‘Stupidly simple’ way to study tornadoes
Party balloons and Styrofoam cups?
Penn State University tornado research published this fall — with a definite twist — turned out to be more timely than expected with two late-season tornadoes hitting the region.
A twister on Monday in Plum and Murrysville tore shingles from roofs, snapped tree trunks and flipped a car. Another one occurred Nov. 5 in Columbiana County, Ohio, which borders Beaver County.
Pennsylvania, on average, has 16 tornadoes a year, but the area has had only five November tornadoes since 1950, the National Weather Service reported.
In the new research, Penn
State relied on inexpensive electronic sensors and a “stupidly simple” strategy involving party supplies — balloons and Styrofoam cups — to advance knowledge of tornado formation, size and endurance.
The helium-filled balloons carried a thermometer, airpressure and humidity gauges, a Global Positioning System unit and a transmitter, all inside a Styrofoam cup and weighing less than a half ounce (13 grams) — the weight of five pennies.
The ingeniously simple system was so effective in gathering data that a tornado researcher with the National Oceanic and Atmospheric Administration said, at least for now, it represents one of the biggest things currently underway “to improve our understanding of tornadoes.”
“There are a lot of other pieces in the puzzle to make [knowledge of tornado formation] coherent overall, but this is a pretty big one,” said Erik Rasmussen, senior research scientist with the Cooperative Institute for Mesoscale Meteorological Studies, a program supported by NOAA and the University of Oklahoma. He’s also project manager for Vortex Southeast, sponsored through NOAA’s National Severe Storms Laboratory.
At least for now, don’t expect the launch of balloons prior to big storms.
“We won’t use balloon swarms to provide advance warning of a tornado’s potential,” said Mr. Rasmussen, who holds a Ph.D. “But it will give us knowledge of what to look for, and I think it will give us new things to look for in the radar data that we’ve been collecting for 20 years.”
Anatomy of a tornado
The plot of the 1996 movie “Twister” finds meteorologists struggling to get their high-tech sensor equipment inside a tornado that’s so powerful that mooing cows are swirling in its winds.
Finally the characters put their pickup truck in cruise control and leap out, transporting their sensor into the tornado.
That outcome proved more important to cinema than science. Today, meteorology researchers are more focused on temperature variations, humidity levels and wind speeds in the cubic miles surrounding large storms to understand how tornadoes take shape.
Last spring, miles ahead of advancing Great Plains storms, Penn State researchers quickly filled pairs of helium-filled balloons and released them with their payloads. Once they reached predetermined altitudes, one of the balloons was jettisoned, leaving behind the Styrofoam cup full of gauges supported by the remaining balloon, which subsequently was pulled through the storm.
The more balloons, the greater the volume of data collected and transmitted on a single frequency to a central computer programmed with an analytical algorithm.
“What isn’t low tech is tracking dozens of balloons on a single frequency, which had been a technical engineering problem,” said Paul Markowski, the Penn State professor of meteorology, who co-led the study with Yvette Richardson, another Penn State professor of meteorology and Scott Richardson, an instrumentation expert. “Usually, tracking two dozen sensors required two dozen frequencies.”
Thunderstorms occur when warm, humid air near the ground is topped with ever cooler layers of air as altitude increases. The instability serves to fuel updrafts of the storms.
Theseupdrafts acquire rotation — a precursor to tornado formation — when vertical wind shear is present in the storm’s surroundings. Vertical wind shear, involving wind variations at different altitudes, is linked to horizontally spinning air similar to the way a football spins. It then can be tipped vertically upward when it is sucked into the storm’s updraft. Storms with this kind of rotating updrafts tend to be the most intense on Earth and are known as super-cell storms, Mr. Markowski said.
In addition to updrafts, thunderstorms also have downdrafts, which play a critical role in development of the super-cell thunderstorm’s rotation all the way to the ground. It’s further intensified by inward-spiraling air (much like a figure skater who spins faster when his or her arms are drawn inward). The result is a tornado.
In the movie “Twister,” the Holy Grail was getting probes inside a funnel cloud.
“But you don’t actually need them inside of the tornado,” Mr. Markowski said. “We pretty much know that inside the tornado it’s windy with low pressure and not very interesting scientifically. But in the movie, it was sexy — the idea of getting to go inside the tornado.
“What is needed are observations in a larger volume of air and observations around the broad area of swirling wind” surrounding the storm, he said.
Using balloons to measure temperature, air pressure and wind patterns is “stupidly simple,” he said. But understanding the complex atmospheric dynamics ahead of larger storms is necessary to explain tornado formation and allow for more accurate and timely tornado alerts.
Last spring the storms used for the research never generated tornadoes but served to prove the method’s ability to gather data. The next challenge is to launch hundreds of pairs of balloons ahead of other storms.
Predicting a tornado
“The National Weather Service’s Storm Prediction Center routinely predicts large outbreaks days in advance,” states an article that the Markowski-Richardson team wrote for The Conversation, an online academic newsletter. Few tornadoes occur by surprise. But the article also notes, “We have less ability to forecast tornadoes in more marginal situations, such as within non-super-cell storms.”
That’s where Penn State research could have an impact.
“Even if the environment is extremely favorable for super-cell tornadoes, forecasters have limited ability to say when or if a specific storm will produce a tornado,” the article stated. “Researchers are studying triggers for tornado production, such as small-scale downdraft surges and descending precipitation shafts on a super-cell storm’s rear flank, and processes that sustain tornadoes once they form.”
Another goal is to understand the impact of uneven terrain, buildings and other objects along the tornado’s path.
Computer models for tornado formation are only as reliable as the data used to develop such models.
“Computers can teach us just about everything we need to know about tornado formation,” Mr. Rasmussen said, noting the importance of the Penn State research. “We can’t trust them until we make key observations to evaluate the accuracy of these computer models.
“We’re probably a decade away from doing with [unmanned aerial vehicles or drones] what Paul is doing with party balloons,” he said.