Thunderstorm Formation• A thunderstorm forms when warm, humid air

rises rapidly within a cumulonimbus cloud.

• Thunderstorms have warm temperatures, moisture, and rising air, which may be supplied by a low-pressure system.

• Thunderstorms have a three-stage life cycle: the cumulus stage, the mature stage, and the dissipation stage.

• The cumulus stage is dominated by cloud formation and updrafts.

• After the cumulus stage, downdrafts, which are air currents moving vertically toward the ground, begin to form.

• In the mature stage, heavy winds, rain, and lightning dominate the area.

• In the dissipation stage, updrafts stop, winds die down, lighting ceases, and precipitation weakens.

Time

Tornadoes

• A tornado is a violent, whirling column of air in contact with the ground.

• Tornadoes form when thunderstorm updrafts begin to rotate.

- Storms

Tornado Formation• Tornadoes can form when warm, humid air

rises rapidly in thick cumulonimbus clouds—the same type of clouds that bring thunderstorms.

- Storms

Tornado Alley• Tornadoes in the U.S. are most likely to occur

in a region known as Tornado Alley.

Tornadoes

• Occur most in May & June• Occur most between 3-8 pm

What conditions are needed????

- Storms

Structure of a Hurricane• In a hurricane, air moves rapidly around a low-

pressure area called the eye.

Begins as a low-pressure area over warm water, or a tropical disturbance

Warm, humid air rises and begins to spiral

As air rises, more warm, moist air is drawn into the system,

and the hurricane gains energy

As winds spiral inward, bands of high winds and heavy rains form.