What is a tropical storm?

How is a tropical storm formed?

1. A strong upward movement of air draws water vapour up from the ocean surface

2. The evaporated air cools as it rises and condenses to form towering cumulomimbus clouds 

3. Several small thunderstorms join together to form a tropical depression (a giant spinning storm)

4. Tropical depressions are classified as tropical storms when they reach 120km per hour

5. The storm develops an eye at its centr where air descends rapidly

6. As the storm grows, it is carried across the ocean, gathering strength

7. On reaching the shore, the storm's energy supply is cut off and friction from the land slows it down as it begins to weaken
   

What conditions are needed for a tropical storm to form?

• sea temperature of at least 27°C

• sea depth of 60-70m

• location 5°N or 5°S of the equator

• low wind sheer

• the Coriolis Effect

Where do the majority of tropical storms generally occur?

• Tropic of Cancer

• Tropic of Capricorn

• Northern Hemisphere 

What are the main characteristics and features of tropical storms?

• up to 600-700km across

• heavy rain

• high wind speeds

• spinning/rotating (the Coriolis Effect)

• eye

• eye wall

• developed between 5-20°N/S of the equator

• moving westwards

• burning out when passing over land surfaces

• spiralling rain bands

What hazards are associated with tropical storms?

• strong winds

• storm surges

• landslides

• flooding

What makes tropical storms spin?

• wind blows from areas of high pressure to low pressure

• as the Earth rotates, the wind bends and sends warm air rising

• the Coriolis Effect brings about the maximum rotation of the air at 5°N/S of the equator

• storms spin anticlockwise in the Northern Hemisphere

• storms spin clockwise in the Southern Hemisphere

How are tropical storms measured?

the Saffir-Simpson scale

What is the frequency of tropical storms?

• over 100 tropical storms form each year

• many tropical storms never reach land and therefore do not develop into major hazards

• storms are more frequent in the Northern Hemisphere between June and November

• storms are more frequent in the Southern Hemisphere between November and April