A subtropical cyclone is a weather system that has some characteristics of both tropical and an extratropical cyclone.
Tropical cyclones and subtropical cyclones are named by various warning centers to simplify communication between forecasters and the general public regarding forecasts, watches and warnings. The names are intended to reduce confusion in the event of concurrent storms in the same basin. Once storms develop sustained wind speeds of more than 33 knots, names are generally assigned to them from predetermined lists, depending on the basin in which they originate. Some tropical depressions are named in the Western Pacific, while tropical cyclones must contain a significant amount of gale-force winds before they are named in the Southern Hemisphere.
Traditionally, areas of tropical cyclone formation are divided into seven basins. These include the north Atlantic Ocean, the eastern and western parts of the northern Pacific Ocean, the southwestern Pacific, the southwestern and southeastern Indian Oceans, and the northern Indian Ocean. The western Pacific is the most active and the north Indian the least active. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones, super typhoons, or major hurricanes.
A South Pacific tropical cyclone is a non-frontal, low pressure system that has developed, within an environment of warm sea surface temperatures and little vertical wind shear aloft in the South Pacific Ocean. Within the Southern Hemisphere there are officially three areas where tropical cyclones develop on a regular basis, these areas are the South-West Indian Ocean between Africa and 90°E, the Australian region between 90°E and 160°E and the South Pacific basin between 160°E and 120°W. The South Pacific basin between 160°E and 120°W is officially monitored by the Fiji Meteorological Service and New Zealand's MetService, while others like the Australian Bureau of Meteorology and the United States National Oceanic and Atmospheric Administration also monitor the basin. Each tropical cyclone year within this basin starts on July 1 and runs throughout the year, encompassing the tropical cyclone season which runs from November 1 and lasts until April 30 each season. Within the basin, most tropical cyclones have their origins within the South Pacific Convergence Zone or within the Northern Australian monsoon trough, both of which form an extensive area of cloudiness and are dominant features of the season. Within this region a tropical disturbance is classified as a tropical cyclone, when it has 10-minute sustained wind speeds of more than 65 km/h (40 mph), that wrap halfway around the low-level circulation centre, while a severe tropical cyclone is classified when the maximum 10-minute sustained wind speeds are greater than 120 km/h (75 mph).
An Australian region tropical cyclone is a non-frontal, low-pressure system that has developed within an environment of warm sea surface temperatures and little vertical wind shear aloft in either the Southern Indian Ocean or the South Pacific Ocean. Within the Southern Hemisphere there are officially three areas where tropical cyclones develop on a regular basis: the South-West Indian Ocean between Africa and 90°E, the Australian region between 90°E and 160°E, and the South Pacific basin between 160°E and 120°W. The Australian region between 90°E and 160°E is officially monitored by the Australian Bureau of Meteorology, the Indonesian Meteorology, Climatology, and Geophysical Agency, and the Papua New Guinea National Weather Service, while others like the Fiji Meteorological Service and the United States National Oceanic and Atmospheric Administration also monitor the basin. Each tropical cyclone year within this basin starts on 1 July and runs throughout the year, encompassing the tropical cyclone season, which runs from 1 November and lasts until 30 April each season. Within the basin, most tropical cyclones have their origins within the South Pacific convergence zone or within the Northern Australian monsoon trough, both of which form an extensive area of cloudiness and are dominant features of the season. Within this region a tropical disturbance is classified as a tropical cyclone when it has 10-minute sustained wind speeds of at least 65 km/h (40 mph) that wrap halfway around the low level circulation centre, while a severe tropical cyclone is classified when the maximum 10-minute sustained wind speeds are greater than 120 km/h (75 mph).
The 1995–96 Australian region cyclone season was an active Australian cyclone season, with Western Australia experiencing a record number of landfalling intense storms in the Pilbara region. The season produced a total of 19 tropical cyclones, of which 14 developed into named storms and 9 reached severe tropical cyclone status. The strongest of the season was Severe Tropical Cyclone Olivia, which also produced the highest recorded wind gust on record of 408 km/h (253 mph). Though several systems impacted land, the general sparsity of population centres in Australia limits the scale of damage. One person was confirmed to have been killed and cumulative losses were estimated at A$77 million (US$58.5 million).
The following outline is provided as an overview of and topical guide to tropical cyclones:
The 1968–69 Australian region cyclone season was an above-average tropical cyclone season, featuring 15 tropical lows, of which 12 of them are named. Amber was the only hurricane-strength tropical cyclone of the season, however, it didn't affect any landmasses. It ran from 1 November 1968 to 30 April 1969, with the regional tropical cyclone operational plan defining a "tropical cyclone year" separately from a "tropical cyclone season", with the "tropical cyclone year" for this season lasting from 1 July 1968 to 30 June 1969.
