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Traditionally, areas of
tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...
formation are divided into seven basins. These include the North
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
, the eastern and western parts of the North
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
, the Southwest Pacific, the Southwest and Southeast
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
s, and the North Indian Ocean (
Arabian Sea The Arabian Sea () is a region of sea in the northern Indian Ocean, bounded on the west by the Arabian Peninsula, Gulf of Aden and Guardafui Channel, on the northwest by Gulf of Oman and Iran, on the north by Pakistan, on the east by India, and ...
and
Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean. Geographically it is positioned between the Indian subcontinent and the Mainland Southeast Asia, Indochinese peninsula, located below the Bengal region. Many South Asian and Southe ...
). The West 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). __TOC__


Overview


Northern Hemisphere


North Atlantic Ocean

This region includes the North
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
, the
Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...
, and the
Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...
. Tropical cyclone formation here varies widely from year to year, ranging from one to over twenty-five per year. Most Atlantic
tropical storms A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...
and hurricanes form between June 1 and November 30. The United States
National Hurricane Center The National Hurricane Center (NHC) is the division of the United States' NOAA/National Weather Service responsible for tracking and predicting tropical weather systems between the IERS Reference Meridian, Prime Meridian and the 140th meridian ...
(NHC) monitors the basin and issues reports, watches and warnings about
tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
weather systems for the Atlantic Basin as one of the
Regional Specialized Meteorological Centre A Regional Specialized Meteorological Centre (RSMC) is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as ...
s for
tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...
s as defined by the
World Meteorological Organization The World Meteorological Organization (WMO) is a List of specialized agencies of the United Nations, specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology an ...
. On average, 14 named storms (of tropical storm or higher strength) occur each season, with an average of 7 becoming hurricanes and 3 becoming major hurricanes. The
climatological Climatology (from Greek , ''klima'', "slope"; and , ''-logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. Climate concerns the atmospheri ...
peak of activity is around September 10 each season. The United States Atlantic coast and Gulf Coast,
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
,
Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
, the
Caribbean Islands Most of the Caribbean countries are islands in the Caribbean Sea, with only a few in inland lakes. The largest islands include Cuba, Hispaniola, Jamaica and Puerto Rico. Some of the smaller islands are referred to as a ''rock'' or ''reef.'' ''I ...
, and
Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...
are frequently affected by storms in this basin. Venezuela, the 4 provinces of
Atlantic Canada Atlantic Canada, also called the Atlantic provinces (), is the list of regions of Canada, region of Eastern Canada comprising four provinces: New Brunswick, Newfoundland and Labrador, Nova Scotia, and Prince Edward Island. As of 2021, the landma ...
, 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 Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
near the
Cape Verde Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...
islands. Occasionally, a hurricane that evolves into an
extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of p ...
can reach western
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
, including Hurricane Gordon, which spread high winds across Spain and the
British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...
in September 2006. Hurricane Vince, which made landfall on the southwestern coast of Spain as a tropical depression in October 2005, and Subtropical Storm Alpha, which made landfall on the coast of Portugal as a subtropical storm in September 2020, are the only known systems to impact mainland Europe as a (sub)tropical cyclone in the NHC study period commencing in 1851 (it is believed a hurricane made landfall in Spain in 1842).


