Milwaukee – Spots of water were seen over Lake Michigan on Wednesday morning, September 13
A waterspout is a swirling column of air and water mist and often occurs over the Great Lakes in August, September, and October when the water is at its warmest level of the year.
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FOX6 News viewer Martha C. Took this photo of a reservoir in Racine’s North Bay
How waterspouts form
A swell occurs when cold air moves over a lake causing a large temperature difference between the warm water and the overriding cold air. They can last a minute or two or 20 minutes or more — and move slowly at 10 to 15 knots.
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Watersheds fall into two categories:
- Fair weather streams Typically developing cumulus clouds form along the dark flat base of a line. This type of watershed is not usually associated with thunderstorms. A fair weather aquifer forms at the surface of the water and works its way up. By the time the funnel is visible, a fair weather reservoir is nearing maturity. Fair weather waterspouts form in light winds, so they usually move very little.
- Tornadic currents Downward development into a thunderstorm.
Although Wednesday morning’s swells were associated with some thunderstorm activity, they resembled fair weather over the watershed due to calm, non-severe conditions.
If a tornado moves ashore, the National Weather Service issues a tornado warning, as some of them can cause significant damage and injury to people. Generally, fair weather water spouts dissipate quickly when they make landfall and rarely penetrate inland.