Transcript Guided Notes on Thunderstorms

Guided Notes on
Thunderstorms
Chapter 13, Section 1
Describe the 3 conditions that must
exist for a thunderstorm to form:
1. Abundant moisture in the lower levels of
the atmosphere
2. A mechanism must lift the air so that
moisture will condense and release latent
heat
3. The portion of the atmosphere through
which the cloud grows must be unstable
2. Typical thunderstorms last only
about 30 minutes, and individual
storms are only about 24
kilometers in diameter.
3. Thunderstorms are classified according to
the mechanism that caused the air to rise.
An air mass thunderstorm forms if the air
rose because of unequal heating of Earth’s
surface within one air mass. This reaches
its maximum during mid-afternoon, so airmass thunderstorms are most common
then.
4. Mountain thunderstorms occur
when an air mass rises because
of orographic lifting.
5. Sea-breeze thunderstorms are local airmass thunderstorms caused by
temperature differences between the air
over land and the air over water. They are
most common in coastal areas during the
summer, especially in the tropics and
subtropics.
6. Frontal thunderstorms are produced
by advancing cold fronts and rarely,
warm fronts. Because they are not
dependent on daytime heating, these
thunderstorms can persist long into
the night.
Describe the 3 stages of
thunderstorm development:
Cumulus Stage: air rises vertically, creating
updrafts which transport moisture to the
upper reaches of the cloud
Mature Stage: as precipitation falls, it cools
the air around it, creating downdrafts that
produce gusty surface winds
Dissipation Stage: the supply of warm, moist
air runs out because downdrafts spread in
all directions as they reach the surface