Storm Hazards

Question 1

What are tropical storms?

Answer 1

Tropical storms are huge spinning storms with strong winds and torrential rain.

Question 2

How are Tropical storms created?

Answer 2

They develop over warm water. As warm, moist air rises and condenses, it releases energy that increases wind speed.

Question 3

Conditions needed

Answer 3

A disturbance near the sea-surface that triggers the storm (e.g. an area of low pressure).
Sea water that’s warm (above 27°C to at least 50 m below the surface), so lots of water will evaporate. Convergence of air in the lower atmosphere - either within the ITCZ or along the boundary between warm and cold air masses. This forces warm air to rise.
The Coriolis effect is a force It deflects the path of winds, but it’s weak at the Equator.
A location at least 5° from the Equator. They don’t form 0-5° either side of the Equator because the Coriolis effect isn’t strong enough to make them spin

Question 4

Coriolis effect

Answer 4

Is a force caused by the earth’s rotation. It deflects the path of winds but it’s weak at the Equator.

Question 5

Tropical storms characteristics

Answer 5

Tropical storms are circular in shape, hundreds of kilometres wide and usually last 7-14 days. They spin anticlockwise in the northern hemisphere, and clockwise in the southern hemisphere.
At the centre of the storm is an area of very low pressure called the eye.
Rising air spirals around the eye in the eyewall, causing strong winds.
Near the top of the storm, there is an outflow of moisture-laden air, so cloud cover extends for a long distance either side of the eye.

Question 6

High winds

Answer 6

Wind speeds on the ground can reach more than 300 km/h. Wind can destroy buildings, uproot trees, and carry debris (e.g. cars and trees) long distances before smashing them into other objects.

Question 6

Storm surges

Answer 6

A storm surge is a large rise in sea level caused by high winds pushing water towards the coast, and by the low pressure of a storm.

Question 7

Heavy rain

Answer 7

As warm, moist air rises it cools and condenses, causing torrential rain. E.g. in 1966, over 1000 mm of rain fell in 12 hours at La Réunion (an island in the Indian Ocean) during Tropical Storm Denise.

Question 8

Flooding

Answer 8

Heavy downpours can cause river discharge to increase suddenly, causing rivers to overtop their banks and flood the surrounding area. Heavy rain and storm surges can also cause flooding in coastal areas.

Question 9

Landslides

Answer 9

Water infiltrates soil and rock, making it less stable and increasing the risk of landslides