Air Masses and Fronts Air masses are classified according to temperature and humidity 4 major types of air masses: Maritime tropical: form over the ocean and bring in warm, humid air Continental tropical: form over dry land areas and bring in hot, dry air (form only in the summer) Maritime polar: form over the ocean and bring in cool, humid air Continental polar: form over land and bring in cool or cold air Fronts form when air masses meet and do not mix because of densities (like oil and water)

Air Masses and Fronts 4 major types of fronts: Cold front: forms when cold air moves underneath warm air, forcing the warm air to rise (picture pg. 499) – how does this affect local weather? Warm front: forms when warm air moves over cold air (picture pg. 500) – how does this affect local weather? Stationary front: when warm and cold air masses meet, however aren’t strong enough to move the other Occluded Front: forms when a cold air mass and a cool air mass come together, the warm air caught between them is forced upward. What is the difference between a cyclone and anticyclone?

Air Masses and Fronts What two main characteristics are used to classify air masses? What is a front? Name and describe the 4 types. What is a cyclone? What type of weather does it bring? Why do maritime polar air masses have more effect on the West Coast than the East Coast? Classify the 4 types of air masses according to whether they are dry or humid.

Storms Thunderstorms form within large cumulonimbus clouds, or thunderheads (this is when warm, humid air rises rapidly) These produce strong upward and downward winds and often occur in spring and early summer – late in the afternoon when the ground is warm. During the storm, positive and negative electrical charges build up in clouds. The release of this energy is lightning. Lightning jumps within clouds, between clouds or to the ground The lightning bolt produces thunder – how does this happen? To remain safe during thunderstorms, avoid touching metal objects because they can conduct electricity from lightning into your body

Storms Tornadoes develop in low, heavy cumulonimbus clouds – why do these clouds sound familiar? These often occur in spring and early summer – late in the afternoon when the ground is warm. The safest place to be during a tornado is in the basement of a well-built building What is the difference between a tornado watch and a tornado warning?

Storms Hurricanes form over warm water as a low-pressure area or tropical disturbance and gets its energy from the warm, humid air at the ocean’s surface Winds get stronger as the eye approaches, however the eye of the storm is very calm These are the longest lasting storms Describe the damage that can occur from hurricanes – what is a storm surge? How do you remain safe during a hurricane?

Storms Describe a winter storm. What is lake-effect snow? How do you remain safe? What weather conditions are most likely to cause thunderstorms and tornadoes? What is the most common path for the hurricanes that strike the United States? What safety precautions should you take if a tornado is predicted in your area? If a hurricane is predicted in your area? In the winter, cool, humid air from the Pacific Ocean blows across the cold land of southern Alaska. What kind of storm do you think this causes?

Floods The most dangerous weather-related event in the US. Floods cause almost half of weather related fatalities. Occur when so much water pours into a stream or river that it overflows its banks and covers the land on either side of the channel Describe what happens when a flash flood occurs – why are they so dangerous? To stay safe during floods, move to higher ground. If your family is in a car, don’t drive across flood waters. 60 cm of fast moving water can sweep a car away.

Floods How can precipitation cause flooding? How can you stay safe during a flood? What is the difference between a flood watch and a flood warning? Name three tools that supply information used in forecasting floods and providing flood information (hint: look at the bottom of pg. 516) Describe 2 weather situations in which you would expect floods to occur.

Predicting Weather Change What does a barometer measure? Describe the weather resulting in a change in the barometer. Air pressure. Falling air pressure usually indicates an approaching low-pressure area, possibly bringing rain or snow Describe what weather would occur if cumulus clouds started growing larger and taller. They would become cumulonimbus clouds, bringing thunderstorms Do meteorologists study meteors? Explain what their job is. Where do meteorologists get their information?

Predicting Weather Change Changes in technology for making predictions have occurred in 2 areas: gathering weather data and using computers to make forecasts. Weather balloons can measure temperature, air pressure and humidity while weather satellites photograph Earth’s surface, clouds, storms, ice, snow Computers start with weather conditions reported from weather stations over a large area. They work through calculations to predict the weather and adjust their reports as new data comes in.

Predicting Weather Change Describe what happens with the winds and water during an El Nino event. What evidence do scientists use to predict an El Nino? Explain the word isobar – iso…? …bar? Think of other words that use “iso” and “bar”. Let’s look at a weather map in more detail

Predicting Weather Change What kinds of technology do meteorologists use to help predict the weather? Name at least 3 types of information you could get from a weather map of your area. What lines on a weather map connect points that have the same temperature? If you observe that air pressure is rising, what kind of weather do you think is coming?