Tropical Cyclones in Western Australia - Extremes

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Extremes

Strongest Wind Gust

The strongest wind gust recorded on the Australian mainland is 267 km/h. The gust was recorded during cyclone Vance at 11:50 am (WST) 22 March 1999 at Learmonth Meteorological Office, 35 km south of Exmouth.

A gust of 267 km/h was also recorded at Varanus Island during cyclone Olivia in 1996. Wind gusts of 259 km/h at Mardie and 246 km/h at Onslow were measured during cyclone Trixie in February 1975.

By definition a category 5 cyclone produces gusts of at least 280 km/h. This means these gusts have gone unrecorded when category 5 cyclones have crossed the coast. Also, measurements of such winds are inherently going to be suspect as instruments often are completely destroyed or damaged at these speeds. The Onslow anemometer was destroyed after measuring the gust of 246 km/h during Trixie in 1975 as was the Darwin anemometer during Tracy also in 1974.

Lowest Pressure

The lowest pressure recorded in Western Australia was 905 hPa at North Rankin A gas platform during cyclone Orson on 22-23 April 1989. On the Western Australian mainland the lowest pressure measured was 921 hPa at Onslow in 1961. In January 1980, 932 hPa was recorded at Goldsworthy as cyclone Amy passed approximately 10 km to the west.

Highest Rainfall

The maximum rainfall recorded during a Western Australian cyclone was 927 mm in 36 hours (747 mm in 24 hours) at Whim Creek in 1898. La Grange (now Bidyadanga) recorded 616 mm of rain in 72 hours during cyclone Bessie in January 1964 and 532 mm (24 hours) during cyclone Sally in December 1971. Cyclone Joan produced rainfall totals in excess of 600 mm near Tom Price in December 1975.

Globally, the highest rainfall events seem to have occurred at La Reunion in the western Indian Ocean.
12 h: 1144 mm at Foc-Foc (2290 m altitude) in Tropical Cyclone Denise, 7-8 January 1966;
24 h - 1825 mm at Foc-Foc (2290 m altitude), La Reunion during Tropical Cyclone Denise, 7-8 January, 1966;
48 h - 2467 mm at Aurere (940 m altitude), La Reunion on 8-10 April, 1958;
72 h - 3240 mm Grand-Ilet (1150 m altitude), La Reunion during Tropical Cyclone Hyacinthe 24-27 January, 1980.

Highest Sea Waves

There are few accurate recordings of the magnitude of waves generated by cyclones in the Australian region, but examination of damage to the underside of the North Rankin A gas platform following tropical cyclone Orson on 22-23 April 1989 indicated that waves in excess of 20 m had battered the base of the rig.

During a typhoon in the northwest Pacific on 6-7 February, 1933 the USS Ramapo recorded a wave of 34 m. Also in the northwest Pacific, a wave of 25 m was recorded on 26 September, 1935.

Highest Storm Surge

The large tidal range along the northwest coast reduces the incidence of storm surge flooding, but if tropical cyclones cross the coast at the time of high tide, storm surges could be devastating, particularly in semi-enclosed shallow waters. In the cyclone of February 1937, tidal waters estimated to be 4 to 5 m deep covered 14 km of the road from Hamelin Pool to Denham. In 1939, a storm surge at Port Hedland coincided with high tide causing a tide of 5.7 m Australian Height Datum (AHD). Seawater penetrated the sea wall washing away several houses and flooding the Pier and Esplanade Hotels. During cyclone Vance in 1999 the storm surge was measured to be 3.6 m at Exmouth and estimated to be 4 m at Onslow, increasing to an estimated maximum of more than 5 m west of Onslow near Tubridgi Point.

Most Deaths

There have been several historical Western Australian cyclones causing a significant loss of lives at sea. In March 1912 over 150 lives were claimed at sea. The coastal passenger vessel the Koombana was lost after setting out from Port Hedland to Broome with about 140 people on board. At least another 15 people died as other vessels went down in the same event. Click here for more information on this event.

There have been two events in WA when about 140 men perished in pearling fleet disasters:
- 22 April 1887 off Ninety Mile Beach.
- 26-27 March 1935 near the Lacepede Islands off Broome.

The greatest number of deaths from an Australian cyclone was in 1899 at Bathurst Bay in Queensland when a storm surge was responsible for the deaths of more than 300 people. The death toll in the infamous Bangladesh Cyclone of 1970 has had several estimates, some wildly speculative, but it seems certain that at least 300,000 people died from the associated storm tide in the low-lying deltas. In the 1991 Bangladesh cyclone more than 140,000 people drowned, primarily because of the storm surge.

Most Damage

Assessing the overall cost of cyclones is almost impossible to objectively quantify. Most estimates are based on insured losses and so neglect the true overall cost. In the Northwest much of the economic losses are a result of the impact on the mining industry in terms of both damage and lost production and these are usually unreported. According to the Emergency Management Australia database of Australian disasters, the costliest Western Australian cyclones have been TC Joan (1975) -$74M, TC Hazel (1979) -$41M, TC Alby (1978) -$39M and TC Vance (1999) -$35M (1998 dollars). Australia's most damaging cyclone was TC Tracy that destroyed 80 per cent of houses in Darwin costing an estimated $4 billion (1998 dollars). Globally, the costliest cyclone was Hurricane Andrew (1992) at Miami, for which unconfirmed estimates of US$20-25 billion in damage have been made.