Northeastern Pacific Ocean

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
hurricane A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its ...
s, and 4–5 major hurricanes (storms of Category 3 intensity or greater) annually in the basin. Storms that form here often affect western
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
, and less commonly the
Continental United States The contiguous United States, also known as the U.S. mainland, officially referred to as the conterminous United States, consists of the 48 adjoining U.S. states and the District of Columbia of the United States in central North America. The te ...
(in particular
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
), or northern
Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
. No hurricane included in the modern database has made landfall in California; however, historical records from 1858 speak of a
storm A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstor ...
that brought
San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...
winds over (marginal hurricane force), though it is not known if the storm actually made landfall. Tropical storms in
1939 This year also marks the start of the World War II, Second World War, the largest and deadliest conflict in human history. Events Events related to World War II have a "WWII" prefix. January * January 1 ** Coming into effect in Nazi Ger ...
,
1976 Events January * January 2 – The International Covenant on Economic, Social and Cultural Rights enters into force. * January 5 – The Pol Pot regime proclaims a new constitution for Democratic Kampuchea. * January 18 – Full diplomatic ...
,
1997 Events January * January 1 – The Emergency Alert System is introduced in the United States. * January 11 – Turkey threatens Cyprus on account of a deal to buy Russian S-300 missiles, prompting the Cypriot Missile Crisis. * January 1 ...
and
2023 Catastrophic natural disasters in 2023 included the Lists of 21st-century earthquakes, 5th-deadliest earthquake of the 21st century 2023 Turkey–Syria earthquakes, striking Turkey and Syria, leaving up to 62,000 people dead; Cyclone Freddy ...
brought gale-force winds to California. The
Central Pacific Hurricane Center The Central Pacific Hurricane Center (CPHC) of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central Pacif ...
's
area of responsibility Area of responsibility (AOR) is a pre-defined geographic region assigned to Combatant commanders of the Unified Command Plan (UCP), that are used to define an area with specific geographic boundaries where they have the authority to plan and c ...
(AOR) begins at the boundary with the
National Hurricane Center The National Hurricane Center (NHC) is the division of the United States' NOAA/National Weather Service responsible for tracking and predicting tropical weather systems between the IERS Reference Meridian, Prime Meridian and the 140th meridian ...
's 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 The Joint Typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South P ...
. 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
landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...
s are rare; however, they occur occasionally, as with
Hurricane Iniki Hurricane Iniki ( ; Hawaiian: ''iniki'' meaning "strong and piercing wind") was a hurricane that struck the island of Kauai on September 11, 1992. It was the most powerful hurricane to strike Hawaii in recorded history, and the only hurricane to ...
in 1992, which made landfall on
Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
, and
Hurricane Ioke Hurricane Ioke, also referred to as Typhoon Ioke, was a record-breaking, long-lived and extremely powerful tropical cyclone that traversed the Pacific for 17 days, becoming a Category 5 hurricane on the Saffir–Simpson scale on three ...
in 2006, which made a direct hit on
Johnston Atoll Johnston Atoll is an Unincorporated territories of the United States, unincorporated territory of the United States, under the jurisdiction of the United States Air Force (USAF). The island is closed to public entry, and limited access for mana ...
.


Northwestern Pacific Ocean

The Northwest Pacific Ocean, or Western North Pacific, 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 A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its lo ...
strength or greater; also, an average of 16
typhoon A typhoon is a tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere and which produces sustained hurricane-force winds of at least . This region is referred to as the Northwestern Pacific Basin, accounting for a ...
s occurred each year during the 1968–1989 period. The basin occupies all the territory north of the
equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...
and west of the International Date Line, including the
South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by South China, in the west by the Indochinese Peninsula, in the east by the islands of Taiwan island, Taiwan and northwestern Philippines (mainly Luz ...
. 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 China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
,
Hong Kong Hong Kong)., Legally Hong Kong, China in international treaties and organizations. is a special administrative region of China. With 7.5 million residents in a territory, Hong Kong is the fourth most densely populated region in the wor ...
,
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
, the Koreas,
Macau Macau or Macao is a special administrative regions of China, special administrative region of the People's Republic of China (PRC). With a population of about people and a land area of , it is the most List of countries and dependencies by p ...
,
Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
,
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
and
Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...
, plus numerous
Oceania Oceania ( , ) is a region, geographical region including Australasia, Melanesia, Micronesia, and Polynesia. Outside of the English-speaking world, Oceania is generally considered a continent, while Mainland Australia is regarded as its co ...
n islands such as
Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...
, the
Northern Marianas The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an unincorporated territory and commonwealth of the United States consisting of 14 islands in the northwestern Pacific Ocean.Lin, Tom C.W.Ameri ...
and
Palau Palau, officially the Republic of Palau, is an island country in the Micronesia subregion of Oceania in the western Pacific Ocean. The Republic of Palau consists of approximately 340 islands and is the western part of the Caroline Islands ...
. Sometimes, tropical storms in this region are powerful and long lasting enough to affect the more inland South East Asian nations of
Laos Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and ...
,
Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
, and
Cambodia Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. It is bordered by Thailand to the northwest, Laos to the north, and Vietnam to the east, and has a coastline ...
, and in extreme cases, even the equatorial nations of
Singapore Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...
,
Brunei Brunei, officially Brunei Darussalam, is a country in Southeast Asia, situated on the northern coast of the island of Borneo. Apart from its coastline on the South China Sea, it is completely surrounded by the Malaysian state of Sarawak, with ...
,
Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...
, and
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
. The coast of China sees the most landfalling tropical cyclones worldwide. The
Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
receives an average of 6–7 tropical cyclone landfalls per year, with typhoons Haiyan and Goni in 2013 and 2020 being the strongest and most powerful landfalling storms to date.


