Tornadoes touched down across Eastern Iowa and Northern Illinois on Thursday, causing significant damage and at least one fatality in Fairdale, Illinois.
News 8 tracked a tornadic supercell that overturned semi trucks along I-80 and US-61 during the evening rush hour. As the storm moved through Donahue, Iowa, the tornado was confirmed on the ground. The storm tracked east and moved toward the Mississippi River Valley. As it descended the valley, a multi-vortex tornado was reported by a stormchaser near the Clinton Municipal Airport. The tornado then crossed the Mississippi and caused significant damage to a storage facility in Fulton, Illinois.
It is a long-standing myth that river valleys offer protection against tornadoes. But one photo taken on Thursday should change the minds of those who think that valleys and rivers offer protection.
This photo posted to Twitter by @OnTheChase is proof of the myth. This was taken along Highway 84 near Albany, Illinois, looking across the river to the northwest as the tornado is about to cross from Iowa into Illinois. The top of the thunderstorm at this time was 46,000 feet. That’s more than 8 1/2 miles tall! A storm that tall, strong enough to produce a tornado on top of a hill, has the same opportunity to produce one in a valley. A few hundred feet of elevation will have little impact on the storm’s ability to produce a tornado.
But even though this is a tornado myth, there is science that suggests that a tornado’s severity will be less significant in smaller valleys. The sole reason for this is the fact that a tornado’s wind usually increases with height. As a tornado moves over a valley, the circulation at the ground can be slower and less intense than the funnel’s circulation at a previous higher elevation.
Large cities in river valleys like St. Louis and Louisville have seen tornadoes. There have even been tornadoes along the Mississippi in the Quad Cities. But the myth seems to gain more belief the longer we go without a tornado in a large valley.
-Meteorologist Eric Sorensen
