1. Vocabulary Watch Video. You will need to log onto discovery education.
Use your earphones!
Severe weather video –

2. Fronts & Air Masses

3. Air Mass:
An air mass is a huge body of air that has similar temperature, humidity, and air pressure at any given height.
Air masses are classified by 2 characteristics
Temperature
Humidity
The characteristics of an air mass depend on the temperatures and moisture content of the region over which the air mass formed.
Tropical: warm, air masses formed in the tropics
Polar: cold, air masses formed north or south of 50º latitude
Maritime: air masses formed on oceans or seas
Continental: air masses formed over land

4. The colder the air the higher the air pressure subsequently the hotter the air the lower the air pressure.
Cold air  more dense
Hot air  less dense
There are 4 major types of air masses that affect the weather of the U.S.
Maritime tropical
Maritime polar
Continental tropical
Continental polar

5. Maritime tropical Warm, wet air masses
On the east coast they are formed over the Gulf of Mexico & south Atlantic Ocean.
Influence weather along the entire east coast.
Summer: thunderstorms & summer showers
Winter: heavy snow or rain
On the west coast they form over the southern Pacific Ocean.

6. Maritime polar Cold, wet air masses
On the east coast they are formed over the north Atlantic Ocean.
On the west coast they are formed over the north Pacific Ocean.
Influence the weather of the west coast more so than that of the east coast.
Summer/Winter: fog, rain, & cooler temperatures

7. Continental tropical Warm, dry air masses
Typically form over the southwest (New Mexico, Arizona, Nevada, as well as northern Mexico) during the summer months.
Influence the weather of the southwestern part of the US & southern Great Plains (Kansas, Oklahoma, Texas, Iowa).
Summer: Hot, dry

8. Continental polar Cold, dry air masses
Typically form over central & northern Canada as well as Alaska.
Influence the weather of the entire United States.
Winter: Clear, cold, dry
Summer: Potential for storms due to interaction with Maritime tropical air moving up from the Gulf of Mexico.

9. 2 primary methods for air mass movement
Prevailing Westerlies
Pushes air masses from west to east.
Jet streams
Pushes fast moving air masses from west to east.

10. Assignment!
Air Mass Chart – You are to fill it in!

11. Fronts The boundary between two air masses. Types of fronts Cold front
Air masses do not easily mix with
each other due to the differences
in…
Density (Air pressure)
Temperature
Moisture content
Storms & different types of weather phenomena occur along fronts.
Types of fronts
Cold front
Fast moving cold air mass overtakes a slower moving warm air mass.
Can cause abrupt weather changes particularly thunderstorms.
Clear skies, a change in wind, & lower temperatures usually follow a cold front.

12. Warm front Stationary front Occluded front
A fast moving warm air mass overtakes a slow moving cold air mass.
Can cause extended periods of rainy or cloudy weather.
Warm, humid weather usually follows a warm front.
Stationary front
A cold and warm air mass meet but neither can move the other.
Can cause extended periods
of precipitation; snow, rain,
fog or clouds.
Occluded front
A warm air mass is caught
between 2 cooler air masses.

13. Possible Weather Associated with Fronts
Type of Weather Associated With It
Front
Clouds
Storms with heavy precipitation
Cold Front
Light Precipitation
Warm Front
Precipitation
Stationary Front
Occluded Front

14. Music by Mr. Parr
Fronts music video

15. Cyclones - Low Pressure System
Greek for “wheel”
Formed around centers of low pressure.
Caused as the boundary between fronts
become distorted by surface features;
mountains or strong winds.
Represented on weather maps by an L.
Warm air rises and spins counterclockwise around the center.
Storms and precipitation are
associated with areas of low pressure
as the warm air rises & condenses to
form clouds & precipitation.

16. Anticyclones – High Pressure Systems
Formed around centers of high pressure.
Represented on weather maps by an H.
Cold air sinks and spins clockwise around the center.
Dry weather and clear skies are associated with areas of high pressure as the cooler air falls & becomes warmer causing a drop in relative humidity.

17. Foldable Fronts Directions Check out the teacher’s example if you need help
Fold your paper in half – hot dog style
Divide your paper into four sections and cut the top sheet only!
Write the four types of fronts on the outside flap and make it colorful
On the inside left, draw a picture of the front (add some color to the picture)
On the inside right, include the following information:
Definition
Symbol
Type of weather associated with the front

18. Severe Weather and Storms

19. Storms: Violent disturbances within the atmosphere.
Caused by sudden changes in air pressure which cause rapid air movement in an area.
Similar conditions often produce different types of storms.

20. Types of storms Thunderstorms
Fast moving storms that are often accompanied by heavy precipitation, frequent thunder and visible lightning.
Lightning: sudden spark or electrical discharge typically caused by the build up of positive charges on Earth with negative charges within the air.
Cloud to cloud
Cloud to ground
Ground to cloud (rare)
Thunder is caused as air is superheated (30,000ºC), expands, and explodes.
Thunder is the sound wave created from the explosion.
Because sound travels slower than light, thunder always comes after lightning not the other way around.

