6-4.4 Fronts and Storms.pptx

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Air masses + Fronts + Pressure Systems

=

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Air Masses

• _{Large body of air with the}_{same density,} temperature and moisture levels

• _{Form over water or land in tropical or polar}

regions.

• _{Temperature and humidity conditions}

(warm/cold air, humid/dry air) within air

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- cP continental Polar cold and dry - cT continental Tropical Hot and dry - mP marine Polar (cold and moist)

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Fronts

• _{Fronts: the boundary where air masses meet and}

weather occurs

• _{Depending upon the air masses involved different}

fronts can develop:

Warm

Cold

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Warm Front

• _{Air movement:}

– _{warm air mass}_{collides and rides over a}

cold air mass

• _{Because warm air is less dense and rises above}

more dense cold air

• _{Weather at the Warm Front}

Boundary:

– _{may produce long periods of steady,}

light precipitation, warmer

temperatures, and (rainy) stratus clouds

• _{Weather After the Warm Front}

Boundary Passes:

– _{Humid (moister air) and warmer, may}

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• _{A warm front is represented as a red line with}

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• _{Warm front (general case)}

– _{Warm moist air (mT) from the south pushes north and}

raises over a cool and moist air mass (mP) that sitting to the north and east of the warm front.

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Cold Front

• _{Air Movement:}

– _{Cold air mass collides and}_{slides under}

a warm air mass

• _{Cold air is more dense and sinks under}

warm air, less dense warm air is pushed up

• _{Weather at the Cold Front}

Boundary:

– _{May produce thunderstorms and}

sometimes tornadoes and cooler temperatures, cumulonimbus clouds

• _{Weather After Cold Front Boundary}

Passes:

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• _{Cold Front (general case}₎

– _{Cold, dense continental polar (cP) air from the north}

meets warm moist maritime tropical (mT) air from the SE

• _{Front moves from X to X’ (shown at the bottom)}

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• A cold front is

represented as a blue line with the teeth pointing

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• _{Weather Fronts} • _https://

www.youtube.com/watch?v=tkK4_F0VKhM

• _3:22

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Stationary Front

– _{Cold and warm mass}

meet each other but

neither moves; they are stationary (still) at the frontal boundary

• _{Weather At the Stationary Frontal Boundary:}

– _{Produces long periods of precipitation, sometimes}

resulting in flooding

• _{Weather After the Stationary Front Passes:}

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Occluded Front

– _{When a cold air mass pushes}

into a warm air mass that is

behind a cool air mass, the warm air mass is pushed up above the cooler air masses.

• _{Cold front chasing a warm front (cold fronts are}

faster than warm fronts)

• _{Weather At the Occluded Front Boundary:}

– _{Cloudy and rainy for a long period of time,}

sometimes stormy

• _{Weather After the Occluded Front}

Boundary:

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• _{Represented by a purple}

line with teeth and half circles.

Faster Cold Front going E

Warm Front going NE

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• _{http://www.phschool.com/atschool/phsciexp/}

active_art/weather_fronts/

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Front Symbols

What kind of front does each symbol represent?

1

2

3

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Air Pressure

• _{Air pressure}

– _{Measurement of the force of air pressing}

down on earth’s surface

– _{Can vary depending on density of the air}

• _{Density = Mass/Volume (D= M/V)}

– _{Measured with a barometer}

• _{Factors that affect air pressure}

– _{Temperature, water vapor, elevation}

• _{What causes high and low pressure systems?}

– _{Warm air rising or cold air sinking combined with the}

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A lti tu d e   A ir P re ss u re

Warm Air = Less Dense

Cold Air = More Dense

Humid Air = Less Dense

Dry Air = More Dense

Rising Warm moist air

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• _{Water Density} • _https://

www.youtube.com/watch?v=Ak9CBB1bTcc&fe ature=related

• _2:12

• _{Skip to 45 seconds}

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High (

H

) Pressure System

• _Temperature

– _{Cold air sinking}

• _{Cold makes molecules move slower + condense (closer}

together)  more dense and sink

• _{Amount of water vapor}

– _{Dry air}_{(less water vapor)}

• _{Usually signal more good}_{fair weather}

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• _Cold_Blue (like Code Blue- someone having a heart attack laying on the floor)

• _{HIGH Pressure}

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Low (

L

) Pressure System

• _Temperature

– _{Warm air rising}

• _{Heat makes molecules move faster}

and spread out  less dense and rise

• _{Amount of water vapor}

– _{More water vapor}_{= less air molecules}

• _{Often result in}_{rainy and/or stormy weather}

conditions

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• _RED_HOT • _{Rise Up}

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Air Pressure Systems

Factor Increase/Decrease Air Pressure (L/H)

Density ↑ (more molecules)

(less molecules)↓

Temperature ↑ (warmer)

(colder) ↓

Water Vapor ↑ (more wet)

(dry)↓

Altitude ↑

↓

H

(cold air sinks)

L

(warm air rises)

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System and

Symbol Air Temperature Air Movement Diagram Weather Rotation (CW/CCW)

High pressure

H

Cold air Sinks

Clear skies, fair weather

Clockwise (CW)

Low pressure

L

Warm air Rises

Cloudy skies, rainy or stormy

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CCW

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Air Pressure Explained

• _https://

www.youtube.com/watch?v=jmQ8FWnM0fA

• _4:28

• _{Skip homemade}

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Which map correctly shows the wind directions of the high-pressure and low-pressure systems?

