Air Masses and Fronts

1
Table of Contents

• Air Masses and Fronts
• Storms
• Predicting the Weather

2
Comparing and Contrasting
- Air Masses and Fronts

• As you read, compare and contrast the four types
  of fronts by completing a table like the one
  below.

Types of Weather
Front
How It Forms
Cold front
A cold air mass overtakes a warm air mass.
Clouds, possibly storms with heavy precipitation
Warm front
A warm air mass overtakes a cold air mass.
Clouds, light precipitation
Stationary front
Cold and warm air masses meet, but neither can
move the other.
Clouds, precipitation
Occluded front
A warm air mass is caught between two cold air
masses.
Clouds, precipitation
3
Types of Air Masses
- Air Masses and Fronts

• Air masses can be warm or cold, and humid or dry.
  As an air mass moves into an area, the weather
  changes.

4
Classifying Air Masses
- Air Masses and Fronts

• Four major types of air masses influence the
  weather in North America maritime tropical,
  continental tropical, maritime polar, and
  continental polar.

5
Air Masses and Fronts

• Introduction Pg. 596
• What is an air mass?
• An air mass is a huge body of air that has
  similar temperature, humidity, and air pressure
  at any given height.
• Types of Air Masses pg. 597-598
• 2. Scientists classify air masses according to
  ____ and ____.
• temperature and humidity
• 3. Polar air masses typically have low air
  pressure.
• False
• 4. Compare/Contrast Chart.
• A. Maritime Tropical
• B. Maritime Polar
• C. Continental Tropical
• D. Continental Polar

6
Air Masses and Fronts

• 4e. How are maritime tropical and maritime alike,
  how are they different?
• They are alike in that they are both humid. They
  are different because the tropical air mass is
  warm and the polar air mass is cool.
• 4.f. How are continental tropical and continental
  polar air masses alike, and how are they
  different?
• They are alike in that they are both dry. They
  are different because the tropical air mass is
  warm and the polar air mass is cool.

7
Air Masses and Fronts

• How Air Masses Move pg. 599
• 5. In the continental United States, major wind
  belts generally push air masses from ____ to
  ____.
• west to east
• 6. How do jet streams affect air masses?
• As the jet streams blow from west to east, air
  masses are carried along their track.
• Types of Fronts pg. 600-601
• 7. Drawings
• Cold Front
• Warm Front

8
How a Front Forms
- Air Masses and Fronts

• The boundary where unlike air masses meet is
  called a front.

9
Types of Fronts
- Air Masses and Fronts

• Colliding air masses can form four types of
  fronts cold fronts, warm fronts, stationary
  fronts, and occluded fronts.

10
Air Masses and Fronts

• Types of Fronts
• 8. Cold front
• C- A rapidly moving cold air mass runs into a
  slowly moving warm air mass
• 9. Warm front
• A- A moving warm air mass overtakes a slowly
  moving cold air mass.
• 10. Stationary front
• D- A cold air mass and a warm air mass meet and
  remain stalled over an area.
• 11. Occluded front
• B-A warm air mass is caught between two cooler
  air masses.

11
Air Masses and Fronts

• 12. Sentences that are true about fronts
• Cold fronts can bring violent thunderstorms.
• Warm fronts are associated with clouds and rain.
• Stationary fronts may bring many days of clouds
  and precipitation.
• Cyclones and Anticyclones pg.602-603
• 13. A swirling center of low air pressure is
  called a(an) ___.
• cyclone
• 14. Winds spiral inward toward the center of a
  cyclone.
• True

12
Air Masses and Fronts

• 15. What type of weather is associated with
  cyclones?
• Storms and precipitation are associated with
  cyclones.
• 16. Winds in an anticyclone spin clockwise in the
  Northern Hemisphere.
• True
• 17. What type of weather is generally associated
  with anticyclones?
• Dry, clear weather is generally associated with
  anticyclones.

13
Cyclones and Anticyclones
- Air Masses and Fronts

• Winds spiral inward towards the low-pressure
  center of a cyclone. Winds spiral outward from
  the high-pressure center of an anticyclone.

14
Weather Fronts Activity
- Air Masses and Fronts

• Click the Active Art button to open a browser
  window and access Active Art about weather fronts.

