"That's why tornadoes rarely rip through the middle of cities, but just kind of bounce around them."
I have no idea what the "why" is. So this is less of a lesson than an opportunity to make up science.
I imagined the city like a mountain, and the tornado bouncing off of it as some immovable bit of topography, like the Appalachians, and the tornado spun off in another direction.
Maybe the tornadoes bounce around the cities because all our collective energy, concentrated in this concrete pocket, is more than any tornado wants to deal with.
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It's because of two factors: 1) heat trapped by the stone and steel rises, creating turbulence and movement in the air above the city, and 2) in the presence of any breeze, the buildings create massive turbulence themselves- since the air on a flat plain tends to move in one direction (gently up, during the day from the heat rising off the land, or sideways in the wind)- there isn't all that much turbulence. Even on a breezy day, without tall irregular physical objects to create wind blocks, the air doesn't mix much, vertically.
ReplyDeleteWith a lot of turbulence in the air, and air of differing temperatures mixing up there, the air is actively moving- when a cold air mass comes in above the turbulent air mass, and falls through it, it won't slice through the turbulent layer like a knife- it'll get mixed up and turbulent, too. Without a sharp thermocline (a meeting place between two masses where temperature is greatly different), you just get a downdraft, and a nasty thunderstorm.
With a sharp thermocline, the cold air mass shoves aside the warm air mass and slowly falls to earth. As it does this, and the world turns, it starts to rotate. Since air of differing temperatures doesn't mix without turbulence present, this makes a cone-shaped stormcloud, as the air will fall faster as it cools more- so the slow fall to earth speeds up as it gets closer to the ground, and the thermocline gets reshaped into a more conical shape. When the air THEN starts to mix more , and the thermocline breaks down, it's like having a gate opened- the energy released by these warm and cold air masses meeting suddenly gets dumped into the funnel-shaped air mass, and the tornado forms.
So what you're saying is that a city is like a mountain, right? :)
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