Radar Characteristics of Observed Supercell Thunderstorms Interacting with the Appalachian Mountains

Abstract:

Few studies have ventured to understand how supercell thunderstorms behave while interacting with complex terrain, though it poses a significant short-term forecasting problem. The few that have investigated this relationship tended to use small sample sizes, limited idealized simulations, or only focused on convection initiated by the terrain. This study aims to fill that gap by analyzing a large observed dataset of supercells interacting with the Appalachian Mountains.

A total of 138 isolated supercells observed within the central and southern Appalachians between 2008 and 2019 were analyzed in this study. Each supercell was categorized based on the extent of their interaction with the terrain (either crossing or non-crossing); the majority (110) were classified as non-crossing, while a small minority (29) were classified as crossing. Initial analysis of storm tracks suggest that terrain effects are sensitive to the local topography, meaning that results should be examined within various subregions of the Appalachians.

To better understand how supercells respond to variations in terrain, each supercell was tracked over its lifetime using GR2 software. Additionally, GIS was used to obtain additional information about the elevation, slope, angle of approach, and aspect. A variety of radar characteristics were collected for each of these storms, including reflectivity, velocity, maximum expected hail size (MEHS), echo tops, and mesocyclone intensity, depth and diameter. These parameters will be compared to variations with the terrain among the crossing and non-crossing categories, and will also be correlated to the production of severe weather. Further statistical analysis will be used to compare crossing storms to non-crossing storms.

The goals of this study are to understand how radar characteristics change as supercells interact with complex terrain and to provide forecasters with a better understanding of what supercells are more likely to produce severe weather for more accurate forecasts.