A dangerous tropical cyclone with destructive winds and a potentially devastating storm surge is bearing down on the northeast coast of Australia. Named Ita, it is forecast to make landfall between Cape Melville and Cape Tribulation in Queensland late Friday local time. The violent storm has maximum wind gusts of over 185 mph (300 km/h) according to the Australia Bureau of Meteorology.
The storm is classified as a severe category 5 tropical cyclone on Australia’s 1-5 scale. This scale is slightly different from the Saffir-Simpson wind scale used in the U.S. and has a lower threshold for category 5. But Ita’s 185 mph gusts, and sustained winds of nearly 150 mph (according to the forecast of the Joint Typhoon Warning Center) would make it the equivalent of a major category 4 storm in the U.S.
The storm’s greatest potential hazard may well be its storm surge, the wall of ocean water powered onshore by the storm’s circulation and ocean waves. Hal Needham, a storm surge specialist at Louisiana State University, warns the cyclone is making landfall near the site of the largest storm surge ever recorded on Earth:
Ita will likely produce a large storm surge north of Cairns, with the highest levels likely north of Cape Flattery. Interestingly, the peak surge will likely be located just south of the location of Severe Tropical Cyclone Mahina’s massive storm surge in 1899. Although scientific sources disagree about the details of Mahina’s surge, many sources indicate that Mahina generated a 13.7-m (45 ft) storm tide near Bathurst Bay, Queensland. This water level ties Mahina with a Bangladesh surge in 1876 for the highest credible storm surge observation in the scientific literature. In short, Severe Tropical Cyclone Ita will likely produce a massive storm surge near the world’s highest (tied for highest) historical storm surge site.
(Needham notes that Ita with a central pressure of 934 mb is not quite as strong as Mahina at 915 mb, and probably won’t generate as large a surge).
A silver lining is that Ita’s projected landfall zone is not heavily populated.
“Ita is expected to hit the coast in a sparsely populated area. Only 9000 people live in the 200km stretch between Cape Melville and Cape Tribulation,” writes the Australian.
The Australia Bureau of Meteorology is urging those in the storm’s path to prepare:
Coastal residents between Cape Melville and Cape Tribulation including Cooktown are specifically warned of the dangerous storm tide as the cyclone crosses the coast later today. The sea is likely to rise steadily up to a level which will be significantly above the normal tide, with damaging waves, strong currents and flooding of low-lying areas extending some way inland.
The Weather Channel correctly points out: “The severity of the impacts in any one location will be dictated by exactly where the center of Ita tracks, which remains somewhat uncertain.”
According to the Australian, officials are concerned that if the storm shifts south towards Cairns (population of 150,000), more people are vulnerable.
Tropical cyclones on the north coast of Australia are fairly common from November to April.
“On average 4.7 tropical cyclones per year affect the Queensland Tropical Cyclone Warning Centre Area of Responsibility,” notes the Australia Bureau of Meteorology.