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Cyclone Tracy
Severe Tropical Cyclone Tracy was a small but destructive tropical cyclone that devastated the city of Darwin, in the Northern Territory of Australia, in December 1974. The small but developing easterly storm was originally expected to pass clear of the city, but it turned towards it early on 24 December. After 10:00 p.m. ACST, damage became severe, with wind gusts reaching 217 km/h (117 kn; 135 mph) before instruments failed. The anemometer in Darwin Airport control tower had its needle bent in half by the strength of the gusts.
Residents of Darwin were celebrating Christmas, and they did not immediately acknowledge the emergency, partly because they had been alerted to an earlier cyclone (Selma) which passed west of the city, not affecting it in any way. Additionally, news outlets had only a skeleton crew on duty over the holiday.
The fatality count from Tracy was 66 people, while the damage it caused was A$837 million (about A$7.69 billion in 2022; approximately US$5.2 billion in 2022). It destroyed more than 70 percent of Darwin's buildings, including 80 percent of houses. It left more than 25,000 out of the 47,000 inhabitants of the city homeless prior to landfall and required the evacuation of over 30,000 people, of whom many never returned. After the storm passed, the city was rebuilt using more stringent standards "to cyclone code". At the time, Tracy held the record worldwide for the smallest tropical cyclone in terms of gale-force wind diameter, a record that was held for 34 years until it was broken by Tropical Storm Marco in the Atlantic basin of 2008.
On 20 December 1974, the United States' ESSA-8 environmental satellite recorded a large cloud mass centred over the Arafura Sea about 370 km (230 mi) northeast of Darwin. This disturbance was tracked by the Darwin Weather Bureau's regional director Ray Wilkie, and by senior meteorologist Geoff Crane. On 21 December, the ESSA-8 satellite showed evidence of a newly formed circular centre near latitude 8° south and longitude 135° east. Crane - the meteorological duty officer at the time - issued the initial tropical cyclone alert, describing the storm as a tropical low that could develop into a tropical cyclone.
Later in the evening, the Darwin meteorological office received an infrared satellite image from the National Oceanic and Atmospheric Administration's satellite, NOAA-4, showing that the low pressure had developed further and that spiralling clouds could be observed. The storm was officially pronounced a tropical cyclone at around 10 p.m. on 21 December, when it was around 200 km (125 mi) to the north-northeast of Cape Don (360 km (225 mi) northeast of Darwin). Cyclone Tracy was first observed on the Darwin radar on the morning of 22 December.
Over the next few days, the cyclone moved in a southwesterly direction, passing north of Darwin on 22 December. A broadcast on ABC Radio that day stated that Cyclone Tracy posed no immediate threat to Darwin. However, early in the morning of 24 December, Tracy rounded Cape Fourcroy on the western tip of Bathurst Island, and moved in a southeasterly direction, straight towards Darwin. The bureau's weather station at Cape Fourcroy measured a mean wind speed of 120 km/h (75 mph) at 9:00 that morning.
By late afternoon on 24 December, the sky over the city was heavily overcast, with low clouds, and was experiencing strong rain. Wind gusts increased in strength; between 10 p.m. (local time) and midnight, the damage became serious, and residents began to realise that the cyclone would not pass by the city, but over it. On 25 December at around 3:30 a.m., Tracy's centre crossed the coast near Fannie Bay. The highest recorded wind gust from the cyclone was 217 kilometres per hour (135 mph), which was recorded around 3:05 a.m. at Darwin Airport. The anemometer (wind speed instrument) failed at around 3:10 a.m., with the wind vane (wind direction) destroyed after the cyclone's eye passed over. The Bureau of Meteorology's official estimates suggested that Tracy's gusts had reached 240 kilometres per hour (150 mph). The lowest air pressure reading during Tracy was 950 hectopascals (28.05 inHg), which was taken at around 4 a.m., by a Bureau staff member at Darwin Airport. This was recorded during the eye of the cyclone. From around 6:30 a.m., the winds began to ease, with the rainfall ceasing at around 8:30 a.m. After making landfall, Tracy rapidly weakened, dissipating on 26 December. Total rainfall in Darwin from Cyclone Tracy was at least 255 mm (10.0 in).
Darwin had been severely battered by cyclones before: in January 1897 and again in March 1937. However, in the 20 years leading up to Cyclone Tracy, the city had undergone a period of rapid expansion. E.P. Milliken estimated that on the eve of the cyclone there were 43,500 people living in 12,000 dwellings in the Darwin area. Though building standards at the time required that some attention be given to the possibility of cyclones, most buildings were not capable of withstanding the force of a cyclone's direct hit.
