Tropical Storm Superlatives for Australia and the Indian Ocean
Tropical Storm Superlatives for Australia and the Indian Ocean
In this last blog of my series on tropical storm superlatives, I cover the Indian Ocean Basin which includes the Bay of Bengal where the world’s deadliest tropical storms occur, as well Australia’s cyclone superlatives. Both the east and west coasts of Australia are occasionally pounded by intense tropical storms that originate in the South Pacific and Indian Ocean respectively, but for the sake of simplicity I am lumping both sources that affect Australia in this single blog.
This map shows the average number of tropical storms on an annual basis to affect the Australian and the southern Indian Ocean regions. Map courtesy of the Australian Bureau of Meteorology.
Australian Tropical Storm Superlatives
Most Intense Australian Cyclone
Tropical storms are called cyclones in both the Indian Ocean region and Australia. Since Australia does not have the equivalent of America’s hurricane hunter air reconnaissance the minimum barometric pressures of cyclones in the region are normally estimated using Dvorak and satellite observations rather than actual measurements when the storms are still offshore. Consequently there are differences of opinion between various agencies that monitor storms approaching Australia.
The above maps show the paths of all tropical storms to affect Australia during the period of 1906-2006 (top map). Unfortunately, the meaning of the various colors used for the paths is not explained although I assume they have to do with relative intensities of the individual storms that are tracked. Map courtesy of the Australian Bureau of Meteorology.
According to Australia’s Tropical Cyclone Warning Centre (based in Brisbane) Severe Tropical Cyclone Monica reached its greatest intensity on April 23, 2006 after it had crossed Queensland and entered the Gulf of Carpentaria north of Australia when a central barometric pressure of 905mb (26.72”) was reached. However, the U.S. Navy Joint Typhoon Warning Center, which was also monitoring the cyclone, estimated the pressure to have been at least 879mb (25.96”) and some calculations even came up with a figure of 969mb (25.66”), which would be a world record if true. In any case, even at 905 mb, Monica would at least tie with Cyclone Orson in April 1989) as Australia’s most intense tropical storm. Sustained winds of 185mph with gust to 225mph were theorized. Fortunately, Monica passed over sparsely populated areas of Australia and no fatalities and little damage were reported.
An infrared image of Cyclone Monica at her peak intensity on April 23, 2006. Her Dvorak intensity was a perfect 8.0 at this, time the highest on the scale, and winds were estimated to be gusting over 200mph. Image from wunderground.com
Below is a list of the ten most intense cyclones to strike Australia in terms of lowest barometric pressure measured at a land location:
Most Destructive Australian Cyclone
Cyclone Tracy struck the city of Darwin on the coast of Australia’s Northern Territory on Christmas Day 1974 killing 71 and destroying 70% of the city’s structures. The storm was extremely compact with gale winds extending only in a 31 miles radius from its 4 mile-wide eye. In spite of its small size, winds at its center were estimated to be as high as 150mph with a gust of 135mph actually measured at Darwin Airport before the anemometer was blown away. 41,000 of the city’s 47,000 residents were rendered homeless and damage was calculated at $800 million in 1974 US dollars (about $3.5 billion in current dollars).
A photo of the incredible destruction to Darwin following the passage of Cyclone Tracy on Dec. 25, 1974. 70% of the city was destroyed and 71 lives were lost. Photo credit unknown.
The deadliest cyclone in Australian history, and the country’s deadliest natural disaster, was the Great Bathurst Bay Cyclone of 1899. Some 300-400 lives were lost along the far northeastern coast of Queensland mostly the crews of pearling vessels.
Highest Measured Wind Speeds in Australian Cyclones
The highest wind speed ever ‘officially’ recorded on earth occurred when Cyclone Olivia passed over a gas platform off the coast of Barrow Island in Western Australia and produced a measured wind gust of 253mph (408km/h) on Oct. 4, 1996. Although Olivia was not one of Australia’s most potent cyclones it is suspected that a mesovortex in the eye wall of the storm passed directly over the observation site producing the extraordinary value. The anemometer ( a heavy duty three-cup Synchrotac) was subsequently checked for accuracy and passed several tests for such.
