Cyclone Olivia
Encyclopedia
Severe Tropical Cyclone Olivia was a powerful Category 4 cyclone that produced the highest non-tornadic
winds on record, 408 km/h (253 mph).
over Indonesia
north of Darwin, Australia
on 2 April. The system slowly became better organized despite strong wind shear
as it sharply turned south. Early on 5 April, the Joint Typhoon Warning Center
(JTWC) classified the system as Tropical Depression 25S as it resumed its westward track. Shortly thereafter, the Bureau of Meteorology upgraded the system to a Category 1 cyclone, designating the storm as Tropical Cyclone Olivia. The westward turn occurred in response to a mid-level ridge
to the south of Olivia strengthened. Shortly after being upgraded by the Bureau of Meteorology, the JTWC followed suit and classified the system as a tropical storm.
Over the following several days, persistent wind shear prevented convection
from developing around the center of circulation
. However, by 8 April, an upper-level trough
passed to the south of the developing cyclone, leading to lower shear. Following this, the system had developed sufficiently for the JTWC to upgrade it to a Category 1 equivalent on the Saffir–Simpson Hurricane Scale (SSHS), with winds estimated at 120 km/h (75 mph 1-minute sustained) around the center of the storm. Around the same time, the Bureau of Meteorology upgraded Olivia to a severe tropical cyclone, having similar wind speeds. After reaching this intensity, the mid-level ridge south of the cyclone began to weaken, leading to Olivia turning towards the southwest. By 9 April, the system attained Category 4 intensity as it continued to strengthen.
During the afternoon of 9 April, Olivia attained its lowest barometric pressure of 925 hPa
(mbar
) and sustained winds were estimated at 195 km/h (120 mph 10-minute sustained) by the Bureau of Meteorology. Several hours later, the JTWC assessed the cyclone to have attained Category 4 status on the SSHS with winds of 230 km/h (145 mph 1-minute sustained). By this time, another trough bypassed the cyclone, this time causing Olivia to turn southward before rapidly tracking southeast. Early on 10 April, data from a nearby weather radar
at the Learmonth Airport
near Exmouth, Western Australia
, showed that the storm had developed a 65 km (40 mi) wide eye
.
Late on 10 April, the center of Olivia passed near Barrow Island
at peak intensity. Shortly thereafter, the storm passed near Varanus Island
as a high-end Category 4 or low-end Category 5 cyclone. Within several hours of passing by Varanus Island, Olivia made landfall
near Mardie at peak intensity. Shortly thereafter, the storm began to weaken overland. Accelerating to the southeast, the storm became disorganized and winds decreased below hurricane-force. During the afternoon of 11 April, Olivia weakened to a tropical low over southern Australia before moving over the Great Australian Bight
and losing its identity as a gale-force low.
, Olivia brought minor rainfall and gusty winds to parts of the Northern Territory
. Over land, no damage was reported despite a 2 m (6.6 ft) storm surge
in localized areas. An oil rig in the Timor Sea recorded a wind gust of 127 km/h (78.9 mph) during the storm's passage.
Offshore, Cyclone Olivia produced large swells
up to 21 m (68.9 ft). These waves, in combination with record breaking winds exceeding 265 km/h (165 mph), caused several million dollars in losses to oil platforms. On Barrow Island, a world-record wind gust of 408 km/h (253 mph) was recorded at the local airport. Initially, this gust was subject to confirmation and not released to the public. It was not until 26 January 2010 that the World Meteorological Organization announced the confirmation of this wind gust. This gust surpassed the previous non-tornadic wind speed of 374 km/h (232 mph) on Mount Washington
in the United States
in April, 1934.
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
winds on record, 408 km/h (253 mph).
Meteorological history
Severe Tropical Cyclone Olivia was first identified by the Bureau of Meteorology as a low to mid-level 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...
over Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
north of Darwin, Australia
Darwin, Northern Territory
Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 127,500, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities...
on 2 April. The system slowly became better organized despite strong wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
as it sharply turned south. Early on 5 April, 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 Tropical Depression 25S as it resumed its westward track. Shortly thereafter, the Bureau of Meteorology upgraded the system to a Category 1 cyclone, designating the storm as Tropical Cyclone Olivia. The westward turn occurred in response to a mid-level ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to the south of Olivia strengthened. Shortly after being upgraded by the Bureau of Meteorology, the JTWC followed suit and classified the system as a tropical storm.
Over the following several days, persistent wind shear prevented 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...
from developing around the center of circulation
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...
. However, by 8 April, an upper-level trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
passed to the south of the developing cyclone, leading to lower shear. Following this, the system had developed sufficiently for the JTWC to upgrade it to a Category 1 equivalent on the Saffir–Simpson Hurricane Scale (SSHS), with winds estimated at 120 km/h (75 mph 1-minute sustained) around the center of the storm. Around the same time, the Bureau of Meteorology upgraded Olivia to a severe tropical cyclone, having similar wind speeds. After reaching this intensity, the mid-level ridge south of the cyclone began to weaken, leading to Olivia turning towards the southwest. By 9 April, the system attained Category 4 intensity as it continued to strengthen.
