Saturday night (day before yesterday) we heard the tornado sirens blowing, and our NOAA weather radio sounded the alarm. A tornado had been spotted (either didn't touch down or just came down in empty fields) about 30 miles away.

We looked at the weather map online. There was a huge air mass containing storms, and the map showed an arc extending from Michigan to Wyoming. Inside it and to the south was a straighter line of storms. It was that line that produced the tornado in Joplin.

The latest figure I've seen says that 30% of Joplin is destroyed.