1. Unit 9, Concept 4, page 134

2. Severe Weather  It may be more accurate to refer to this as severe weather as not everything we talk about will be a storm

3. Floods  When so much precipitation falls water begins to flood normally dry land  Can happen gradually or quickly  Flash floods are when flooding happens over a few hours with streams or rivers overflowing their banks  Flood plain: area where flooding is possible http://www.flickr.com/photos/akalat/3945410213/http://www.flickr.com/photos/akalat/3945410213/ by Andrew Kalat

4. Thunderstorms http://en.wikipedia.org/wiki/File:Thunderstorm_formation.jpg

5. Thunderstorms  To form they need Rising warm moist air An unstable atmosphere (colder air around the warmer air)  Lightning is the release of built up electrical charges Within the cloud Cloud to cloud Cloud to ground  Thunder forms as the rapid heating causes the air to expand explosively  Severe thunderstorms include high wind, hail, and/or tornadoes

6. Tornadoes  Happen in only 1% of all thunderstorms  75% of the world’s tornadoes occur in the U.S.  Rotating column of air that develops in a super cell thunderstorm  Classified on the Enhanced Fujita scale  Develop when warm moist air comes into contact with cold, dry air so are most common in spring and early summer http://en.wikipedia.org/wiki/File:Dszpics1.jpg

7. Hurricanes http://en.wikipedia.org/wiki/File:Hurricane_Fran_sept_1996.jpg

8. Hurricanes http://en.wikipedia.org/wiki/File:Global_tropical_cyclone_tracks-edit2.jpg

9. Hurricanes  Form over tropical or subtropical areas  Huge low pressure systems  Not associated with a front  Rotate counterclockwise in the Northern Hemisphere  Well defined center that the storm spins around called the eye  Powered by evaporating warm water  Lose strength when they travel over land  High winds and thunderstorms  Sustained surface winds of 74 mph or higher

10. Blizzards  A snow storm with high winds  The high winds blow the snow around causing low visibility © Copyright Mike Quinn and licensed for reuse under this Creative Commons Licence.Mike QuinnreuseCreative Commons Licence