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 (Arabian Sea and Bay of Bengal). 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 (at least of Category 3 intensity).
|Tropical cyclone basins and official warning centre.|
|Basin||Warning Center||Area of responsibility||Refs|
| North Atlantic |
|United States National Hurricane Center |
United States Central Pacific Hurricane Center
|Equator northward, African Coast – 140°W|
Equator northward, 140°W-180
|Western Pacific||Japan Meteorological Agency||Equator-60°N, 180-100°E|
|North Indian Ocean||India Meteorological Department||Equator northward, 100°E-45°E|
|South-West Indian Ocean||Meteo France Reunion||Equator-40°S, African Coast-90°E|
|Australian region|| Badan Meteorologi, Klimatologi, dan Geofisika |
Papua New Guinea National Weather Service
Australian Bureau of Meteorology
|Southern Pacific|| Fiji Meteorological Service |
Meteorological Service of New Zealand
This region includes the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico. Tropical cyclone formation here varies widely from year to year, ranging from one to over twenty-five per year.Most Atlantic tropical storms and hurricanes form between June 1 and November 30. The United States National Hurricane Center (NHC) monitors the basin and issues reports, watches and warnings about tropical weather systems for the Atlantic Basin as one of the Regional Specialized Meteorological Centres for tropical cyclones as defined by the World Meteorological Organization. On average, 11 named storms (of tropical storm or higher strength) occur each season, with an average of 6 becoming hurricanes and 2 becoming major hurricanes. The climatological peak of activity is around September 10 each season.
The United States Atlantic coast and Gulf Coast, Mexico, Central America, the Caribbean Islands, and Bermuda are frequently affected by storms in this basin. Venezuela, the 4 provinces of Atlantic Canada, and Atlantic Macaronesian islands also are occasionally affected. Many of the more intense Atlantic storms are Cape Verde-type hurricanes, which form off the west coast of Africa near the Cape Verde islands. Occasionally, a hurricane that evolves into an extratropical cyclone can reach western Europe, including Hurricane Gordon, which spread high winds across Spain and the British Isles in September 2006.Hurricane Vince, which made landfall on the southwestern coast of Spain as a tropical depression in October 2005, is the only known system to impact mainland Europe as a tropical cyclone in the NHC study period commencing in 1851 (it is believed a hurricane made landfall in Spain in 1842).
The Northeastern Pacific is the second most active basin and has the highest number of storms per unit area. The hurricane season runs between May 15 and November 30 each year, and encompasses the vast majority of tropical cyclone activity in the region.In the 1971–2005 period, there were an average of 15–16 tropical storms, 9 hurricanes, and 4–5 major hurricanes (storms of Category 3 intensity or greater) annually in the basin.
Storms that form here often affect western Mexico, and less commonly the Continental United States (in particular California), or northern Central America. No hurricane included in the modern database has made landfall in California; however, historical records from 1858 speak of a storm that brought San Diego winds over 75 mph (65 kn; 121 km/h) (marginal hurricane force), though it is not known if the storm actually made landfall. Tropical storms in 1939, 1976 and 1997 brought gale-force winds to California.
The Central Pacific Hurricane Center's area of responsibility (AOR) begins at the boundary with the National Hurricane Center' AOR (at 140 °W), and ends at the International Date Line, where the Northwestern Pacific begins. The hurricane season in the North Central Pacific runs annually from June 1 to November 30; The Central Pacific Hurricane Center monitors the storms that develop or move into the defined area of responsibility. The CPHC previously tasked with monitoring tropical activity in the basin was originally known as the Joint Hurricane Warning Center; today it is called the Joint Typhoon Warning Center.
Central Pacific hurricanes are rare and on average 4 to 5 storms form or move in this area annually.As there are no large contiguous landmasses in the basin, direct hits and landfalls are rare; however, they occur occasionally, as with Hurricane Iniki in 1992, which made landfall on Hawaii, and Hurricane Ioke in 2006, which made a direct hit on Johnston Atoll.
