Cyclone Alby
Encyclopedia
Severe Tropical Cyclone Alby was regarded as the most devastating tropical cyclone
to impact southwestern Western Australia
on record. Forming out of an area of low pressure
on 27 March, Alby steadily developed as it tracked southwestward, parallel to Western Australia. Between 1 and 2 April, the storm quickly intensified and attained its peak intensity as a Category 5 cyclone on the Australian cyclone intensity scale. After turning to the southeast, the storm underwent an extratropical transition
as it neared Cape Leeuwin
. The storm brushed the cape on 4 April, bringing hurricane-force winds, before rapidly losing its identity the following day.
In Western Australia, the combination of Alby's fast movement and hurricane-force winds caused widespread damage. Along the coast, large swells
flooded low-lying areas and numerous homes lost their roofs from high winds. Further inland, bushfires were worsened by the storm as it brought little rain, generally less than 20 mm (0.78740157480315 in) along the coast. These fires burned roughly 114,000 hectare
s (281,700 acre
s) and destroyed two towns. Five fatalities are directly attributed to Alby while two more resulted from the fires. The resulting damage was extensive, with monetary losses reaching A$50 million ($45 million USD).
situated roughly 800 km (497.1 mi) north-northwest of Karratha. At this time, the system was characterised as a large cluster of convection
converging around the low. Notable development took place over the following three days as the system drifted towards the southwest. Convection began wrapping around the storm, forming banding features
. Early on March 29, the Joint Typhoon Warning Center
(JTWC), classified the system as a tropical storm. Shortly thereafter, the Bureau of Meteorology
in Perth
classified it as a tropical cyclone, assigning it with the name Alby. Gale force winds were later confirmed on 30 March by the Martha Bakke, located 385 km (239.2 mi) west-northwest of the storm's centre. By then, a large ragged eye
developed and Alby steadily intensified through 2 April. At the end of this strengthening, Cyclone Alby attained its peak intensity as a Category 5 on the Australian cyclone intensity scale; a barometric pressure of 930 mbar (hPa; 27.46 inHg) was measured at the time and peak winds were estimated to be 205 km/h (125 mph) based on the Dvorak technique
. Additionally, the JTWC assessed the storm to have attained winds of 215 km/h (135 mph), a low-range Category 4 on the Saffir–Simpson Hurricane Scale.
Shortly after reaching this intensity, Alby slowed as it began turning towards the southeast. By 3 April, the storm rapidly accelerated and attained a forward speed of 50 km/h (31.1 mph). This rapid acceleration was due to the cyclone's interaction with a cold front
to its south. Gradually weakening, Alby also underwent an extratropical transition
as the storm's structure became asymmetrical. Around 1300 UTC, the storm passed within 100 km (65 mi) of Cape Leeuwin
as an extratropical storm. Due to the rapid movement of Alby, the system maintained winds of 120 km/h (75 mph) as it reached this point, making it one of the most intense storms to strike the region. By 5 April, the cyclone rapidly lost its identity as it became caught up in a northwesterly flow before merging with the cold front over the Great Australian Bight
.
. In Perth
, a peak gust of 130 km/h (80 mph) was measured, the third-highest in the city's history. The intense winds, considered unprecedented for many in the region, were attributed to the fast movement of the storm and its location in relation to land. Moving at speeds up to 90 km/h (55.9 mph), winds along the northeastern edge of the storm were increased by that amount due to Alby's clockwise rotation. It also allowed for winds to cover a large area northeast of the centre, impacting many areas far from the storm. In general, rainfall was limited and generally less than 20 mm (0.78740157480315 in); this was due to the fast movement, as well as the asymmetrical structure with most of the thunderstorms south of the center.
These winds resulted in widespread agricultural, environmental and structural damage. Hundreds of structures sustained severe damage, mostly consisting of roofs blowing off. The most severe losses took place in Albany where most homes had partial or complete roof failure. Air-borne debris also damaged buildings during the storm. Nearly 80% of the apple crop was lost in the Donnybrook
-Manjimup
area. A total of 154,400 m3 (5.4 million ft3) of timber
was lost as well as a potential 200,000 m3 (7 million ft3) of future growth on established trees. Widespread dust storm
s also ruined crops and removed topsoil
from many areas. Near the coast, the combined effects of strong, onshore winds and little rain led to significant inland sea spray
. Numerous power lines and stations failed during the storm due to winds as well as dust and salt accretion. Large portions of the South-West Land Division were without electricity due to Cyclone Alby; Perth nearly sustained a complete breakdown of power services. This led to secondary losses attributable to the storm such as production failure.