During the afternoon of 9 April, Olivia attained its lowest barometric pressure of 925 hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
(mbar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
) and sustained winds were estimated at 195 km/h (120 mph 10-minute sustained) by the Bureau of Meteorology. Several hours later, the JTWC assessed the cyclone to have attained Category 4 status on the SSHS with winds of 230 km/h (145 mph 1-minute sustained). By this time, another trough bypassed the cyclone, this time causing Olivia to turn southward before rapidly tracking southeast. Early on 10 April, data from a nearby weather radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
at the Learmonth Airport
RAAF Learmonth
RAAF Learmonth, also known as Learmonth Airport , is a joint use Royal Australian Air Force base and civil airport. It is located near the town of Exmouth on the north-west coast of Western Australia. As an RAAF base, Learmonth is one of the RAAF's three 'bare bases'...
near Exmouth, Western Australia
Exmouth, Western Australia
-Further reading:* Western Australia. Ministry for Planning. Exmouth-Learmonth structure plan. Perth, W.A. : Western Australian Planning Commission...
, showed that the storm had developed a 65 km (40 mi) wide 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...
.
Late on 10 April, the center of Olivia passed near Barrow Island
Barrow Island (Western Australia)
Barrow Island is a island located northwest off the coast of Western Australia. The island is the second largest in Western Australia after Dirk Hartog Island.-Discovery and early history:...
at peak intensity. Shortly thereafter, the storm passed near Varanus Island
Varanus Island
Varanus Island is the largest of the Lowendal Islands, an archipelago off the north west coast of Western Australia, near Karratha in the Pilbara region...
as a high-end Category 4 or low-end Category 5 cyclone. Within several hours of passing by Varanus Island, Olivia made landfall
Landfall (meteorology)
Landfall is the event of a tropical cyclone or a waterspout coming onto land after being over water. When a waterspout makes landfall it is reclassified as a tornado, which can then cause damage inland...
near Mardie at peak intensity. Shortly thereafter, the storm began to weaken overland. Accelerating to the southeast, the storm became disorganized and winds decreased below hurricane-force. During the afternoon of 11 April, Olivia weakened to a tropical low over southern Australia before moving 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:...
and losing its identity as a gale-force low.
Impact and records
As a minimal cyclone in the Timor SeaTimor Sea
The Timor Sea is a relatively shallow sea bounded to the north by the island of Timor, to the east by the Arafura Sea, to the south by Australia and to the west by the Indian Ocean....
, Olivia brought minor rainfall and gusty winds to parts of the Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
. Over land, no damage was reported despite a 2 m (6.6 ft) 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...
in localized areas. An oil rig in the Timor Sea recorded a wind gust of 127 km/h (78.9 mph) during the storm's passage.
Offshore, Cyclone Olivia produced 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...
up to 21 m (68.9 ft). These waves, in combination with record breaking winds exceeding 265 km/h (165 mph), caused several million dollars in losses to oil platforms. On Barrow Island, a world-record wind gust of 408 km/h (253 mph) was recorded at the local airport. Initially, this gust was subject to confirmation and not released to the public. It was not until 26 January 2010 that the World Meteorological Organization announced the confirmation of this wind gust. This gust surpassed the previous non-tornadic wind speed of 374 km/h (232 mph) on Mount Washington
Mount Washington (New Hampshire)
Mount Washington is the highest peak in the Northeastern United States at , famous for dangerously erratic weather. For 76 years, a weather observatory on the summit held the record for the highest wind gust directly measured at the Earth's surface, , on the afternoon of April 12, 1934...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in April, 1934.
See also
- 1995–96 Southern Hemisphere tropical cyclone season
- 1999 Oklahoma tornado outbreak – produced an F5Fujita scaleThe Fujita scale , or Fujita-Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation...
tornado which had winds estimated at 511 km/h (318 mph) by the dopplerPulse-doppler radarPulse-Doppler is a 4D radar system capable of detecting both target 3D location as well as measuring radial velocity . It uses the Doppler effect to avoid overloading computers and operators as well as to reduce power consumption...
data of the weather radarWeather radarWeather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the... - Mount WashingtonMount Washington (New Hampshire)Mount Washington is the highest peak in the Northeastern United States at , famous for dangerously erratic weather. For 76 years, a weather observatory on the summit held the record for the highest wind gust directly measured at the Earth's surface, , on the afternoon of April 12, 1934...
– location of the previous highest non-tornadic winds, 374 km/h (232 mph) - Hurricane GustavHurricane GustavThe name Gustav has been used for five tropical cyclones in the Atlantic Ocean:* 1984's Tropical Storm Gustav - Spent most of its existence as a tropical depression hovering over Bermuda, no major damage was reported....
– thought to have produced the highest wind gust in a tropical cyclone at 340 km/h (211 mph)