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End of SectionAir Masses and Fronts
16
Sequencing
- Storms

• 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 windsand
heavy rains form.
17
Thunderstorm Formation
- Storms

• A thunderstorm forms when warm, humid air rises
  rapidly within a cumulonimbus cloud.

18
Storms

• Introduction pg.604
• What is a storm?
• A storm is a violent disturbance in the
  atmosphere.
• Thunderstorm pg. 605-606
• 2. Types of clouds in which thunderstorms form
• Cumulonimbus
• 3. A sudden energy discharge between parts of a
  cloud, between nearby clouds, or between a cloud
  and the ground is called ____.
• lightning
• 4. Sentences that are true about thunder.
• You hear it after you see the lightning that
  caused it.
• It occurs because lightning heats the air.

19
Storms

• 5. A sudden, violent flood that occurs within a
  few hours, or even minutes, of a storm is called
  a(n) ____.
• flash flood
• 6. Sentences that is a way to stay safe in a
  thunderstorm
• Avoid touching electrical appliances
• Get out of the water if you are swimming.
• Dont use the telephone.
• Tornadoes pg.606-608
• 7. What is a tornado?
• A tornado is a rapidly whirling, funnel-shaped
  cloud that reaches down from a storm cloud to
  touch Earths surface.

20
Storms

• 8. Tornadoes develop in the same type of clouds
  that bring thunderstorms.
• True
• 9. Sentences that are true about where and when
  tornadoes occur.
• Tornadoes occur often in the Great Plains.
• Tornadoes occur more often in the United States
  than in any other country.

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Storms

• 10. Flowchart
• 1. Warm air is forced upward along a a._____
  front.
• a. cold
• 2. As the air rises, it b. _______.
• b. cools
• 3. c.______ falls.
• c. Heavy rain (sometimes with hail)
• 11. Where is the safest place to be during a
  tornado?
• The safest place to be is in the basement of a
  well-built building.

22
Tornado Formation
- Storms

• Tornadoes can form when warm, humid air rises
  rapidly in thick cumulonimbus cloudsthe same
  type of clouds that bring thunderstorms.

23
Tornado Alley
- Storms

• Tornadoes in the U.S. are most likely to occur in
  a region known as Tornado Alley.

24
Structure of a Hurricane
- Storms

• In a hurricane, air moves rapidly around a
  low-pressure area called the eye.

25
Hurricane Andrew
- Storms

• The path of Hurricane Andrew over three
  consecutive days can be seen below.

26
Storms

• Hurricanes pg.610-611
• 12.Sentences that are true about a hurricane
• It is a tropical storm.
• It forms over water.
• 13. The center of a hurricane is called the ____.
• eye
• 14. Hurricanes do not last as long as other
  storms.
• False

27
Storms

• 15. A dome of water that sweeps across the
  coast where the hurricane lands is called a(n)
  ____.
• storm surge
• 16. If you hear a hurricane warning and are told
  to evacuate, you should leave the area
  immediately.
• True
• Winter Storms
• 17. When does snow fall?
• Snow falls during a storm when the whole
  atmosphere is colder than 0 degrees Celsius.

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Storms

• 18. Sentences that are true about lake-effect
  snow
• It occurs because land cools more rapidly than
  water.
• It occurs when humid air rises over a body of
  water and later cools over land.
• 19. What should you do if you are caught in a
  snowstorm?
• You should try to find shelter from the wind,
  cover exposed parts of your body, and stay dry.
  If you are in a car, the driver should keep the
  engine running only if the exhaust pipe is clear
  of snow.

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Lake-Effect Snow
- Storms

• 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.

30
More on Thunder and Lightning
- Storms

• Click the Planet Diary button for an activity
  aboutthunder and lightning.

31
Tornadoes
- Storms

• Click the Video button to watch a movie about
  tornadoes.

32
Hurricanes
- Storms

• Click the Video button to watch a movie about
  hurricanes.

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End of SectionStorms
34
Previewing Visuals
- Predicting the Weather

• 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
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Predicting the Weather

• Weather Forecasting pg. 617
• Scientists who study the causes of weather and
  try to predicting it are called ____.
• Meteorologist
• 2. Sources of weather information for
  meteorologists
• Radar
• Instruments carried by balloons
• Satellites
• Weather Technology pg. 618-619
• 3. In what two areas have improvements in
  technology improved the accuracy of weather
  forecasts?
• The areas are gathering weather data and using
  computers to make forecasts.

