Behind the Forecast: Can rivers weaken thunderstorms?

LOUISVILLE, Ky. (WAVE) - There’s a common misconception that rivers can disturb large storm systems and keep tornadoes from forming. That’s a myth.

Cumulonimbus clouds (thunderstorm clouds) can climb 40,000 to 60,000 feet into the atmosphere (7.5 to 11 miles). Thunderstorms are very rarely affected by small features of the earth’s surface, including rivers. Data shows that rivers, even as big as the Mississippi, don’t affect thunderstorms.

Larger bodies of water, like the Great Lakes, are more likely to impact a weather system. The Great Lakes range in size from Lake Ontario at just over 7,000 square miles to Lake Superior at 31,700 square miles. At its widest point, the Ohio River is around 1 mile wide (near Smithland, KY).

The belief that rivers protect a region from tornadoes is also flawed. Tornadoes usually have intermittent paths in general. Plus, data shows tornadoes crossing over rivers in many circumstances. In 1925, the Great Tri-State Tornado traveled from southeastern Missouri into southern Illinois and southwestern Indiana, killing 695 people. That tornado crossed two rivers; the Mississippi and then, the Wabash.

There are numerous records of tornadoes crossing over the Ohio River from Indiana into Kentucky or vice versa. The March 2, 2012, tornado that destroyed parts of Henryville, Indiana, is a perfect example. After initially touching down in Washington County, Indiana, the tornado traveled into Clark County, where it wreaked havoc in Henryville, and eventually crossed into Jefferson County, Indiana. The tornado crossed the Ohio River from Jefferson County into Trimble County, where it caused even more damage.

It’s also important to remember that waterspouts are just tornadoes that form over bodies of water or move from land to water. They can be just as dangerous as a regular tornado.