P2B 05Hurricanes: Key Themes and Facts

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What are hurricanes and their key features?

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Hurricanes are very strong tropical storms that bring heavy rainfall (up to 500 mm in 24 hours), strong winds, and high waves. They also cause flooding and mudslides. In other parts of the world, they are known as cyclones and typhoons.

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What conditions are necessary for the formation of hurricanes?

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Hurricanes start from thunderstorm systems in warm tropical oceans. Sea temperatures must be over 27°C to provide heat and moisture. They form between 5° and 30° latitude north/south of the equator, where the Coriolis force is strong enough to cause them to spin.

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How are hurricanes classified?

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Hurricanes are classified by wind speed using the Saffir-Simpson scale. Category 1 has winds of 119-153 kph, while Category 5 has winds of 252+ kph.

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What is the typical path of a hurricane?

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Hurricanes develop in the tropics where the Easterlies blow, causing them to move from east to west. They move away from the equator due to the influence of the Coriolis force and decline when they reach cooler water or land.

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Describe the structure of a hurricane.

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The eye is a calm central area where winds spiral rapidly upwards. The most intense winds (250 km/h) are found in the eye wall. The atmospheric pressure inside the eye is very low. The whole storm moves forward at a speed of roughly 50 km/h.

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What is a storm surge and how is it caused?

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A storm surge is a sudden rise in ocean level under the storm's center, up to 8 meters high. It is caused by inward spiralling winds that blow the ocean into a dome shape and the intense low atmospheric pressure within the eye of the storm.

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What factors determine the impact of hurricanes on coastal areas?

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The impact depends on the strength of the hurricane, type of coastlines, low elevation coastlines, and level of development. Stronger hurricanes and lower coastal elevation result in greater impact. Coastlines protected by mangrove forests are less affected than bare coastlines.