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 lowpressure 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.