India, May 21 -- A powerful tornado barreled through northern Alabama on Monday, triggering emergency alerts and leaving communities in Madison and Athens bracing for impact. As the radar lit up with intense rotation and hail cores, veteran storm chaser Reed Timmer found himself face-to-face with nature's raw fury.

Timmer, who has made a career out of chasing and documenting tornadoes, was near Athens when the massive twister touched down. In a heart-pounding video, he "zero-metered" the tornado with a Doppler radar or a similar device used to measure wind speeds and other data inside a tornado.

The winds roared, debris flew, and for a few tense seconds, the scene was total chaos. Timmer's team can be heard shouting, panicking, and, las...