21. Formed within cumulonimbus clouds or thunderheads.
Typically form on hot, humid afternoons or when a fast moving warm front over takes a slower cold front.
Within the cloud fast moving updrafts & downdraft.
Because thunderstorms have the potential to dump a lot of water in a small amount of time, flooding is a potential problem.
Flash floods: flooding of low lying areas within a short time period; less than 6 hours.
Thunderstorm safety
Safest place is indoors away from objects that can conduct electricity.
The metal cage of a car will provide protection if trapped inside a car however try to avoid touching any part of the metal frame.
If outside find a low lying area & lay down.

22. Tornadoes
Tornadoes can form in any situation that produces severe weather.
Typically form during the Spring & Summer under the same conditions as those of a thunderstorm.
Tornado formation
Warm, moist air flows in at the bottom of a cumulonimbus cloud & rapidly moves upward generating a low pressure area inside the cloud.
The warm air begins to rotate due to winds within the cloud blowing in different directions: The result is the cloud begins to spin like a top.
As part of the cloud descends to touch the ground, a tornado or funnel cloud is generated with winds up to 340 mph.

23. The Fujita Scale Tornado alley
Used to determine the severity of a tornado.
Based on the amount of damage created as well as the wind speed.
F-0: Gale tornado, mph winds
F-1: Moderate tornado, mph winds
F-2: Significant tornado, mph winds
F-3: Severe tornado, mph winds
F-4: Devastating tornado, mph winds
F-5: Incredible tornado, mph winds
Tornado alley
Located in the Midwest region of the U.S. & is known for the development of tornadoes.
Includes the states of S. Dakota, Iowa, Nebraska, Kansas, Oklahoma, and Texas.

24. Hurricanes Tropical cyclone (low pressure) that
typically measures miles across
with winds from mph.
Comes from the West Indian word
Huracan or “big wind.”
Called Typhoons when formed
in the Pacific Ocean;
Chinese word, Táifēng or “great wind.”
Hurricanes are named by the World Meteorological Organization.
Guided or directed by the Trade winds.
Can only form over water that is at least 80ºF.
Typically forms during the months of late July to early October.

25. Stages of Hurricane Development
Stage 1: Tropical disturbance; mph
Stage 2: Tropical depression; mph
Stage 3: Tropical storm; mph
Stage 4: Hurricane; 74 mph
The Saffir-Simpson scale
Scale used to determine the severity of a hurricane.
Category 1: wind speed mph; storm surge 4-5 feet.
Category 2: wind speed mph; storm surge 6-8 feet.
Category 3: wind speed mph; storm surge 9-12 feet.
Category 4: wind speed mph; storm surge feet.
Category 5: wind speed 155+ mph; storm surge 18+ feet
Hurricane Katrina was a category 3 hurricane when it made landfall near New Orleans, La on August 29, 2008.
Costliest natural disaster
6th strongest to form, 3rd strongest to make landfall
1 of the 5 deadliest

26. Tornado Alley Worksheet
Music Video
Worksheet and map
Worst Tornados in History
Tornado Rampage 2011

27. Culture- Myths
In the past, people from many cultures interpreted the weather as signs from the gods. Angry gods might send lightning to strike a person or place.
Some Native Americans believe that giant birds called thunderbirds beat their wings to produce thunder. The flashing of their eyes creates lightning.
An ancient Chinese myth tells how a thunderstorm is created by different gods. The thunder god is helped by Mother Lightning. She produces lightning using mirrors in her hands. The Master of the Rain sprinkles water from his pot with a sword. The Little Boy of the Clouds, piles up the clouds, while the Prince of Wind releases winds from a bag.
According to Kenyan legend, God creates two rainbows, one male and one female, which must work together to stop the rain.

28. It's raining cats and dogs
According to the Library of Congress, the true origin of the phrase is unknown. Some popular ideas about the origin of the phrase include references to Norse and Greek mythology. Witches, which were associated with black cats, and the Norse god of storms, which was associated with dogs, may have been an early reference to storms. dogs" may refer to a storm with wind (dogs) and heavy rain (cats). Cata doxa, a Greek expression meaning "contrary to experience or belief" may have meant it is raining unusually hard.

29. Weather Folklore
Red sky at night, sailors delight; red sky in morning, sailors take warning. What does that mean?
Winter weather folklore forecasting
Weather Folklore Activity Sheet and poems

30. Create your own myth
Example - The Vikings believed thunder was caused by Thor. In Norse mythology, Thor was the god of thunder. He produces thunder with his hammer, called Mjolnir, which means "The Destroyer". This hammer was made by dwarfs, and would magically return to Thor's hand whenever he needed it.
Create an original weather myth to explain some aspect of weather in words and in pictures.

31. Video and Questions United Streaming:
Hurricanes, Tornadoes and Thunderstorms – 24min.
Video Questions and answers

32. Characteristics of Weather
Organize the characteristics into categories.
Write down an explanation of how you organized the characteristics and why you categorized them that way.
Share your categories and explanation with the class.