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An Overview and Brief History of Southern Hemisphere Tropical Cyclones
(Released June 2012)

podcast link 
  by Adam Arnold  


Key Citations




Australian and Southwest Pacific Regions


The Australian and Southwest Pacific areas consist of two main regions warned by the Australian Bureau of Meteorology (consisting of three RSMCs at the Perth, Darwin, and Brisbane Tropical Cyclone Warning Centres) and RSMC Nadi, Fiji. There are also two smaller regions warned by RSMC Port Moresby, Papua New Guinea and RSMC Wellington, New Zealand.  The Australian region is the most active region in the southern hemisphere for tropical cyclones with the western Australian region being the most pronounced for activity. The strongest tropical cyclone on official record in the southern hemisphere was located in the Fiji region. Within the Australian region, the Bureau of Meteorology uses a classification scale for tropical cyclones that is similar to the Saffir-Simpson scale with a few notable exceptions. The Saffir-Simpson scale is based on 1-minute average sustained winds, while the Australian scale uses peak gusts. In addition, there are only five categories on the Australian scale compared to seven on the Saffir-Simpson (including tropical depression and tropical storm strengths).  Tropical Cyclone Mahina, sometimes known as the Bathurst Bay Hurricane/Cyclone of 1899, produced the largest recorded storm surge (roughly 13 m or 42 ft) when it made landfall in the far north of Queensland, which resulted in fish and dolphins being found on top of 15 m cliffs (Hurricane Research Division, “Frequently Asked Questions”).

Similar to how we usually think of hurricanes such as Camille, Andrew, and Katrina with respect to memorable tropical cyclones in the United States, Severe Tropical Cyclone Tracy is the general standard for tropical cyclones in Australia. Tracy was classified as a tropical cyclone on 21 December 1974 while in the Arafura Sea between Australia and New Guinea. For the next few days, Tracy traveled southwest while intensifying. By 24 December 1974, Tracy had turned east-southeastwards towards Darwin. Late on the same day, Tracy reached its peak intensity of maximum gusts of 236 km/h- a category 4 cyclone on the Australian scale. Tracy would maintain this intensity until it made landfall near Darwin, Northern Territory early on 25 December 1974. Due to the fact that it was Christmas, and because a tropical cyclone of such intensity had not hit Darwin in many years, many residents were caught unprepared for the storm (Australia, “Cyclone Tracy, Christmas 1974”), resulting in 65 people perishing in the tropical cyclone. In addition, the building standards of that time were lax resulting in very loosely fabricated structures. This resulted in the destruction of a majority of buildings in Darwin. This immense devastation disrupted the lives of all Darwinians, and several weeks later, three-quarters of the population of the city left. Today, Darwin is the thriving capital city of the Northern Territory, but it took many years of recovery and public education towards stricter building codes and planning.
Tropical cyclone scales
A comparison of the Saffir-Simpson Hurricane Scale and the Australian Region Tropical Cyclone Intensity Scale

Severe Tropical Cyclone Yasi was one of the most intense cyclones to make landfall on the eastern Queensland coast. Yasi was classified as a tropical cyclone by RSMC Nadi on 30 January 2011 while north of Vanuatu. While moving westward, Yasi intensified quickly, becoming a category 3 on the Australian scale by the evening of the 31 January 2011. By the 02 February 2011, Yasi was moving west-southwestwards through the Coral Sea, reaching category 5 strength. Yasi was able to maintain this strength until it made landfall on the Queensland coast near Mission Beach very early on 03 February 2011. Due to Yasi’s very large size, it was still classified as a tropical cyclone for an abnormally long amount of time as it moved inland, finally weakening to a tropical low near 10 PM on 03 February 2011 near Mount Isa, Queensland. One major fear during Yasi’s approach to the coast was that it would make landfall near high tide resulting in a much larger storm surge, but fortunately Yasi was slow enough to avoid this, making landfall as the tides were falling. Still, the surge was immense, with a 5 m storm surge being recorded at a tidal gauge in Cardwell, and possibly higher surges up to 7 m closer to the center. These storm surge levels resulted in the annihilation of most structures along the coast near the center of landfall. In addition, winds gusting up to 290 km/h were estimated to occur near the center at landfall (“Yasi Wreaks Havoc But No Fatalities”). These impacts, along with torrential rain, resulted in many towns being devastated. The town of Tully was described as a “war zone” (Agius 2011) with 90% of structures along the town’s main street extensively damaged (“Yasi Wreaks Havoc But No Fatalities”). In addition, the larger coastal towns of Cardwell, Innisfail, and Townsville received varying ranges of storm surge inundation in addition to high winds which caused damage to many buildings.
Satellite image of Tropical Cyclone Yasi
In this GOES satellite image from the National Oceanic and Atmosphere Administration (NOAA), category five cyclone Yasi nears the north coast of Queensland, Australia on February 2, 2011 as seen from space.

The most intense tropical cyclone on record in the southern hemisphere was Tropical Cyclone Zoe in 2002. Zoe was classified as a tropical cyclone by RSMC Nadi on 25 December 2002 while several hundred miles north of Fiji in the southwest Pacific Ocean. Over the next few days, Zoe intensified steadily, but quickly, while moving towards the west-southwest. By 27 December 2002, Zoe had become a category 5 cyclone on the Australian scale with 1-minute sustained winds of 285 km/h. At this time, Zoe became the strongest tropical cyclone on record in the southern hemisphere by recording a record low minimum barometric pressure of 890 hPa. Between the 27 and 29 December 2002, Zoe moved very slowly while passing over or near several small islands in Vanuatu and the Solomon Islands. Two of these islands, Tikopia and Anuta, bore the brunt of Zoe’s 350 km/h wind gusts and 12 m waves. Aerial photographs revealed that vegetation had been stripped from the islands, and the sites of 15 villages appeared as just sand and debris (Chapman 2003). The people of Tikopia, initially thought to be lost, had taken shelter in caves on the island resulting in no loss of life. On 29 December 2002, Zoe began moving southeasterly towards colder waters and weakening, finally dissipating on 01 January 2003 several hundred miles south-southwest of Fiji.

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