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.
Accumulated cyclone energy (ACE) is a metric used to compare overall activity of tropical cyclones, utilizing the available records of windspeeds at six-hour intervals to synthesize storm duration and strength into a single index value. The ACE index may refer to a single storm or to groups of storms such as those within a particular month, a full season or combined seasons. It is calculated by summing the square of tropical cyclones' maximum sustained winds, as recorded every six hours, but only for windspeeds of at least tropical storm strength ; the resulting figure is divided by 10,000 to place it on a more manageable scale.
In the Indian Ocean north of the equator, tropical cyclones can form throughout the year on either side of the Indian subcontinent, although most frequently between April and June, and between October and December.
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but other scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
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.
In meteorology, an invest is a designated area of disturbed weather that is being monitored for potential tropical cyclone development. Invests are designated by three separate United States forecast centers: the National Hurricane Center, the Central Pacific Hurricane Center, and the Joint Typhoon Warning Center.
The 1973 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 1974 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 practice of using names to identify tropical cyclones goes back several centuries, with storms named after places, saints or things they hit before the formal start of naming in each basin. Examples of such names are the 1928 Okeechobee hurricane and the 1938 New England hurricane. The system currently in place provides identification of tropical cyclones in a brief form that is easily understood and recognized by the public. The credit for the first usage of personal names for weather systems is given to the Queensland Government Meteorologist Clement Wragge, who named tropical cyclones and anticyclones between 1887 and 1907. This system of naming fell into disuse for several years after Wragge retired, until it was revived in the latter part of World War II for the Western Pacific. Over the following decades, formal naming schemes were introduced for several tropical cyclone basins, including the North and South Atlantic, Eastern, Central, Western and Southern Pacific basins as well as the Australian region and Indian Ocean.
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 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 142 systems formed, with 100 of these developing further and being named by the responsible warning centre. The strongest tropical cyclone of the year was Typhoon Halong, with a minimum barometric pressure of 905 hPa (26.72 inHg). Cyclone Idai became the deadliest tropical cyclone of the year, after killing at least 1,303 people in Mozambique, Malawi, Zimbabwe, and Madagascar. The costliest tropical cyclone of the year was Typhoon Hagibis, which caused more than $15 billion in damage after striking Japan.
2020 was regarded as the most active tropical cyclone year on record, documenting 104 named tropical systems. During the year, 142 tropical cyclones formed in bodies of water known as tropical cyclone basins. Of these, a record-high of 104, including three subtropical cyclones in the South Atlantic Ocean and three tropical-like cyclones in the Mediterranean, were named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest storm of the year was Typhoon Goni, peaking with a pressure of 905 hPa (26.72 inHg). The deadliest storm of the year was Hurricane Eta which caused 175 fatalities and another 100+ to be missing in Central America and the US, while the costliest storm of the year was Hurricane Laura, with a damage cost around $19.1 billion in the Greater Antilles, The Bahamas, and the Gulf Coast of the United States.
The 1965 North Indian Ocean cyclone season had no bounds, but cyclones tend to form between April and December, with peaks in May and November. 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 releases unofficial advisories. An average of four to six storms 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 1966 North Indian Ocean cyclone season had no bounds, but cyclones tend to form between April and December, with peaks in May and November. 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 releases unofficial advisories. An average of four to six storms 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 1967 North Indian Ocean cyclone season had no bounds, but cyclones tend to form between April and December, with peaks in May and November. 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 releases unofficial advisories. An average of four to six storms 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 following is a list of North Indian Ocean tropical cyclones from 1920 to 1929. Records from before the 1970s were extremely unreliable, and storms that stayed at sea were often only reported by ship reports.
During 1996, 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 139 tropical cyclones formed in bodies of water known as tropical cyclone basins. 90 of them were named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest tropical cyclone of the year was Cyclone Daniella, peaking with a pressure of 915 hPa (27.02 inHg) in the open waters of the Indian Ocean. Hurricane Fran and Typhoon Herb tie for the costliest storm of the year, both with a damage cost of $5 billion. The deadliest tropical cyclone of the year was the 1996 Andhra Pradesh cyclone, which was blamed for over 1,000 fatalities as it directly affected the state of Andhra Pradesh in India. Five Category 5 tropical cyclones were formed in 1996. The accumulated cyclone energy (ACE) index for the 1996, as calculated by Colorado State University was 960 units.
