Over the weekend, storms in Illinois and Indiana produced heavy rain, high winds, as well as several funnel clouds. The National Weather Service issued a statement on Sunday afternoon that some of the storms could generate funnel clouds, though it said these clouds would dissipate before ever touching the ground and becoming a tornado.
Then again today, several funnel clouds were reported with thunderstorms in Iowa. Some of you have asked why are funnel clouds never tornado warned, since funnel clouds eventually lead to tornadoes? Sometimes during non-supercellular thunderstorms, there is enough shear, or rotation present in the storm, that a funnel quickly spins up. These funnels are usually almost always weak. Until the funnel is fully able to create contact with the ground, or a debris swirl is present at surface, this is when a funnel becomes a tornado.
On rare occasions in these weak thunderstorms, the funnel is able to reach the ground, making it a tornado. Because of this, the National Weather Service often issues a special weather statement, when atmospheric conditions are favorable for funnel clouds. If a funnel does ever reach the ground, that is when the National Weather Service issues a tornado warning. Sometimes in these non-supercellular thunderstorms, the rotation is very broad, and weak, that it is not until visual confirmation that a tornado warning is issued.
If you ever see a funnel cloud, make sure you are in a safe place, just in case the funnel does turn into a tornado. Safety is always first priority. After that, report it to your local law enforcement or the National Weather Service.
-Header Image: Sue Feltman, Waterloo, Iowa
— WeatherNation (@WeatherNation) August 28, 2016