Monster Alabama tornado spawned by rare “perfect storm”

National Geographic : The tornado that devastated Tuscaloosa, Alabama, on Wednesday was the result of an unusual confluence of meteorological conditions. Current estimates put the twister’s wind speed at about 260 mph, and it may have remained in contact with the ground for more than 200 miles. An unusually strong jet stream over the region, with wind speeds of 150 mph, caused intense upward motion in the atmosphere. The colder, drier air within combined with the warm, moist air already in place to create rotating thunderstorms known as supercells—one of the few types of storms that spawn tornadoes. A 50 mph wind closer to the ground only increased the storms’ rotation. Wednesday’s tornado outbreak included more than 100 twisters across 6 states and killed at least 283 people, making it the worst outbreak since 3 April 1974, when 330 people were killed in an area that stretched from Alabama to Indiana.