Tornado warnings can give people time to seek shelter, but meteorologists still face a fundamental challenge in delivering accurate warnings: determining which storms will actually produce a tornado.
Supported by a new three-year, $1,099,777 grant awarded by the U.S. National Science Foundation's Atmospheric and Geospace Sciences Program, researchers in the Department of Meteorology and Atmospheric Science in the College of Earth and Mineral Sciences will investigate what triggers some storms to produce tornadoes - and when - with the goal of helping forecasters issue more precise and timely warnings so people have time to protect themselves. In this project, the team will specifically study how turbulence in the lowest part of the atmosphere, which starts at the ground and stretches beyond the clouds, can help determine which storms go on to produce tornadoes.
This new grant follows a 2024 publication by Paul Markowski, distinguished professor and head of the meteorology department, who performed computer simulations of supercell storms - intense thunderstorms with rotating updrafts - in realistic, turbulent environments. More recently, researchers in Oklahoma reported seeing similar turbulent structures in field observations of supercell thunderstorms, matching Markowski's simulations.
"The simulations revealed that tornadoes may form differently from the mechanisms previously identified in simulations with less realistic, turbulence-free environments, raising the possibility that turbulence plays an important role in how tornadoes form," Markowski said. "However, whether these turbulent structures actually facilitate tornado formation in the atmosphere remains an open question."
For this project, Markowski and his co-principal investigators, including Kevin Bowley, associate teaching professor of meteorology and atmospheric science; Yvette Richardson, professor of meteorology and atmospheric science and senior associate dean for undergraduate education; and George Bryan, research professor of meteorology and atmospheric science, will combine numerical modeling, machine learning and previous field measurements to gather more evidence on the impact of turbulence on tornadogenesis.
"The way we approach tornado forecasting could be profoundly impacted if this work continues to reinforce the idea that turbulence is a key predictor for tornado formation," Bowley said. "These types of turbulent streaks often occur when heating of the atmosphere by Earth's surface dissipates, typically in the early evening, and under windy conditions. Such conditions could become a more reliable predictor for which supercells may be more likely to form tornadoes."
Researchers will use simulations, run on Penn State's Roar supercomputer, to determine not only the role of turbulence on tornadoes, but how sensitive they are to different atmospheric conditions in a wide range of storm environments.
"Supercells, and subsequently tornadoes, can form under a range of conditions linked to how unstable the atmosphere is and how the winds change with height," Bowley said. "By exploring a diversity of conditions, we can test whether this turbulence mechanism is a primary mechanism for all conditions or just some conditions."
Together, these efforts aim to refine theoretical models and advance short-term forecasting of tornado formation.
"When you're observing phenomena in real time, you can never observe everything you need to observe, and the observations themselves have errors," Markowski said. "In a high-resolution simulation, you have the full volume of observations with terabytes of information, offering us a level of control and detail that is impossible to achieve with observations alone."
In addition to the computer simulations, the researchers plan to further analyze measurements of temperature and pressure within supercells, which were collected by Markowski and Richardson in prior NSF-funded field projects between 2017 and 2022. The researchers used a novel process to obtain the measurements using sensors carried by swarms of small balloons.
"For my part, I look forward to collaborating on the idealized simulations and compositing our thermodynamic measurements to better understand environments occurring inside supercells, such as winds, temperature and moisture as we go up in the atmosphere at a given location," Richardson said. "The more we understand about how tornadoes form, the more we know what to look for in those environments and can turn that understanding into better forecasts and warnings that can help communities prepare for severe weather."
Brandon Garcia, doctoral student in meteorology and atmospheric science, also will contribute to this work.