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Cyclone Tracy
Severe Tropical Cyclone Tracy was a small but destructive tropical cyclone that devastated the city of Darwin, in the Northern Territory of Australia, in December 1974. The small but developing easterly storm was originally expected to pass clear of the city, but it turned towards it early on 24 December. After 10:00 p.m. ACST, damage became severe, with wind gusts reaching 217 km/h (117 kn; 135 mph) before instruments failed. The anemometer in Darwin Airport control tower had its needle bent in half by the strength of the gusts.
Residents of Darwin were celebrating Christmas, and they did not immediately acknowledge the emergency, partly because they had been alerted to an earlier cyclone (Selma) which passed west of the city, not affecting it in any way. Additionally, news outlets had only a skeleton crew on duty over the holiday.
The fatality count from Tracy was 66 people, while the damage it caused was A$837 million (about A$7.69 billion in 2022; approximately US$5.2 billion in 2022). It destroyed more than 70 percent of Darwin's buildings, including 80 percent of houses. It left more than 25,000 out of the 47,000 inhabitants of the city homeless prior to landfall and required the evacuation of over 30,000 people, of whom many never returned. After the storm passed, the city was rebuilt using more stringent standards "to cyclone code". At the time, Tracy held the record worldwide for the smallest tropical cyclone in terms of gale-force wind diameter, a record that was held for 34 years until it was broken by Tropical Storm Marco in the Atlantic basin of 2008.
On 20 December 1974, the United States' ESSA-8 environmental satellite recorded a large cloud mass centred over the Arafura Sea about 370 km (230 mi) northeast of Darwin. This disturbance was tracked by the Darwin Weather Bureau's regional director Ray Wilkie, and by senior meteorologist Geoff Crane. On 21 December, the ESSA-8 satellite showed evidence of a newly formed circular centre near latitude 8° south and longitude 135° east. Crane - the meteorological duty officer at the time - issued the initial tropical cyclone alert, describing the storm as a tropical low that could develop into a tropical cyclone.
Later in the evening, the Darwin meteorological office received an infrared satellite image from the National Oceanic and Atmospheric Administration's satellite, NOAA-4, showing that the low pressure had developed further and that spiralling clouds could be observed. The storm was officially pronounced a tropical cyclone at around 10 p.m. on 21 December, when it was around 200 km (125 mi) to the north-northeast of Cape Don (360 km (225 mi) northeast of Darwin). Cyclone Tracy was first observed on the Darwin radar on the morning of 22 December.
Over the next few days, the cyclone moved in a southwesterly direction, passing north of Darwin on 22 December. A broadcast on ABC Radio that day stated that Cyclone Tracy posed no immediate threat to Darwin. However, early in the morning of 24 December, Tracy rounded Cape Fourcroy on the western tip of Bathurst Island, and moved in a southeasterly direction, straight towards Darwin. The bureau's weather station at Cape Fourcroy measured a mean wind speed of 120 km/h (75 mph) at 9:00 that morning.
By late afternoon on 24 December, the sky over the city was heavily overcast, with low clouds, and was experiencing strong rain. Wind gusts increased in strength; between 10 p.m. (local time) and midnight, the damage became serious, and residents began to realise that the cyclone would not pass by the city, but over it. On 25 December at around 3:30 a.m., Tracy's centre crossed the coast near Fannie Bay. The highest recorded wind gust from the cyclone was 217 kilometres per hour (135 mph), which was recorded around 3:05 a.m. at Darwin Airport. The anemometer (wind speed instrument) failed at around 3:10 a.m., with the wind vane (wind direction) destroyed after the cyclone's eye passed over. The Bureau of Meteorology's official estimates suggested that Tracy's gusts had reached 240 kilometres per hour (150 mph). The lowest air pressure reading during Tracy was 950 hectopascals (28.05 inHg), which was taken at around 4 a.m., by a Bureau staff member at Darwin Airport. This was recorded during the eye of the cyclone. From around 6:30 a.m., the winds began to ease, with the rainfall ceasing at around 8:30 a.m. After making landfall, Tracy rapidly weakened, dissipating on 26 December. Total rainfall in Darwin from Cyclone Tracy was at least 255 mm (10.0 in).
Darwin had been severely battered by cyclones before: in January 1897 and again in March 1937. However, in the 20 years leading up to Cyclone Tracy, the city had undergone a period of rapid expansion. E.P. Milliken estimated that on the eve of the cyclone there were 43,500 people living in 12,000 dwellings in the Darwin area. Though building standards at the time required that some attention be given to the possibility of cyclones, most buildings were not capable of withstanding the force of a cyclone's direct hit.