Terrifying Twisters

Some severe thunderstorms may produce tornadoes. These are violently rotating columns of air in contact with the Earth’s surface. The United States has more tornadoes than anywhere else on earth, with about one thousand occurring every year. The wind inside a tornado can reach speeds of more than 200 mph. Government meteorologists may issue a tornado watch if they think thunderstorms could be severe enough to produce tornadoes.  If someone reports a tornado, or if weather radar indicates a thunderstorm is strong enough to produce a tornado, local National Weather Service meteorologists issue a tornado warning.  If you hear a tornado warning, act quickly and get to a closet or hallway on the lowest floor of your home, away from outside walls and windows until the danger passes. It is best for your family to have an emergency plan before storms hit.  Go here for some ideas.

Ice from the Sky

Hail forms in strong thunderstorms.  These storms contain very strong updrafts, which are winds blowing up through the thunderstorms clouds.  They can be as strong as one hundred miles per hour.  Those strong updrafts suspend rain in mid-air with temperatures around the raindrop of below 32 degrees. Those cold temperatures allow the rain to freeze into small hailstones. As more freezing raindrops get caught in the updraft, they collide with the hailstones, adding layer after layer of ice. When hail becomes too heavy for the updrafts to keep it aloft, it falls to the ground.  In strong updrafts, the hail has time to collect lots of ice, so the hail is bigger. In weak updrafts, the hail doesn't have to get as big before it is able to fall to the ground. Sometimes the updrafts can be so strong that the hailstones can grow larger than softballs

Rain So Heavy

Rainfall in a thunderstorm can be very heavy.  Cumulonimbus clouds contain huge amounts of moisture.  Several inches of rain can fall in a short time.  That's why thunderstorms sometimes result in flooding.


1. How Far Away?
The next time you see lightning, count the seconds until you hear thunder.  Since light travels faster than sound, the sound of thunder takes longer to get to you; about five seconds to travel one mile.  If you count to five just before you hear the thunder, the lightning is about one mile away.  If it is very close, the thunder will sound like a loud crack.  If the lightning is far away, it will sound more like a low rumble. If the lightning is more than fifteen miles away, you may not hear it at all. 

2. Thunder Boomer
Blow up a small paper bag. Pop it. What happened?  You made the air inside expand quickly, the same way air expands when heated by lightning. You made thunder!

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