Saturday, Jan 29, 2011 at 00:43
Reading through the posts it gives me the impression many of you think this cannot happen so far South,
READ ON.
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 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 eached its closest approach to the mainland about 60 km south of
Cape Leeuwin and 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.
FollowupID:
715436