Climatology and Trends of Tornado-Favorable Atmospheric Ingredients in the United States

Moore, Todd W.; Clair, Jennifer M. St.; McGuire, Michael P.

doi:10.1080/24694452.2021.1910479

Cited by 10 publications

(9 citation statements)

References 81 publications

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“…The spatial distribution of tornadoes in the United States has also changed over time (Agee et al ., 2016; Ashley and Strader, 2016; Moore, 2018b; Moore and DeBoer, 2019). Studies are beginning to show that, while population dynamics and improved coverage of the Doppler radar network explain some of this change (Nouri et al ., 2021), physical mechanisms also play a role, particularly spatiotemporal trends in tornado‐favourable atmospheric conditions (e.g., atmospheric instability, wind shear, low‐level moisture, and composites of these variables (Gensini and Brooks, 2018; Taszarek et al ., 2021; Koch et al ., 2021; Moore et al ., 2021). In contrast, no physical mechanisms have been analysed to explain the increased concentration of tornadoes on fewer days or the decreased trends of consecutive‐day tornado events.…”

Section: Discussionmentioning

confidence: 99%

Decreasing trends in consecutive‐day tornado events in the United States

Moore

2021

Intl Journal of Climatology

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Days with many tornadoes in the United States have become more common over time. These days tend to occur in consecutive-day tornado events, but trends in the characteristics of consecutive-day tornado events have not been documented. The Mann-Kendall trend test and Theil-Sen slope estimator were used in this study to detect trends and estimate rates of change over time in multiple metrics of consecutive-day tornado events. Results show that the number of consecutive-day events, the number of days occurring in consecutiveday events, and the number of tornadoes occurring in consecutive-day events have decreased over time. The percentages of annual tornadoes and tornadodays occurring in consecutive-day events have also decreased over time. These trends suggest that the percentage of tornadoes occurring on isolated days has, alternatively, increased over time. K E Y W O R D Sconsecutive-day events, tornadoes, trends

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Section: Discussionmentioning

confidence: 99%

Decreasing trends in consecutive‐day tornado events in the United States

Moore

2021

Intl Journal of Climatology

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“…MERRA-2 is a high-quality, next-generation reanalysis that includes the stratosphere and assimilates aerosol data. Previous tornado climatology studies have used the NARR [ 10 , 26 , 30 ], which is a higher resolution dataset but only includes the lower stratosphere. Compared with other reanalyses, there is more emphasis on stratospheric ozone and aerosol information.…”

Section: Methodsmentioning

confidence: 99%

“…Taszarek et al (2021) reveal disagreements between ERA5 and rawinsonde observations over some regions, and suggest to use caution when interpreting results for any one region based on a single dataset [ 25 ]. To date, most retrospective studies have used the North American Regional Reanalysis (NARR) [ 10 , 26 , 30 ] or, more recently, the ECMWF Reanalysis version 5 (ERA5) [ 31 , 32 ] to assess trends in severe weather environments using proxies. Due to regional biases and overall uncertainties in reliability of a single dataset, it is important to look at historical trends in severe weather environments in multiple high quality reanalyses.…”

Section: Introductionmentioning

confidence: 99%

Long term temporal trends in synoptic-scale weather conditions favoring significant tornado occurrence over the central United States

