Weatherz School: Tornadoes
Let’s play true or false starting with a statement you may have heard before: A tornado can’t hit Duluth because of Lake Superior and the hill. Is this statement true or false?
… This is a big false. Tornadoes have been known to cross over lakes and rivers and move over much higher elevation than we have in the Twin Ports.
The statement that the cool air over Lake Superior can limit instability, is true. In this way, the lake can chip away at one of the key factors of tornado development.
But, here’s one more critical statement: The stability caused by Lake Superior isn’t enough to prevent a strong enough thunderstorm from producing a tornado. This is the big truth.
It’s also worth mentioning that the stability over Lake Superior decreases as the surface temperature rises. By late August, the lake doesn’t do much for us.
Let’s break down how a tornado forms. We need wind shear, which is a change in wind speed and direction with height. Strong upper-level winds are key. The wind shear creates a rotating column of air on a horizontal axis. That rotation can be lifted by a thunderstorm updraft and set on a vertical axis.
A wall cloud can creep down from that rotating updraft. A column of spinning air then continues to build downward. If it doesn’t reach the ground, it’s a funnel cloud. If it does, it’s a tornado.
Tornadoes can happen anywhere, even here. What it comes down to is whether or not a thunderstorm can become strong enough to produce a tornado. That’s why we take the potential for severe thunderstorms seriously.