Impacts of cold pool strength on tornado production in quasi-linear convective systems

In recent years, several studies have explored the link between cold pool strength and tornadogenesis in quasi-linear convective systems (QLCSs). Novel observations from the Verifications of the Origins of Rotations in Tornadoes Experiment-Southeast (VORTEX-SE) and Propagation, Evolution, and Rotation in Linear Storms (PERiLS) field campaigns have allowed researchers to investigate virtual potential temperature perturbations (θ′v) and cold pool depths in QLCSs in the southeastern U.S. Analyses of these QLCSs have also revealed characteristics and variability of pre-convective environments, particularly with instability and vertical wind shear. However, such studies have been limited to cases from field projects and thus exhibit a small domain and sample size. To bridge this gap, this study investigates cold pool strength and pre-convective line vertical wind shear for 94 tornadic and nontornadic QLCSs in the central and eastern United States from 2017–2022. Cold pool strength was quantified by the virtual potential temperature perturbation from the base state using 1-minute observations from Automated Surface Observing System (ASOS) sites. Low-level and deep-layer vertical wind shear and storm-relative helicity (SRH) were obtained from hourly 13 km resolution Rapid Refresh model (RAP) analyses at the nearest hour prior to the arrival of the QLCS cold pool. Every ASOS site selected to represent a QLCS was classified as featuring a tornadic environment or a nontornadic environment. Additionally, each QLCS was categorized based on the number and strength of tornadoes produced, as well as whether it was purely cold pool-driven or associated with a surface front. While previous studies present evidence that cold pool strength is key to QLCS maintenance in conjunction with vertical wind shear, the results of this study reveal that cold pool strength alone is not correlated with tornado production in QLCSs, nor is it correlated with sites featuring tornadic QLCS environments. Conversely, stronger environmental vertical wind shear is shown to be a common feature in most QLCS tornado outbreaks. SRH is also strongly correlated with overall tornado production in QLCSs, as the majority of QLCS tornado outbreaks featured 0–1 km SRH of at least 100 m2 s−2 and 0–3 km SRH of at least 200 m2 s−2. For operational forecasting, it follows that cold pool characteristics are not nearly as important as assessing vertical wind shear when aiming to predict the tornadic potential of a QLCS, particularly in the cold and spring seasons.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Atmospheric Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Statum, Garrett

Contributors dc:contributor

• Frame, Jeffrey W
• Nesbitt, Stephen
• Trapp, Robert

• QLCS
• tornado

Statement dc:rights

• Copyright 2025 Garrett Statum

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132649

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132649