A team of aerospace engineers from the University of Colorado Boulder (CU) recently spent the first half of June traveling across the Midwest in search of monster storms.

During this time period, the CU team, which was made up of 16 CU employees and students, encountered a storm on June 8 outside Norris, South Dakota, and used one of its three “TTwistor” UAS to fly through the dark skies to collect data from the storm.

“It is amazing to me how you're driving along for several hours and it's nice, clear, sunny skies, and all of sudden you're under these clouds and it gets dark pretty fast,” says Eric Frew, CU associate professor, via the Daily Camera.

Frew, who is also the associate director of technology at CU's Integrated Remote and In Situ Sensing (IRISS), drove one of the vehicles in a three-vehicle convoy straight towards the supercell thunderstorm outside Norris, South Dakota, and the TTwistor UAS flew above the convoy.

Equipped with the specialized UAS that they have spent years building and honing, the CU team met meteorologists from the University of Nebraska-Lincoln and Texas Tech University, who plan to use the UAS data to improve understanding and forecasting of tornadoes.

“It's still very much an open question of: Why does this type of storm become a tornado?” Frew says.

“Most of the strong, violent tornadoes are created from supercell thunderstorms, but very few supercell thunderstorms create tornadoes. You know what storms to go study, but you still don't know why they do or don't produce tornadoes.”

The three yellow TTwistor UAS that the CU team brought for these flights were built to collect the data requested by the meteorologists, including the pressure, temperature and humidity of the air and the speed and direction of the wind.

The UAS, which look like small airplanes and have propellers on each wing, have sensors embedded in the nose of the UAS, and a video camera is embedded in the tail.

The UAS are built to take off from the roof of Ford Explorers equipped with special racks, and are programmed to follow the vehicles into storms.

The UAS are FAA-compliant, and the FAA requires a sightline on the UAS at all times. The storms are capable of moving faster than 30 miles per hour, so the only way to keep the UAS in sight is by driving with them.

According to Frew, UAS are the only way to safely collect the data that the meteorologists desire.

“We're in these environments because nobody in their right mind would pilot an aircraft in these environments,” Frew says.

This was the first trip that a UAS was used to fly head-on into a storm.

The CU team drove each day—sometimes for as many as six hours—in areas between North Dakota and southern Oklahoma, and in the afternoon, they searched for the brewing storms. The June 8 storm in South Dakota was the most successful "good" weather mission during their two-week trip.

On the day of the June 8 storm, the CU team launched its UAS from the Ford Explorer. A small contingent drove in that vehicle, while the rest of the team stayed behind with a meteorologist and waited for the mission to end so they could help pack up the UAS and avoid the worst of the storm.

The Ford Explorer followed two other cars; one of which carried meteorologists who tracked the conditions, and another that acted as a scout car and drove about a mile ahead to keep an eye out for conditions that would damage the UAS.

“We just drove straight to the storm, and the storm came right to us,” Frew says.

​Some of the footage picked up by the UAS' tail camera shows massive, dark clouds; a glowing blue patch where hail formed; and flashes of lightning. The group traveling towards the storm turned around when the scout car encountered hail, as the UAS cannot fly through sustained hail.

Now, the CU team will compile the data collected by the UAS and share it with the meteorologists for further study.

This initiative was the culmination of a three-year grant by the National Science Foundation, but Frew notes that their work and partnerships are ongoing, and anticipates continuing to learn and chase storms with them.

“These are measurements that the meteorology world wants, and you cannot get without being in the storm,” Frew says. “That's the key.”