Tropical Cyclones Affecting Exmouth

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Located on the western tip of the Pilbara coast, the most cyclone-prone part of Australia's coast, Exmouth has felt the full force of one of the strongest cyclones in Australia's history. In March 1999 tropical cyclone Vance moved down Exmouth Gulf causing winds recorded to 267 km/h, the highest ever wind gust measured on the Australian mainland (see TC Vance (pdf report)).

It is difficult to compare historical cyclones prior to Exmouth being developed in the 1960s. The pearling fleet from Port Hedland regularly visited Exmouth Gulf in the late 1800s and in December 1875 a cyclone devastated the fleet sinking several boats and claiming 59 lives. Pastoral stations and then the Cape Vlamingh lighthouse (1911) provided some details of cyclones during the early years. The first recorded major cyclone impact was in February 1945 when the three-year old naval base was extensively damaged and troops were withdrawn.

Overall it is estimated that a cyclone impact causing wind gusts in excess of 90 km/h in the vicinity of Exmouth occurs about once every two to three years on average. However, the frequency is not evenly distributed. Since 1982 there have only been three cyclones causing gales, including Vance, but there were fourteen cyclones in the previous twenty years. Although the inadequacy of early wind records make it difficult to compare events, it is estimated that there have been four severe cyclones causing winds of at least 170 km/h since 1910: 1945, 1953, 1964 (Katie) and 1999 (Vance).

Along the central Pilbara coast the cyclone season runs from mid December to April peaking in February and March as shown in the graph of monthly occurrence (figure 4).

The development of the offshore oil and gas industries, and more recently, the tourism industry has increased the damage potential of cyclones in the region. Substantial economic losses can be incurred even with the threat of a cyclone impact owing to lost production or disruptions to shipping activities. Fortunately modern structures are built according to cyclone wind ratings and are far less susceptible to damaging winds than those constructed in earlier times.

Figure 1. Satellite image of TC Vance near Exmouth, 22 March 1999.

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Figure 2. Radar image of TC Vance near Exmouth, 22 March 1999. Click on image to enlarge.

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Tracks

Cyclones that impact Exmouth typically form over warm ocean waters to the north of the state. The typical steering of these systems is to the southwest and they tend to take a more southerly track as they move further south as shown in figure 3. Some cyclones have originated from near the west Kimberley coast while a few have arrived from the north or northwest. Fortunately cyclones that cross the coast more than 100 km to the east, usually have a minimal impact on Exmouth, for example Orson 1989, Bobby 1995, Olivia 1996, and Monty2004.

See also the Interactive Tropical Cyclone Plotting web page to access tracks of historical tropical cyclones.

Figure 3. Tracks of notable cyclones affecting the Exmouth region. Click on image to enlarge.

Figure 4. Monthly occurrence of cyclones affecting the Exmouth region. Click on image to enlarge.

Flooding

By not being on a major river, Exmouth is not at risk of major flooding caused by rainfall alone. Localised flooding is certainly possible in susceptible areas especially near creeks and low-lying areas. The road link to the south is particularly vulnerable to being cut-off for a period following heavy rain. Major flooding in Exmouth is typically associated with storm surge, as discussed in the next section.

The heaviest rainfall is not necessarily associated with the most intense cyclones but rather with the cyclone's track, speed and areal extent. A tropical cyclone in 1918 caused 377.1 mm over two days at Exmouth Gulf station. Cyclone Rita in 1971 produced 226.6 mm of rain at Learmonth and 194.8 mm at Exmouth. Wind damage was minimal in both of these events.

Storm Surge

Storm surge is a major threat around Exmouth Gulf. Storm surge is a complex function of cyclone intensity and motion, extent of maximum winds, bathymetry and coastline shape. The actual water level, called the storm tide is a combination of the storm surge and tidal variation. The worst case scenario is to have a severe cyclone pass near the town at the time of high tide, in which case the water level will be many metres above the highest astronomical tide. Given the significant tidal variations in the region, this is a rare occurrence. Even with an intense cyclone the highest surge is typically restricted to less than 80 km of the coast owing to the nature of the extent of a cyclone's maximum winds.

The graphic impact of TC Vance on the coast around Exmouth Gulf indicates how a storm surge can change the appearance of the coastline (see TC Vance report (pdf)). However, even during this event it was fortunate the 3.5 m storm surge did not occur at the time of high tide (see storm surge graph).

Figure 5. The altered coastline east of Exmouth towards Onslow from TC Vance, 1999.

Some Notable Cyclones Impacting Exmouth

Tropical CycloneWind Gust (km/h) Impact Description
24 Dec. 1875- A total of 59 lives were lost as a cyclone wrecked the pearling fleet in Exmouth Gulf. The schooners Lily of the Lake, Wild Wave and Blossom were lost, while others were either wrecked or severely damaged. The barometer was measured to 27.9 inches (945 hPa).
20 Jan. 1909-

The schooner Rescue and three luggers were dismasted.

Water rose 7.2 m above the high water mark.

28 Feb 1943- The house and sheds were unroofed, a windmill was blown down and a tank burst. Other windmills were put out of order. Trees were uprooted and sandhills shifted.
2 Feb 1945190 (Exmouth Gulf) Iron telegraph poles were bent level with the ground. A barge was blown onto the airstrip. All RAAF huts and most US Army huts were demolished. Three RAAF personnel were drowned and two US sailors were washed off a destroyer and drowned off North West Cape. All buildings and windmills were wrecked at Exmouth Gulf and Mia Mia stations and most were severely damaged at Yardie Creek station.
22 Mar 1953- Learmonth recorded its highest daily fall of 254 mm. Damage was estimated at 35,000 pounds at Learmonth. The eye passed over Mia Mia Station between 9:10 and 10:30pm. Seventeen buildings were destroyed or damaged, many stock were drowned, and rivers and creeks were flooded. Considerable damage was also done to Exmouth Gulf and Yardie Creek stations.
Katie, 29 Mar 1964213 (Exmouth Gulf) At Learmonth, the construction camp and other facilities, including the mess hall, were damaged. A pile driving barge broke loose and was swamped, and two lighters were blown down at Learmonth and North West Cape. The US Navy barracks at Northwest Cape were severely damaged. Exmouth Gulf recorded 246 mm of rain.
Glynis, 1 Feb 1970213 (Navy Base) At Exmouth Gulf roofs of over 60 houses were damaged. Two houses were completely unroofed, several other buildings were wrecked or substantially damaged, and 20 caravans damaged beyond repair.
Ingrid, 15 Feb 1970- The second cyclone in two weeks damaged thirty houses and destroyed 18 m of the Learmonth fishing jetty.
Beverley, 31 March 1975152 (Navy Base)

Trees were uprooted and power lines brought down at Exmouth Gulf.

Three prawn trawlers were blown onto the beach. Structural damage was caused to the Pistol Club, the Yacht Club and Norcape Lodge.

Extensive repair work was required on the Learmonth jetty as some of the vertical timbers were also damaged. Damage in the area was estimated at $600,000.

The Coral Bay jetty was also washed away.

Vance, 22 March 1999267 One of the strongest cyclones to ever affect mainland Australia, Vance passed down Exmouth Gulf. Damage to Exmouth was extensive although most modern buildings withstood the winds. A 3.5 m storm surge caused widespread damage near the marina (see TC Vance report (pdf)).