The Doppler on Wheels (DOW) vehicle scans a supercell thunderstorm during a tornado research mission, May 8, 2017 in Elbert County near Agate, Colorado. Doppler on Wheels (DOW) is a mobile doppler radar mounted on a truck that brings instruments directly into storms, allowing scientists to scan storms and tornadoes and make 3-D maps of wind and debris. (Photo by Drew Angerer/Getty Images)

Nyibol Lual, 13 years old, helps her family to prepare the land for cultivation on May 31, 2017, in Panthau, Northern Bahr al Ghazal, South Sudan. The family has a small land where they cultivate sorghum. An estimated 63 per cent of the population in Northern Bahr al Ghazal is experiencing severe food insecurity, according to the latest Integrated Food Security Phase Classification (IPC) report. The situation is particularly bad in Aweil West and Aweil South counties, where the exhaustion of household food stocks and growing dependence on financially inaccessible markets have left the population facing Emergency levels of food insecurity. (Photo by Albert Gonzalez Farran/AFP Photo)

A police officer stands at a police cordon near the scene of a terror attack in London, U.K., on Sunday, June 4, 2017. A van swerved into Saturday-night crowds on London Bridge, before three men got out and went on a stabbing rampage through nearby bars. (Photo by Luke MacGregor/Bloomberg)

Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

A model has her hair done backstage before the Taoray Wang fashion show during New York Fashion Week in New York, New York, 09 February 2019. New York Fashion Week for designer's autumn and winter lines is being held from 06 to 13 February 2019. (Photo by Peter Foley/EPA/EFE)

An Afghan Hound waits in the benching area during the Daytime Session in the Breed Judging across the Hound, Toy, Non-Sporting and Herding groups at the 143rd Annual Westminster Kennel Club Dog Show at Pier 92/94 in New York City on February 11, 2019. (Photo by Timothy A. Clary/AFP Photo)

An art wall painting representing performance artist Marina Abramovic by Italian artist Maurizio Cattellan to publicize his upcoming exhibition The Artist is Present, in Shanghai, China, is displayed on a facade of a building, in Milan, Italy, Wednesday, September 19, 2018. (Photo by Luca Bruno/AP Photo)

Britain's Camilla, Duchess of Cornwall watches a performance during a salsa school visit in Havana, Cuba March 26, 2019. (Photo by Phil Noble/Reuters)