They're called "cold air funnels" and while they seldom cause any harm, at least one such cloud caused quite the stir in Kankakee County around lunch today. As the Bears were holding their first practice of the season in Bourbonnais, wind and humidity conditions were just right to create a funnel cloud. Several photos have appeared in print (I posted one on my Facebook page, btw) taken between 12:10 and 12:30 over Kankakee, Bradley and Bourbonnais. Cold air funnels are weaker cousins of true tornadic funnel clouds. They are almost always higher in the sky, are not associated with thunderstorms, and typically don't touch down. Sometimes, after a cold frontal passage, there's just enough turning of the atmosphere to generate a rotating motion in a cloud. If there's enough moisture present, that rotation can appear as a condensation funnel, protruding down from the base of the cloud. Sirens sounded but nothing ever touched ground.
Mike
