Earth Science
Chapter 17
Section 2
A. Storms:
A storm is a violent disturbance in the atmosphere.
Storms involve sudden changes in air pressure, which cause
rapid air movement.
1. Thunderstorms:
- Thunderstorms are heavy rainstorms accompanied
by thunder and lightning
- T-storms form within large cumulonimbus
clouds, or thunderheads.
- Most T-storms are formed when warm moist air is
forced upward at a cold front.
- Cumulonimbus clouds also form on hot, humid
afternoons in the spring and summer.
- As warm, moist air rises rapidly thunderheads are
formed.
- Heavy rain falls, sometimes along with hail.
- T-storms produce strong upward and downward
moving air called updrafts and downdrafts.
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Thunder and Lightning
-Lightning is a sudden spark, or energy discharge.
-This discharge can be between clouds or from the
cloud to the ground.
-Thunder is the sound wave produced by rapidly
expanding air.
-A lightning bolt can heat the air near it to as much as
30,000 C, hotter than the surface of the sun.
-The rapidly heated air expands suddenly and
explosively.
-Thunder is the sound of the explosion.
-T-storm Safety:
-During T-storms, avoid touching metal objects.
-Avoid being one of the tallest objects.
-Cars are a safe place to be.
2. Tornadoes:
- A tornado is a rapidly whirling, funnel-shaped cloud
that reaches down from a T-storm cloud.
- A tornado that occurs over water is called a
waterspout.
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- Tornadoes develop in low, heavy cumulonimbus
clouds. The same clouds that bring thunderstorms.
- The clashing of warm moist air from the Gulf of
Mexico and cold dry air from Canada.
- Cold air causes warm moist air to rise rapidly
forming T-storm clouds along a cold front.
- This line of T-storms along a cold front is called a
squall line.
- This occurs during the spring and early summer in an
area that runs from north-central Texas, across
central Oklahoma, Kansas, and Nebraska. This area
is known as Tornado-Alley.
Tornado Safety:
- The safest place to be during a tornado is in the
basement of a well-constructed building.
- If no basement, move to the center of the building on
the ground floor.
- If outdoors, move to a building or lie in a ditch.
3. Hurricanes:
- A hurricane is a tropical storm that has winds of 119
Km/hr (74 mph).
- A typical hurricane is about 600 Km across.
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- Hurricanes in the Atlantic and Caribbean and called
hurricanes.
- Hurricanes in the pacific and Indian oceans are called
Typhoons. (some times referred to cyclones in the
Indian also).
How do Hurricanes form?:
- A hurricane begins over warm water as a low-pressure
area, or a tropical disturbance.
- A hurricane gets its energy from warm, humid air at the
ocean’s surface.
- Winds spiral inward toward the low-pressure area at the
center.
- Inside the storm are bands of high winds and heavy
rains.
- Hurricane wind may reach 320 Km/hr (192 mph).
- At the center of the storm is an area of calm called the
eye of the storm. The winds grow calm and the sky
clears.
- After the eye passes, the storm resumes, but winds blow
in the opposite direction.
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Hurricane damage:
Most of the damage and death is caused by the
hurricane storm surge.
The storm surge is a dome or water that is sucked up by
the low pressure of the storm. It follows the storm as it
travel and washes onto the shore as the storm make
landfall.
Hurricane safety:
EVACUATE!!
Lake –Effect Snow:
Cold dry air moves across the warmer lake water, it picks up water
vapor.
When the air reaches land and cools, snow will fall.
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