Section 13.3
Tropical Storms
Objectives
Identify the conditions required for tropical
cyclones to form.
Describe the life cycle of a tropical cyclone.
Recognize the dangers of hurricanes.
Section 13.3
Tropical Storms
Normally peaceful, tropical oceans are capable
of producing one of Earth’s most violent
weather systems—the tropical cyclone.
Review Vocabulary
Coriolis effect: caused by Earth’s rotation,
moving particles, such as air, are deflected to
the right north of the equator, and to the left
south of the equator
Section 13.3
Tropical Storms
New Vocabulary
eye
Saffir-Simpson
hurricane scale
eyewall
storm surge
tropical cyclone
Section 13.3
Tropical Storms
Overview of Tropical Cyclones
During summer and fall, the tropics
experience conditions ideal for the
formation of large, rotating, low-pressure
tropical storms called tropical cyclones.
Section 13.3
Tropical Storms
Overview of Tropical Cyclones
Cyclone location
Favorable conditions for cyclone formation
exist in all tropical oceans except the South
Atlantic Ocean and the Pacific Ocean off the
west coast of South America( because the
waters are not warm enough).
Section 13.3
Tropical Storms
Overview of Tropical Cyclones
Cyclone formation- conditions.
Tropical cyclones require two basic conditions
to form:
1.an abundant supply of warm ocean water
and
2.some sort of mechanism to lift warm air and
keep it rising.
Cyclone formation - stages
1. tropical disturbance – Low pressure above
ocean waters.
2. tropical depression - the disturbance acquires
a cyclonic circulation around the low pressure.
3. tropical storm - wind speeds around the lowpressure exceed 65 km/h.
4. cyclone/hurricane - If air pressure continues to
fall and winds reach at least 120 km/h.
Cyclone dissipates on reaching land or cold
waters.
Section 13.3
Tropical Storms
Overview of Tropical Cyclones
Cyclone formation
Once winds reach at least 120 km/h,
another phenomenon occurs—the
development of a calm center of the storm
called the eye.
The eye of the cyclone is a span of 30 to
60 km of calm weather and blue sky.
Section 13.3
Tropical Storms
Overview of Tropical Cyclones
Cyclone formation
The strongest winds in a hurricane are
usually concentrated in the eyewall—a tall
band of strong winds and dense clouds that
surrounds the eye.
Section 13.3
Tropical Storms
Overview of Tropical Cyclones
Tropical cyclone movement
Like all large-scale storms, tropical
cyclones move according to the wind
currents that steer them.
Section 13.3
Tropical Storms
Hurricane Hazards
The Saffir-Simpson
hurricane scale
classifies hurricanes
according to
1. wind speed,
2. potential for flooding
due to the effect on
the height of sea level,
3. potential for property
damage.
Section 13.3
Tropical Storms
Hurricane Hazards
Damage
Hurricanes can cause extensive damage,
particularly along coastal areas, which tend
to be where human populations are the
most dense.
Section 13.3
Tropical Storms
Hurricane Hazards
1. Winds
2. storm surge occurs when hurricane-force
winds drive a mound of ocean water toward
coastal areas where it washes over the land.
3.Torrential rain.
Section 13.3
Tropical Storms
Hurricane Hazards
Hurricane advisories and safety
The National Hurricane Center issues a
hurricane warning at least 24 hours before a
hurricane is predicted to strike.
Awareness, combined with proper safety
precautions, has greatly reduced death tolls
associated with hurricanes in recent years.
CH
Study Guide
Key Concepts
Section 13.3 Tropical
Storms
Normally peaceful, tropical oceans
are capable of producing one of Earth’s most
violent weather systems—the tropical cyclone.
 Cyclones rotate counterclockwise in the
northern hemisphere.
 Cyclones are also known as hurricanes
and typhoons.
CH
Study Guide
Key Concepts
Section 13.3 Tropical
Storms
 Cyclones go through the same stages of
formation and dissipation as other storms.
 Cyclones are moved by various wind systems
after they form.
 The most dangerous part of a tropical cyclone
is the storm surge.
 Hurricane alerts are given at least 24 hours
before the hurricane arrives.
CH
The Nature of Storms
13.3 Section Questions
At what latitudes do tropical cyclones
usually form?
a. between 0 and 5
b. between 5 and 30
c. between 30 and 50
d. between 50 and 70
CH
The Nature of Storms
13.3 Section Questions
What weather condition usually exists within the
eye of a hurricane?
a. high wind
b. calm wind
c. tornadoes
d. lightning
CH
The Nature of Storms
13.3 Section Questions
What is the source of a hurricane’s energy?
Answer: A hurricane’s energy comes from
the warm water over which it develops. As
ocean water evaporates, some heat is taken
from the ocean. The water vapor then rises
high into the atmosphere. The heat that was
taken from the ocean is released to the
atmosphere as the water vapor condenses.