Captain Curiosity
™
Guide to the Universe
Topic: THUNDERSTORMS
EVER WONDER WHAT CAUSES RAIN CLOUDS?
Clouds are tiny water
droplets and ice crystals
suspended in the air.
When the sun heats
water (such as lakes,
streams and oceans), evaporation sends water vapor into
the air. The air closest to the Earth is warmer and can hold
a lot of vapor; but as it rises and cools, it begins to release
water. This extra vapor often condenses around dust
particles and forms a cloud. When a cloud can’t hold any
more moisture, it releases water; this is rain. Rain clouds
look grey because they are so full of water that very little sunlight shines through. When the
air is cold enough, the water falling from the clouds freezes into sleet, hail or snow.
EVER WONDER WHAT CAUSES THUNDERSTORMS? Wind, thunder and lightning – the
hallmarks of a thunderstorm – are caused by unstable air. Unstable air results from the collision of
very warm air and very cool air in the atmosphere; this is called a weather front. As the warm air rises
and cool air sinks, clouds form and wind begins to blow. Lightning begins when the water molecules in
the clouds begin to churn and bump together, causing a buildup of positive and
negative electrical charges. When a negative charge in one cloud moves close to a
positive charge, either in another cloud or on a spot on Earth, electricity flows
between the two points. This is lightning. Lightning, which is extremely hot (about
18,000 degrees Fahrenheit), burns a path through the air. When the air around
this path crashes back in, we hear thunder. In other words, thunder is the sound
that lightning makes! Because light travels faster than sound, we usually see a
lightning bolt before we hear a thunder boom. If you ever see bolt and hear a
boom at the same time, it means the storm is very close by.
EVER WONDER WHAT CAUSES TORNADOS? A tornado
can form only under very specific circumstances. First, the energy of a
very strong thunderstorm (called a “supercell”) must be present. A
supercell can contain 20-100 times the energy of a nuclear warhead!
This energy must then cause a very strong updraft to form. Finally,
there must be a change in wind direction that causes the whole air
column to start spinning. If all of that happens – voila, a tornado!
You can do it!
Visit the website www.wunderground.com and check out their WunderMap.™ It allows you
to track thunderstorms in real time. You can see the air temperature, the track of the storm
cells, and the direction and speed of the wind, among other things.
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