1. Severe Weather
Weather describes the conditions in the atmosphere in an area over a short period of time.
Weather that is extreme and outside of normal conditions is considered severe weather.

2. What variables affect weather?
Temperature: amount of heat
Humidity: amount of water vapor
Pressure: amount of force exerted by air
Precipitation: amount of water falling from clouds
Wind: movement of the air

3. Types of Severe Weather
Hurricane (A column of spinning air and water that forms over warm ocean)
Tornado (A column of spinning air that forms over land)
Drought (Extended periods of low precipitation)
Thunderstorm (An electric rainstorm that forms when cold air masses meet warm air masses)
Blizzard (Heavy snow storms)

4. What Causes Hurricanes?
Warm, humid air over the ocean begins to rise and condense
Low pressure forms in the center of the rising air
Air rushes into the low pressure area and begins to spin
Wind created by the spinning air causes even more water vapor to rise and the storm gets stronger
If winds reach 74 miles per hour a hurricane has formed

5. What Causes Tornadoes?
Warm, humid air moves over land and becomes even more heated
Cool, dense air meets the warm, humid air
The cool air rushes in and the warm air starts to spin
Wind created by the spinning air causes more water vapor to rise
The center of the funnel has extremely low pressure compared to the outside of the funnel and a “vacuum” forms

6. Air Masses
A weather front is the place where masses of different temperature air meet.

8. Weather Map Symbols
Cold Front
Warm Front
Stationary Front

9. Weather Map Forecasting