1. The Nature of Storms
There are 3 Stages of a thunderstorm:
Cumulus Stage
2)Mature Stage
3)Dissipation Stage

2. The Nature of Storms
Cumulus Stage – air starts to rise upward creating updrafts of moisture. Cloud droplets coalesce and form larger droplets.

3. The Nature of Storms
Mature Stage – Precipitation falls creating downdrafts. The updrafts and downdrafts form a convection cell with gusty winds.

4. The Nature of Storms
Dissipation Stage – The convection cell is losing its steady supply of warm, moist air from the downdrafts. The updrafts cease and the precipitation stops.

5. Severe Weather
Severe thunderstorms can develop supercells, which have intense, rotating updrafts.
About 10% of thunderstorms are severe.

6. Severe Weather
Lightning – friction between the clouds creates regions of air with opposite charges.

7. Severe Weather
To balance, a stepped leader (channel of (-) air) nears the ground and a return stroke (channel of (+) air) rushes upward to meet it.

8. Severe Weather Lightning heats the air to about 300,000 C.
Thunder – sound made by the rapid expansion of air around the lightning bolt.

9. Severe Weather Hazards of thunderstorms: lightning violent winds hail
floods
tornadoes

10. Severe Weather
Hail – precipitation in the form of balls or lumps of ice. Most commonly occurs in the spring.

11. Severe Weather
Floods – produced when the rain falls faster than the ground can absorb it or faster than streams and rivers can transport it out of the area. Floods are the main cause of thunderstorm-related deaths each year.

12. Severe Weather
Tornadoes – violent, whirling column of air in contact with the ground. Before it reaches the ground, it is called a funnel cloud.

13. Severe Weather
The Fujita tornado intensity scale –classifies tornadoes.
They usually form in the spring in the late afternoon. Tornado alley – northern Texas through Oklahoma, Kansas, and Missouri.

14. Severe Weather
Tropical cyclones (Hurricanes) – large, rotating, low-pressure storms.
common in the summer and fall
thrives on energy from warm, tropical oceans
air pressure in the center is low
moves because wind currents steer them
eye – the calm center of the storm
eyewall – band immediately surrounding the eye that has the strongest winds

15. Severe Weather
The Saffir-Simpson hurricane scale classifies hurricanes according to their wind speed, air pressure in the center, and potential for property damage.
The Saffir-Simpson hurricane scale classifies hurricanes according to their wind speed, air pressure in the center, and potential for property damage.

16. Severe Weather
A hurricane will end when it moves over land and no longer has access to the warm ocean surface to draw its energy, or when it moves over colder water.

17. Severe Weather A storm surge occurs when hurricane-force winds
drive a mound of ocean water toward coastal areas, where it washes over the land. They can reach 6m above normal sea level. Lots of rain and flooding also causes enormous damage.