Best Practices for Severe Thunderstorm Detection with Limited Low-Level Radar Data

The National Weather Service Doppler radar located in Corpus Christi, Texas, along with other Doppler radars located in Brackettville, Brownsville, and New Braunfels, Texas are all at least 80 miles away from Webb County in Texas. Webb County has an area of 3376 square miles located in the western Brush Country of South Texas. It is sparsely populated with the main exception being the major trade and border city of Laredo, which has a population of just over a quarter of a million residents and is the 10^thlargest city in Texas. Given its proximity to the Gulf of Mexico and the Sierra Madre mountain range, severe thunderstorms are frequently observed across Webb County, most notably in April and May. Within the past 10 years, the National Weather Service in Corpus Christi has issued 23 tornado warnings and 204 severe thunderstorm warnings for Webb County. The main challenge during these severe thunderstorm events is the extensive distance from available radars and the inability to adequately observe low level storm structure, which numerous studies have shown to play an important role in relation to severe thunderstorm development.

The goal of this study is to analyze a variety of modern forecasting techniques to aid forecasters when issuing severe thunderstorm warnings in areas with limited low level radar data. Dual polarization data, multi-radar multi-sensor data, the Donovan technique, the Mid-Altitude Radial Convergence (MARC) signature, storm-top divergence, satellite imagery, and environmental conditions will all be analyzed for severe thunderstorm events which occurred in Webb County between 2013 and 2017. With a better understanding of these datasets, this study develops best practices which will help enhance the timing and confidence of severe weather warnings for areas with limited low level radar data.