36
Predicting the Weather

• 4. Weather forecasts for over three days into the
  future are never reliable.
• False
• 5. Flowchart
• A. weather station
• B. Satellites
• C. Computers
• D. Meteorologists
• E. Weather forecast

37
Predicting the Weather

• 5f. What happens to the calculations in step 3 if
  the data collected is step 1 changes?
• The calculations would change to reflect the
  revised weather data.
• 5g. How would this change what is prepared in
  step 5?
• The forecast prepared by meteorologists would
  change to reflect the revised calculations
  produced by the computer.

38
Predicting the Weather

• 6. Sentences that are true about weather balloons
  or weather satellites
• Weather balloons can carry instruments as high
  as the stratosphere.
• Weather balloons often carry instruments that
  measure temperature, air pressure, and humidity.
• Weather satellites take pictures of Earth from
  the exosphere.
• 7. Sentences that are true about computer weather
  forecasts
• Computer forecasts are based on weather
  conditions from many weather stations.
• When new weather data come in, new computer
  forecasts are produced.

39
Reading Weather Maps
- Predicting the Weather

• This is the type of weather map produced by the
  National Weather Service. It shows data collected
  from many weather stations.

40
Reading Weather Maps
- Predicting the Weather

• Weather maps in newspapers use symbols to show
  fronts, high- and low-pressure areas, and
  precipitation. Color bands indicate different
  temperature ranges.

41
Reading Weather Map Symbols
- Predicting the Weather

• The figure below shows what various weather
  symbols mean.

42
Predicting the Weather

• Reading Weather Maps pg. 620-622
• 8. What data are indicated by symbols on a
  weather map?
• The symbols indicate amount of cloud cover,
  atmospheric pressure, wind direction, wind speed,
  and temperature for individual weather stations.
  Weather maps also show the location of air masses
  and fronts.
• 9. What are the temperature, air pressure, and
  wind direction at the weather station represented
  by the symbol show?
• The temperature is 55 degrees Farenheight, the
  air pressure is 1028 millibars, and the wind is
  from the south-west at 21-25 miles per hour.

43
Predicting the Weather

• 10. Isobars
• B-Lines on a weather map joining places that
  have the same air pressure.
• 11. Isotherms
• A- Lines on a weather map joining places that
  have the same temperature
• 12. What do the standard symbols on newspaper
  weather maps show?
• The symbols show fronts, areas of high and low
  pressure, types of precipitation, and temperature
  range.

44
Predicting the Weather

• 13. The butterfly effect refers to the fact
  that a small change in the weather today can mean
  a larger weather change in the future.
• True

45
Predicting the Weather

• Key Terms
• Storm
• Polar
• Maritime
• Isobars
• Occluded
• Tropical
• Lightning
• Isotherms
• Tornado
• Hurricane
• meteorologist

46
Red Sky
- Predicting the Weather

• A red sky is one kind of observation that helps
  people to predict the weather.

47
Computer Weather Forecasting
- Predicting the Weather

• 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.

48
Computer Weather Forecasting
- Predicting the Weather

• Reading Graphs
• What two variables are being graphed?

• Time of day and air pressure

49
Computer Weather Forecasting
- Predicting the Weather

• 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.

50
Computer Weather Forecasting
- Predicting the Weather

• Inferring
• Which computer model most closely matches the
  actual air pressure data?

• Model B

51
Computer Weather Forecasting
- Predicting the Weather

• Predicting
• What weather would you forecast for Monday and
  Tuesday? Explain.

• Stormy weather, clouds, and precipitation
  accompany low air pressure.

52
More on Weather Maps
- Predicting the Weather

• Click the Planet Diary button for an activity
  aboutweather maps.

53
More on Doppler Radar

• Click the PHSchool.com button for an
  activityabout Doppler radar.

54
End of SectionPredicting the Weather
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Graphic Organizer

Typical Time of Year
Type of Storm
Where Forms
Safety Rules
Within large cumulonimbus clouds
Seek shelter, avoid trees and water.
Spring or Summer
Thunderstorms
Move to a storm shelter or basement if possible
stay away from windows and doors.
Tornado
Spring, early summer
Cumulonimbus cloud
Evacuate or move inside a well-built building.
Over warm ocean water
Late summer and into autumn
Hurricane
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End of SectionGraphic Organizer