Storm Hazards

Question 1

What is the Coriolis effect?

Answer 1

The rotation of the Earth causes the air to move around the centre of the eye in a circular or rotating motion.

Question 2

What are the conditions needed for a tropical storm to occur?

Answer 2

• Ocean temperatures of 27°C
• Ocean depth of >50m.
• Unstable air pressure (areas of convergence where high and low pressures meet).
• Wind shear (swirling motions needed) and speeds of 199 kmph.
• 5° to 30° latitude, North and South of the equator.

Question 3

Explain how tropical storms form:

Answer 3

1. Warm, moist air rises, leaving an area of low pressure below- causing warm air from surrounding areas of higher pressure to move into this low pressure area and rise too.
2. The warm air rises, cools and condenses into thunderstorm clouds.
3. The Coriolis effect causes storms in the southern hemisphere to spin clockwise, and anticlockwise in the northern.
4. The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds. At 119 kmph the storm can be classed as a tropical storm.
5. Cool, dry air descends in the eye, causing the weather to be relatively calm and cloud free.
6. Surrounding the eye is the eyewall. Warm, moist air rapidly rises here, with extremely high winds and torrential rain. When winds reach 199 kmph, it becomes a hurricane/cyclone/typhoon.
7. When the storm reaches a coast, the low pressure and high winds will cause a large amount of sea water to be taken into the system and then released as a storm surge.

Question 4

What system is used to measure intensity of a storm?

Answer 4

Saffir-Simpson scale.

Question 5

Why are high winds a hazard caused by a storm?

Answer 5

• Can destroy infrastructure.
• Blow debris at high speeds

Question 6

Why is flooding a hazard caused by a storm?

Answer 6

• Can be caused by coastal/river flooding from storm surges and heavy rain.
• River flooding also sends more floodwater elsewhere which can cause areas outside of the tropical storm’s path to flood also.

Question 7

Why are landslides a hazard caused by a storm?

Answer 7

• Soil becomes heavy when saturated with water (e.g. high levels of rain).