Cyclone season extends from 1 November to 30 April. When a cyclone approaches you should listen to your local radio station or monitor your television for cyclone information.
The Shire of Exmouth produces a cyclone information booklet
free of charge for its residents every year at the beginning of the cyclone season. Most residents will receive a booklet through their Post office box. They can also be collected from the Shire's Administration Office and Library. The booklet contains information on preparing for cyclones, the location of the welfare centre, cyclone alerts, warning sign locations and important phone numbers.
Tropical cyclones are a seasonally occurring natural hazard that cause considerable loss of life and material damage. In March 1999 Severe Tropical Cyclone Vance, the strongest cyclone ever to cross onto the Australian mainland, caused millions of dollars worth of damage to Exmouth and Onslow. Fortunately, there was no loss of life.
In Australia, Cyclone Tracy caused the loss of 55 lives in Darwin on Christmas Day 1974. Five lives were lost when Cyclone Alby passed through the south-west of WA in April 1978 and the most recent loss of life (7) occurred at Onslow during Cyclone Bobby in 1995.
Definition and Occurrence
A tropical cyclone is a circular rotating storm of tropical origin in which the mean wind speed exceeds 63 km/h (gale force). Gale force is the threshold speed at which a cyclone is named. Wind speeds in excess of 100km/h are common by the time a cyclone crosses the coast and higher wind speeds frequently occur. Tropical cyclones can occur at any time of the year, but they are very rare outside the cyclone "season" from the beginning of November to the end of April.
Once they cross the coast, cyclones tend to decay within 24 to 48 hours and the strong central winds die away. Dangerous flooding can occur as heavy rain falls from the decaying system.
Cyclones threaten life and property in 3 ways:
- Fluctuating wind pressure can weaken and possibly cause the collapse of buildings and other structures.
- Loose objects, such as patio furniture, rubbish bins, dog kennels or building material, become lethal wind borne projectiles that can cause severe structural damage to homes and kill or injure people in their path.
- Flooding, due to an abnormal rise in the level of the ocean (storm surge) caused by the cyclone or as a result of heavy rainfall in river catchments.
As cyclones often adopt an erratic course, or suddenly change speed, it is important that you be aware of any changes at the earliest possible time. In order to do this, keep your radio tuned to the ABC or your local commercial station, WA/FAM, and listen for the most up-to-date cyclone information which is broadcast at regular intervals.