2023

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We perform a statistical climatological study of the synoptic- to meso-scale weather conditions favoring significant tornado occurrence to empirically investigate the existence of long term temporal trends. To identify environments that favor tornadoes, we apply an empirical orthogonal function (EOF) analysis to temperature, relative humidity, and winds from the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) dataset. We consider MERRA-2 data and tornado data from 1980 to 2017 over four adjacent study regions that span the Central, Midwestern, and Southeastern United States. To identify which EOFs are related to significant tornado occurrence, we fit two separate groups of logistic regression models. The first group (LEOF models) estimates the probability of occurrence of a significant tornado day (EF2-EF5) within each region. The second group (IEOF models) classifies the intensity of tornadic days either as strong (EF3-EF5) or weak (EF1-EF2). When compared to approaches using proxies such as convective available potential energy, our EOF approach is advantageous for two main reasons: first, the EOF approach allows for the discovery of important synoptic- to mesoscale variables previously not considered in the tornado science literature; second, proxy-based analyses may not capture important aspects of three-dimensional atmospheric conditions represented by the EOFs. Indeed, one of our main novel findings is the importance of a stratospheric forcing mode on occurrence of significant tornadoes. Other important novel findings are the existence of long-term temporal trends in the stratospheric forcing mode, in a dry line mode, and in an ageostrophic circulation mode related to the jet stream configuration. A relative risk analysis also indicates that changes in stratospheric forcings are partially or completely offsetting increased tornado risk associated with the dry line mode, except in the eastern Midwest region where tornado risk is increasing.

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“…Others describe subseasonal and seasonal changes in low‐moisture patterns (Raddatz and Cummine, 2003; Molina et al ., 2018) and their effect on tornado frequencies. Additionally, spatial and temporal trends in tornado activity have been studied in association with global climate change (Diffenbaugh et al ., 2008; Lee, 2012; Tippett et al ., 2016; Gensini and Brooks, 2018; Moore et al ., 2021). Despite such examples, there are few studies that focus entirely on finding commonalities among atmospheric patterns associated with the largest historic TOs.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, it has been demonstrated that distinct patterns in 500‐hPa geopotential height field can be associated with enhanced TO potential (Mercer et al ., 2012) and used as a predictability measure in seasonal tornado outbreak forecasting (Sparrow and Mercer, 2016; Gensini et al ., 2019). Many different environmental variables on various spatial scales must be present to support TO development (Anderson‐Frey et al ., 2018; Mercer and Bates, 2019; Schroder and Elsner, 2020; Moore et al ., 2021). However, in this work, we chose to focus on the large‐scale atmospheric conditions with emphasis on 500‐hPa geopotential height field because of its potential utility in further TO‐oriented, including TO climatology or prediction (as in Sparrow and Mercer, 2016 or Gensini et al ., 2019).…”

Section: Introductionmentioning

confidence: 99%

Climatology of 500‐hPa geopotential height anomalies associated with May tornado outbreaks in the United States

Ćwik

McPherson

Richman

et al. 2022

Intl Journal of Climatology

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This study supports efforts directed toward research on large-scale atmospheric patterns and on the variability of tornado outbreaks. Specifically, we applied rotated principal component analysis to identify synoptic-scale patterns of 500-hPa geopotential height associated with tornado outbreaks in the United States. We created a database of historic tornado outbreaks using kernel density estimation on events composed of at least seven tornadoes of magnitude (E)F2 or higher (major tornado outbreaks) that occurred in May from 1950 to 2019 (91 events). Results of the analysis show that the first three principal components explained the majority, that is, 74% of the total variation. Based on the analysis of congruence coefficients, the Promax oblique transformation was chosen as the most representative rotation in portraying physically meaningful modes and resulted in three main atmospheric patterns. Two of these, to the best of our knowledge, have not been yet identified as the most representative of tornado outbreaks in any previous studies. Additionally, results suggest that although synoptic patterns associated with major May tornado outbreaks remain the same over time, partial variability in their geographic location exhibits some cyclical behaviour, especially on decadal and multidecadal scales. Identifying these patterns can serve as a first step in determining how they may change under anthropogenic climate change in the future. K E Y W O R D S 500-hPa geopotential height, climate change, climatology, large-scale atmospheric patterns, principal component analysis, tornado outbreaks, United States

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Climatology and Trends of Tornado-Favorable Atmospheric Ingredients in the United States

Cited by 10 publications

References 81 publications

Decreasing trends in consecutive‐day tornado events in the United States

Decreasing trends in consecutive‐day tornado events in the United States

Long term temporal trends in synoptic-scale weather conditions favoring significant tornado occurrence over the central United States

Climatology of 500‐hPa geopotential height anomalies associated with May tornado outbreaks in the United States

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