TUCSON, Ariz. (KOLD News 13) - During the monsoon, funnel clouds sometimes create a unique spectacle in the sky.
When the monsoon flow from the tropics is moving very rapidly, wind aloft will be quite strong. In contrast, wind at the surface will be much slower.
This difference can, and sometimes does, create a pinwheel effect in between the strong wind aloft and the weaker wind below.
When a gust of wind comes along, it can flip the rotation on its side, resulting in a swirling funnel cloud forming from the cloud.
Add to this any area of low pressure, like an inverted trough, and the rotation characteristics of the low pressure system itself can be magnified in a single storm, helping to increase the chance for funnel development.
If a funnel cloud makes contact with the ground, it then becomes a tornado.
Most tornadoes during the monsoon are quite weak.
More damage comes from straight-line wind generated in a microburst than in the typical Arizona tornado.