Claudio D. answered 04/09/20
Ph.D. in the humanities with 10+ years college teaching experience
For sentences 2 and 3:
2. There has been a pattern over the last few years in the United States of seeing more than a thousand tornados a year, the majority of which touch down in Tornado Alley.
The United States has seen over a thousand yearly tornados in the last few years, mostly in the Tornado Alley.
3. It used to be the case that residents of Tornado Alley got little notice or warning in the event that a storm was on its way.
Tornado Alley residents used to get little warning of oncoming storms.