10) Describe tropical cyclones, including their origin, patterns of movement, and the types of
destruction caused by these atmospheric events. How are the number and frequency of cyclones
related to latitude and season?
Answer: Tropical cyclones are huge rotating masses of low pressure characterized by strong
winds and torrential rain. They are the largest storm systems on Earth, though they are not
associated with any fronts. What powers tropical storms is the latent heat of evaporation and
condensation of water. A tropical cyclone begins as a low-pressure cell that breaks away from the
equatorial low-pressure belt and grows as it picks up heat energy in the following manner.
Surface winds feed moisture (in the form of water vapor) into the storm. When water evaporates,
it stores tremendous amounts of heat in the form of latent heat of evaporation. When water vapor
condenses into a liquid (in this case, clouds and rain), it releases this stored heat—latent heat of
condensation—into the surrounding atmosphere, which causes the atmosphere to warm and the
air to rise. This rising air causes surface pressure to decrease, drawing additional warm moist
surface air into the storm. This air, as it rises and cools, condenses into clouds and releases even
more energy, further powering the storm and continuously repeating itself as a feedback loop,
each time intensifying the storm. These conditions are found during the late summer and early
fall, when the tropical and subtropical oceans are at their maximum temperature. Even though
hurricanes sometimes form outside hurricane season, the official Atlantic basin hurricane season
is from June 1 to November 30 each year. These dates conventionally delimit the period when
most tropical cyclones form in the Atlantic basin. When hurricanes are initiated in the low
latitudes, they are affected by the trade winds and generally move from east to west across ocean
basins. Hurricanes typically last from 5 to 10 days and sometimes migrate into the middle
latitudes. Destruction from hurricanes is caused by high winds and flooding from intense rainfall.
Storm surge causes the majority of a hurricane’s coastal destruction. In fact, storm surge is
responsible for 90% of the deaths associated with hurricanes. The majority of the world’s tropical
cyclones are formed in the waters north of the equator in the western Pacific Ocean. These
storms, called typhoons, do enormous damage to coastal areas and islands in Southeast Asia.
Diff: 3
Bloom’s Taxonomy: Applying/Analyzing
Section: 6.5 How Does the Ocean Influence Global Weather Phenomena and Climate Patterns?
Essent’l Concept: 6.5 Describe how the ocean influences global weather phenomena and
climate patterns
OSLP: 3 The ocean is a major influence on weather and climate.
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