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Deadly Downbursts
Thu Feb 27, 2003
Listen in RealAudio 
Hi, I'm Bryan Yeaton for The Weather Notebook. Today, Robin White explores an uncommon, but
deadly, atmospheric event.
According to atmospheric scientist Paul Doherty of the Exploratorium in San Francisco, walking
in a thunderstorm in California's Sierra Nevada Mountains is one of the best places to see a
rare and frightening weather phenomenon. It's called a downburst and Doherty says it's caused
by a dying cumulus cloud.
PD: The cold air inside the cloud begins to collapse toward the ground, so this giant
fist-shaped cloud comes out of the bottom of the flat cumulus and ... races toward the ground
and it's a pile driver of cold air rushing toward the ground and it smacks into the ground and
spreads out to the side.
Doherty says the mountains are good places to watch them because you are half way to the
clouds. But they happen everywhere and sometimes they even come with light
rainstorms.
PD: Sometimes one of these downbursts will just come down and smack into the ground at 100
miles an hour and just flatten a house. Just in the middle of nowhere all of a sudden --
Pawhump -- the house is smashed and you say, "What was that?"
What it is, is falling precipitation that evaporates and cools a portion of the air, making it
heavier than the air around. The rush downwards can exceed hurricane forces. Sometimes
downbursts break off trees and throw cars. They are especially dangerous for pilots. In 1985,
134 people died when a plane was hit by a downburst and flew into a highway in Dallas. These
days planes have new radars which spot the downbursts and give pilots warning. For The
Weather Notebook, I'm Robin White.
The Weather Notebook is funded by Subaru of America, and the National Science Foundation.
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