mobile radars at a 5 min interval from 0300 to 0530, providing context to interpret measurements of the MCS and its inflow environment from mobile mesonets, mobile and fixed soundings, and profiles from AERIs and Doppler wind lidars. These combined in situ and profiling observations and the time-spaced wind syntheses will be assimilated into a diabatic Lagrangian analysis (DLA) to derive information about the evolving thermodynamic, cloud, and precipitation structure of the MCS.
One of the main goals of PECAN is to determine whether nocturnal MCSs are elevated or surface-based and how the stable nocturnal boundary layer influences the structure, evolution, and movement of the MCS. A sample 4-radar analysis of the 26 June MCS in a NW-SE oriented vertical cross-section at 0500 (see attached image) reveals a rear-to-front (RTF) flow that descends toward the surface behind and through the main reflectivity cores and ultimately reaches the surface as an inferred surface-based cold pool. The 0500 wind synthesis also reveals MCS inflow air rising from the surface via multiple updrafts to form an ascending front-to-rear (FTR) flow, and also reveals a new updraft developing along or ahead of the leading edge of the inferred cold pool. Calculated Lagrangian trajectories from time-series wind analyses will reveal the source layers of air parcels (surface or elevated), allow us to determine the evolution of source levels as the MCS develops from the initial convective line to the mature MCS stage, and how radar properties of air parcels change while traversing the different sections of the MCS. Combining these 3-D airflow analyses with DLA, we will additionally infer the altitude and thermodynamic origins of updraft, downdraft, and mesoscale cold pool parcels, assess the diabatic thermodynamic forcing along selected air trajectories, derive the mesoscale cold pool depth and structure, and determine whether the MCS updrafts, downdrafts, and cold pool are elevated or surface-based.
Corresponding author:
Rachel L. Miller
Cooperative Institute for Mesoscale Meteorological Studies (CIMMS)
120 David L. Boren Blvd.
Norman, OK 73072-7323
email: rachel.miller@noaa.gov
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