CW

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1. Where is the warm front located? (A B C D) 2. Cold front? (A B C D)

3. What direction is the warm front moving? 4. Cold front?

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-Wind and Front direction from the NORTHWEST (NW).

-Use the wind and front direction arrows to help you decide which type of front and the direction it is moving.

1. Which orange letter represents a location of the front boundary? 2. Is this showing a warm or cold front?

3. What would best symbolize the front?

A

B

C

D

B

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4. What kind of weather would you predict for Illinois (IL) and Indiana (IN)?

5. Does this front move quickly or slowly?

IL

IN

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1. Where are each of the following fronts?

a. Cold ___, b. Warm ___, c. Stationary ___, d. Occluded ___

1

2

4

3 5

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2. What kind of air mass would the north Atlantic be in? (mT, mP, cT, cP) 3. This air mass is:

a. cold and dry b. hot and dry c. cold and moist d. warm and very humid

1

2

4

3 5

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4. In what direction is the front near Phoenix (#2) moving?

5. Would Los Angeles have clear or cloudy skies? Why?

1

2

4

3 5

SE

LA is near a High Pressure system that sinks CW

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6. Front #3 came from the Miami area. What type of air mass affected the region?

7. How did the air mass and front affect the area?

1

2

4

3 5

Maritime tropical

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Storms

• _Storms

–

_{Severe weather conditions that}

_{occur when}

pressure differences cause rapid air

movement

• _{Conditions that bring one kind of storm}

can also cause other kinds of storms in

the same area.

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Thunderstorm

• _{A storm with thunder, lightning, heavy rains}

and strong winds;

• _{Form within large}_{cumulonimbus clouds}_;

• _{Usually form}_{along a cold front}_{but can form}

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• _{MONSTER Severe thunderstorms in HD!}

Ground-dragging shelf clouds - Charleston, WV

•

https://www.youtube.com/watch?v=Ms-276iEwuM

• _2:40

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Tornado

• _{Rapidly whirling,}_{funnel-shaped cloud}

that extends down from a storm cloud;

• _{The very low pressure and strong}

winds can cause great damage to people and property;

• _{Are likely to form}_{within the frontal}

regions where strong thunderstorms are also present.

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• _{Huge Tornado That Hit Rochelle 4/9/15 at}

5:50pm Just before Grubsteakers demolished

• _https://

www.youtube.com/watch?v=didkQXhjeVQ

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21 Deadliest Tornadoes EVER - Caught in HD VIDEOhttps://

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• _{Booker, TX supercell timelapse} • _https://

www.youtube.com/watch?v=mSORpd9QFSA

• _5:00

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Hurricane

• _{Low pressure tropical storm that forms over}_warm ocean water;

• _{Winds form a}_{spinning circular pattern around the} center (eye) of the storm;

• _{The lower the air pressure at the center, the faster}

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• _{Hurricane Destruction}

• _{https://www.youtube.com/watch?}

v=H9VpwmtnOZc

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Other Weather Conditions

• _{Since weather is a condition of Earth’s}

atmosphere at any time,

weather conditions

may include

– _{fair weather,}

– _{showers or light rain,} – _{humid conditions,}

– _{clear skies with cold conditions,} – _{days of clouds and precipitation,}

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BrainPop

• _{Thunderstorms} • _Tornadoes

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Identify each front.

stationary _cold

warm occluded

1. 2.

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1. Storm wind speeds were recorded. Which would have the lowest pressure?

A. 40 mph B. 50 mph C. 65 mph D. 74 mph

2. What causes storm clouds to develop? B. Dry air descending and warming

C. Dry air rising and cooling

D. Humid air descending and warming E. Humid air rising and cooling

3. What might cause a thundercloud to start releasing rain?

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4. What are the characteristics of a high-pressure system? A. Clear skies and sun

B. Extremely hot temperatures C. Humidity and thunder

D. Wind and rain

5. What’s the best reason to stay away from metal objects during a thunderstorm?

E. Metal can be destroyed by thunder. F. Metal heats up easily.

G. Metal is a good conductor of electricity. H. Metal rusts when it rains.

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7. At which location in the room will density be the greatest?

8. Which statement best describes why low

pressure systems usually have bad weather?

A. In a low pressure system, warm moist air rises,

it then cools causing the water vapor to condense and form clouds. B. In a low pressure system, cold air sinks and brings lots of moisture

down to Earth’s surface.

9. It has been cloudy and rainy for over a week. This is most likely a __________ front.

10. Yesterday it was very stormy, but today it

is clear, cool, and breezy. This is most likely a _____ front.

stationary

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11. What can you infer about low and high-pressure air masses? A. Low pressure systems are associated with stormy weather. B. High pressure systems are associated with cyclones.

C. Low and high pressure systems must meet to form a hurricane. D. Low pressure systems are associated with the southern

Hemisphere.

12. The largest storm, in terms of size is a __.

E. thunderstorm B. tornado C. hurricane D. rainstorm