Cyclone Joan
| Category 5 severe tropical cyclone (Aus scale) | |
|---|---|
| Category 4 (Saffir–Simpson scale) | |
Cyclone Joan at peak intensity
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| Formed | 30 November 1975 |
| Dissipated | 10 December 1975 |
| Highest winds |
10-minute sustained: 230 km/h (145 mph) 1-minute sustained: 230 km/h (145 mph) |
| Highest gust | Gusts: 260 km/h (160 mph) |
| Lowest pressure | 915 hPa (mbar); 27.02 inHg |
| Fatalities | None |
| Damage | $31 million (1975 USD) |
| Areas affected | Western Australia |
| Part of the 1975–76 Australian region cyclone season | |
Severe Tropical Cyclone Joan was an intense tropical cyclone that ravaged areas of Western Australia. Forming out of a tropical low on 30 November 1975, Joan gradually intensified as it tracked towards the west. After attaining Category 5 intensity on 5 December, the storm abruptly began to track southward and accelerated. The following day, the cyclone reached its peak intensity with winds of 230 km/h (140 mph) and a barometric pressure of 915 hPa (mbar; 27.02 inHg). Joan only slightly weakened before making landfall in the vicinity of Mundabullagana. The cyclone rapidly weakened after landfall before dissipating over Western Australia on 12 December.
Although no fatalities resulted from Joan, the cyclone caused widespread destruction across areas of Western Australia. In Port Hedland, most of the structures were damaged as a result of the storm. In addition 1,000 homes in the town were damaged or destroyed. Further inland record rainfall caused widespread flooding in many areas, causing many rivers and streams to overflow. Due to the severity of the storm, the name Joan was retired after the season.
Cyclone Joan originated from a large cloud mass that formed northwest of Darwin on 30 November 1975. Due to its possibility of formation, the Australian Bureau of Meteorology began to monitor the system, issuing a tropical cyclone alert on the same day. Tracking southwest, the system gained organization, at which time it received the name Joan on the next day. As Joan progressed to the southwest, it steadily intensified in favorable conditions, strengthening into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale on the same day.
Joan continued to steadily intensify as it moved to the southwest, attaining Category 3 status on 2 December, classifying Joan as a severe tropical cyclone. On 5 December, the cyclone intensified into a Category 5 cyclone, the highest rating on the Australian tropical cyclone intensity scale with winds of 200 km/h (120 mph). The next day, the forward motion of the storm slowed as it passed to the north of Rowley Shoals before abruptly turning towards the south toward the Australian coast. Joan reached peak intensity on 7 December as it was moving south, with maximum wind speeds of 230 km/h (140 mph) and a minimum barometric pressure of 915 hPa (mbar; 27.02 inHg), based on Dvorak satellite intensity estimates.
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