Abstract

Results from recent modeling and observational work have connected the size or area of convective updrafts with hazardous weather, including tornadoes and large hail. Additional studies have hypothesized that elements of the near-storm environment (NSE) controls updraft size. However, observationally, little is known about the evolution of updraft sizes in quasi-linear convective systems (QLCSs) and what impact the NSE has on the updraft sizes at mid-levels. A recent and ongoing multi-agency integrated field project focused on better understanding the development and life cycles of tornadoes in QLCSs provides an opportunity to do so. The Propagation, Evolution, and Rotation in Linear Storms (PERiLS) field project completed its first year of deployments in March-May of 2022 in the Southeast U.S. In 2022, there were four PERiLS Intensive Observation Periods (IOPs), each lasting several hours. WSR-88D and extensive near storm environment data were analyzed in a detailed study of the relationship between the changes in midlevel updraft size proxies (ZDR columns) and any changes in the NSE. In order to mimic information that would be available to forecasters, data from the nearby WSR-88D radars were used to estimate QLCS updraft size and variability over time using ZDR column size as an updraft size proxy. These data were then combined with NSE data obtained by the multitude of mobile sounding teams on PERiLS. The main topics of study include: single and total updraft size variability throughout deployment periods and spatial and temporal changes in the NSE that are evident as observable changes in updraft proxy size. All four deployments had at least one substantial individual updraft growth throughout the duration of the QLCS. Three out of the four PERiLS IOPs provided usable NSE data around the time of these updraft growths. Contrary to previous findings in supercell studies, the LCL heights and the storm-relative winds decreased during the time of an updraft growth. In times when updrafts did not change in size, LCL heights and storm-relative winds either increased or stayed the same. Reasoning behind the null result and future avenues for research are also discussed

Year

2023

Document Type

Thesis

Keywords

thunderstorms, QLCS, ZDR columns, radar

Degree Name

Master of Science (MS)

Advisor

Dr. Michael French

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