The large expanse of gale-force winds without precipitation exacerbated 92 ongoing brush fires in the region. These fires erupted into full-fledged wildfires, expanding at a rate of 5 to 10 km/h (3.1 to 6.2 mph). A total of 114,000 hectare
s (281,700 acre
s) of land was burned throughout Western Australia as a result of the fires. Within this area, more than 10,000 sheep and 500 cattle
and horses were killed. Over 100 structures, 1300 km (807.8 mi) of fencing and tens of thousands of hay bales were destroyed. According to newspaper reports, two towns were leveled by the wildfires. At least 50 individual fires were fanned by the storm across the region, prompting more than 1,000 firefighters to assist in putting them out. Two fatalities were attributed to these fires.
Along the coast, large swells
produced by the storm resulted in two fatalities in Albany Harbour as well as significant coastal damage. Tide
s across the region were expected to increase. Unexpectedly, all forecast values were exceeded by at least 0.3 m (0.984251968503937 ft). The highest storm tide
was in Busselton
at 2.5 m (8.2 ft), leading to a storm surge
of 1.1 m (3.6 ft). Here, the surge penetrated roughly 200 m (656.2 ft) inland, forcing several evacuations. This led to significant coastal flooding that damaged dozens of structures. In Bunbury
, water breached the sea wall, inundating 100 homes and prompting the evacuation of 130 residents. Throughout Western Australia, Cyclone Alby was responsible for seven fatalities and A$50 million (A$213 million 2011; $284 million 2011 USD) in damage. There was also severe beach erosion associated with the storm, with some areas losing 30 m (98.4 ft) of land. Due to the extensive damage, the name Alby was retired from the list of Western Australian cyclone names following its usage.
In the wake of Cyclone Alby, an appeal for relief in the affected region was made by The Lord Mayor's Distress Relief Fund. The unprecedented scale of damage prompted meteorologists to vastly improve forecasting in the region to be better prepared for a similar storm in the future. At the time, little to no warning was given to residents in the South-West Land Division; this was the result of Alby's abrupt acceleration along a cold front, a complex forecasting situation. It was also regarded as a "wake up call" for the region, reminding residents that they are not immune to the effects of tropical cyclones. Cyclone Alby has been used as a benchmark to compare future storms in the region to, such as Severe Tropical Cyclone Bianca in 2011.
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
to impact southwestern Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
on record. Forming out of an area of low pressure
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
on 27 March, Alby steadily developed as it tracked southwestward, parallel to Western Australia. Between 1 and 2 April, the storm quickly intensified and attained its peak intensity as a Category 5 cyclone on the Australian cyclone intensity scale. After turning to the southeast, the storm underwent an extratropical transition
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
as it neared Cape Leeuwin
Cape Leeuwin
Cape Leeuwin is the most south-westerly mainland point of the Australian Continent, in the state of Western Australia.A few small islands and rocks, the St Alouarn Islands, extend further to the south. The nearest settlement, north of the cape, is Augusta. South-east of Cape Leeuwin, the coast...
. The storm brushed the cape on 4 April, bringing hurricane-force winds, before rapidly losing its identity the following day.
In Western Australia, the combination of Alby's fast movement and hurricane-force winds caused widespread damage. Along the coast, large swells
Swell (ocean)
A swell, in the context of an ocean, sea or lake, is a series surface gravity waves that is not generated by the local wind. Swell waves often have a long wavelength but this varies with the size of the water body, e.g. rarely more than 150 m in the Mediterranean, and from event to event, with...
flooded low-lying areas and numerous homes lost their roofs from high winds. Further inland, bushfires were worsened by the storm as it brought little rain, generally less than 20 mm (0.78740157480315 in) along the coast. These fires burned roughly 114,000 hectare
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
s (281,700 acre
Acre
The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...
s) and destroyed two towns. Five fatalities are directly attributed to Alby while two more resulted from the fires. The resulting damage was extensive, with monetary losses reaching A$50 million ($45 million USD).
Meteorological history
Severe Tropical Cyclone Alby was first identified on 27 March 1978 as a disorganized area of low pressureLow pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
situated roughly 800 km (497.1 mi) north-northwest of Karratha. At this time, the system was characterised as a large cluster of convection
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
converging around the low. Notable development took place over the following three days as the system drifted towards the southwest. Convection began wrapping around the storm, forming banding features
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...
