Arizona "eddy" tornadoes

"The number of tornadoes and funnel clouds·reported in Arizona per year has increased dramatically in the past 10 years--from 1 in 1963 to 20 in 1972. This increase is not believed to be related to changing meteoroloical conditions, but to other factors such as: 1. Increase in population; 2. Increase in public awareness due to disaster publicity; 3. Over-reaction due to the 1971 tornado in Tempe, and 4. The fact that not alI localized circular storms are true tornadoes"--Page 1. Robert S. Ingram. Includes bibliographical references (pages 8-9).