Wild Land

The most powerful storm to graze Australia’s Queensland coast since Tropical Cyclone Rona in 1999 has rapidly deepened overnight.

Sunday 8th March 2009

A cyclone watch was issued by Australia’s Bureau of Meteorology on Thursday for residents of Queensland coastal communities between Cape Melville and Bowen, an area which includes Cairns and Townsville. The warning suggested that a low pressure system in the Coral Sea was expected to intensify and develop into a tropical cyclone as it drifted southward.

That evening, the low pressure system was formally identified as a category 1 tropical cyclone moving southward along the coast at 8 km/h. By Friday morning, the system had further intensified, being classed as a category 2 cyclone. The central pressure of the system continued dropping, with the category being raised to 3 around midnight. Category 3 cyclones pack wind gusts of 165-224 km/h.

During Saturday, the system deepened further, reaching category 4 (wind gusts between 225 and 279 km/h) mid-afternoon. Mackay, on Queensland’s coast, received over 170 mm of rain in five hours. Evacuations were ordred for some of the Whitsunday Islands.

By 10 p.m. Saturday, the Bureau of Meteorology had upgraded TC Hamish to category 5, reporting wind gusts of 295 km/h near the centre. The system had sped up a little, moving southeast at 17 km/h from a position outside the Great Barrier Reef, north-east of Townsville.

Current projections by the Bureau of Meteorology show TC Hamish tracking south-east offshore from Gladstone, reaching Lady Elliot Island (north-east of Bundaberg) on the morning of Tuesday 10th.

Queensland is no stranger to tropical cyclones. In March 2006 TC Larry (a category 4 cyclone) caused hundreds of millions of dollars-worth of damage to structures and crops but fortunately took no lives. Larry also brought torrential rain and a storm surge of about 2 metres to coastal communities.

Many of us also remember TC Monica, a category 5 cyclone which crossed the Cape York Peninsula heading west a month later. Fortunately, Monica weakened as she passed over the peninsula, but caused great alarm by deepening again over the Gulf of Carpentaria. In the end Monica also took no lives, but shredded trees and caused a storm surge on the coast.

Ingrid is another well-remembered cyclone of category 5 which followed a westerly path similar to Monica. This March 2005 cyclone wreaked havoc in Queensland, Northern Territory and West Australia by bringing heavy rain.

Memories of cyclone Ada of January 1970 send shivers down some spines. Ada brought flooding to mainland coastal communities and took 14 lives as it wrecked tourist resorts. Like Hamish, Ada passed through the Whitsunday Islands where it caused most damage.

A search for Queensland’s deadliest cyclone suggests that it was an event on the 10th of March 1918, when the town of Innisfail was flattened. The Bureau of Meteorology website notes that Innisfail had 3,500 residents at the time, and only 12 houses were left intact. It is estimated that 37 people died at Innisfail, and 40-60 at centres nearby. The associated storm surge reached 4.65 metres at Maria Creek.

Discussion on the New Zealand Weather Forum this morning considered the impact that a category 5 TC Hamish would have as it passes close to populated centres. One poster noted that building codes in North Queensland specify new buildings must survive a category 3 cyclone, while codes further south on the Sunshine Coast are more relaxed.

For New Zealand, this tropical cyclone is a timely reminder to check storm drains and spouting and make sure that they are clear of leaves and other debris. These weather systems often head our way, weakening as they do so. However, they can bring heavy rain and, if conditions are right, can deepen again as they approach our coasts.

[sources: New Zealand Weather Forum, family records and observations, projections and forecasts from the Australian Bureau of Meteorology. ]

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