Rachel Miller- April 26- Convective Meteorology Seminar

Name:     Rachel Miller

Title:    Idealized Simulations of the 25-26 June 2015 Kansas MCS during PECAN

Location: NWC 5600

Date:     2019/04/26

Time:     3:30 PM

Series:   Convective Meteorology (Mesoscale Dynamics)

Abstract: The Plains Elevated Convection at Night (PECAN) Experiment was designed to study nocturnal convective initiation (CI) and maintenance of mesoscale convective systems (MCSs). On June 26, 2015 around 0230 UTC, CI occurred on the cold side of a stationary front with updrafts ingesting air from the 2-3 km elevated residual layer (ERL). By 0400 UTC, these cells were observed to grow upscale into a line which underwent an elevated to surface-based transition between 0400 and 0430 UTC according to multiple-Doppler analysis. The MCS further intensified after this transition and developed several bowing segments. The main findings of the case study are that frontal and mesoscale isentropic ascent acted to cool and moisten an ERL which primed the environment for CI and the eventual mature MCS passage. Additionally, a surface-based mesoscale cold pool developed from rear inflow descending to the surface behind the strongest convective cores to locally enhanced cold pools at the surfac

e. These merged overtime as the line strengthened to form a larger mesoscale cold pool. Finally, trajectory analysis indicate that the main source region for updrafts evolved from 2-3 km (ERL) before 0400 UTC to the lowest 0.5-1 km by 0440 UTC supporting kinematic analysis that shows an elevated to surface-based transition.

An idealized model simulation using COMMAS will be presented used to try to simulate the 25-26 June MCS. The objective of the simulation is to investigate the dynamics of the elevated to surface-based transition including development of the cold pool and interactions with the frontal inversion. Simulations were run using observed soundings taken during the PECAN IOP in the vicinity of CI and the MCS. Two of the soundings (0300 and 0347 UTC) produced CI but never underwent upscale growth while the other soundings (0215, 0430, and 0304 UTC) produced CI and grew upscale. However, none of the simulations that grew upscale resembled the observed system most likely due to the failed development of a mesoscale cold pool. Future work will incorporate the stationary front into the idealized simulation using a sounding north and a sounding south of the front for initialization.