North Indian Ocean

This basin is divided into two areas: the
Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean. Geographically it is positioned between the Indian subcontinent and the Mainland Southeast Asia, Indochinese peninsula, located below the Bengal region. Many South Asian and Southe ...
and the
Arabian Sea The Arabian Sea () is a region of sea in the northern Indian Ocean, bounded on the west by the Arabian Peninsula, Gulf of Aden and Guardafui Channel, on the northwest by Gulf of Oman and Iran, on the north by Pakistan, on the east by India, and ...
, 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 Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical o ...
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 The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...
, 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 The Arabian Peninsula (, , or , , ) or Arabia, is a peninsula in West Asia, situated north-east of Africa on the Arabian plate. At , comparable in size to India, the Arabian Peninsula is the largest peninsula in the world. Geographically, the ...
or
Somalia Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. The country is located in the Horn of Africa and is bordered by Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, th ...
; 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 The Ganges ( ; in India: Ganga, ; in Bangladesh: Padma, ). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international which goes through India, Bangladesh, Nepal and China." is a trans-boundary rive ...
and Ayeyarwady Deltas mean that the deadliest tropical cyclones in the world have formed here, including the
1970 Bhola cyclone The 1970 Bhola cyclone (also known as the Great Cyclone of 1970) was a catastrophic and extremely deadly tropical cyclone that struck East Pakistan (present-day Bangladesh) and India's West Bengal on 12 November 1970. It remains the deadliest t ...
, which killed 500,000 people. Nations affected include
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
,
Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...
,
Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
,
Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
,
Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
, and
Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...
.


Mediterranean Sea

On rare occasions, tropical-like systems that can reach the intensity of hurricanes, occur over the
Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
. Such a phenomenon is called a Medicane (Mediterranean-hurricane). Although the geographical dimensions of tropical
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
s and the
Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...
Sea are clearly different, the precursor mechanisms of these perturbations, based on the air-sea thermodynamic imbalance, are similar.Medicanes: cataloguing criteria and exploration of meteorological environments
". www.tethys.cat.
Their origins are typically non-tropical, and develop over open waters under strong, initially cold-core
cyclone In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an ant ...
s, 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 temperature Sea surface temperature (or ocean surface temperature) is the ocean temperature, temperature of ocean water close to the surface. The exact meaning of ''surface'' varies in the literature and in practice. It is usually between and below the sea ...
s in late-August and early-September are quite high over the basin (24/28 °C or 75/82 °F), though research indicates water temperatures of 20 °C (68 °F) are normally required for development.Microsoft Word – EGS2000-Plinius-II-Meneguzzo.doc
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. The 1995 system developed a well-defined
eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...
, and a ship recorded winds, along with an
atmospheric pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013. ...
of 975
hPa The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an S ...
. Although it had the structure of a tropical cyclone, it occurred over water temperatures, suggesting it could have been a polar low.DR. JACK BEVEN'S Images of the Mediterranean 'Hurricane' (1995)
". www.mindspring.com.


Southern Hemisphere

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 The World Meteorological Organization (WMO) is a List of specialized agencies of the United Nations, specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology an ...
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 The Joint Typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South P ...
also monitors the whole region, but splits it at 135°E into the South Pacific and the Southern Indian Ocean.


South-West 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.


Australian region

Through the middle of 1985, this basin extended westward to 80°E. Since then, its western boundary has been 90°E. Tropical activity in this region affects
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
and
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
. According to the Australian Bureau of Meteorology, the most frequently hit portion of Australia is between
Exmouth Exmouth is a harbor, port town, civil parishes in England, civil parish and seaside resort situated on the east bank of the mouth of the River Exe, southeast of Exeter. In 2011 it had a population of 34,432, making Exmouth the List of settl ...
and Broome in
Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...
. 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 .


South Pacific Ocean

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 The Fiji Meteorological Service (FMS) is a Department of the government of Fiji responsible for providing weather forecasts and is based on the grounds of Nadi Airport in Nadi. The current director of Fiji Meteorological Service is Misaeli Funak ...
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 El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variation in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some semblance of cyc ...
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.


South Atlantic Ocean

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 The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for ...
, and the only full-blown tropical cyclones on record were the Angola tropical storm in 1991, Hurricane Catarina in 2004, Tropical Storm Anita in 2010, Tropical Storm Iba in 2019, Tropical Storm 01Q in 2021 and Tropical Storm Akará in 2024. 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 The Brazilian Navy () is the navy, naval service branch of the Brazilian Armed Forces, responsible for conducting naval warfare, naval operations. The navy was involved in War of Independence of Brazil#Naval action, Brazil's war of independence ...
Hydrographic Center started to assign names to tropical and subtropical systems in this basin, when they have sustained wind speeds of at least .


See also

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Regional Specialized Meteorological Centre A Regional Specialized Meteorological Centre (RSMC) is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as ...
* Outline of tropical cyclones


References

{{Use mdy dates, date=May 2013 Tropical cyclones Tropical cyclone meteorology