2026-09-22T13:40:15Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/108035 2023-07-11 col_2142_5131 col_2142_14839 com_2142_5130 com_2142_14838 com_2142_13459 com_2142_8903

2020-08-26T21:58:02Z Trapp, Robert Chehak, Devin Andrew 2020-08-26T21:58:02Z 2020-05-13 2020-05 The primary goal of this research was to quantify occurrence frequencies of the two main proposed mechanisms of tornadogenesis in quasi-linear convective systems (QLCSs), namely, tilting and stretching (T&S) and HSI and stretching (H&S). This research then sought to investigate differences and similarities between the characteristics of the T&S- and H&S- associated tornadoes and their supporting environments. A combined Doppler radar, tornado report, and environment dataset was compiled for this purpose. Lastly, this research aimed to quantify National Weather Service (NWS) warning performance for both mechanisms. From a strict consideration of only the first tornado generated by a QLCS during 2016-2018, 152 QLCS tornado cases were identified. Of these, 145 where determined to be the result of T&S, and 7 where determined to be the result of H&S, indicating that T&S is far more likely to be the tornadogenesis mechanism of the first tornado in a QLCS. QLCS tornadoes tended to be focused in the southern U.S. during winter and spring and the northern U.S. during summer. Tornadogenesis through H&S occurred relatively earlier in the year and earlier in the day, and resulted in relatively weaker tornadoes than did tornadogenesis through T&S. Environmental analysis showed that H&S environments had relatively lower values of CAPE and relatively higher values of low-level shear compared to T&S. Analysis of NWS warnings showed that H&S tornadoes had relatively lower tornado warning frequencies than did T&S tornadoes, while having, on average, half the warning lead time. Finally, based on a consideration of pre-tornadic Doppler radar data, it was found that H&S low-level circulations tended to form more rapidly than did T&S low-level circulations, thus providing less potential lead time. Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2020-08-25 without embargo terms The student, Devin Chehak, accepted the attached license on 2020-05-11 at 13:46. The student, Devin Chehak, submitted this Thesis for approval on 2020-05-11 at 13:55. This Thesis was approved for publication on 2020-05-13 at 16:49. DSpace SAF Submission Ingestion Package generated from Vireo submission #15326 on 2020-08-25 at 17:13:57 Made available in DSpace on 2020-08-26T21:58:02Z (GMT). No. of bitstreams: 2 CHEHAK-THESIS-2020.pdf: 7078131 bytes, checksum: 2ff572f64c9c5317bd60a5c0b7946cc0 (MD5) LICENSE.txt: 4209 bytes, checksum: 60b5a56eb6aed482c24a2718a33d2411 (MD5) Previous issue date: 2020-05-13 application/pdf http://hdl.handle.net/2142/108035 en Copyright 2020 Devin Chehak Severe Weather, Tornado, QLCS, Squall Line, MCS Analyses of quasi-linear convective system tornado characteristics, environments, and genesis mechanisms text Thesis Atmospheric Sciences Atmospheric Sciences University of Illinois at Urbana-Champaign Thesis M.S.