Waterspout Science

Today featured multiple reports of funnel clouds and waterspouts over Lake Michigan near Chicago, and over Lake Erie near Cleveland, Ohio. Waterspouts are essentially tornadoes over water, but they do not require a large supercell-like thunderstorm like typical tornadoes do over land. Waterspouts can occur with right dynamic set-up, and only need showers (sometimes even just clouds) to develop. Thus, these waterspouts are usually weak compared to their land counterparts. However, that does not mean waterspouts cannot be strong. They actually can become strong if they are associated with a strong thunderstorm.

Waterspouts can also move onto land at any time and thus become a tornado. But why was today a day with so many waterspouts? And just how do they form? That is what I will dive into now.

Waterspouts form more often in the fall when you have cool, fall-like airmasses moving south from Canada behind strong low pressure systems and cold fronts. These cool airmasses run over the warmer lake waters since lake water takes much longer to cool off because of the characteristics of water. When that happens, the cooler air flows into warm, moist, and rising air over the lake's surface. This combination can sometimes result in a vortex near the surface of the lake as the cool air converges with the rising warm air.

Sometimes these vortexes can mature into a funnel cloud and eventually a waterspout. A dark spot on the surface of the water is a good sign of a possible waterspout forming.

More often, waterspouts are found in tropical and subtropical areas down in the Florida Keys, along the Gulf of Mexico, etc.