What is a Tropical Cyclone?

1. What is a Tropical Cyclone?

2. How does a Tropical Cyclone form? Tropical Cyclones are formed by low pressure systems above warm tropical oceans. They ‘eye’ (centre) of the cyclone is surrounded by gale force winds measuring between 60km/h up to 90km/h. These winds are sustained as the tropical cyclone moves and circulate the eye in a clockwise direction(Southern Hemisphere). Surrounding the centre of the cyclone are gale force winds that can extend for hundreds of kilometres away form the eye and that measure up to 170km/h. Structure of a Cyclone

3. The Eye • A.K.A. the circular eye • Categorized by light winds and often clear skies • Diameter= 10-100km long or an average of 40 kilometres long • Surrounding the eye is the ‘eye wall’ which is a dense ring of cloud approximately 16 kilometres tall • The eye wall signifies the zone of strongest winds and heaviest rainfall

4. Energy of a Tropical Cyclone • Tropical cyclones gain their energy from warm tropical oceans with a temperature over 26.5°C • Can last for many days • They dissipate over cold oceans or land but can survive without warm water for numerous days

5. Impact: Wind • Gusts: Centre regions=up to 280km/h Outer Regions= up to 90km/h • A tropical cyclones winds can cause extensive damage to anything in its path • A tropical cyclone “turns airborne debris into potentially lethal missiles” (http://www.bom.gov.au/cyclone/about/#danger) • The eye does not produce winds as strong as other regions of the cyclone, so it is important to remember that destructive winds will return as the eye passes

6. Impact: Rain • Heavy rainfall caused by cyclones can create flooding in effected regions • Pose risks to humans and environments. Eg. Drowning and damage to ecosystems

7. Impact: Storm Surge • Definition: a raised dome of water generally 60-80km wide and 2-5 meters higher than normal tides • Surge causes destruction within low-lying areas, harbours and vessels out at sea

8. Categories