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Dr. Hooda
Text Book : Pages 450 - 459
A violent disturbance in the atmosphere.
1. Involves sudden changes in air pressure
2. Cause rapid air movement
3. Conditions that bring one kind of
storm in one area often cause other
kinds of storms in the same area
• Thunderstorm - A small storm often accompanied
by heavy precipitation and frequent thunder and
lightning.
• Tornado – A rapidly whirling, funnel-shaped
cloud that reaches down from a storm cloud to
touch Earth’s surface and is formed over land in
the mid-latitudes.
• Hurricane – A tropical storm that forms over
warm (80 degrees) tropical seas and has winds of
about 119 kilometers per hour or higher.
• A thunderstorm forms when warm, humid air rises rapidly
within a cumulonimbus cloud and a cold air moves downward.
• Increased surface moisture would increase the chance of a
thunderstorm.
• Is often accompanied by heavy rain, lightning and thunder.
• Issued by National Weather Service
• This means that conditions are favorable for
a thunderstorm
• Length is multiple hours.
• Issued By Local Weather Service
• Means a severe storm has been spotted by dopplar
radar
• Usually lasts for only an hour
• Because light travels much faster than sound.
• Stay indoors, away from doors and windows.
• Avoid objects that conducts electricity, such as metal objects and
bodies of water.
• Do not seek shelter under the trees.
• Do not use phones with cords.
Remember: Cars are pretty safe…
A tornado is a rapidly whirling, funnel shaped cloud
that reaches down from a cloud to touch Earth’s
surface.
Happen in spring and early
summer, often late in the
afternoon when the ground is
warm.
Happen late in the day, when
earth’s surface is very warm,
convection (the flow of heat
through a material, causing hot
parts to rise and cooler parts to
sink) can get very strong.
What type of air masses are involved in the
formation of a tornado ?
Tornadoes happen where dry, cold air
masses mix with moist, warm air masses.
• More tornadoes occur in the United States than in
any other country, especially in the area known as
TORNADO ALLEY.
• About 800
tornadoes
every year in
the United
States.
Tornado
Alley
Tornado Happenings in
Tornado Alley
1. A warm, humid air mass moves
north from the Gulf of Mexico
into the lower great Plains.
2. A cold, dry air mass moves
south from Canada.
3. When the air masses meet, the
cold air moves under the warm
air, forcing it to rise.
4. A storm line, or narrow band of
thunderstorms, is likely to
form, with storms traveling
from southwest to northeast.
5. A single storm line can produce
ten or more tornadoes.
• Conditions are favorable for a tornado to form
• A tornado has formed.
• The safest place to take a shelter is in a storm shelter
or the basement of a well-built building.
http://environment.nationalgeographic.com/environment/natural-disasters/forces-of-nature/
On June 3, 1980, a series of tornadoes
devastated the city of Grand Island,
Nebraska. Seven tornadoes hit within a
three hour period. The storm did
massive damage and closed the city
down for three days.
• A tropical storm that forms over warm (80 degrees) tropical
seas and has winds of about 119 kilometers per hour or higher.
• Hurricanes form over warm tropical (7 – 15 degrees latitude)
seas, Atlantic, Pacific, and Indian Oceans
• In the western Pacific Oceans, hurricanes are called typhoons.
• Storm usually doesn’t last for more than 7-10 days.
• As it moves inland it continues to move across the land but it
begins to weaken
Late summer and Fall between (between July and October).
1. Begins as a low-pressure area over warm water,
or a tropical disturbance.
2. Warm, humid air rises and begins to spiral.
3. As air rises, more warm, moist air is drawn into the
system and the hurricane gains energy.
4. As winds spiral inward, bands of high winds
and heavy rains form.
How Hurricanes Move
• In a hurricane, air moves rapidly around a low-pressure area
called the eye. There is a calm air inside the eye of a hurricane.
• In the Atlantic ocean, hurricanes are steered by trade winds
toward the Caribbean islands and southeastern United Stares.
Map Symbols
•
•
•
•
A list of names from A-W (excluding Q)
Alternate from male to female
6 lists, repeated in cycle
Big name storms retired, like KATRINA.
• A hurricane poses a possible threat within the next
36 hours
• Hurricane conditions expected within 24
hours
• Best plan is to evacuate
– Towns have voluntary evacuation during a watch, and
some switch to mandatory during a warning.
• Plan early in advance
•
•
•
•
Board all windows
Prepare Flashlights, avoid candles
Stay tuned to radio
Stay indoors
http://environment.nationalgeographic.com/environment/natural-disasters/forces-of-nature/
The Saffir-Simpson Scale
http://www.nhc.noaa.gov/aboutsshws
.php
Saffir-Simpson Wind Scale and
Animations
http://www.nhc.noaa.gov/surge/
Storm Surge Overview and
Animations
If a storm has sustained
winds speed below 74
mph, then the storm is
called a Tropical Storm.
Category Wind Speed
1
74-95 mph
2
96-110 mph
3
111-129 mph
4
130-156 mph
5
157 mph or greater
Scale
developed
to
categorize
the
hurricane
based on
wind’s
speed.