Severe Tropical Cyclone Joan was an intense tropical cyclone that ravaged areas of

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

. Forming out of a tropical low on 30 November 1975, Joan gradually intensified as it tracked towards the west. After attaining Category 5 intensity on 5 December, the storm abruptly began to track southward and accelerated. The following day, the cyclone reached its peak intensity with winds of 215 km/h (130 mph) and a

barometric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...

of 915 hPa (27.02 inHg). Joan only weakened slightly before making landfall in the vicinity of Mundabullagana. The cyclone rapidly weakened after landfall before dissipating over Western Australia on 12 December. Although no fatalities resulted from Joan, the cyclone caused widespread destruction across areas of Western Australia. In

Port Hedland A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Ha ...

, most of the structures were damaged as a result of the storm. In addition, 1,000 homes in the town were damaged or destroyed. Further inland, record rainfall caused widespread

flooding A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrolog ...

in many areas, causing many rivers and streams to overflow. Due to the severity of the storm, the name ''Joan'' was retired after the season.

Meteorological history

Cyclone Joan originated from a mass of

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the conve ...

that formed northwest of Darwin on 30 November 1975. Due to its possibility of tropical development, the

Australian Bureau of Meteorology Australian(s) may refer to: Australia * Australia, a country * Australians, citizens of the Commonwealth of Australia ** European Australians ** Anglo-Celtic Australians, Australians descended principally from British colonists ** Aboriginal Au ...

began to monitor the system, issuing a tropical cyclone alert on the same day. Tracking southwest, the system gained organization, at which time it received the name ''Joan'' on the next day. As Joan progressed to the southwest, it steadily intensified in favorable conditions, strengthening into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale on the same day. Joan continued to steadily intensify as it moved to the southwest, attaining Category 3 status on 2 December, classifying Joan as a severe tropical cyclone. On 5 December, the cyclone intensified into a Category 5 cyclone, the highest rating on the Australian tropical cyclone intensity scale with winds of . On the next day, the forward motion of the storm slowed as while it passed to the north of Rowley Shoals, before abruptly turning towards the south, toward the Australian coast. Joan reached its peak intensity on 7 December, as it was moving south, with maximum wind speeds of 215 km/h (130 mph) and a minimum

of 915

hPa HPA may refer to: Organizations * Harry Potter Alliance, a charity * Halifax Port Authority, Canada * Hamburg Port Authority, Germany * Hawaii Preparatory Academy, a school in Hawaii, US * Health Protection Agency, UK * Heerespersonalamt, the Ger ...

(

mbar The bar is a metric unit of pressure, but not part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa (100 kPa), or slightly less than the current average atmospheric pressure on Earth at sea lev ...

; 27.02 inHg), based on Dvorak satellite intensity estimates. Heading towards the south, Joan made landfall near Mundabullangana, Western Australia late on 7 December with winds of and an estimated pressure of 915 hPa (mbar; 27.02 inHg). After making landfall, the cyclone steadily weakened over land as it passed over areas of Western Australia. However, after crossing the

Hamersley Range The Hamersley Range is a mountainous region of the Pilbara region of Western Australia. The range was named on 12 June 1861 by explorer Francis Thomas Gregory after Edward Hamersley, a prominent promoter of his exploration expedition to the n ...

on 8 December, Joan began a phase a rapid weakening, and by the end of the day, its

maximum sustained wind The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unl ...

was only . The system became merged with a broad

low pressure area In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible ...

the next day before dissipating on 10 December. However, the Bureau of Meteorology continued to track the storm until 12 December.

Preparations and impact

Prior to making landfall on Western Australia, six tropical cyclone alerts and 63 cyclone warnings were issued by the Bureau of Meteorology on Joan. The most severe type, the second cyclone warning phase, began to be initiated in three hour intervals beginning on 6 December after Joan made an abrupt turn towards the south. A total of 23 warnings were issued in the second cyclone warning phase. All locations along the coast from

Kuri Bay Kuri Bay is a remote coastal bay in the far north of Western Australia in the Kimberley region, about north of Broome. It is a designated point on the Western Australian Forecast Areas, utilised by the Bureau of Meteorology as a boundary for ...

Exmouth Exmouth is a port town, civil parish and seaside resort, sited on the east bank of the mouth of the River Exe and southeast of Exeter. In 2011 it had a population of 34,432, making Exmouth the 5th most populous settlement in Devon. Histo ...

were issued a tropical cyclone alert or warning at least once during the duration of Cyclone Joan. Upon making landfall on 7 December, a storm surge was measured in

, although surge was estimated to have peaked at . However, since this occurred during lower

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

s, inundation of inland areas was not as severe as past tropical cyclones affecting the Port Hedland area. An estimated 85% of houses on Port Hedland were destroyed, with all structures near the coast being damaged to some degree. Due to nearly constant wave action,

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc sh ...

sand was piled to a depth of . An estimated 1,000 houses were destroyed in the town due to Joan. 50 families in Port Hedland were left homeless as a result of the cyclone. Further inland

resulted from heavy rains dropped by a weakening Joan. Rainfall peaked at near the

Marandoo mine The Marandoo mine is an iron ore mine located in the Pilbara region of Western Australia, 45 kilometres east of Tom Price. The mine is fully owned and operated by Rio Tinto Iron Ore and is one of seventeen iron ore mines the company operates ...

. Multiple locations recorded either near 24-hour rainfall records or broke the previous 24-hour rainfall records. Flooded streams resulted in

washaway A washaway is a particular kind of landslide that can affect man-made structures such as cuttings, embankments and bridges. They are thus a hazard to railways and road traffic. Overview The biggest danger with washaways is that they may be ...

s along railway lines. In addition the

Yule River The Yule River is an ephemeral river in the Pilbara region of Western Australia. It was named on 10 August 1861 by the surveyor and explorer Frank Gregory while on expedition in the area, after Thomas Newte Yule, at times farmer of Toodyay, w ...

was flooded by the heavy rains. The total repair cost of damages caused by floods in the

Pilbara The Pilbara () is a large, dry, thinly populated region in the north of Western Australia. It is known for its Aboriginal peoples; its ancient landscapes; the red earth; and its vast mineral deposits, in particular iron ore. It is also a g ...

region totaled to A$1.5 million (US$1.9 million). Food supply to Wittenoom became drastically limited after several roads were washed away. It was estimated that the

return period A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods, landslides, or river discharge flows to occur. It is a statistical measurement typ ...

s of the floods caused by Joan were in excess of 50 years. Total damages from the storm were estimated to be at least A$25 million (US$31 million), although no casualties were reported as a result of Cyclone Joan. Due to the severity of the storm, the name ''Joan'' was retired after the season.

Notes

References

External links

{{DEFAULTSORT:Joan

Joan Joan may refer to: People and fictional characters * Joan (given name), including a list of women, men and fictional characters *:Joan of Arc, a French military heroine * Joan (surname) Weather events *Tropical Storm Joan (disambiguation), multip ...

Retired Australian region cyclones 1975 in Australia 1974–75 Australian region cyclone season

Meteorological history

Preparations and impact

See also

Notes

References

External links