Cyclone Kathy

Meteorological history

On 16 March 1984, the Bureau of Meteorology began monitoring a tropical low off the southern coast of Papua New Guinea for possible development into a tropical cyclone. Over the following day, the system quickly developed and attained gale-force winds as it neared the Cape York Peninsula. Attaining a pressure of 990 hPa (mbar; 29.23 inHg), the weak system made landfall just north of Weipa, Queensland on 19 March before losing strength. Though already considered a tropical cyclone for two days by the Bureau, the Joint Typhoon Warning Center (JTWC) issued their first advisory on the system just prior to its landfall; however, they considered it to be a tropical depression rather than a storm. After roughly 12 hours over land, a weakened Kathy emerged over the warm waters of the Gulf of Carpentaria on 20 March. Once over water, the JTWC classified the system as a tropical storm. Turning southwestward, the storm entered a region favoring significant development and soon began a period of rapid intensification.

Intensification took place through 22 March as convection deepened around Kathy's centre and a well-defined eye formed. The system reached its peak strength as a Category 5 severe tropical cyclone on the Australian tropical cyclone intensity scale with ten-minute sustained winds of 205 km/h (125 mph). Operational analysis of the storm indicated a minimum pressure of 920 hPa (mbar; 27.17 inHg); however, a reassessment in 2009 concluded that Kathy's pressure had been slightly lower, bottoming out at 916 hPa (mbar; 27.05 inHg). Additionally, the JTWC assessed the system to have been slightly stronger, estimating peak one-minute sustained winds at 250 km/h (155 mph). At this time, the storm was estimated to have a Dvorak technique rating of 7.0, equivalent to a Category 5 on the Saffir–Simpson Hurricane Scale;

As Cyclone Kathy neared the Australia coastline later on 22 March, it began to weaken as it interacted with land. Radar imagery depicted the system as having an eye 10.8 km (6.7 mi) in diameter. Roughly 5 hours after peaking, the storm passed directly over the Sir Edward Pellew Group of Islands, resulting in a degrading structure. Near midnight, the system weakened to a Category 4 cyclone and made landfall in a remote region near Borroloola. Based on a wind gust to sustained ratio of 1.4, Kathy was estimated to have moved onshore with winds between 165 and 185 km/h (105 and 115 mph). In the hours after landfall, Kathy rapid weakened, no longer retaining gale-force winds once 200 km (120 mi) away from the Gulf on 23 March. Later that day, the system turned south-westward and persisted for another 24 hours before dissipating.

Impact

In Far North Queensland, Kathy brought moderate rainfall and strong winds to much of the region. No measurements from the centre of the storm were made, although a wind gust of 60 km/h (37 mph) was recorded in Batavia Downs, Queensland, about 55 km (34 mi) south-southeast of the cyclone. Between 18 and 21 March, a total of 126.7 mm (4.99 in) of rain fell near Batavia Downs. Due to the relatively low intensity of the storm, damage was minimal and mainly confined to trees.

Striking the Sir Edward Pellew Group of Islands as a high-end Category 4 cyclone, Kathy wrought significant damage in the region. A storm surge of 4.2 m (14 ft) struck Vanderlin Island, destroying much of the nesting ground for sea turtles. Winds were recorded up to 232 km/h (144 mph) before the station's anemometer failed. Several camps across the islands were destroyed. Offshore, 20 vessels were caught in the storm, one of which sank and three others ran aground. One person perished on board the ship that sank during the storm. Losses sustained by the ships were placed at A$5 million (A$12.7 million 2011 AUD; US$10 million 2011 USD).

Though a powerful storm, only light to moderate rains fell along the cyclone's path with totals generally less than 100 mm (3.9 in). The remnants, however, triggered thunderstorms near Tennant Creek that produced 325 mm (12.8 in) of rain in 24 hours. Reports indicate that several sea turtles and dugongs were washed up to 8 km (5.0 mi) inland by Kathy's surge. The only population center significantly affected by the storm was Borroloola, where moderate to severe damage took place. At least one home was destroyed and many more were damaged in the town. Along the mouth of the McArthur River, near where Kathy struck the mainland, the combination of severe winds and storm surge killed 80% (±20%) of the Rhizophoraceae mangrove trees in the region. Along the entire length of the river, 45% (±15.3%) of the Rhizophoraceae, Bruguiera and Ceriops as well as 18.5% (±11.4%) of the Exoecaria agallocha, Lumnitzera racemosa and Avicennia marina perished. In all, losses from the storm were placed at A$12 ,million (A$30.5 million 2011 AUD; US$24.1 million 2011 USD).

In the wake of the storm, Australian Prime Minister Bob Hawke promised residents of Borroloola that they would receive all possible help from the government. About 400 people in the town were left homeless by Cyclone Kathy. By 25 March, a Royal Australian Air Force aircraft was sent to the region carrying emergency supplies for sheltering displaced persons. Two patrol boats from the Royal Australian Navy were also sent to assist in relief efforts. One brought fuel and medical supplies and the other assisted trawlers set adrift or grounded by the storm. Following its usage, the name Kathy was retired from Brisbane's list of cyclone names and will never be used again.