Central Indiana’s rapid temperature shift this week has produced the possibility for a rare weather condition: the cold air funnel.
Mike Baldwin, a meteorology professor in Purdue University’s Department of Earth, Atmospheric and Planetary Sciences, says it’s a type of weak tornado.
“During the day when the sun comes out, even a little bit of sunshine will warm up the surface and the low-level air enough for that air to become unstable,” Baldwin says.
At that point, Baldwin says, heat rising from the earth mixes with cold air higher up into the atmosphere and the meeting of cold and warm air can produce a thunderstorm capable of making funnel clouds.
Baldwin says cold air funnels don’t occur often and rarely produce winds in excess of about 80 miles per hour. That barely registers as an “EF0” on the Enhanced Fujita Scale, which is used to measure tornado force, meaning the storm isn’t usually capable of doing more than minor damage to people or property.