Below is a list of the highest measured wind gusts at land locations in Australia during the passage of severe tropical cyclones:
Greatest Rainfall Associated with Cyclones in Australia
The greatest precipitation total as a result of a tropical storm was the 99.09” that fell over a three-day period at Bellenden Ker, Queensland January 4-6, 1979. This same storm also produced Australia’s greatest 24-hour total of 44.92” at Bellenden Ker on Jan. 4, 1979. A cyclone in February 1893 deposited 67.52” in three days at Mooloolah, Queensland.
Greatest Cyclone Storm Surge in Australia
The Great Bathurst Bay Cyclone of March 5, 1899 produced a storm surge of some 42 feet when it crashed ashore in northern Queensland according to eyewitness accounts and debris damage. This is the highest storm surge reliably recorded anywhere on earth.
Indian Ocean Cyclone Superlatives
The cyclones in the Indian Ocean basin primarily occur in the Bay of Bengal region between India and Burma (Myanmar), the Arabian Sea between India and the Arabian Peninsula, and in the Southern Indian Ocean between Australia and Madagascar off Africa’s east coast. The former is most noteworthy for the mass casualties that occur in India, Bangladesh, and Burma, and the latter for the world-record rainfalls that happen on the island of Reunion some 500 miles east of Madagascar.
A map showing the paths of all tropical storms in the Bay of Bengal and Arabian Sea between 1986-2006.
Most Intense Indian Ocean Cyclones
Cyclone data details are sketchy for this entire region so far as tropical storm intensities are concerned but the lowest barometric pressure actually measured in the Bay of Bengal was during a severe cyclone in 1833 when the British vessel S.S. Duke of York reported a measurement of 891mb (26.30”) while passing through the eye of a cyclone.
This map illustrates how cyclones affect India by time of year of occurrence, regions most often affected, and historical storm surges observed at various points along the coastline. Map from Compare Infobase Ltd.
The lowest pressure reached in a Southwest Indian Ocean cyclone I am aware of was 895mb (26.42”) during Cyclone Gafilo on March 6, 2004 just prior to striking Madagascar (see end of blog entry about ‘Deadliest Cyclones to affect Africa’).
Deadliest Indian Ocean Cyclones
All of the deadliest tropical storms on earth have occurred in the Bay of Bengal when tremendous storm surges have swamped the low-lying coastal regions of Bangladesh, India, and Burma. The worst of all was the Great Boha Cyclone of November 12-13, 1970 when a 40-foot storm surge overwhelmed the delta islands of the Brahmaputra and Ganges Rivers in Bangladesh. An estimated 300,000-500,000 perished. This storm is also considered to have produced the greatest storm surge of any Indian Ocean cyclone although similar surges may have occurred during the 1733 and 1876 cyclones.
A storm surge graphic of the Great Boha Cyclone of November 1970. The bars indicate how high the storm surge was at various locations along the coasts of India and Bangladesh in feet. Each bar is ’48 feet’ long and the green shading inside the bars shows how many feet (out of 48’) the surge reached. The greatest height was 40 feet at Hatia, Bangladesh. Graphic from ‘Extreme Weather: A Guide and Record Book’ based upon data supplied by the Indian Meteorological Department.
Below is a list of the ten deadliest cyclones to affect this region (these figures vary from source to source, and the Chittagong Cyclone casualties may have been much lower, hence the list is composed of 11 cyclones rather than ten):
The deadliest cyclone to affect the western coast of India (Arabian Sea region) was that of 1882 when 100,000 were killed in and around Bombay.
Greatest Rainfall Associated with Indian Ocean Cyclones
Many of the world’s greatest point rainfall records can be attributed to cyclones that pass over the Indian Ocean island of Reunion. The reason for this is that the island has a 10,000-foot volcanic peak that produces a tremendous orographic effect on the moisture associated with tropical storms. The French Meteorological Service maintains a network of rain gauges on the slopes of the mountain. Below is a list of the world-record rainfalls that have been recorded here during cyclone events:
Deadliest and Most Destructive Cyclone to Hit Eastern Africa
Cyclone Gafilo (mentioned above) was the most intense tropical cyclone to strike Africa when it hit Madagascar with winds estimated at 150mph on March 6, 2004. The storm caused the deaths of 285 people on the island and when a ferry was sunk offshore with the loss of 113. Probably the deadliest cyclone to hit Africa in modern records was Cyclone Leon-Eline that brought devastating floods to Mozambique and South Africa after striking the coast of Mozambique on Feb. 22, 2000. At least 1,000 deaths were directly attributed to this storm.
Christopher C. Burt