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Thunderstorms

Thunderstorms. Thunderstorms. At any given moment, nearly 2000 thunderstorms are occurring around the world. Some are capable of producing hail the size of baseballs, swirling tornadoes, and surface winds of more than 160 km/h.

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Thunderstorms

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  1. Thunderstorms

  2. Thunderstorms • At any given moment, nearly 2000 thunderstorms are occurring around the world. • Some are capable of producing hail the size of baseballs, swirling tornadoes, and surface winds of more than 160 km/h. • All thunderstorms, regardless of intensity, have certain characteristics in common.

  3. How Thunderstorms Form • For a thunderstorm to form, three conditions must exist. • abundant moisture • mechanism to lift the air • atmosphere must be unstable

  4. How Thunderstorms Form • Limits to Growth • The air in a thunderstorm will keep rising until: • It meets a layer of stable air • The air cools

  5. Types of Thunderstorms • Classified based on the mechanism that caused the air to rise • Air mass thunderstorms • Frontal thunderstorms

  6. Air-Mass Thunderstorms • Air rising because of unequal heating of Earth’s surface within one air mass

  7. Air-Mass Thunderstorms • Mountain thunderstorms • orographic lifting • Sea-breeze thunderstorms – • temperature differences between the air over land and the air over water

  8. Frontal Thunderstorms • Produced by advancing cold and warm fronts. • Because they are not dependent on daytime heating, they can persist long into the night.

  9. Stages of Development • A thunderstorm usually has three stages • The stages are classified according to the direction in which the air is moving.

  10. Stages of Development • Cumulus Stage • Air starts to rise nearly vertically. • Cloud forms. • Coalescence  larger droplets  precipitation

  11. Stages of Development • Mature Stage • Air cools as precipitation falls. • More dense air sinks, creating downdrafts. • The updrafts and downdrafts form a convection cell.

  12. Stages of Development • Dissipation Stage • The supply of warm, moist air runs out. • Without the warm air, no updrafts and no precipitation. • Lingering downdrafts

  13. Severe Weather • Lightning • Hail • Wind • Tornado • Flooding

  14. Severe Thunderstorms • When the strength of the storm’s updrafts and downdrafts intensifies, the storm is considered to be severe. (10%)

  15. Severe Thunderstorms • Supercells • intense, rotating updrafts. • extremely powerful • self-sustaining

  16. Lightning • Lightning is an electrical discharge – static electricity • Winds in a cloud create regions of air with opposite charges.

  17. The Fury of the Wind • Downbursts are violent downdrafts that are concentrated in a local area and can contain wind speeds of more than 160 km/h. • Microburst • Macroburst

  18. Hail • Balls or lumps of ice • Caught in up and downdrafts and constantly growing • Eventually they become too heavy and fall to Earth as hail.

  19. Hail

  20. Floods • A storm dumps rain over a limited location • Main cause of thunderstorm-related deaths in the United States each year.

  21. Tornadoes • Violent, whirling column of air in contact with the ground. • Before a tornado reaches the ground, it is called a funnel cloud. • Often associated with supercells. • The air is made visible by dust, debris, or by the condensation of water vapor.

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