The Northwest Pacific Ocean is the most active basin on the planet, accounting for one-third of all tropical cyclone activity. Annually, an average of 25.7 tropical cyclones in the basin acquire tropical storm strength or greater; also, an average of 16 typhoons occurred each year during the 1968–1989 period.The basin occupies all the territory north of the equator and west of the International Date Line, including the South China Sea. The basin sees activity year-round; however, tropical activity is at its minimum in February and March.
Tropical storms in this region often affect China, Hong Kong, Macau, Japan, Korea, Philippines, Taiwan and Vietnam, plus numerous Oceanian islands such as Guam, the Northern Marianas and Palau. Sometimes, tropical storms in this region affect Laos, Thailand, Cambodia and even Singapore, Malaysia and Indonesia. The coast of China sees the most landfalling tropical cyclones worldwide.The Philippines receives an average of 6–7 tropical cyclone landfalls per year, with Super Typhoon Haiyan being the strongest and most powerful to date since its landfall in November 8, 2013.
This basin is divided into two areas: the Bay of Bengal and the Arabian Sea, with the Bay of Bengal dominating (5 to 6 times more activity). Still, this basin is the least active worldwide, with only 4 to 6 storms per year.
This basin’s season has a double peak: one in April and May, before the onset of the monsoon, and another in October and November, just after.This double peak occurs because powerful vertical wind shear in between the surface monsoonal low and upper tropospheric high during the monsoon season tears apart incipient cyclones. High shear explains why no cyclones can form in the Red Sea, which possesses the necessary depth, vorticity and surface temperatures year-round. Rarely do tropical cyclones that form elsewhere in this basin affect the Arabian Peninsula or Somalia; however, Cyclone Gonu caused heavy damage in Oman on the peninsula in 2007.
Although the North Indian Ocean is a relatively inactive basin, extremely high population densities in the Ganges and Ayeyarwady Deltas mean that the deadliest tropical cyclones in the world have formed here, including the 1970 Bhola cyclone, which killed 500,000 people. Nations affected include India, Bangladesh, Sri Lanka, Thailand, Myanmar, and Pakistan.
On rare occasions, tropical-like systems that can reach the intensity of hurricanes, occur over the Mediterranean Sea. Such a phenomenon is called a Medicane (Mediterranean-hurricane). Although the geographical dimensions of tropical oceans and the Mediterranean Sea are clearly different, the precursor mechanisms of these perturbations, based on the air-sea thermodynamic imbalance, are similar. °C or 75/82 °F), though research indicates water temperatures of 20 °C (68 °F) are normally required for development.Their origins are typically non-tropical, and develop over open waters under strong, initially cold-core cyclones, similar to subtropical cyclones or anomalous tropical cyclones in the Atlantic Basin, like Karl (1980), Vince (2005), Grace (2009), Chris (2012), or Ophelia (2017). Sea surface temperatures in late-August and early-September are quite high over the basin (24/28
Meteorological literature document that such systems occurred in September 1947, September 1969, January 1982, September 1983, January 1995, October 1996, September 2006, November 2011, November 2014, and November 2017. mph (140 km/h) winds, along with an atmospheric pressure of 975 mbar. Although it had the structure of a tropical cyclone, it occurred over 61 °F (16 °C) water temperatures, suggesting it could have been a polar low.The 1995 system developed a well-defined eye, and a ship recorded 85
Within the Southern Hemisphere tropical cyclones generally form on a regular basis between the African coast and the middle of the South Pacific. Tropical and Subtropical Cyclones have also been noted occurring in the Southern Atlantic Ocean at times. For various reasons including where tropical cyclones form, there are several different ways to split the area between the American and African coasts. For instance the World Meteorological Organization define three different basins for the tracking and warning of tropical cyclones. These are the South-West Indian Ocean between the African Coast and 90°E, the Australian region between 90°E and 160°E and the South Pacific between 160°E and 120°W. The United States Joint Typhoon Warning Center also monitors the whole region, but splits it at 135°E into the South Pacific and the Southern Indian Ocean.
