1. Severe Weather Storms

2. Objectives
List and describe the main types of storms and explain how they form
Standards:
S6E4.b – Relate unequal heating of land and water surfaces to form large global wind systems and weather events such as tornadoes and thunderstorms.
S6E4.c – Relate how moisture evaporating from the oceans affects weather patterns and the weather events such as hurricanes.

3. STORMS A storm is a violent disturbance in the atmosphere.
They involve sudden changes in air pressure.
Changes in air pressure causes rapid air movement (wind).

4. Thunderstorms Formation Temperature Precipitation Safety
Within large cumulonimbus, or thunderheads
Form when warm air is forced upward at a cold front
Temperature
Hot, humid afternoons in the spring and summer
Precipitation
Heavy rainfall
Sometimes hail
Safety
Avoid touching metal objects
Install metal lightening rods
Find a low area away from trees
Stay away from water

5. Thunderstorms
During a thunderstorm, positive and negative electrical charges build up in the clouds.
The discharge of the electricity between clouds is lightening.
Lightening is as hot as 30,000°C, hotter than the sun.
The heated air expands and explodes producing thunder.

6. Checkpoint What is El Nino? What is a storm?
Weather pattern related to the temperature of the water in the tropical Pacific Ocean.
Any type of violent disturbance in the atmosphere.

7. Tornado
Rapidly whirling, funneled-shaped cloud that reaches down from a storm cloud to touch Earth’s surface
Most frightening & disruptive storm
Usually brief, touching the ground approx. 15 minutes or less
Wind speeds may reach 480 km/hr

8. Tornado Formation Precipitation Safety Temperature
Develop in low, heavy cumulonimbus clouds
When warm dry air mass and cool air mass collide
Temperature
Warm humid air
Spring and early summer when ground is warm
Precipitation
Heavy rain and wind
Safety
Listen for watches & warnings
Basement level, or to the middle room on ground floor
Stay away from windows
Lie in a ditch

9. Tornado Tornado Watch – tornadoes are possibly in your area
Tornado Warning – tornadoes have been seen in the sky or on weather radar
Occur most often in the US
Approx. 800 tornadoes a year

10. Checkpoint Where do tornadoes form? Why is there a tornado valley?
What states make up tornado valley?
Low heavy cumulonimbus clouds
Warm humid air mass moves north from Gulf of Mexico and meets a cold dry mass that is moving south from Canada
SD, Iowa, Nebraska, Kansas, Missouri, Oklahoma, TX, NM, and Arkansas

11. Hurricanes Tropical storm that has winds of 119 km/hr
Usually occur between June and November in the eastern US
Hurricanes that occur in western US are called typhoons
Bring much needed rainfall to S Asia & SE Asia

12. Hurricanes Formation Temperature Precipitation Safety
Begins over warm water as a low pressure area, tropical disturbance
Gets its energy from warm humid air at the ocean’s surface
Temperature
Warm temperatures
Precipitation
Strong winds
Rain which generally causes flooding
Safety
Evacuate
Move into the interior room and stay away from windows

13. Hurricanes Occur between June and November
Effect people that live on the coast of the Atlantic, Pacific, and Indian Oceans
Hurricanes bring needed rainfall to S Asia and SE Asia
Eye – center of a hurricane

14. Winter Storms
Lake-effect Snow – In the fall and winter, land cools faster than the lakes.
When cool air mass moves from Canada across Great Lakes it picks up water vapor and heat from lakes.
After the air mass
passes the lakes it begins
to cool and the water vapor
condenses and falls as snow