. Early on March 29, the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...
(JTWC), classified the system as a tropical storm. Shortly thereafter, the Bureau of Meteorology
Bureau of Meteorology
The Bureau of Meteorology is an Executive Agency of the Australian Government responsible for providing weather services to Australia and surrounding areas. It was established in 1906 under the Meteorology Act, and brought together the state meteorological services that existed before then...
in Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
classified it as a tropical cyclone, assigning it with the name Alby. Gale force winds were later confirmed on 30 March by the Martha Bakke, located 385 km (239.2 mi) west-northwest of the storm's centre. By then, a large ragged eye
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
developed and Alby steadily intensified through 2 April. At the end of this strengthening, Cyclone Alby attained its peak intensity as a Category 5 on the Australian cyclone intensity scale; a barometric pressure of 930 mbar (hPa; 27.46 inHg) was measured at the time and peak winds were estimated to be 205 km/h (125 mph) based on the Dvorak technique
Dvorak technique
The Dvorak technique is a widely used system to subjectively estimate tropical cyclone intensity based solely on visible and infrared satellite images. Several agencies issue Dvorak intensity numbers for cyclones of sufficient intensity...
. Additionally, the JTWC assessed the storm to have attained winds of 215 km/h (135 mph), a low-range Category 4 on the Saffir–Simpson Hurricane Scale.
Shortly after reaching this intensity, Alby slowed as it began turning towards the southeast. By 3 April, the storm rapidly accelerated and attained a forward speed of 50 km/h (31.1 mph). This rapid acceleration was due to the cyclone's interaction with a cold front
Weather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
to its south. Gradually weakening, Alby also underwent an extratropical transition
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
as the storm's structure became asymmetrical. Around 1300 UTC, the storm passed within 100 km (65 mi) of Cape Leeuwin
Cape Leeuwin
Cape Leeuwin is the most south-westerly mainland point of the Australian Continent, in the state of Western Australia.A few small islands and rocks, the St Alouarn Islands, extend further to the south. The nearest settlement, north of the cape, is Augusta. South-east of Cape Leeuwin, the coast...
as an extratropical storm. Due to the rapid movement of Alby, the system maintained winds of 120 km/h (75 mph) as it reached this point, making it one of the most intense storms to strike the region. By 5 April, the cyclone rapidly lost its identity as it became caught up in a northwesterly flow before merging with the cold front over the Great Australian Bight
Great Australian Bight
The Great Australian Bight is a large bight, or open bay, off the central and western portions of the southern coastline of mainland Australia.-Extent:...
.
Impact and aftermath
Retaining winds in excess of 120 km/h (75 mph), Cyclone Alby brought damaging winds to much of the region in and around Cape Leeuwin. The highest winds reached 150 km/h (90 mph) in AlbanyAlbany, Western Australia
Albany is a port city in the Great Southern region of Western Australia, some 418 km SE of Perth, the state capital. As of 2009, Albany's population was estimated at 33,600, making it the 6th-largest city in the state....
. In Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
, a peak gust of 130 km/h (80 mph) was measured, the third-highest in the city's history. The intense winds, considered unprecedented for many in the region, were attributed to the fast movement of the storm and its location in relation to land. Moving at speeds up to 90 km/h (55.9 mph), winds along the northeastern edge of the storm were increased by that amount due to Alby's clockwise rotation. It also allowed for winds to cover a large area northeast of the centre, impacting many areas far from the storm. In general, rainfall was limited and generally less than 20 mm (0.78740157480315 in); this was due to the fast movement, as well as the asymmetrical structure with most of the thunderstorms south of the center.
These winds resulted in widespread agricultural, environmental and structural damage. Hundreds of structures sustained severe damage, mostly consisting of roofs blowing off. The most severe losses took place in Albany where most homes had partial or complete roof failure. Air-borne debris also damaged buildings during the storm. Nearly 80% of the apple crop was lost in the Donnybrook
Donnybrook, Western Australia
-Tourism:Donnybrook has many town icons bearing the apple. On the main street, apple-shaped lights line the entrance of the Old Railway Station. These lights have recently been restored. Atop the east Donnybrook hill is a high tower with an apple at the top...
