Earth and Space Science / Unit 7: The Atmosphere and Weather
7.6 Severe Weather
Notes
- Thunderstorms need moist air, rising motion (instability) and a trigger. Lightning heats air, which expands and makes thunder.
- Sound travels about 340 m/s, light is nearly instant. Count seconds between flash and thunder and divide by 3 to get km: 9 s means about 3 km.
- Tornadoes: rotating funnels, rated EF0-EF5 by damage.
- Hurricanes: tropical cyclones forming over warm ocean water (above about 26.5°C), with winds at least 119 km/h (74 mph). They weaken over land or cold water. Storm surge (a rise in sea level pushed onto land) causes much of the damage and many deaths.
- Watch means conditions are favorable; warning means it is happening or imminent.
Practice
A hurricane gets its energy mainly from:
Evaporation and condensation release heat that powers it.
You see lightning and hear thunder 6 seconds later. The storm is about how far away (sound at 340 m/s)?
$6 \times 340 = 2040$ m, about 2 km.
A tornado warning means:
A warning means immediate danger.
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