Collaborative Research: Understanding Tornado Development and Maintenance in Supercells with an Emphasis on "High-End" Events

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

In 2011, tornadoes in the United States killed 553 people and caused $28 billion in property damage. Most of the damage and fatalities were caused by violent tornadoes spawned by supercell thunderstorms, with six tornadoes receiving EF5 rankings, the most violent category of the Enhanced Fujita scale. Last year, several outbreaks occurred with over 140 confirmed tornadoes rated between EF2 and EF4 that resulted in substantial damage and over 30 deaths. While significant advances in our knowledge of supercell thunderstorms and tornadoes have occurred in recent decades, understanding of the fundamental processes occurring within supercells that result in tornadoes remains elusive. This void in knowledge is especially concerning for violent tornadoes that are responsible for a disproportionate number of fatalities and injuries as well as damage. Until these tornado genesis and maintenance processes are understood, our ability to forecast such events is severely limited. The primary goal of this research is to improve the fundamental understanding of processes underlying the formation and maintenance of tornadoes in supercell thunderstorms, especially as these processes relate to violent tornadoes. This knowledge is critical for improving tornado forecasts, tornado warning lead times, and estimations of potential tornado strength and longevity, and is especially applicable to tornadoes of strong and violent intensity. In conjunction with an awarded NSF grant providing continued access to the NSF-funded Blue Waters supercomputer, the research will analyze petabytes of data to study the processes occurring in supercells that result in tornadoes of varying strength, longevity, and structure. Intellectual Merit: Despite advances in observational and modeling/computing technology, much still needs to be understood about the evolution of tornadoes. Few computer simulations exist in which a well-resolved tornado forms within its parent supercell, and this work uses the highest resolution simulations of violently tornadic supercells conducted to date. A control simulation with 30 meter grid spacing has been completed where twenty fields in a volume centered on the tornado during its entire life cycle have been saved to disk every model time step, which will facilitate the most accurate analysis possible. 20 m and 15 m simulations containing long-track EF5 tornadoes have also been completed, and additional runs at these resolutions will be executed as needed. Tools to efficiently interrogate and analyze model data saved every time step will be improved and new tools will be developed. New simulations will be conducted in other environments in which violent tornadoes were observed. By analyzing simulated storms in different environments and comparing tornadogenesis failure cases to cases where violent tornadoes occur, the research team aims to identify processes common within unusually violent supercells involved in the formation and maintenance of tornadoes. Broader Impacts: A better fundamental understanding of tornado development in supercell thunderstorms should help guide future field programs in which new features identified in these numerical simulations are targeted for study, and ultimately lead to improvements in our ability to accurately forecast significant tornadic events and increase tornado warning lead times. Improving our fundamental understanding of tornado maintenance, made possible through analysis of the simulations described, should provide insight critical for National Weather Service forecasters to better predict, once a tornado has developed, how long a particular tornado may last. This type of information is invaluable, especially when pertaining to high-end, long-track events. The improved understanding of tornadoes in addition to cutting-edge visualizations of this research will facilitate science education in forums ranging from formal courses for students to learning venues for the general public. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.