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Weather Patterns
Table of Contents
Air Masses and Fronts
Storms
Predicting the Weather
Weather Patterns - Air Masses and Fronts
Classifying Air Masses
Four major types of air
masses influence the
weather in North America:
maritime tropical, continental
tropical, maritime polar, and
continental polar.
Weather Patterns - Air Masses and Fronts
Types of Air Masses
Air masses can be warm or cold, and humid or dry. As an air
mass moves into an area, the weather changes.
Weather Patterns - Air Masses and Fronts
How a Front Forms
The boundary where unlike air masses meet is called a front.
Weather Patterns - Air Masses and Fronts
Types of Fronts
Colliding air masses can form four types of fronts: cold fronts,
warm fronts, stationary fronts, and occluded fronts.
Weather Patterns - Air Masses and Fronts
Weather Fronts Activity
Click the Active Art button to open a browser window and
access Active Art about weather fronts.
Weather Patterns - Air Masses and Fronts
Cyclones and Anticyclones
Winds spiral inward towards the low-pressure center of a
cyclone. Winds spiral outward from the high-pressure center
of an anticyclone.
Weather Patterns - Air Masses and Fronts
Comparing and Contrasting
As you read, compare and contrast the four types of fronts
by completing a table like the one below.
Front
How It Forms
Cold front
A cold air mass
overtakes a warm air
mass.
A warm air mass
overtakes a cold air
mass.
Cold and warm air
masses meet, but neither
can move the other.
A warm air mass is caught
between two cold air
masses.
Warm front
Stationary front
Occluded front
Types of
Weather
Clouds, possibly storms
with heavy precipitation
Clouds, light
precipitation
Clouds, precipitation
Clouds, precipitation
Weather Patterns
End of Section:
Air Masses and
Fronts
Weather Patterns - Storms
Thunderstorm Formation
A thunderstorm forms when warm, humid air rises rapidly
within a cumulonimbus cloud.
Weather Patterns - Storms
Tornado Formation
Tornadoes can form when warm, humid air rises rapidly in
thick cumulonimbus clouds—the same type of clouds that
bring thunderstorms.
Weather Patterns - Storms
Tornado Alley
Tornadoes in the U.S. are most likely to occur in a region
known as Tornado Alley.
Weather Patterns - Storms
Structure of a Hurricane
In a hurricane, air moves rapidly around a low-pressure area
called the eye.
Weather Patterns - Storms
Hurricane Andrew
The path of Hurricane Andrew over three consecutive days
can be seen below.
Weather Patterns - Storms
Lake-Effect Snow
As cold dry air moves across the warmer water, it becomes
more humid as water vapor evaporates from the lake
surface. When the air reaches land and cools, snow falls.
Weather Patterns - Storms
Sequencing
As you read, make a flowchart like the one below that shows
how a hurricane forms. Write each step of the process in a
separate box in the order in which it occurs.
Hurricane Formation
Begins as a low-pressure area over warm water,
or a tropical disturbance.
Warm, humid air rises and begins to spiral.
As air rises, more warm, moist air is drawn into the
system and the hurricane gains energy.
As winds spiral inward, bands of high winds
and heavy rains form.
Weather Patterns - Storms
More on Thunder and Lightning
Click the Planet Diary button for an activity about
thunder and lightning.
Weather Patterns - Storms
Tornadoes
Click the Video button to watch a movie about tornadoes.
Weather Patterns - Storms
Hurricanes
Click the Video button to watch a movie about hurricanes.
Weather Patterns
End of Section:
Storms
Weather Patterns - Predicting the Weather
Red Sky
A red sky is one kind of observation that helps people to
predict the weather.
Weather Patterns - Predicting the Weather
Computer Weather Forecasting
Scientists use computers to
develop different models of how
a front may move. These
predictions are then used to
make weather forecasts. As
more data become available,
some models are found to be
incorrect, while others are found
to closely fit the predicted
conditions. The upper graph
shows the predicted air pressure
from two models. The lower
graph shows actual data for air
pressure.
Weather Patterns - Predicting the Weather
Computer Weather Forecasting
Reading Graphs:
What two variables are being
graphed?
Time of day and air pressure
Weather Patterns - Predicting the Weather
Computer Weather Forecasting
Interpreting Data:
How is air pressure predicted
to change according to each
model in the top graph?
According to model A, air
pressure will drop slightly
then increase. According to
model B, air pressure will
steadily decrease.
Weather Patterns - Predicting the Weather
Computer Weather Forecasting
Inferring:
Which computer model most
closely matches the actual air
pressure data?
Model B
Weather Patterns - Predicting the Weather
Computer Weather Forecasting
Predicting:
What weather would you
forecast for Monday and
Tuesday? Explain.
Stormy weather, clouds, and
precipitation accompany low
air pressure.
Weather Patterns - Predicting the Weather
Reading Weather Map Symbols
The figure below shows what various weather symbols
mean.
Weather Patterns - Predicting the Weather
Reading Weather Maps
This is the type of weather map produced by the National
Weather Service. It shows data collected from many weather
stations.
Weather Patterns - Predicting the Weather
Reading Weather Maps
Weather maps in newspapers use symbols to show fronts,
high- and low-pressure areas, and precipitation. Color bands
indicate different temperature ranges.
Weather Patterns - Predicting the Weather
Previewing Visuals
Before you read, preview Figure 21, a weather map. Then
write four questions that you have about the map in a graphic
organizer like the one below. As you read, answer your
questions.
Previewing Figure 21
Q. What type of front is located west of Okalahoma City?
A. A cold front
Q. What do the stick symbols indicate?
A. Amount of cloud cover, atmospheric pressure, wind direction
and speed, and temperature
Q. What are the slender, curvy lines?
A. Isobars, which join places with the same air pressure
Q. What does the symbol to the east of Florida mean?
A. A hurricane
Weather Patterns - Predicting the Weather
More on Weather Maps
Click the Planet Diary button for an activity about
weather maps.
Weather Patterns
More on Doppler Radar
Click the PHSchool.com button for an activity
about Doppler radar.
Weather Patterns
End of Section:
Predicting the
Weather
Weather Patterns
Graphic Organizer
Type of Storm
Thunderstorms
Tornado
Hurricane
Where Forms
Within large
cumulonimbus clouds
Cumulonimbus cloud
Over warm ocean
water
Typical Time of
Year
Spring or Summer
Spring, early summer
Late summer and into
autumn
Safety Rules
Seek shelter, avoid
trees and water.
Move to a storm shelter
or basement if possible;
stay away from windows
and doors.
Evacuate or move inside
a well-built building.
Weather Patterns
End of Section:
Graphic Organizer