An enormous tornado a mile wide, with 200 mph. winds ripped through Oklahoma City suburbs on Monday. This twister flattened neighborhoods and crushed a school, which killed at least 24 people.
Officials say the death the toll is expected to rise. The city of Moore was heavily hit, and public safety officials continue their search for survivors.
Tornadoes are difficult to predict. This documentary from NASA is a good introduction to how they work.
Alexis Madrigal's "Tornadoes in America: The Oklahoma Disaster in Context" has more on the science of the storm that hit Moore, Oklahoma.
For more videos from NASA, visit http://www.nasa.gov/