Transcript Sec 13.4 - Highland High School

Section 13.4
Recurrent Weather
Objectives
Describe recurring weather patterns and
the problems they create.
Identify atmospheric events that cause
recurring weather patterns.
Distinguish between heat waves and
cold waves.
Section 13.4
Recurrent Weather
Even a relatively mild weather system can
become destructive and dangerous if it
persists for long periods of time.
Review Vocabulary
Fahrenheit scale: a temperature scale in
which water freezes at 32 and boils at 212
Section 13.4
Recurrent Weather
New Vocabulary
drought
cold wave
heat wave
wind-chill index
Section 13.4
Recurrent Weather
Floods
The most extensive flooding occurs as a
result of heavy and persistent rain, saturated
soil, and low-lying ground.
Floods can also occur when weather patterns
cause even mild storms to persist over the
same area.
Section 13.4
Recurrent Weather
Floods
Low-lying areas are most susceptible to
flooding, making coastlines particularly
vulnerable to storm surges during hurricanes.
Rivers in narrow-walled valleys and
streambeds can rise rapidly, creating highpowered and destructive walls of water.
Section 13.4
Recurrent Weather
Droughts
Droughts are extended periods of wellbelow-average rainfall.
Droughts are usually the result of highpressure systems that persist for weeks
or months over continental areas.
Section 13.4
Recurrent Weather
Droughts
Because the sinking air prevents humid air
from rising, condensation cannot occur, and
drought sets in until global patterns shift
enough to move the high-pressure system.
Section 13.4
Recurrent Weather
Droughts
Heat waves
An unpleasant side effect of droughts often
comes in the form of heat waves, which
are extended periods of above-average
temperatures.
Heat waves can be formed by the same
high-pressure systems that cause droughts.
Section 13.4
Recurrent Weather
Droughts
Heat waves
Because of the dangers posed by a
combination of heat and humidity, the
National Weather Service (NWS) routinely
reports the heat index.
The heat index assesses the effect of the
body’s difficulty in regulating its internal
temperature as relative humidity rises.
Section 13.4
Recurrent Weather
Please click the image above to view the interactive table.
Section 13.4
Recurrent Weather
Cold Waves
The opposite of a heat wave is a cold wave,
which is an extended period of belowaverage temperatures.
Cold waves are also brought on by large,
high-pressure systems. However, cold waves
are caused by systems of continental polar or
arctic origin.
Section 13.4
Recurrent Weather
Cold Waves
Because of the location and the time of
year in which they occur, winter highpressure systems are much more
influenced by the jet stream than are
summer high-pressure systems.
Section 13.4
Recurrent Weather
Cold Waves
The winter location of the jet stream can
remain essentially unchanged for days or
even weeks. This means that several polar
high-pressure systems can follow the same
path and subject the same areas to
continuous numbing cold.
Section 13.4
Recurrent Weather
Cold Waves
Wind-chill index
The effects of cold air on the human body are
magnified by wind. Known as the wind-chill
factor, this phenomenon is measured by the
wind-chill index.
Section 13.4
Recurrent Weather
Cold Waves
Wind-chill index
The wind-chill chart
was designed to show
the dangers of cold
and wind.
CH
Study Guide
Key Concepts
Section 13.4 Recurrent
Weather
Even a relatively mild weather
system can become destructive and dangerous
if it persists for long periods of time.
 Too much heat and too little precipitation
causes droughts.
 Too little heat and a stalled jet stream can
cause weeks of cold weather in an area.
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Study Guide
Key Concepts
Section 13.4 Recurrent
Weather
 Heat index estimates the effect on the
human body when the air is hot and the
humidity is high.
 Cold index tells how wind, humidity, and
temperature affect your body in winter.
 Wind chill is a factor used to warn about
the effect of cold air and wind on the
human body.
CH
The Nature of Storms
13.4 Section Questions
The temperature is 0F and the wind speed is
30 miles per hour. What is the wind chill?
a. –5F
b. –10F
c. –26F
d. –58F
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The Nature of Storms
13.4 Section Questions
What happens to air at the center of a
high-pressure system?
a. It sinks and water vapor condenses.
b. It sinks and water vapor resists condensation.
c. It rises and water vapor condenses.
d. It rises and water vapor resists condensation.
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The Nature of Storms
13.4 Section Questions
What conditions result in extensive flooding?
Possible answer: The most extensive
flooding occurs as a result of heavy and
persistent rain, saturated soil, and lowlying ground.
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The Nature of Storms
Chapter Assessment
Questions
Which weather event is often related to
the presence of persistent high pressure
over a region?
a. a flood
b. a drought
c. a tornado
d. a blizzard
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The Nature of Storms
Chapter Assessment
Questions
Which type of movement describes the air
flow in the eyewall of a hurricane?
a. counterclockwise upward spiral
b. clockwise upward spiral
c. counterclockwise downward spiral
d. clockwise downward spiral
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The Nature of Storms
Chapter Assessment
Questions
Why do people feel less comfortable on a hot
day when the humidity is high?
a. The air is less dense.
b. The air moves less.
c. Less evaporation occurs.
d. Less precipitation occurs.
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The Nature of Storms
Chapter Assessment
Questions
Which type of thunderstorm
could form as a result of the
air circulation shown?
a. mountain thunderstorm
b. sea-breeze thunderstorm
c. cold-front thunderstorm
d. warm-front thunderstorm
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The Nature of Storms
Chapter Assessment
Questions
What hazards do hurricanes cause when
they make landfall?
Possible answer: Hurricanes making
landfall bring high wind, tornadoes, and
sometimes severe lightning. Storm surge
causes flooding along the coast, and heavy
rain causes flooding inland.
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The Nature of Storms
Standardized Test
Practice
What forms as superheated air expands
and produces a shock wave?
a. lightning
b. thunder
c. tornado
d. microburst
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The Nature of Storms
Standardized Test
Practice
What is the Saffir-Simpson scale?
a. a scale for classifying tornadoes
b. a scale for classifying hurricanes
c. a scale for classifying thunderstorms
d. a scale for classifying lightning
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The Nature of Storms
Standardized Test
Practice
On which side of a northern hemisphere tropical
cyclone does the wind blow from the south?
a. north side
b. west side
c. south side
d. east side
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The Nature of Storms
Standardized Test
Practice
How is the life cycle of a supercell thunderstorm
similar to the life cycle of a hurricane?
Possible answer: Both storms form from
energy supplied by rising moist air, and both
storms dissipate when the supply of rising
moist air is cut off.
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The Nature of Storms
Standardized Test
Practice
Why do hailstones consist of concentric layers?
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The Nature of Storms
Standardized Test
Practice
Possible answer: The layers form as
hailstones are tossed in a thunderstorm by
strong updrafts. A new layer of ice is added
each time the hailstone moves into a level of
supercooled water droplets. These water
droplets exist at temperatures that are well
below the normal freezing point of water and
so change to ice as soon as they come into
contact with the hailstone.