Convective Meteorology (Mesoscale Dynamics)

WRF Simulations and Observations of a Long-Lived Mesoscale Convective System on 06 October 2014

Manda Chasteen

School of Meteorology

22 April 2016, 3:00 PM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Mesoscale convective systems (MCSs) are well known to have a significant influence on the warm season nocturnal precipitation maximum over the Great Plains. As such, several climatologies of these systems have been conducted, and it has been well established that they frequently weaken or dissipate in the morning with the cessation of the nocturnal low-level jet (LLJ). However, that is not always the case, and previous research has shown that around 28% of these MCSs remain steady or strengthen during the late morning. Less research has been dedicated to understanding the mechanisms responsible for the daytime persistence of these systems, despite the challenges faced by short-term forecasters when trying to predict their evolutions.

The system presented herein is a long-lived MCS that persisted through much of the diurnal cycle and was poorly forecast operationally. This MCS initiated around 02 UTC in an environment thought to have minimal convective available potential energy (CAPE) and went on to produce numerous wind and hail reports and one EF-1 tornado near 06 UTC. Thus, this system was not completely elevated throughout the nighttime despite the most-unstable CAPE existing aloft. WRF simulations in tandem with mesonet observations were utilized to study the evolution of the system as it encountered environments with different thermodynamic and kinematic characteristics and to better understand why the system persisted during the daytime as the boundary layer was destabilizing. Some preliminary results of the system structure and environment gathered from the WRF simulations will be presented. Additionally, the sensitivity of the simulated convection to horizontal grid spacing and initial and boundary conditions will be discussed.

Convective Meteorology (Mesoscale Dynamics) Seminar Series website