1. THUNDERSTORMS

2. Severe Thunderstorms
Most thunderstorms include heavy rains, strong winds, lightning, and sometimes hail.
Storm clouds and darkening skies indicate that a thunderstorm is approaching.

4. How thunderstorms form
For a thunderstorm to form, three conditions must exist.

5. #1
There must be an abundant source of moisture in the lower levels of the atmosphere
As the moisture condenses, it releases latent heat
The release of latent heat keeps the cloud warmer than the air around it, which is crucial in maintaining the upward motion of the cloud

6. #2
Some mechanism (orographic lifting, temperature differences, fronts) must lift the air so that the moisture can condense and release heat.

7. #3
The portion of the atmosphere through which the cloud grows must be unstable. (It must continue to cool with increasing altitude for the growing cloud to stay warmer than the surrounding air.)

8. Most Important!
Two of the most important ingredients for thunderstorm formation are instability (unstable air) and moisture.

9. Types of Thunderstorms
There are three main types of thunderstorms; orographic, air mass, and frontal.

10. Air mass thunderstorms are the result of localized convection in an unstable air mass.

11. Frontal thunderstorms occur along the boundaries of weather fronts (e
Frontal thunderstorms occur along the boundaries of weather fronts (e.g. cold front).

12. Orographic thunderstorms are caused by air that is forced up by a mountain or hillside.

13. Stages of Development A thunderstorm usually has three stages:
The cumulus stage
The mature stage
The dissipation stage
(the stages are classified according to the direction in which the air is moving)

14. The cumulus stage of a thunderstorm is characterized mainly by updrafts. The mature stage is characterized by strong updrafts and downdrafts. The storm loses energy in the dissipation stage.

15. What causes a storm to be severe?
Greater temperature differences form between upper and lower parts of the storm
This causes air to become more unstable.
As instability of the air increases, strength of the storm’s updrafts/downdrafts intensifies and the storm is said to be “severe”

16. Supercells
Severe thunderstorms may develop into self-sustaining, extremely powerful storms called “supercells,” which are characterized by intense, rotating updrafts.

20. Results of severe thunderstorms
Lightning
Thunder
Wind
Hail
Floods
Tornados

21. Lightening
The sky is filled with electric charge. The positively and negatively charged particles are separated by updrafts and downdrafts, separating the charges into two levels.

24. Thunder
Lightning is a giant spark. A single stroke of lightning can heat the air around it to 54,000 degrees Fahrenheit! This extreme heating causes the air to expand at an explosive rate.
The expansion creates a shock wave that turns into a booming sound wave, better known as thunder.

26. Wind
During strong or severe thunderstorms, a burst of intense winds often flatten buildings and knock down trees.
These winds, known as "downbursts," are often mistaken for tornadoes due to the severity of the damage.
A downburst features air diving toward the surface, whereas a tornado is composed of rising air.

28. Hail
Hail forms when: strong currents of rising air, known as updrafts, carry water droplets high enough in a thunderstorm for the water droplets to freeze.

30. Floods
When a storm dumps its rain over a limited location, rather than spreading it over a large area.
If rain falls faster than the ground can absorb it, or faster than streams and rivers can transport it out of the area, flooding can occur.