Question

This world map shows the tracks and intensities of thousands of hurricanes and other tropical cyclones. It was put together by the National Hurricane Center and the Joint Typhoon Warning Center. a. What area has experienced the greatest number of category 4 and 5 storms? b. Why do hurricanes not form in the very heart of the tropics, astride the equator? c. Explain the absence of storms in the South Atlantic and the eastern South Pacific.

Short answer

a. Western Pacific Ocean. b. Weak Coriolis effect. c. Cool waters and high wind shear.

Step-by-step solution

Analyzing Storm Data for Category 4 and 5

Examine the map for clusters of category 4 and 5 hurricanes. Notice that areas with the most concentrated tracks indicating higher intensity storms are key. Typically, regions like the western Pacific Ocean, especially near the Philippines, Taiwan, and Japan, show the highest concentration of category 4 and 5 storms.

Understanding Lack of Equatorial Hurricanes

Research the Coriolis effect, which influences hurricane formation. Understand that the Coriolis effect is weakest at the equator, which means there isn't enough force to establish the cyclonic rotation needed for storm development in these regions.

Investigating the Absence in South Atlantic and Eastern South Pacific

Identify atmospheric and oceanic conditions such as sea surface temperatures and wind shear. These regions have cooler waters and higher vertical wind shear, which inhibits the development of hurricanes. Additionally, the South Atlantic has high atmospheric stability and a lack of pre-existing atmospheric disturbances.

Key concepts

Hurricane Formation

Hurricanes, also known as tropical cyclones, are fueled by warm, moist air. The formation begins over warm ocean waters, typically above 27°C (80°F). When warm air rises from the ocean surface, it creates an area of lower pressure beneath.
Nearby high-pressure air rushes in to fill the void, heating up as it comes into contact with the warm ocean. This air then rises, cools, and condenses into clouds. The continuous cycle of rising warm air and falling cool air creates a cycle that sustains the hurricane.

• Warm ocean temperatures are crucial.
• Low wind shear allows the storm to grow.
• High levels of humidity in the atmosphere fuel the system.

Coriolis Effect

The Coriolis Effect is a phenomenon that affects the movement of air masses over the Earth's surface. It's caused by the Earth's rotation, which causes moving air to turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
The Coriolis Effect is crucial for the formation of hurricanes because it helps initiate the cyclonic rotation. This rotation is essential for a storm to organize and intensify.
Near the equator, the Coriolis Effect is minimal, which makes it difficult for hurricanes to form. Without this spinning force, the necessary cyclonic motion cannot develop, explaining the absence of hurricanes directly at the equator.

Sea Surface Temperature

The temperature of the ocean surface, also known as sea surface temperature, plays a vital role in tropical cyclone formation. For hurricanes to develop, the sea surface temperature must be sufficiently warm, usually exceeding 27°C (80°F).
Warm waters provide the energy needed for the storm's growth.

• Warm water increases evaporation, providing moisture and latent heat which fuels the storm.
• Regions with warmer sea surfaces are more prone to intense storms.
• Cooler waters, such as those in the South Atlantic, are not conducive to hurricane formation.

Wind Shear

Wind shear refers to the change in wind speed or direction with height in the atmosphere. Low wind shear is essential for hurricane development, as it allows the storm to maintain its structure and vertically organized convection.
High wind shear can disrupt the storm's formation by tilting the circulation and dispersing moisture.
In regions with high wind shear, such as parts of the South Atlantic, the hurricane's ability to mature is inhibited.
When wind shear is low, the atmospheric conditions are more supportive of the storm's growth and intensification.

Category 4 and 5 Storms

Category 4 and 5 storms are the most intense classifications on the Saffir-Simpson Hurricane Wind Scale. These storms are marked by extremely high winds and potential for catastrophic damage.

• Category 4 storms have sustained winds of 130-156 mph.
• Category 5 storms have winds exceeding 157 mph.
• The western Pacific Ocean often experiences these intense hurricanes, partly due to optimal warm sea temperatures and favorable wind shear conditions.

These powerful storms tend to concentrate in regions where environmental conditions consistently align, highlighting the importance of atmospheric and oceanic conditions in determining hurricane behavior and intensity.
Understanding these aspects can help predict and prepare for future storms, aiming to mitigate their impact.