The 1972–73 Australian region cyclone season was an above-average tropical cyclone season, in terms of activity. Additionally, it is also the deadliest tropical cyclone season recorded in the Australian region, with Cyclone Flores killing an estimated 1,650 people alone, making Flores the single-deadliest tropical cyclone recorded in the entire Southern Hemisphere.
Throughout 2006, 133 tropical cyclones formed in seven bodies of water known as tropical cyclone basins. Of these, 80 have been named, including two tropical cyclones in the South Atlantic Ocean, and a tropical cyclone in the Mediterranean Sea, by various weather agencies when they attained maximum sustained winds of 65 km/h (40 mph). The strongest storms of the year were Typhoon Yagi in the Western Pacific, and Cyclone Glenda of the Australian region. The deadliest and costliest storms of the year were a series of five typhoons that struck the Philippines and China; Chanchu, Bilis, Saomai, Xangsane, and Durian, with most of the damage being caused by Durian of November. So far, 27 Category 3 tropical cyclones formed, including five Category 5 tropical cyclones in the year.
The following is a list of tropical cyclones by year. Since the year 957, there have been at least 12,791 recorded tropical or subtropical cyclones in the Atlantic, Pacific, and Indian Oceans, which are known as basins. Collectively, tropical cyclones caused more than US$1.2 trillion in damage, unadjusted for inflation, and have killed more than 2.6 million people. Most of these deaths were caused by a few deadly cyclones, including the 1737 Calcutta cyclone, the 1839 Coringa cyclone, the 1931 Shanghai typhoon, the 1970 Bhola cyclone, Typhoon Nina in 1975, the 1991 Bangladesh cyclone, and Cyclone Nargis in 2008.
During 2011, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 131 tropical cyclones had formed this year to date. 71 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). Thirty-nine of these named systems eventually intensified into hurricane-equivalent tropical cyclones. The most active basin in the year was the Western Pacific, which documented 21 named storms. North Atlantic basin documented 19 named storms, continuing the consecutive third-most active season trends from the previous year, due to the 2010–12 La Niña event. Conversely, the Eastern Pacific basin featured slightly more activity than the previous season, with 11 named storms. The least active basin in the year was the North Indian Ocean basin which documented only 2 named storms, the lowest since the 1993 season. Activity across the Southern Hemisphere were almost evenly spread, with the South-West Indian Ocean basin recording 10 tropical cyclones, the Australian region recording 17 tropical cyclones, and the South Pacific basin also recording 10 tropical cyclones, respectively. Twenty-one Category 3 tropical cyclones formed in the year, including three Category 5 tropical cyclones.
The 2023–24 Australian region cyclone season is an upcoming weather event in the southern hemipshere. The season will officially start on 1 November 2023 and end on 30 April 2024, however, a tropical cyclone could form at any time between 1 July 2023 and 30 June 2024 and would count towards the season total. During the season, tropical cyclones will be officially monitored by one of the three tropical cyclone warning centres (TCWCs) for the region which are operated by the Australian Bureau of Meteorology, National Weather Service of Papua New Guinea and the Indonesian Agency for Meteorology, Climatology and Geophysics. The United States Joint Typhoon Warning Center (JTWC) and other national meteorological services including Météo-France and the Fiji Meteorological Service will also monitor the basin during the season.
The 2023–24 South Pacific cyclone season is an upcoming weather event, South Pacific Ocean to the east of 160°E. The season will officially start on November 1, 2023, and end on April 30, 2024, however a tropical cyclone could form at any time between July 1, 2023, and June 30, 2024, and would count towards the season total. During the season, tropical cyclones will be officially monitored by the Fiji Meteorological Service, Australian Bureau of Meteorology and New Zealand's MetService. The United States Armed Forces through the Joint Typhoon Warning Center (JTWC) will also monitor the basin and issue unofficial warnings for American interests. The FMS attaches a number and an F suffix to tropical disturbances that form in or move into the basin while the JTWC designates significant tropical cyclones with a number and a P suffix. The BoM, FMS and MetService all use the Australian Tropical Cyclone Intensity Scale and estimate windspeeds with a period of approximately ten minutes, while the JTWC estimates sustained winds over a 1-minute period, which are subsequently compared to the Saffir–Simpson hurricane wind scale (SSHWS).
The 2023–24 South-West Indian Ocean cyclone season is an upcoming event of the annual cycle of tropical cyclone and subtropical cyclone formation. It begins on 15 November 2023, and will end on 30 April 2024, with the exception for Mauritius and the Seychelles, for which it will end on 15 May 2024. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. However, tropical cyclones can form year-round, and all tropical cyclones that will form between 1 July 2023 and 30 June 2024 will be part of the season. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion and unofficially by the Joint Typhoon Warning Center.