Download Weather and Climate Part 3 - Violent Storms

Weather and Climate
Part 3 - Violent Storms
CGF3M
Crescent School
Text source: http://weathereye.kgan.com
Hurricanes
Thunder and Lightning
Hail Storms
Tornadoes
Winter Precipitation
HURRICANES
There is a separate slide show dealing with Hurricanes in more detail
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What is a storm surge:
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THUNDER AND LIGHTNING AND HAIL
How Lightning is created:
In storm clouds, tiny particles in the cloud move
around picking up positive or negative energy
charges, like when shoes scuff a rug. The positive
charged particles stay light, and rise to the top of the
cloud. The negative charged particles get heavier,
and collect at the bottom of the cloud. As more
particles become charged, they divide into opposing
groups in the cloud. When the power of attraction
between them gets too great, the particles
discharge their energy at each other, completing a
path for electricity to travel through the air. We call
this flow of electricity lightning.
It's the negative charges in the bottom of the cloud
that cause lightning to strike the ground. When the
negatively charged particles group together, they
begin to seek out positive charges from the ground
below. The excess electrons create a channel of
charged air called a leader that reaches down to
the ground below. The leaders attract other charged
ground-based channels called streamers.
How Thunder is created:
The flash of a lightning strike and resulting thunder
occur at roughly the same time. But light travels at
186,000 miles in a second, almost a million times
the speed of sound. Sound travels at the slower
speed of one-fifth of a mile in the same time. So
the flash of lightning is seen before thunder is
heard. By counting the seconds between the flash
and the thunder and dividing by 5, you can
estimate your distance from the strike (in miles).
But why does lightning cause thunder at the same
time it strikes? Lightning causes thunder
because a strike of lightning is incredibly hot. A
typical bolt of lightning can immediately heat the
air to between 15,000 to 60,000 degrees
Fahrenheit. That's hotter than the surface of the
sun! A lightning strike can heat the air in a fraction
of a second. When air is heated that quickly, it
expands violently and then contracts, like an
explosion that happens in the blink of an eye. It's
that explosion of air that creates sound waves,
which we hear and call thunder.
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How does Hail form?
Hail is created when small water droplets are
caught in the updraft of a thunderstorm. These
water droplets are lifted higher and higher into the
atmosphere until they freeze into ice. Once they
become so heavy they will start to fall. It all depends
on the storms strength. If the smaller hail stones get
caught in the updraft again they get more water on
them. They get lifted again freeze and fall. This
happens over and over until the hailstone is too
heavy, and then falls.
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TORNADOES
Tornado conditions are caused when different
temperatures and humidity meet to form
thunderclouds. In the United States, warm, wet
winds from the Gulf of Mexico move northward in
spring and summer, meeting colder, dry Canadian
winds moving southward. The place where these
two winds meet is called a dry line.
High, dry air coming from the north piles on top of
low-moving, moist Gulf air at a height of over
10,000 feet. The warm southern winds try to rise,
but the cold northern air blocks them. This clash
causes the warm, trapped air to rotate
horizontally between the two air masses.
At the same time, the sun heats the earth below,
warming more air that continues to try and rise.
Finally, the rising warm wind become strong
enough to force itself up through the colder air
layer. When this occurs, the cold air on top begins
to sink, sending the rising warm wind spinning
upward.
The warm winds rotate faster and faster in a high
column. When the updraft is strong, the column can
rise to heights of 10 miles or more, twisting at
speeds of up to 100 miles an hour. The rotating
winds produce strong storm clouds about 70,000
feet high, sometimes spreading 10 miles wide.
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Click here to see an interesting animated
example of how a Tornado forms:
http://news.bbc.co.uk/2/hi/5328524.stm
Check out the one for Hurricanes as well.
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Flash Corner:
Tornadoes
Hurricanes
THE END