Tornado Alley
Although tornadoes are not unique to the area, the violent, rotating, funnel-shaped clouds and their trails of destruction are so common in the central United States that the area is called Tornado Alley. Severe thunderstorms and the super-cell tornadoes that they spawn are formed when warm, moist air from the Gulf of Mexico becomes trapped beneath hot, dry air from the southwest desert region. Above the hot, dry air, cold, dry air sweeps in from the Rocky Mountains. The interaction between highaltitude winds and thunderstorms creates the funnel-shaped vortex of high-speed winds known as a tornado.

The largest outbreak of tornadoes in this region occurred in April of 1974. Before the storms ended, 148 separate tornadoes roared through 13 different states. More than 300 people lost their lives, and another 5,000 people were injured. More than 1,300 buildings were destroyed.

a. What makes tornadoes so much more difficult to predict than other severe weather systems?