4 April 1978
Tropical Cyclone Alby passed close to the southwest corner of WA on 4 April 1978 killing five people and causing widespread but mostly minor damage to the southwest. The damage bill was estimated to be $39 million (2003 dollars). One man was blown from the roof of a shed and a woman was killed by a falling pine tree. Another man was killed when a tree fell on the bulldozer he was operating and two men drowned at Albany when their dinghy overturned. Storm surge and large waves caused coastal inundation and erosion from Perth to Busselton. Fires fanned by the very strong winds burned an estimated 114 000 ha of forest and farming land.
Track and Intensity
A low developed on 27 March well north of the state, some 800 km north northwest of Karratha. It moved slowly to the southwest and steadily intensified, peaking on 2 April with estimated central pressure of 930 hPa (category 4 intensity) about 850 km west northwest of Carnarvon as shown in figure 1. The satellite image at 6pm (figure 2 (a)) shows a well-developed eye and banding structure - distinctive features of a strong tropical cyclone. Alby subsequently turned to the south southeast and accelerated from about 10 km/h to 25 km/h by midnight on the 3rd when it was 750 km west northwest of Geraldton. At about this time the satellite image (figure 2 (b)) showed a weakening in the eye and banding structure around the centre, and a broad mass of cloud to the south ahead of a cold front approaching from the southwest. This pattern indicates that Alby was changing into an extra-tropical system.
On the 4th Alby continued to accelerate, being captured by strong upper-level northwest winds. The satellite image at 5 pm (figure 2 (c)) showed a complete absence of storms near the centre and the eastern half of the cyclone virtually devoid of cloud. The front had merged with the broad mass of cloud south of the centre. This pattern is very different from that associated with a mature tropical cyclone yet it was still estimated as a category 3 system with a central pressure of 960 hPa. The maintenance of such intensity from the tropics to the mid-latitudes, referred to as 'extra-tropical transition', is explained in detail in Foley and Hanstrum (1994) (see schematic of cyclone undergoing extra-tropical transition). By 9 pm the system reached its closest approach to the mainland about 60 km south of Cape Leeuwin, moving at 80 km/h to the southeast. The centre of the system was 250 km southwest of Perth at its closest. The centre became difficult to locate on the 5th as it moved south of 40°S.
The table below shows the maximum gusts recorded in the South West Land Division during 4 April. Albany recorded the highest gust of 150 km/h while Fremantle registered a gust of 143 km/h. Winds increased abruptly on the 4th as Alby accelerated closer. Gales commenced in Perth city at 2:30 pm and the maximum gust of 130 km/h was the third highest gust recorded at a Perth city site in the record from 1942 to 2004. Gales lasted for almost seven hours at Fremantle, while winds exceeded storm force (90 km/h) for four hours. Gale-force winds were widespread, occurring throughout most of the South West Land Division.
|Location||Highest Gust (km/h)||Time (WST)|
|Collie||>139||12:30 - 20:30|
|Bunbury||>130||18:25 - 21:08|
Figure 1. Track of Alby.
Click on image to enlarge.
Figure 2. Infra-red satellite imagery showing Alby as it moved from the tropics to the mid-latitudes.(GMS images courtesy of Japan Meteorological Agency).
(a) 6pm 2 April
(b) 2 am 4 April
(c) 5pm 4 April 1978
Wind damage was extensive, but the greatest damage occurred in coastal areas south of Perth between Bunbury and Albany. There were no reports of houses being completely destroyed but partial roof damage was common.
Existing fires (normal end-of-harvest burn-off), combined with fires started on that day, exploded into wildfires with measured rates of spread of between 5 and 10 km/h. This resulted in an estimated 114 000 ha of forest and farm land being burned. The strong winds and dry conditions produced extensive dust storms that reduced visibility over a large area of the southwest on the afternoon of the 4th. The deposition on power lines of dust and, in coastal areas, salt eventually caused a failure of the electricity distribution system.
Large waves and a storm surge generated by the northerly winds caused substantial coastal erosion along the Lower West coast, particularly in the Geographe Bay area. Low-lying areas at Bunbury and Busselton were flooded, forcing the evacuation of many homes, including the Bunbury Nursing Home. Photo 2 shows floodwaters through the streets of Bunbury. An approximately 1.1 m storm surge at Busselton caused the tide to peak at 2.5 m about 1 m above the highest astronomical tide. The Busselton Jetty was severely damaged. At Fremantle the surge was about 0.6 m causing a high tide of 1.8 m, about 0.5 m above the highest astronomical tide. While this was not sufficient to cause flooding in Perth it did combine with large waves to scour beaches, as shown in photo 1. A large number of small boating craft were damaged.
By contrast there was little rainfall during the event. Perth did not record any rainfall and the heaviest rainfall in the southwest was less than 40 mm.
Photo 1. Coastal erosion on Perth's beaches.Photo reproduced courtesy of The West Australian.
Photo 2. Flooding in Bunbury.Photo reproduced courtesy of The West Australian.