Environmental Evolution of Supercells Interacting with the Appalachian Mountains

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Purpura, S. (2021). Environmental Evolution of Supercells Interacting with the Appalachian Mountains. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

The Appalachian Mountains within the eastern United States have a considerable impact on day-to-day weather, including severe convection. However, the impact of the Appalachians on supercell thunderstorms is not well understood, posing a significant short-term forecast challenge across the region. While there have been some individual case studies conducted, there has yet to be a broad analysis of storm-scale modifications of supercells as they interact with complex terrain. To address this gap, this study examined 62 isolated supercells that occurred within the central and southern Appalachians between April and July from 2009 to 2019. Each supercell was broadly classified as either a "crosser" or "non-crosser" based on their ability to be maintained during their interaction with terrain; the majority of supercells (37) were not sustained downstream of the Appalachians. To identify the environmental controls resulting in crossing or non-crossing storms, near-storm model soundings (either the Rapid Update Cycle or the Rapid Refresh) were collected for each supercell at three points: (1) upstream of the mountains, (2) near the peak of the terrain, (3) and downstream of the terrain feature. These soundings were used to compute a number of different thermodynamic and kinematic parameters. Results indicate that the lowest 3 km of shear and storm-relative helicity (SRH) appear to best distinguish crossing and non-crossing supercells. Conversely, instability (CAPE and CIN) do not appear to be useful parameters in differentiating between crossers and non-crossers. Forecasters can use the lowest 3 km of SRH and shear, as well as the surface and mixed-layer equivalent potential temperature (θ_e) to aid in the short-term forecasting of isolated crossing supercells. Additionally, syntopic pattern recognition (e.g., the tilt of the upper-level trough, location of the surface low pressure, and the boundary type) of these events may help forecasters identify if supercells will cross the Appalachian Mountains.

Details
Author

Purpura, Sarah

Title

Environmental Evolution of Supercells Interacting with the Appalachian Mountains

Physical Description

1 online resource (143 pages) : PDF

Date

2021

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

The Appalachian Mountains within the eastern United States have a considerable impact on day-to-day weather, including severe convection. However, the impact of the Appalachians on supercell thunderstorms is not well understood, posing a significant short-term forecast challenge across the region. While there have been some individual case studies conducted, there has yet to be a broad analysis of storm-scale modifications of supercells as they interact with complex terrain. To address this gap, this study examined 62 isolated supercells that occurred within the central and southern Appalachians between April and July from 2009 to 2019. Each supercell was broadly classified as either a "crosser" or "non-crosser" based on their ability to be maintained during their interaction with terrain; the majority of supercells (37) were not sustained downstream of the Appalachians. To identify the environmental controls resulting in crossing or non-crossing storms, near-storm model soundings (either the Rapid Update Cycle or the Rapid Refresh) were collected for each supercell at three points: (1) upstream of the mountains, (2) near the peak of the terrain, (3) and downstream of the terrain feature. These soundings were used to compute a number of different thermodynamic and kinematic parameters. Results indicate that the lowest 3 km of shear and storm-relative helicity (SRH) appear to best distinguish crossing and non-crossing supercells. Conversely, instability (CAPE and CIN) do not appear to be useful parameters in differentiating between crossers and non-crossers. Forecasters can use the lowest 3 km of SRH and shear, as well as the surface and mixed-layer equivalent potential temperature (θ_e) to aid in the short-term forecasting of isolated crossing supercells. Additionally, syntopic pattern recognition (e.g., the tilt of the upper-level trough, location of the surface low pressure, and the boundary type) of these events may help forecasters identify if supercells will cross the Appalachian Mountains.

Genre

masters theses

Subjects--Topics

Meteorology

Degree

M.S.

Subject Area

Earth Sciences

Advisor(s)

Davenport, Casey
Eastin, Matthew

Committee Members

Davenport, Casey
Eastin, Matthew
Shirley, Terry

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2021.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Purpura_uncc_0694N_12744

Permalink

http://hdl.handle.net/20.500.13093/etd:2412