JOAN

History

Severe Tropical Cyclone Joan developed from a cluster of convection that appeared northwest of Darwin on 30 November 1975. The Bureau of Meteorology, recognising the system's potential, issued a tropical cyclone alert that same day, and as the low tracked southwest and became better organised it was named Joan on 1 December, reaching Category 1 strength shortly afterwards.

Moving steadily southwest through favourable conditions, Joan strengthened into a severe tropical cyclone at Category 3 on 2 December and continued to deepen, reaching Category 5 — the top of the Australian scale — on 5 December with winds near 200 km/h. The following day its forward speed eased as it passed north of Rowley Shoals, before the system swung sharply to the south and accelerated toward the Pilbara coast. Joan peaked on 7 December with estimated maximum winds of around 215 km/h and a central pressure of 915 hPa, derived from Dvorak satellite estimates. It weakened only marginally before crossing the coast near Mundabullangana late on 7 December as an extremely destructive system. Joan degraded gradually inland, then weakened rapidly after passing over the Hamersley Range on 8 December, with winds down to about 100 km/h by the end of that day. The remnants merged with a broad trough and dissipated around 10 December, though the Bureau continued tracking the system until 12 December.

Ahead of landfall, six alerts and 63 warnings were issued, with the coast from Kuri Bay to Exmouth placed under some form of advice. Port Hedland bore the brunt, recording a 2.6 m storm surge — estimated to have peaked near 3.25 m — although low tides limited inundation. Roughly 85 per cent of the town's houses were destroyed, about 1,000 homes damaged or destroyed, and 50 families left homeless; sand was piled up to 2 m deep along the shore. Inland, rainfall peaked at 591 mm near the Marandoo mine, breaking 24-hour records and flooding the Yule River, washing away railway lines and roads and isolating Wittenoom's food supply. Damage exceeded A$25 million, but no lives were lost. The name Joan was subsequently retired.

Sources: Bureau of Meteorology report Wikipedia