Presentation on theme: "Chapter 8: Lesson 3: What causes severe weather?."— Presentation transcript:
Chapter 8: Lesson 3: What causes severe weather?
Thunderstorms Thunderstorms form in many ways, most often they occur in the following 3 stages: Stage 1: Air currents move upward and clouds form. Stage 2: Air currents are mixed, precipitation begins to fall, pulling some air down with it. Storm now has currents of air moving both upward and downward. Stage 3: All air currents move downward. Clouds get smaller as precipitation falls.
More thunderstorms… Different areas of a thunderstorm have positive and negative electrical charges. Lightning is an electrical spark moving between areas of opposite electrical charge. Lightning increases the temperature of the air which causes vibrations in the air, we hear these vibrations as thunder. A severe thunderstorm watch means that a thunderstorm MIGHT happen. A severe thunderstorm warning means severe thunderstorms HAVE formed and you should prepare for them.
Tornadoes! Layers of wind in a storm blow at different speeds in different directions. Between these layers, a column of air spins on its side. One end of the column is lifted by upward winds. The other end is pushed down by downward winds. The spinning column of air is a funnel cloud. When the funnel cloud reaches the ground it is called a tornado. Tornadoes only last a few minutes, but they can cause great damage.
Hurricanes Hurricanes get their energy from warm ocean water. When water vapor from the ocean condenses, it releases energy. This energy could build and power the winds of a hurricane. Once over land, the hurricanes energy is reduced. Winds from a hurricane can be worse than those from a tornado because 1. They last for days, hitting many locations. 2. They are wide storms. 3. Hurricanes can cause huge waves which can cause damage and floods.