In this handout provided by NASA from its MODIS satellite, a storm system that generated a EF4 tornado is captured at 19:40 UTC on May 20, 2013 over Moore, Oklahoma. (Photo by NASA via Getty Images)
Tornado Outbreak Slams Through Oklahoma
U.S. Department of Defense, two firefighters break through concrete during the search for survivors in the remains of the Plaza Towers Elementary School. (Photo by Maj. Geoff Legler, Oklahoma National Guard Public Affairs/U.S. Department of Defense via Getty Images)
Tornado Outbreak Slams Through Oklahoma
U.S. Soldiers and Airmen with the Oklahoma Army National Guard and the Oklahoma Air National Guard along with firefighters participate in recovery efforts. (Photo by Sgt. 1st Class Kendall James/U.S. Department of Defense via Getty Images)
Tornado Outbreak Slams Through Oklahoma
U.S. Soldiers and Airmen with the Oklahoma Army National Guard and the Oklahoma Air National Guard along with firefighters participate in recovery efforts. (Photo by Sgt. 1st Class Kendall James/U.S. Department of Defense via Getty Images)
Tornado Outbreak Slams Through Oklahoma
Damage caused by a tornado Monday, May 20, 2013 in Moore, Oklahoma. (Photo by Brett Deering/ Getty Images)
Tornado Outbreak Slams Through Oklahoma
Daniel Garbelman begins cleanup of his yard after it was damaged by a tornado May 21, 2013 in Moore, Oklahoma. (Photo by Brett Deering/Getty Images)
Tornado Outbreak Slams Through Oklahoma
Damage caused by a tornado Monday, May 20, 2013 in Moore, Oklahoma. (Photo by Brett Deering/ Getty Images)
Tornado Outbreak Slams Through Oklahoma
Damage caused by a tornado on Monday, May 20, 2013 in Shawnee, Oklahoma.
(Photo by Brett Deering/Getty Images)
Tornado Outbreak Slams Through Oklahoma
Volunteers help clean out Jean McAdams' overturned mobile home caused by a tornado Sunday night on Monday, May 20, 2013 in Shawnee, Oklahoma.
(Photo by Brett Deering/Getty Images)
Tornado Outbreak Slams Through Oklahoma
Volunteers help clean out Jean McAdams' overturned mobile home caused by a tornado Sunday night on Monday, May 20, 2013 in Shawnee, Oklahoma.
(Photo by Brett Deering/Getty Images)
Tornado Outbreak Slams Through Oklahoma
Candice Lopez, left, and Stephanie Davis help clean debris from the mobile home of Thelma Cox destroyed by a tornado Sunday night on Monday, May 20, 2013 in Shawnee, Oklahoma.
(Photo by Brett Deering/Getty Images)
Tornado Outbreak Slams Through Oklahoma
Philip Gotcher stands in the rubble of his house after a powerful tornado ripped through the area on May 20, 2013 in Moore, Oklahoma. (Photo by Brett Deering/Getty Images)
Tornado Outbreak Slams Through Oklahoma
Damage caused by a tornado Monday, May 20, 2013 in Moore, Oklahoma. (Photo by Brett Deering/ Getty Images)
Tornado Outbreak Slams Through Oklahoma
Damage caused by a tornado Monday, May 20, 2013 in Moore, Oklahoma. (Photo by Brett Deering/ Getty Images)
Tornado Outbreak Slams Through Oklahoma
Damage caused by a tornado Monday, May 20, 2013 in Moore, Oklahoma. (Photo by Brett Deering/ Getty Images)
