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UAH AES undergraduate students Caleb Kiser (left) and Michael Yurovchak (back) and graduate student Mariama Feaster (center) examining weather observations taken by UAH ESSC SWIRLL MAPNet Facilities Research vehicle. Courtesy Preston Pangle.

HUNTSVILLE, AL. (FEB. 22, 2023) – As the threat of severe weather loomed across Dixie Alley on Thursday, February 16th, researchers from The University of Alabama in Huntsville (UAH) Department of Atmospheric & Earth Sciences (AES) and Earth System Science Center (ESSC) Severe Weather Institute – Radar & Lightning Laboratories (SWIRLL) had been up since the crack of dawn, setting up weather instrumentation before the storms arrived.

UAH AES ESSC SWIRLL, a part of the University of Alabama system, is one of 12 research institutions chosen to participate in the Propagation, Evolution, and Rotation in Linear Storms (PERiLS), the largest Dixie Alley tornado field campaign to date. 

Researchers from UAH AES ESSC SWIRLL will study how clouds, wind, rain, temperature, and humidity play a role in booming or suppressing tornadic activity in squall lines across Dixie Alley during the spring season.

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UAH AES undergraduate student Sydney Rau (left) and graduate student Meredith Bean (right) launching a weather balloon to collect data on the atmospheric during the morning of Thursday, February 16th, 2023. Courtesy Emily Wisinski

“Storms move very fast, rapidly changing within an hour span of time. We can have tornadoes any point of the day across Dixie Alley,” says Dr. Kevin Knupp, UAH AES professor and Director of SWIRLL


Funded by the National Science Foundation (NSF) and National Oceanic and Atmospheric Administration (NOAA), the PERiLS project is two-years, with its final year occurring this spring


The PERiLS field campaign has eight domains across Dixie Alley. An official call is made four days in advance to set up an intensive observation period (IOP) in one of the domains to observe a potential severe weather event. This allows research institutions time to prepare and book travel.  

Setting up the first intensive observation period (IOP) for the 2023 PERiLS year on February 16th was challenging.

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The radar and profile network for the NSF/NOAA PERiLS first intensive observation period (IOP) in Alabama on Thursday, February 16th, 2023. Courtesy Dr. Kevin Knupp


“There was a lot of uncertainty with the forecast. The forecasting models were not in agreement, which made it tough to determine where the first IOP of the year should be located,” says Knupp.


After extensive analysis of various forecast models, it was determined that UAH AES ESSC SWIRLL research team and the 11 other research institutions would create a small, dense network of weather instrumentation between Eutaw, Demopolis, and Greensboro, Alabama to observe atmospheric conditions for potential severe weather event on February 16th.  

Like clockwork, UAH AES ESSC SWIRLL’s research team, a part of the University of Alabama system, could be seen launching weather balloons into the atmosphere at the top of every hour on February 16th to observe how fast the temperature and moisture was changing. 

The team also used UAH SWIRLL’s Mobile Atmospheric Profiling Network (MAPNet) wind profiling instruments aboard the Mobile Integrated Profiling Systems (MIPS), Rapidly Deployable Atmospheric Profiling System (RaDAPS), and Mobile Operated Doppler Lidar System (MoDLS) to specifically measure how much winds are turning in the atmosphere at various altitudes.

Unfortunately, no severe weather rolled through the IOP area, but tornadic activity was reported in northern Mississippi and southern Tennessee on February 16th.


Far from calling it a bust, the weather observations collected during this IOP will still help UAH SWIRLL researchers in their efforts to understand tornado genesis in squall lines.

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UAH’s MAPNet Facilities Mobile Alabama X-band Dual Polarization Radar (MAX) research vehicle in full operation mode thanks to the UAH ESSC SWIRLL research team. Courtesy Zeb Leffler


“During mid-afternoon, the atmosphere was unstable enough to produce a few individual thunderstorms, but the winds weren’t turning in the atmosphere. By early evening, the cold front of the storm system moved through our IOP but wasn’t strong enough to develop a squall line and spark severe weather,” says Knupp.


“No two storms are alike. To understand how squall lines form and produce severe weather, we in turn, also need to learn what hinders squall lines from developing. We need null cases like this to complete a picture of all what if scenarios,” says Knupp. 


Last year, the PERiLS field campaign had four IOPs. This year, the goal is to deploy for eight IOPs during the spring season. 


“If this research helps scientists better understand tornadic environments and keep people safe, then these sleepless nights during the field campaigns have all been worth it,” says Knupp.