Flow physics could help forecasters predict extreme events

About 1,000 tornadoes strike the United States each year, causing billions of dollars in damage and killing about 60 people on average. Tracking data show that they're becoming increasingly common in the southeast, and less frequent in "Tornado Alley," which stretches across the Great Plains. Scientists lack a clear understanding of how tornadoes form, but a more urgent challenge is to develop more accurate prediction and warning systems. It requires a fine balance: Without warnings, people can't shelter, but if they experience too many false alarms, they'll become inured.