https://www.noaa.gov/photo-story-americas-deadliest-year-for-tornadoes-2011
NOAA
How tornadoes form is still unclear, which is why NOAA researchers conduct field campaigns to uncover answers. Scientists at NOAA laboratories collect data during on-the ground research projects like VORTEX2 (pictured above) to help National Weather Service forecasters better understand the storms that produce tornadoes