Weather Hazards affecting the Perth area

Cool season storms | Warm season storms | Heavy rain & flooding | Tropical Cyclones | Heatwaves | Bushfires | References | Acknowledgements

The Perth region is subject to a range of meteorologically related hazards - winter storms, summer storms, floods, tropical cyclones, heatwaves and bushfires. Of these, cool season storms are the most frequent hazard and on average have the greatest economic impact. Strong fronts cause winds of gale-force intensity near the coastal fringe of the southwest producing mostly minor damage over a wide area. The more significant events also produce an increase in tidal levels known as a storm surge and can combine with large waves to cause coastal erosion. Wind damage, such as fallen power lines, typically occurs over a wide area, with the potential to cause significant power outages and traffic disruption. Often fallen trees and branches cause much of the property damage. These fronts may also spawn severe localised winds including tornadoes. Winds may be strong enough to unroof houses although such damage is fortunately confined to small areas. Historically strong fronts posed a major threat to shipping activities and the loss of the Marquess of Anglesea and damage to other vessels during a gale in 1830 was described a the time as almost a 'death blow to the infant colony'. During the May 1994 event almost one-third of Perth was without power at one stage and it took almost a week to fully restore power to Perth homes.

The meteorological hazards that have individually had the greatest impact on Perth have been floods and tropical cyclones. If Perth was to experience floods of the magnitude of those in 1862, 1872, 1917, 1926 and 1945, then the economic impact would be on the order of many tens of millions of dollars. However, Perth's average annual rainfall has decreased in the last 40 years lessening the risk of a flood of such magnitude. Possibly Perth's single greatest meteorological impact was cyclone Alby in 1978 when damage was estimated at $39 million (2003 dollars). Strong winds damaged properties and fanned bushfires, while a storm surge and large waves caused massive coastal erosion and flooding in low-lying areas.

The fact that Perth has not experienced a major flood or cyclone impact in recent times has led to an increased level of complacency and general unawareness of the risk. This highlights the need of describing and communicating the level of risk so people can be informed and prepared for the next major event when it occurs.

Although storms in the warmer months are much less common in Perth than in most other Australian cities, there is the potential for them to be as severe as the Sydney hailstorm in 1999 that caused over $2 billion damage. Fortunately such a storm has not impacted Perth. Heatwaves, although viewed as a 'passive' hazard, have historically killed more people than any other meteorological phenomenon. However, the impact of heatwaves has reduced because of such factors as increased use of air-conditioners, better housing design and greater awareness of the risk.

For people living in the hills suburbs and in semi-rural areas bushfires are a major threat particularly from January to March on hot and windy days. The West Australian described how a fire front burned through the hills town of Dwellingup:
About 8.30 pm on Tuesday January 24, 1961, hundreds of terrified people watched helplessly as fire engulfed and destroyed most of Dwellingup, a timber milling town 100 km south of Perth. A short time before they had hurriedly abandoned their homes with only the clothes they wore. They watched a petrol station blow up, houses and motor vehicles explode into flames seconds after being abandoned and flames jump hundreds of metres ahead of the main front, fanned by 120 km/h winds. Some people jumped into a well to escape the inferno and workers trapped at a forestry mill lay face down on the ground and took turns spraying water on each other ...