1. What kind of weather would a continental tropical air mass that formed over northern Mexico bring to the southwestern U.S?

2. Fronts
Front - boundary between 2 different air masses. Fronts usually bring some type of precipitation.

3. Cold Front
Cold front – rapidly moving cold air overtakes the slower moving warm air; The warm air quickly rises allowing water vapor to condense. Thunderstorms and severe weather are common at these fronts. (Draw a picture of a cold front.)

5. Cold Front
On a weather map a cold front is represented by blue triangles.

6. Warm Front
Warm front - warmer air slowly moves over colder air and replaces it; Leads to long periods of steady rain or snow. (Draw a picture of a warm front.)

8. Warm Front
On a weather map a warm front is represented by red semi-circles.

9. warm and cold front animations
cold front precipitation
warm front precipitation

10. STAtionary Front
Stationary front - a cold front and a warm front meet, and neither can move the other out of the way; creates days and days of the same weather (rain or dry spells).
(Draw a picture of a stationary front.)

11. STAtionary Front
On a weather map a stationary front is represented by alternating red semi-circles and blue arrows pointing in opposite directions.
stationary front animation

12. Occluded Front
Occluded front – a warm air mass is trapped between a cool air mass and a cold air mass. The warm air is cut off from the surface. This leads to heavy rain. (Draw an occluded front.)

13. Occluded Front- “trapped”

14. Occluded Front
On a weather map, an occluded front is represented by purple semi- circles and arrows pointing in the SAME direction.

15. Pressure Systems Low Pressure Systems
Winds blow into low pressure areas
Warm, moist air will rise, causing cloud formation
Weather is usually cloudy or stormy. Cloudy nights can be warmer than clear nights because clouds trap heat absorbed by Earth during the daylight hours.

16. Pressure Systems High Pressure Systems
Winds blow away from high pressure areas
Sinking motion of air makes it difficult for clouds to form
Weather is usually clear and sunny.

17. What do you notice around the H’s and L’s?

18. Fronts can bring severe weather:
Thunderstorms
Tornadoes
Hurricanes

19. Thunderstorms Thunderstorms are brought by cumulonimbus clouds.

20. Thunderstorm Facts:
A thunderstorm forms when warm, humid air rises rapidly within a cumulonimbus cloud.
Thunderstorms are LOW pressure systems.
A drop in barometric pressure (the measure of air pressure) usually indicates a storm is approaching.
Examine how barometric pressure changes with weather conditions.

21. Put the following sentences in order to create a thunderstorm:
1. These small water droplets collide to form larger ones.
2. Cold air meets warm air and pushes the warm, less dense air upward.
3. Raindrops cool the air around them.
4. This updraft creates winds associated with thunderstorms.
5. Warm, moist air cools rapidly and condenses forming clouds that contain water droplets.
6. Larger droplets fall from cloud toward earth’s surface.
7. This cool air becomes denser and sinks, allowing the warm air at the surface to create an updraft as it rises.

22. The Thunderstorm Song

23. Tornadoes
Tornadoes are violent, whirling winds that form over land.

24. Tornado Facts: Usually form from severe thunderstorms
Not all thunderstorms make tornadoes, conditions have to be just right!
Different winds moving at different speeds in different directions and at different heights cause the air to start spinning (like a paper towel tube).
4) These different winds cause a rotating
column of wind that spin vertically.

25. Tornado Facts: 5. Tornadoes are the fastest moving storms.
6. A tornado is not very wide and does not stay on the ground very long (few seconds to a few minutes)
7. Most tornadoes occur in an area called “tornado alley” because warm moist air masses from the southeast meet cold dry air masses from the north central us.
8. Most happen in the spring and early summer.

26. - Storms
Tornado Alley

27. - Storms
Tornado Formation
Tornadoes can form when warm, humid air rises rapidly in thick cumulonimbus clouds—the same type of clouds that bring thunderstorms.

28. Tornado Clips https://www.youtube.com/watch?v=2GWtfb5l8iA
Tornado Wind Patterns

29. The Fujita-Pearson Scale
The Fujita scale (F-Scale), or Fujita-Pearson scale, is a scale for rating tornado intensity, based on the damage tornadoes inflict on human-built structures and vegetation.
BBC NEWS | Special Reports | Animated guide: Tornadoes

30. Hurricanes
Hurricanes are large, swirling storms that form over the ocean. They are the most powerful storms. Warm, moist air must be present for a hurricane to develop.

31. Hurricane Facts http://www.nhc.noaa.gov/aboutnames.shtml
Hurricanes are a LOW pressure system.
Start as tropical storms; renamed hurricanes if wind speeds reach 73 mph.
Form over warm ocean water near the equator; the warm water and warm moist air supplies its power. It will only lose strength if it loses heat or loses moisture.
Because of the Coriolis Effect, most hurricanes in the Atlantic travel east to west. The hurricanes that affect the Southeast U.S. usually originate off the coast of Africa.
Eye of hurricane – area in storm that is very calm, with very low-pressure and little or no winds
Most happen in late summer or early fall.
Named according to where it forms: Hurricane – Atlantic Ocean Typhoon – Pacific Ocean Cyclone – Indian Ocean

32. Structure of a Hurricane
- Storms
In a hurricane, air moves rapidly around a low-pressure area called the eye.

33. Hurricanes http://www.youtube.com/watch?v=SNEG4YKElgY

34. Severe Weather Overview
Thunderstorms
Hurricanes
Tornadoes
Forms over warm water
Forms over land or water
Forms out of a
Thunderstorm
Caused by warm
wet air from oceans
rising into the
atmosphere
Caused by warm
wet air rising quickly
over cold dry air
Starts out as thunderstorm,
Then air at different heights,
going in different speeds in
different directions begins to
spin and lift vertically
LOW pressure
LOW pressure
LOW pressure

35. Resources
Petroleum is an
example of a nonrenewable
resource.

36. Resources Biomass is an example of a renewable resource/
alternative to fossil fuels.
Alternative fuels are
important because fossil
fuels are not renewable,
and we need other
choices for energy.