Convective Storms Group
Prospective graduate students: We hope to accept and support 1-2 new graduate students to work on either the CSTAR or PECAN projects, starting in 2018. Please contact Dr. Parker for more information.
Understanding fundamental processes and evaluating high-resolution model forecasts in high-shear low-CAPE severe storm environments
Funding source: National Oceanic and Atmospheric Administration, CSTAR program (Collaborative Science, Technology, and Applied Research)
Severe storms in the Southeastern U.S. are associated with higher fatality rates and lower warning skill scores than those in the Plains. Many such events occur in environments characterized by large environmental vertical wind shear ("high shear") but weak instability ("low CAPE"). These high-shear low-CAPE ("HSLC") conditions are associated with both low predictability and high tornado warning false alarm rates. Our regional NWS collaborators have identified these issues as among the most pressing concerns for their WFOs. The goal of this proposal is to address several remaining gaps in our understanding of HSLC severe weather predictability and facilitate an effective transition of the results into operations. To address these challenges and connect the new knowledge to operational practice, we will undertake the following coordinated research projects: 1) observational verification of CAM NWP performance (archived operational CAM output and case study simulations) during HSLC events vs. nulls; 2) hypothesis-driven process studies of HSLC tornadogenesis using an idealized numerical model, with implementation of a radar emulator that links model output to WSR-88D radar data in a physically consistent way.
Measurement and analysis of nocturnal mesoscale convective systems and their stable boundary layer environment during PECAN
Funding source: National Science Foundation
The Plains Elevated Convection At Night (PECAN) experiment will investigate the evolution of nocturnal mesoscale convective systems (MCSs) and convection and their interactions with the evolving nocturnal stable boundary layer (SBL) environment. This project addresses two primary goals of PECAN: 1) To characterize the transition from surface-based to elevated nocturnal MCS structure and the interaction of cold pools generated by MCSs with the nocturnal SBL, and 2) to determine how the organization and evolution of surface-based and elevated MCSs are influenced by the stable boundary layer and the vertical profile of wind and stability above the nocturnal low-level jet (NLLJ). During PECAN (summer 2015) we will observe nocturnal MCSs and convection with mobile ground-based radars, mobile sounding systems, and mobile mesonets in concert with other ground-based and airborne observing platforms. The scientific objectives of the research are then to: (i) document the internal structure and evolution of nocturnal MCSs and convection; (ii) establish the environmental ingredients and related physical mechanisms that control nocturnal MCS evolution; and (iii) test hypotheses concerning MCS dynamical-microphysical forcing and MCS-environment interactions within detailed cloud-resolving models. The research conducted here will advance fundamental knowledge of the internal MCS dynamics and interactions with the SBL.
A substantial fraction of tornadoes in the SE are associated with lower CAPE, higher lower tropospheric vertical wind shear, moister vertical profiles, and a greater frequency of tornadoes from quasi-linear convective systems ("QLCSs") than what is observed in the Plains. The goals of the proposed research are to: 1) Coordinate and collect high temporal resolution mobile upsonde data from three sounding systems during the VORTEX-SE field campaign. These measurements will be used to quantify the spatial and temporal variability of severe storms environments in the SE and compare them to environments that are typical of the Great Plains; 2) Perform idealized and case study simulations of convective storms in observed VORTEX-SE environments in order to understand how within-storm processes differ from case to case, and between Plains (VORTEX2) and SE storm environments. These experiments will also address the interplay between stability and shear in various PBL schemes within an NWP model, and the possible roles of terrain on the regional storm environment. This research is expected to address the differences in variability and predictability between Plains and SE storm environments, and also provide a baseline for designing future field measurements in the SE.