The South-West Indian Ocean is located within the Southern Hemisphere between the Africa's east coast and 90°E and is primarily monitored by the Meteo France's La Reunion RSMC, while the Mauritian, Australian Indonesian, and Malagasy weather services also monitor parts of it.Until the start of the 1985–86 tropical cyclone season the basin only extended to 80°E, with the 10 degrees between 80 and 90E considered to be a part of the Australian region. On average about 9 cyclones per year develop into tropical storms, while 5 of those go on to become tropical cyclones that are equivalent to a hurricane or a typhoon. The tropical cyclones that form in this area can affect some of the various Indian Ocean island nations and or various countries along Africa's east coast.
Through the middle of 1985, this basin extended westward to 80E. Since then, its western boundary has been 90E. 267 km/h (166 mph).Tropical activity in this region affects Australia and Indonesia. According to the Australian Bureau of Meteorology, the most frequently hit portion of Australia is between Exmouth and Broome in Western Australia. The basin sees an average of about seven cyclones each year, although more can form or come in from other basins, such as the South Pacific. The tropical cyclone Cyclone Vance in 1999 produced the highest recorded speed winds in an Australian town or city at around
The South Pacific Ocean basin runs between 160°E and 120°W, with tropical cyclones developing in it officially monitored by the Fiji Meteorological Service and New Zealand's MetService.Tropical Cyclones that develop within this basin generally affect countries to the west of the dateline, though during years of the warm phase of El Niño–Southern Oscillation cyclones have been known to develop to the east of the dateline near French Polynesia. On average the basin sees nine tropical cyclones annually with about half of them becoming severe tropical cyclones.
Cyclones rarely form in other tropical ocean areas, which are not formally considered tropical cyclone basins. Tropical depressions and tropical storms occur occasionally in the South Atlantic, and the only full-blown tropical cyclones on record were 2004's Hurricane Catarina, which made landfall in Brazil, 2010's Tropical Storm Anita, which formed off the coast of Rio Grande do Sul and Tropical Storm Iba in 2019. The South Atlantic Ocean is not officially classified as a tropical cyclone basin by the World Meteorological Organization and does not have a designated regional specialized meteorological center (RSMC). However, beginning in 2011, the Brazilian Navy Hydrographic Center started to assign names to tropical and subtropical systems in this basin, when they have sustained wind speeds of at least 65 km/h (40 mph).
Tropical cyclones and subtropical cyclones are named by various warning centers to provide ease of 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. Generally once storms produce sustained wind speeds of more than 33 knots, names are assigned in order from predetermined lists depending on which basin they originate. However, standards vary from basin to basin: some tropical depressions are named in the Western Pacific, while tropical cyclones must have a significant amount of gale-force winds occurring around the centre before they are named in the Southern Hemisphere.
Tropical cyclone warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate preparation for the cyclone, including evacuation of vulnerable areas where necessary. It is important that interests throughout the area of an alert make preparations to protect life and property, and do not disregard it on the strength of the detailed forecast track. Tropical cyclones are not points, and forecasting their track remains an uncertain science.
A Pacific hurricane is a mature tropical cyclone that develops within the northeastern and central Pacific Ocean to the east of 180°W, north of the equator. For tropical cyclone warning purposes, the northern Pacific is divided into three regions: the eastern, central, and western, while the southern Pacific is divided into 2 sections, the Australian region and the southern Pacific basin between 160°E and 120°W. Identical phenomena in the western north Pacific are called typhoons. This separation between the two basins has a practical convenience, however, as tropical cyclones rarely form in the central north Pacific due to high vertical wind shear, and few cross the dateline.
A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern, central, and western. The Regional Specialized Meteorological Center (RSMC) for tropical cyclone forecasts is in Japan, with other tropical cyclone warning centers for the northwest Pacific in Hawaii, the Philippines and Hong Kong. While the RSMC names each system, the main name list itself is coordinated among 18 countries that have territories threatened by typhoons each year.
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basin(s) they are located in. Only a few scales of classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but some alternative scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
An Atlantic hurricane or tropical storm is a tropical cyclone that forms in the Atlantic Ocean, usually between the months of June and November. A hurricane differs from a cyclone or typhoon only on the basis of location. A hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean.
Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain or squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or Indian Ocean, comparable storms are referred to simply as "tropical cyclones" or "severe cyclonic storms".
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, 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 Australian region between 90°E and 160°E is officially monitored by the Australian Bureau of Meteorology, the Indonesian Agency for Meteorology, Climatology and Geophysics, and the Papua New Guinea National Weather Service and, 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 more than 65 km/h (35 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).
In the south-west Indian Ocean, tropical cyclones form south of the equator and west of 90° E to the coast of Africa.
The 1977 North Indian Ocean cyclone season was part of the annual cycle of tropical cyclone formation. The season has no official bounds but cyclones tend to form between April and December. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean. There are two main seas in the North Indian Ocean—the Bay of Bengal to the east of the Indian subcontinent and the Arabian Sea to the west of India. The official Regional Specialized Meteorological Centre in this basin is the India Meteorological Department (IMD), while the Joint Typhoon Warning Center (JTWC) releases unofficial advisories. An average of five tropical cyclones form in the North Indian Ocean every season with peaks in May and November. Cyclones occurring between the meridians 45°E and 100°E are included in the season by the IMD.
The 1978–79 Australian region cyclone season was the only season in which a reconnaissance aircraft flew into a tropical cyclones. Operationally, Australia's Bureau of Meteorology (BOM) tracked eleven tropical cyclones, while two additional systems were later added to the United States's Joint Typhoon Warning Center (JTWC) best track. Prior to 1985, the Australian region basin was defined as in the southern hemisphere between 80°E and 160°E, with the modern day season boundaries ranging from 1 November to 30 April of the following year. The first storm, an unnamed system, developed on 19 November 1978. The final cyclone, Kevin, dissipated by 12 May 1979. Tropical cyclones in this area were monitored by three Tropical Cyclone Warning Centres (TCWCs): the BOM in Perth, Darwin, and Brisbane.
The following is a glossary of tropical cyclone terms.
During 2018, 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 151 tropical cyclones had formed this year to date. 102 tropical cyclones were named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC).
During 2015, 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 133 tropical cyclones had formed this year to date. 92 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC).
During 2019, 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 143 systems formed with 105 of these developing further and were named by the responsible warning centre. The strongest tropical cyclone of the year was Typhoon Halong, which was estimated to have a minimum barometric pressure of 905 hPa (26.72 inHg) while Hurricane Dorian and was estimated to have sustained winds of 185 mph (295 km/h), the strongest wind speed of 2019.
During 2014, 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 119 tropical cyclones had formed this year to date. 82 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The most active basin in 2014 was the Western Pacific, which documented 23 named systems, while the Eastern Pacific, despite only amounting to 22 named systems, was its basin's most active since 1992. Conversely, both the North Atlantic hurricane and North Indian Ocean cyclone seasons experienced the least number of cyclones reaching tropical storm intensity in recorded history, numbering 9 and 3, respectively. Activity across the southern hemisphere's three basins—South-West Indian, Australian, and South Pacific—was spread evenly, with each region recording seven named storms apiece.
Throughout 2020, tropical cyclones will form within seven different tropical cyclone basins, which are located within various parts of the Atlantic, Pacific and Indian Oceans. During the year a total of 23 tropical cyclones have developed, with 13 of these being named by the appropriate warning centre. Tropical cyclones are primarily monitored by a group of ten warning centres, which have been designated as a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC) by the World Meteorological Organisation. These are the United States National Hurricane Center (NHC) and Central Pacific Hurricane Center, the Japan Meteorological Agency (JMA), the Indian Meteorological Department (IMD), Météo-France, Indonesia's Badan Meteorologi, Klimatologi, dan Geofisika, the Australian Bureau of Meteorology (BOM), Papua New Guinea's National Weather Service, the Fiji Meteorological Service (FMS) as well as New Zealand's MetService. Other notable warning centres include the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) and the United States Joint Typhoon Warning Center (JTWC).