There are 3 Stages of a thunderstorm:

1)Cumulus Stage 2)Mature Stage3)Dissipation

Stage

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

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

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

Severe thunderstorms can develop supercells, which have intense, rotating updrafts.

About 10% of thunderstorms are severe.

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

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

Lightning heats the air to about 300,000 C.

Thunder – sound made by the rapid expansion of air around the lightning bolt.

Hazards of thunderstorms:

• lightning• violent winds• hail• floods• tornadoes

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

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.

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

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.

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

themeye – the calm center of the stormeyewall – band immediately surrounding

the eye that has the strongest winds

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.

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.

A storm surge occurs when hurricane-force windsdrive 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.