-Manjimup
Manjimup, Western Australia
Manjimup is a town in Western Australia, south of the state capital, Perth. The town of Manjimup is a regional centre for the largest shire in the South West of Western Australia. At the 2006 census, Manjimup had a population of 4,239.-History:...
area. A total of 154,400 m3 (5.4 million ft3) of timber
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...
was lost as well as a potential 200,000 m3 (7 million ft3) of future growth on established trees. Widespread dust storm
Dust storm
A dust / sand storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Particles are transported by saltation and suspension, causing soil to move from one place and deposition...
s also ruined crops and removed topsoil
Topsoil
Topsoil is the upper, outermost layer of soil, usually the top to . It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.-Importance:...
from many areas. Near the coast, the combined effects of strong, onshore winds and little rain led to significant inland sea spray
Sea spray
Sea spray is a spray of water that forms when ocean waves crash.-Make up:As a result, salt spray contains a high concentration of mineral salts, particularly chloride anions.-Effects:...
. Numerous power lines and stations failed during the storm due to winds as well as dust and salt accretion. Large portions of the South-West Land Division were without electricity due to Cyclone Alby; Perth nearly sustained a complete breakdown of power services. This led to secondary losses attributable to the storm such as production failure.
The large expanse of gale-force winds without precipitation exacerbated 92 ongoing brush fires in the region. These fires erupted into full-fledged wildfires, expanding at a rate of 5 to 10 km/h (3.1 to 6.2 mph). A total of 114,000 hectare
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
s (281,700 acre
Acre
The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...
s) of land was burned throughout Western Australia as a result of the fires. Within this area, more than 10,000 sheep and 500 cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
and horses were killed. Over 100 structures, 1300 km (807.8 mi) of fencing and tens of thousands of hay bales were destroyed. According to newspaper reports, two towns were leveled by the wildfires. At least 50 individual fires were fanned by the storm across the region, prompting more than 1,000 firefighters to assist in putting them out. Two fatalities were attributed to these fires.
Along the coast, large swells
Swell (ocean)
A swell, in the context of an ocean, sea or lake, is a series surface gravity waves that is not generated by the local wind. Swell waves often have a long wavelength but this varies with the size of the water body, e.g. rarely more than 150 m in the Mediterranean, and from event to event, with...
produced by the storm resulted in two fatalities in Albany Harbour as well as significant coastal damage. Tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
s across the region were expected to increase. Unexpectedly, all forecast values were exceeded by at least 0.3 m (0.984251968503937 ft). The highest storm tide
Storm tide
A storm tide is a tide with a high flood period caused by a storm. Storm tides can be a severe danger to the coast and the people living along the coast. The water level can rise to more than 5 meters above the normal tide....
was in Busselton
Busselton, Western Australia
-Growth and development:According to the Australian Bureau of Statistics the Shire had a permanent resident population of 25,950 in 2004 with the town of Busselton accounting for 67% or 17,400 of the total. The Shire's permanent population is expected to continue to increase significantly to...
at 2.5 m (8.2 ft), leading to a storm surge
Storm surge
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...
of 1.1 m (3.6 ft). Here, the surge penetrated roughly 200 m (656.2 ft) inland, forcing several evacuations. This led to significant coastal flooding that damaged dozens of structures. In Bunbury
Bunbury, Western Australia
The port city of Bunbury is the third largest city in Western Australia after the State Capital Perth and Mandurah. It is situated south of Perth's central business district...
, water breached the sea wall, inundating 100 homes and prompting the evacuation of 130 residents. Throughout Western Australia, Cyclone Alby was responsible for seven fatalities and A$50 million (A$213 million 2011; $284 million 2011 USD) in damage. There was also severe beach erosion associated with the storm, with some areas losing 30 m (98.4 ft) of land. Due to the extensive damage, the name Alby was retired from the list of Western Australian cyclone names following its usage.
In the wake of Cyclone Alby, an appeal for relief in the affected region was made by The Lord Mayor's Distress Relief Fund. The unprecedented scale of damage prompted meteorologists to vastly improve forecasting in the region to be better prepared for a similar storm in the future. At the time, little to no warning was given to residents in the South-West Land Division; this was the result of Alby's abrupt acceleration along a cold front, a complex forecasting situation. It was also regarded as a "wake up call" for the region, reminding residents that they are not immune to the effects of tropical cyclones. Cyclone Alby has been used as a benchmark to compare future storms in the region to, such as Severe Tropical Cyclone Bianca in 2011.