Tropical Cyclones/ Hurricanes
 Different regions refer to the storms by different names
North and Central America  hurricanes
Northwest Pacific typhoons
North Indian Ocean severe cyclonic storms
Southwest Indian Ocean tropical cyclone
 Between 75-90 / year
 Season is June 1- November, most active August to October
 Hurricanes are measured using the Saffir-Simpson scale
How do Tropical Storms Develop?
 Warm seawater heats air above creating a low pressure system
 Winds develop and the Coriolis effect creates a rotation
 Energy (warm air) from ocean continues to flow upwards
intensifying the storm
 Pressure drops in the centre
 Once rain starts to fall -> tropical storm is formed
 if this storm moves onto land, the fuel (warm ocean air)
disappears and the rain will cool the system. In time, the storm
will stop.
 If the storm stays over the water, the storm will continue to gain
energy from the warm water below and therefore the system will
not cool.
 When a tropical storm reaches speeds of 65 knots (74 miles/hr),
it is known as a Hurricane.
 Hurricanes move towards the west with the Trade winds
How are Storms Monitored
 Satellite images
- eye of the storm is plotted to track movements
- Airplanes – fly at low levels to monitor wind speed, rainfall,
pressure.